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PostPosted: Tue May 16, 2017 3:31 am 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 157
Location: Good ole England
Thanks guys,

Why would you end production of one of the few new production valves that actually had a good reputation? Seems like very poor business sense to me? Would have made much more sense to cut a deal with one of the major amp manufacturers I would have thought? Unless there was some other reason, politics probably.

Going to return some of the stock mesa 12AX7'S to the amp and just run something like V4 - 12AT7 and one of the Sylvania's in V1 to see what it sounds like. Money's going to be at a premium for some time so don't wanna burn them all out together. That way I'll have a spare of each. Probably still try the Tungsol in V2 just for kicks. Hope the amp stays sounding the way it does currently as it's incredible right now.

Hope everyone is well.

Wayno.

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Mark V/V4 AT7 Combo
2 x 12 Vertical Cab
Danelectro Fab Overdrive
Dunlop Cry Baby Wah

Gibson LP Studio with alnico ii pro
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PostPosted: Tue May 16, 2017 6:32 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
Wayno,
I have read all about what went down with Svetlanan Electron Devices. In short, audio tubes are not their main business but you have to keep in mind this is not like a US type company. SED (for short) sold the US trade name "Svetlana" to the New Sensor company (they use a different manufacturer who makes majority of the Russian tubes for the US and other Markets. Tubes marked now as Sveltlana with the large S logo (what was used by the original SED company so they changed their logo to =C=). Due to the sale of the trade name, SED could not sell products in the US. They were basically banned from what I understand so do not quote me on facts please. You can do a search on the subject which is a deep rabbit hole to get into