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 Post subject: Re: TC50 Tube discussion
PostPosted: Tue Aug 08, 2017 6:50 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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What I am getting with the SED =C= EL34 is that characteristic 3D swirl in the grind of the punch in power chords. However, where they shine the most is on the clean channel with moderate gain setting. So rich, creamy and soulful which is ideal for blues, even most Rock. I basically got the RA100 as I was not getting the tone and character from the Mark V for classic rock. It just did not sound right. Note that there is not much go gain with various tubes in the preamp, perhaps subtle differences. I have tried the KT77, EHX brand EL34, Tung Sol EL34B, Mullard RI EL34, Ruby EL34, nothing seemed to be as satisfying as the SED =C= EL34 (actually bought them for use in the Mark V but never did). Sometimes you can aid the tone of the amp a small amount to compensate for certain characteristics to pair up with the cabinet. The OS Recto 412 tends to get into the bright side of the spectrum with the RA100. Long plate 12AX7 in the latter gain stages help to cut back on higher frequency due to their inherent roll off. The RA100 never sounded better.

The combo is a different animal. Sure it sounds identical to the other (having the same tubes) though the 412 cab. The combo (essentially open back) leads to a different tonal pallet. For some odd reason I found V30 get fizzy in open enclosures. Celestion Cream Back G12H75 actually have a more smoother response without the fizz in the same application. I found the Mullard RI EL34 to serve up the juice with the combo. Those seem to have an early onset of distortion and they work well with the RA100. There is just something odd with the RA100 that does not seem to do well with the Mesa STR440 6L6GC tubes. It could be the lower plate voltage relative to the TC-50 or other amps that sound great with those tubes. Lower plate voltage may be intentional due to the power soak feature.

The thing with the RA100 is that it saturates easily so dialing back on gain when raising the volume tends to compensate. If it has any presence or feedback circuit (assumed) the gain and volume control seems to also work against you if you are trying to find mega distortion. Similar to the Roadster in some respects as the amp tone improved with a reduction in gain which adds to some brightness of such a dark amp. My experience with either of these, OD pedals just do not work too well.

Mark V or even the JP-2C, the grid slammer just sounds awesome. I thought the JP-2C could not get any better, oh yeah as the grid slammer takes it up another level. Mark V it does help to compensate for its weak tone (with stock tubes).

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 Post subject: Re: TC50 Tube discussion
PostPosted: Wed Aug 09, 2017 8:53 am 
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Mark III
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I've heard great things about the SED =C= EL34 and the Tung Sol EL34B. Have you tried the Mullards or the Svetlana's in your TC50?

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 Post subject: Re: TC50 Tube discussion
PostPosted: Wed Aug 09, 2017 6:57 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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I did briefly try the SED =c= EL34. I did not get the same intense swirl in the gain characteristic like I did with the RA100. They did not sound as amazing. I will or may retry them now as the amp has settled some and sounds really great with the stock tubes. the SED's are well broken in but do not have that many hours on them.

I have not tried the Tung Sol EL34B tubes yet. I was not very fond of them in the RA100 but as back ups they will suffice. Also they do not sound anything like the SED =C= EL34 or even the SED =C= 6L6GC. I have used both in the RA100 (not at the same time mind you) and each type of SED are awesome. I was going to also try the =c= 6L6GC in the TC-50. They should be safe as I have used them in the Roadster, Mark V, Mark IV and the RA100. I have two sets of quads of those. May give them a try or not. I was planning on sticking with the Mesa branded tubes just for kicks as I really do not want to get hooked on tubes that are no longer in production. (do as I say and not as I do..... well I had to get the Siemens tubes for a one time deal). Tubes came today and have not opened up the box yet. I was reloading the Mark V with some old Mesa tubes I had just for kicks as I am thinking of retiring it....

Mullard EL34, not tried them in the TC-50 either. They seem to run wild in the RA100 combo which may have an early onset of distortion that would not benefit the TC-50.

Time to open up the box and see if I got one or two of the Siemens. Website said cost was for a pair.

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 Post subject: Re: TC50 Tube discussion
PostPosted: Wed Aug 09, 2017 10:01 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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For starters the tubes I ordered direct from Mesa arrived today (Mesa 5881 STR 425 and Mesa NOS Siemens EL34 STR450) unbroken and in matched pairs. I would have been pissed if I only got one NOS Siemens tube at that price. The emailed invoice said the 5881 was a duet and the other was just a single (pair that is :P ) I did go for the Siemens tubes first, and while I was at it I took out my box of power tubes to try out (against my better judgement but if I kill the amp I can fix it but doubt anything would go wrong as all of the tubes have been used in the RA100, Mark V, Roadster at some point and no failures occurred) Here is the list of what I tried in the TC-50 other than the new tubes that were delivered with the Mesa logo on the glass: Ruby EL34BHT, SED =C= EL34 (had to open up the RA100 Head to get to them) Tung Sol EL34B, Gold Lion KT77, Mesa STR 447 EL34 (stock tubes) Mesa 5881 STR 425, Mesa STR440 6L6 and then back to the stock Mesa STR 447 EL34. I will do a write up on my notes by this weekend. If I did it now I would be up too late. I can say this, one hunch paid off and the tubes are as good as was claimed in the Rectifier forum. One needs quite more time to work with and has promise. Three of them sounded better in the TC-50 than they did in the RA100, two of which really surprised me and one came out as the Holy Grail (subjective at best). All of the Mesa tubes used had very similar color codes. Most were green and one was gray. I did not include the 6V6 in this comparison, nor did I record anything yet. No harm done to TC-50 as an end result.... I did take a lot of notes with each tube and will try to compress it as much as possible. It may be a long post so I will warn you upfront now before posting.....sorry for not posting the report this evening... In the mean time try to guess what I thought was the holy grail power tube. (if you want a hint, it was a pair from a quad of tubes I used for several months in the Mark V at full power that really impressed me, yeah I ordered them specifically for the Mark V from a Vendor on Ebay who matched them quite well).

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 Post subject: Re: TC50 Tube discussion
PostPosted: Thu Aug 10, 2017 9:15 am 
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Mark III
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Glad to hear they came in pairs, I would have lost it too lol. I'm looking forward to your write up for sure and I don't mind long posts at all, especially if I can learn from them. From the sounds of it so far, stock Mesa tubes are the way to go in the TC50. This makes me even more excited to hear about the NOS Mesa Siemens.

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 Post subject: Re: TC50 Tube discussion
PostPosted: Thu Aug 10, 2017 3:14 pm 
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Joined: Fri Feb 01, 2013 10:51 am
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bandit2013 wrote:
... In the mean time try to guess what I thought was the holy grail power tube. (if you want a hint, it was a pair from a quad of tubes I used for several months in the Mark V at full power that really impressed me, yeah I ordered them specifically for the Mark V from a Vendor on Ebay who matched them quite well).


I have no idea as I'm new-ish around here, but I'm looking forward to your notes.

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 Post subject: Re: TC50 Tube discussion
PostPosted: Thu Aug 10, 2017 7:53 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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I will post them separately but will try to reflect on each as best as I can. I will basically point out differences of what comes stock in the amp. Still the current production Electro Harmonix EL34, selected and re-branded by Mesa is not all that bad and it sounds great in the TC-50 but there are some drawbacks to the tube such that it becomes apparent when you actually have a chance to compare them to others. Here is the beginning of my notes as the first pair of tubes I had to try out was the most expensive pair of the bunch (relating to the actual purchase cost when I bought them). The rest were run in no particular order. Sorry for those who are waiting on feedback of the Mesa 5881, if you are waiting, they are great and way better than the Mesa 6L6 STR440.

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 Post subject: Re: TC50 Tube discussion
PostPosted: Thu Aug 10, 2017 8:01 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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This is just for one tube..... a short intro to start....

I have completed running seven different sets of power tubes in the Mesa TC-50. Five different varieties of the EL34 tube including three variants (two of which are EL34Bs and one is a KT77). The other two are Mesa 6L6 type tubes to complete the sixth and seventh set. The list of tubes trialed are as follows: Mesa NOS Siemens EL34 STR 450, Ruby EL34BHT, SED =C= EL34, Tung Sol EL34B, Gold Lion KT77 which ends the EL34 tube sets. Then Followed by the Mesa 5881 STR 425 and the Mesa 6L6GC STR440.


First up: NOS Siemens EL34

8) Mesa NOS Siemens EL34 STR450 (Gray color code): Narrow and tall tube similar to the Mesa EL34 STR447 tub but definitely not the same tube. The base has all 8 pins present. Very large heat sinks above the top mica spacer. Large ring halo getter on a single post rising above the heat sinks. Plates are gray in color and crimped closed. Very well constructed and internals would not vibrate when tapped. Internals are supported by mica spacers with finger cuts on the sides and held in place by compression against the glass bottle. Yeah it is a tube alright. How it sounds when used in the TC-50 is more important.
Clean channel (normal mode) characteristics are pleasant and very different from the current production EL34. Plenty of top end chime and smooth tonal response. Midrange is present and sweet in character and the bass is bold and responsive. Very well balanced and just right for clean blues style. This tube lacks any harshness that may be common with the current production EL34 offered by Mesa. Clean switch to drive mode the tone is pleasant and not as aggressive as the other Mesa EL34 tube. The vintage vibe is there and wakes up with a little more push on the gain control. Definitely need more play time with this tube as I had re-installed them after running though all of the tube choices I have at my disposal. Lo gain channel (CH2) rings out with authority. This amp rocks extremely well with the NOS Siemens EL34 tubes on CH2. Full range of frequencies that are well balanced from bass to treble. Well balanced midrange that does not overtake the overall tone. Harmonics can be pinched off just about anywhere on the fret board including the G string at the 12 and 14th fret. (I have noticed with some tubes that may choke off parts of the midrange appear to make one think you have a dead spot on the fret board. Not with this tube. No change in pick attack. Palm muting on the gain channels is rewarding with each slide of the pick across the muted strings. Not exactly a dry tone like with the other tubes (including the current production EL34) but it is a pleasing tone. Perfect for accurate replication of Classic Rock from the late 60’s up to early 80’s as the tube when pushed by the preamp does not get overly grainy or too aggressive. Lo Gain tight mode engaged and the tubes compress a bit and really become more aggressive in character. Bass response bold and does not muddy up the channel even with the gain pushed to 90%. Hi gain channel (CH3) as you know adds more gain to the characteristics. The NOS tubes hold up well and take on more of an aggressive tone (actually it is the preamp that is becoming more aggressive). Bottom end is still bold and tight and overall tone has changed and becomes thicker. Definitely getting into Mark / JP-2C territory. CH3 switched to tight mode gains more compression and a bit of loss of note definition. I really want to hear how these tubes sound with more than 20 minutes on the clock. So far I am liking them right out of the box. Overall a great tube. Noticed that the volume seems a bit louder than the stock supplied tubes. Yes, the NOS Siemens EL34 do share some similarities to the stock Mesa EL34 but yet the differences are quite notable. The stock EL34 tube even after 20+ hours of use still choke off the midrange to some extent. They have gotten better but not ideal. The Siemens tube is full tone, not choking of frequencies. A bit brighter but yet not harsh or lacking in tonal quality one would expect for the cost paid per pair. Good choice but expensive. Will have to see what kind of life I get from them and if the character changes with more heating cycles on the cathode. Perhaps some changes in the preamp tube arrangement would really waken these tubes up into beast hood like the SED =C= EL34 have become with the right preamp tubes in the RA100. So far I like what I have heard with the NOS Siemens EL34 tubes. I generally do not go for NOS tubes due to limited supply and if you really like them and you cannot get them or if the quantity is low with high demand you get gouged. I like to be conservative but if it is really worth it why not.... Do I think these are worth $178, yes. Does it turn the TC-50 in to a fire breathing beast, no. Actually it reveals the quality of design within the preamp. I really do want to tube roll the preamp to get the most out of these tubes. I will break them in for a bit and store them for future use. Note that the channel characteristics are not held back by any means with these tubes. I do believe there is huge potential but unfortunately it is a tube out of production and harder to get more the longer I wait. There is hope as there are two that are fire breathing freaks yet to be discussed. Based on the list of tubes, try to think what they may be. 8)

Next installment will be on the Ruby EL34BHT.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


Last edited by bandit2013 on Fri Aug 11, 2017 6:49 pm, edited 1 time in total.

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 Post subject: Re: TC50 Tube discussion
PostPosted: Fri Aug 11, 2017 6:48 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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Location: North Carolina
Second installment: Two tubes Ruby EL34BHT and the SED =C= EL34.


:twisted: Ruby EL34 BHT (resource Dougs Tubs: TC rating 3125): This one is a tall large bottle EL34. Almost the same diameter as a 6L6GC tube but does not fall into the 6CA7 category as it has the proper number of grid posts poking though the top mica spacer as well as lacks bent over metal tabs that would indicate a beam forming plate. Welded plates, and a single round pan getter (actually attached to the plate which is different than the others as they are generally attached to the outer grid post). Clean channel characteristics with the CH1 switch set to normal is quite similar to the Siemens EL34 tube. Bold and full tone character but not as bright on the top end but bright enough. In Clean Drive mode the tube becomes more aggressive. Not as acidic as the Mesa EL34 STR 447 tube. I was really impressed with these tubes as they did not sound all that great in the RA100. Lo gain channel set to normal mode and the amp screams as the beast is unleashed. It can be tamed with adjustment of the gain control. I had it set to about 75%. Also had to adjust the tone controls just a bit to compensate for the different tube. This was quite riveting as I did not expect such a transformation. Not overbearing gain characteristic like you would get with the stock tube. Drive mode really added some zing as the channel compressed a bit. Still quite bold on the bottom end and just perfect across the frequency range. Much smoother in the distortion character but still crisp on attack, tight bottom and some interesting harmonics. I really like the way some tubes sound when palm muting, actually the Stock Mesa EL34 tubes are awesome for that effect as you get a dry tone and emergence of the midrange you thought was missing. The Ruby EL34BHT has that same effect. Not quite as dry but still impressive. Hi gain channel was where the fire started. Normal mode on CH3 was breath taking and the amp was smoking away and churning out this tone I really did not expect. What a beast this amp has become. (no actual smoke here but dang did this sound really good). Harmonics and musical content was just intense. Hold a note and get a bit of feedback and you can control that for days (assuming you could actually do it that long). I would almost think this tube was a 6CA7 but it is not. 6CA7 have a distinctive tone to them which is awesome experience. However this EL34 was not shy by any means and really pushed the grind with authority. CH3 tight added a some compression and thickened up the mids. A bit too much gain on CH3 will get a bit soupy (drop in note definition) but about the same as the Stock EL34 but not as fizzy. Overall this tube brings out the best features of the TC-50. I actually had to drop the volume a bit as these tubes seemed to be much louder. A matched pair of these will run you just under $40.00. If you really are into heavy metal these tubes will rock the house and almost raise the demons if you are into that sort of thing. Wait for it…… it is coming…. There is another… that walks all over this one…. And it is not the next one coming up either. :twisted:


8) SED =C= EL34 (St Petersburg, Russia) (Resource “TheTubeStore” in Canada): Medium diameter glass envelope, heat sink fins on top are about the same size as that on the Mesa EL34 STR447. This tube has dual small round cup getters on each side. No common wire to bridge them together. Plates are welded together. I bought these as soon as I found out the Svetlana Electron Devices was no longer making audio tubes for consumer grade electronics. I originally bought them for use in the Mark V as that was the amp I specified when I purchased them. When I did try them in the Mark V they sounded very similar to the EHX EL34 tubes had tried just for kicks. I do not remember if I had the RA100 at that time and since I did not use them in the Mark V (was hooked on the SED =C=6L6GC tubes) I set them aside for later use. The =C= EL34 has that iconic SED characteristic when pushed a bit into saturation, that swirling 3D effect and so far the RA100 is a perfect match for these tubes, even more so when you tune the preamp with the correct mix of preamp tubes. I am not ready to explore that in the TC-50. Power tubes, sure as all of the tubes I currently have in my inventory have been used with Mesa amps (RA100, Mark V, Roadster. I have not gotten around to other tubes in the JP-2C but that is a 6L6 only amp). Enough ramble…. How do they sound…. In most respects they sound very similar to the NOS Siemens tubes. Clean channel in normal they are as pleasant as the Siemens tube, bold lows, well balanced midrange and treble response. Clean in drive mode and the tube just sounds rich with just a hint of some aggressive clip waiting to hit you but it remains compliant with the channel settings. The SED =C= EL34 is awesome for classic rock and blues (clean or dirty). Lo gain and Hi gain was about the same as the NOS Siemens tubes. A bit more aggressive than the Siemens tube with moderate gain settings but not quite as explosive and aggressive as they could be (RA100 is a monster with a quad of these tubes, I had to return the pair when I was done with them in the TC-50, I really did not have to but wanted too). 8)

So far the three tubes shortly described as used in the TC-50 are worth every penny (Mesa NOS Siemens EL34 STR450, Ruby EL34BHT and the SED =C= EL34. Out of the two reviewed thus far there is one that makes the TC-50 a true beast and that would be the Ruby EL34BHT. Don’t get them just yet as there was another pair of EL34 tubes that really blew me away in more ways than one and not just on the Hi/Lo gain channel either. I have four more reviews to write up yet.

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Old friends I sometimes miss:
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 Post subject: Re: TC50 Tube discussion
PostPosted: Fri Aug 11, 2017 7:46 pm 
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Dual Recto

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Update on the Mesa NOS Siemens EL34 STR450's ... They are getting better with a few heat cycles on the cathodes. Way better than the first run on them. Clean channel is about the same but there is more bite with the drive. Lo gain is now getting to beast hood and Hi Gain is really growing on me. I may have to rethink my notes.... nah. first impressions usually stick with you but they are getting on the sinister side for with the grind on Hi and Lo gain. Still bold, tight in character and tone has not changed much. Right now they are equivalent in the TC-50 as are the SED =C= EL34 in the RA100. Yeah, they are putting a smile on my face too. :mrgreen: Still the beast tube is yet to be revealed. You probably have already guessed it by now.....Two more EL34 variants to go (the type B tubes would be a variant as they are just a bit different than the standard EL34, KT77 is not an EL34 but works with the same bias and current range. I may go further with the 6L6 variants and throw in the SED =C= 6L6GC, Tung Sol 7581 and that would basically cover what I have other than the Svetlana 6L6 (new sensor).

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Old friends I sometimes miss:
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 Post subject: Re: TC50 Tube discussion
PostPosted: Sat Aug 12, 2017 9:01 am 
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Dual Recto

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This is the remaining of the EL34 tubes (and the variants I have at my disposal). Too bad I do not have any 6CA7 to try out. This one will be much longer than the other two. Sorry for wordiness in the following passage. I will complete the full run though on all of the tubes when I post the next block of the comparison of the Mesa 6L6GC STR440 and the Mesa 5881 STR425. (in short the Mesa 5881 STR425 will not disappoint you. You may still notice a slight volume drop with the 5881 tube like you will get with the 6L6GC tube but the overall of the 5881 is amazing on all channels.) To finish up the last two EL34 tubes and reveal what I thought was the top dog in the TC-50, think about my question and see if you guessed the answer. You have two choices to choose from: Tung Sol EL34B or the Gold Lion KT77.

Here ends the EL34 comparison: :roll:

8) :| Tung Sol EL34B (resource “TheTubeStore” code on tube 39). Another EL34 Variant with a lower impedance. Tube has welded plates, dual heat sinks similar in size and shape as the =C= and Siemens EL34. Glass bottle diameter is the same as the =C= tube. Single getter pan supported by u shaped wire loop. I have tried this tube in other amps such as the Roadster and RA100. Not bad but not great either. As a substitute it is suitable. In the TC-50, it does seem to have a different characteristic. It is more than obvious that the TC-50 has a different bias than the other two mentioned. Clean channel was warm and rich in tone such that you may make you think this is a 6L6 tube. With CH1 set to drive the overall experience is about the same warm tone with a hint of grit. In characteristics on drive, it is very similar to the 6L6. This tube is definitely a solution for an amp that only runs an EL34 tube and you desire a 6L6 character. The tube lacks a beam plate so it does not meet the 6CA7 construction. Really good for blues playing if you are into that sort of thing (which I am). There is a hint of EL34 peaking out in the mix but not very dramatic.

CH2 low gain (normal)TS EL34B; dynamics improved and the EL34 spirit started to liven up. Tone became more aggressive the louder you set the amp. Still had some 6L6 tone thing going on. It is much louder than an actual 6L6 tube in the TC-50 so there does not appear to be the shift in volume level. Tight mode made the overall tone more aggressive but not quite like the other EL34 tubes. I would consider this a mild tube verses the others as some of the distorted content is rolling off on the top end. Had a slight choke on some of the mid range frequencies but not quite like the Mesa 6L6GC STR440 tube.

CH3 Hi gain TS EL34B: normal setting had a thicker response than the other EL34 tubes in the trial. Not as articulate, perhaps a bit cloudy without the meatballs. Muddy does not quite describe the tone, cloudy is more appropriate. Saturated and less dynamic…. I preferred the Lo gain channel with this tube than the Hi gain channel. It only got worse with the tight mode on CH3. It is not a bad tube but does not seem to be a good fit for the TC-50. Still it performed better in the TC than it did in the RA. If I was after a 6L6 character but had a fixed bias or strictly and EL34 amp this tube would do it for you. Possible change in preamp tubes may bring out some better characteristics but at the moment I am sticking with the stock Mesa 12AX7 tubes. I was able to coax a bit more thunder out of this tube with the RA100 and preamp tube change. Still not a preferred tube for me. I just was not impressed with the tube as the claims about it were “similar to SED =C=”. That is a bit broad, are they referring to the EL34 or the 6L6? What amp are they using ? It does not sound anything close to either SED =C= tubes I have. Perhaps this tube will shine better in a different amp. 8) :|


Yep if you guessed correctly: Gold Lion KT77 is the top Dog! :P 8) :shock: :twisted:

The BEAST that took them all down! This I did not expect at all as when I tried them in the RA100 I was not overly impressed. The tubes had more headroom that I would like to have. I originally bought them strictly for use with the Mark V and I would assume they were performance matched for that amp in question. No doubt they were killer tubes in the Mark V and they survived 3 months of heavy use at full power. At the time I bought a quad of them, they were a bit more expensive than the SED =C= 6L6GC tubes (just after the price increase when SED consumer factory shut down). The best performing tube that I tried thus far in the TC-50 is the Gold Lion KT77. (These may say Genalex on the box, but that is only a trade name as they are made by the same company that manufactures the Tung Sol, EHX, Mullard which is brokered through New Sensor. Made by Reflektor Co in Saratov. ) These tubes are of the beam powered tetrode family similar to the 6CA7 but very different in design. These tubes sport heat sinks on the grid similar to the EL34 but they lack the suppressor grid. Instead they have a beam forming plate similar to the 6L6 construction. Features that the KT77 do not have are holes or slots on the plates and lack any formed ribs in the plate surface. Moderate sized flat getter plate mounted to a ring and supported by a U shaped wire support connected to the plate. Glass bottle is a medium diameter and the same size as the Tung Sol EL34B and SED =C=.

GLKT77 Clean: The CH1 clean channel performance was unrivaled but similar to the Tung Sol EL34B but different as the Tung Sol had a warmer tone. Tight bold bottom end and top end chime similar to the Siemens EL34 tube. Very pleasing to the ear with some overtones of the EL34 characteristics. These tubes are in a class of their own. Setting the clean channel to Drive is where the true nature comes to light. Nice edgy tone but still smooth in character which is quite similar to the Siemens tube. The smile has returned as I was delighted to hear what was coming out of the Vertical 212 cabinet. Perfect for blues or classic rock. Full tone and well balanced characteristics in the tone. A slight more aggressive than the Siemens with driven hard on the Clean channel. This is where the similarities of the KT77 and the Siemens EL34 differ on the Lo Gain Channel 2.

Lo Gain GLKT77: In the normal mode of CH2 the tube becomes a bit more aggressive and retains its composure. WOW, the harmonic texture is just amazing. The KT77 does for the TC-50 as the SED =C= does for the RA100. I could not believe my ears. Push the envelope a bit harder and the tone becomes more aggressive with tight bottom end and just the right balance of midrange and top end. It does not get any better than this or does it? Tight mode just brings it up another level. Adds a bit of compression but that enriches the tone considerably. Almost into the beast. Note detail and articulation of each string is just enhanced. Palm muting also retains the dry characteristic I was getting with the Mesa EL34 STR447 (which I really love) but only better in tone quality as it is less acidic than the Mesa EL34 STR447. For a current production tube I am overly impressed. I would compare this to the Siemens EL34 characteristic but it just sounds much better. The more gain the more aggressive the overall character becomes and not cloudy in detail either.

Hi Gain GLKT77: CH3 normal mode just blew me away completely. The beast has been found! The detail and rich harmonic swirl in the grinding power chord just was rewarding. Sinister best describes this tone and the only time I ever heard this amazing sound was with the Mark IV running a pair of TAD 6L6GC STR tubes in the outer position and a pair of SED =C= 6L6GC (NOS versions from 1990 Groove tubes Gold, good thing is I still have those tubes). The TC-50 with a pair of Gold Lion KT77 was much more of a beast than the Roadster, JP-2C or Mark V could ever be. We are not talking blurred vision or hearing loss as every note was still well defined. Switch into tight mode and the tone becomes more compressed and explosive at the same time. It did not seem to thin out. I think when I retire the Siemens EL34 tubes, the KT77 are going in next. I will probably get a new pair as these tubes have a many hours on them. Rest assured they should last longer than the Typical EL34 tube if I believe the specifications sheets. Nirvana at its best. I found the KT77 to release the full potential of the TC-50 on all channels. From expressive cleans to aggressive distortion. Now I am really in love with the TC-50. No need to change preamp tubes as the Gold Lion KT77 just sounded perfect (subjective like everything else). If you want to really get heavy for that Metal tone? the KT77 will do it. If you like to be expressive with your blues or classic rock? KT77 again. The Gold Lion KT77 just did it all. However if you want a bit of mud in your tone you can use the Tung Sol EL34B. The Ruby EL34BHT came in a close second as it did get more saturated on the Hi gain channel (a slight sacrifice of definition). If you want precision and aggressive tone that cannot be touched with tight bass response and does not require you to dial it out, the Gold Lion KT77 delivers the goods. OMG these tubes just impressed me to no end. Overall loudness of the KT77 was more than the Siemens or Tung Sol. :P 8) :shock: :twisted:

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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 Post subject: Re: TC50 Tube discussion
PostPosted: Sat Aug 12, 2017 2:15 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2644
Location: North Carolina
Here is the last part on the 5881 also a reference to the 6L6 tube.

The 6L6GC and its variants:

:shock: :P Mesa 5881 STR425: The tube pair I received from the Mesa Store had the Green color code. The tube is a shorter glass bottle but the same width as the standard 6L6GC tube. Getter flash envelopes most of the upper section of the tube. There is a small u shaped heat sink connected to the control grid posts, an odd formed metal component that appears to be connected to the cathode that spans out from the between the U in the heat shield and spans out across the mica spacer. The beam plate appears to be nickel or chrome plated. Plates are crimped onto the posts and the seams are welded. This tube has a small plastic base such that the bear claw clamp will only touch the glass which is okay as tension applied to the bottle will reduce vibration effects on the tube.
Clean (CH1) 5881: Tone is warm, tight base with a sweet midrange and a pleasant top end chime. Overall tone is well balanced and nothing peaks out as overwhelming. Very easy to dial in a range of tone with the tone controls. Bold ant precise seems to best describe the clean characteristics. In Drive mode, the tube really wakes up and into a nice crunch that is suitable for most classic rock. This alone is quite impressive for a 6L6 variant. I am hearing some similarities to the smaller 6V6 tube but with more power available.
Lo Gain CH2 5881: Normal mode, well this is interesting but expected as I am driving the gain at 70%. The TC-50 and the 5881 perform quite well with an aggressive and massive sound. Way better than the standard 6L6GC STR440 tube. There is no lack or choking of the mids and the characteristics are well balanced, and detailed. Drive mode the TC-50 with the 5881 becomes very aggressive and the beast is unleashed into incredible overtones and a grind that rings out like the a Mark series amp.
Hi Gain CH3 5881: Normal mode, now we are definitely stealing money from the Mark amps as the TC-50 roars with authority on channel 3. Tone is still retaining the tight bottom end and balanced midrange and treble but with more explosive harmonic content that says this is the big brother to the 6V6 tube and way louder. Tight mode brings in more compression and saturation and takes away some of the sonic detail as the normal mode. Still quite aggressive and defined.
The Mesa 5881 STR 425 really lives up to the hype I read about in the Rectifier forum and in the tube forum. This tube is a winner for sure. Definitely worth the money spent. I may have to get some more to stuff into the Roadster. I think Mesa needs to rewrite their description on their website to include also suitable for high gain aggressive or progressive rock with emphasis on heavy Metal grunge if used in the TC-50. This tube is more ideal than the Mesa 6L6GC STR440 with the TC-50. Probably because it does not pull back on the midrange frequencies like you get with the 6L6STR440 tube which is more ideal for the Mark series amps. Perhaps it is a bit different than the 6V6 tonal character but just as pleasing on all channels and much higher volume. One thing to point out that there is one common trait shared by the 5881 (STR 425) and the 6L6 (STR 440), and that is there appears to be a slight reduction in overall volume levels when compared to the Stock EL34 (STR447) or any of the EL34 variants I tested. . The better 6L6 alternative is the 5881 (still a 6L6 tube but made to military standards). Also this is a Russian tube and probably is the same as the Sovtek 5881/6L6WGC. If the bias setting on your TC-50 is set to 6L6, the Mesa 5881 STR425 is your friend and will make you happy. :P 8) :shock:

:| 8) Mesa 6L6GC STR440, Green color code. Stock tubes on most of the Mesa amps. This is the same tube as the Ruby 6L6GC MSTR, manufactured in China. I do like the characteristics of this tube in the JP-2C and Roadster as their bias is set to achieve a specific tone along with the preamp circuits that were tuned to take advantage of the tube (assumed). The TC-50 sounds ok with the 6L6 tube but it seems that part of the midrange is being choked off. Also the tube has more of a fizzy tone to it when compared to the 5881. There is more top end with the 6L6 which adds to the fizzy tone when driven hard or pushed into clipping by the higher gain channels. I can live with it if there were no other alternatives. At least Mesa has an alternative that provides better tonal quality in the TC-50 that does not void your warranty which would the Mesa 5881 STR425. I like the Mesa STR440 a bit better in the TC-50 than say the RA100. Still it is ok of a tube for use in the Triple Crown. :|

I am trying to stay within the bounds set forth in the applied warranty. Perhaps I blew it with the EL34 tube comparison but no damage was done to the amp during the exploratory evaluation of the different power tubes. Such is life. Damn did those KT77 rocked the house. The NOS Siemens are waking up and getting quite close to awesomeness even though they were perfect from the start. I did not pull out the other tubes as I am not willing to write a novel here. Tubes like the Tung Sol 7581, SED =C= 6L6GC, or even the Mullard Reissue EL34 were tempting. Note that the Mullard EL34 are in use in my RA100 Combo and there seem to be far more screws to remove to get to them. Besides those in particular seem to be on the early distortion side of the tube spectrum but that may be the nature of the beast. This brings my tube quest to an end. In short the NOS Siemens are winners, KT77 blew me away, and the 5881 are definitely recommended over the 6L6 STR 440 for the TC-50. I can live with the Mesa EL34 STR 447 (stock tubes) as they are very aggressive in temperament. A bit fizzy but it is not bad at all. At the moment I will have to find out what a few hours of use on the Siemens EL34 brings out.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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 Post subject: Re: TC50 Tube discussion
PostPosted: Sun Aug 13, 2017 9:51 am 
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Bottle Rocket

Joined: Sun Jul 16, 2017 7:56 am
Posts: 10
After bandits post about the gold lions...and other ideas..i bought a bunch of tubes. I haven't even received my amp yet and im changing things lol!


Power tubes - gold lion kt 77

Preamp tubes

v1 and 2 NOS JAN GE 12AX7WA

V3 NOS Westinghouse (USA) 12AX7 Short Plate

v 4 and v7 NOS RFT 12AX7

1 v6 Electro Harmonix 12AX7

v 5 fx loop NOS Mullard CV4024 (12AT7)


I'm sure i will change things around but, i got so excited i couldn't resist trying ! TUBE GAS!


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 Post subject: Re: TC50 Tube discussion
PostPosted: Sun Aug 13, 2017 10:22 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2644
Location: North Carolina
I would see what the amp sounds like when you get it. Break in the stock tubes first before making any changes. If all is good with the amp, then proceed with your tube roll. Also this helps you develop a baseline from the stock form. If and when you do change the preamp tubes, mark the tube with a number when you pull it out (black sharpie will be fine) so you know where to put it back if you need to, or want to return to the stock format to hear the baseline performance again.

Note that tubes that fall in the later gain stages (generally the phase inverter in this case) will be a lower grade tube vs what you will find in the front end. TC-50 has two front ends. V1 is the clean channel first stage, V3 is the first gain stage of CH2 and CH3. The preamp for CH3 is shared with CH2, the Clean channel (CH1) has its own independent preamp section.

The Gold Lions KT77 definitely set the bar on performance level.

I have not dug into the preamp tubes yet. I am liking what I am hearing with the Siemens tube. I did notice the amp becomes sensitive to feedback on CH3 so I need to back off the gain a bit or move farther away from the amp as I am sitting right in front of it. I am surprised I can still hear.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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 Post subject: Re: TC50 Tube discussion
PostPosted: Sun Aug 13, 2017 11:08 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2644
Location: North Carolina
I think what would have more merit to this thread would be to get some recordings of the tubes in action. It will take some time to do this as I will need to wait for the cool down between tube changes. Setup may be tricky too as I have not been recording in some time. I will probably forego the mixer and just use the recorder direct. First I will dial in the preferred settings for each channel with the NOS Siemens tubes but will start the recording process with the Stock Mesa STR447 EL34 tubes and run though the list of tubes in the same order if time is permitting. However for the 6L6 section I will use the general mill 6L6STR440 first before I throw in the 5881 tubes. Last would be the 6V6. Now to figure out what to play is the next thing. I will try to keep it simple and just use the drive on CH1, CH2 normal/tight and CH3 normal. I will see how it goes with the stock tubes first as I want to be able to capture the tube characteristic as best as I can. I will not use the attenuator for this one. If I have to bring out the Mixer I can do that but makes things more complicated. Preamp section will remain stock. Once I narrow down the settings for each channel I will take a picture of it and use that as the image for the sound cloud. I will leave the settings alone and only change power tubes. Once I post it I will try to mark the sections when I change tubes and will indicate which tube is in use, and when the channel changes. For some reason I am eager to do this but as I have a need to get back into recording again. The only effect I will use is the reverb and will hold back on wanting to use my effects. It will take some time to complete but I think it would be fun to do as the written work only says so much and you are relying on my opinion. A recording will allow you to formulate what you think sounds better. This may take a week or longer to complete. At least you will get an idea though a recording to what I have experienced with the tube test. Still it may not capture the "in the room" effect. That is one thing I have struggled to capture but will see..... :roll: (this may be more than I can chew in one evening.... but why not give it a try..)

_________________
Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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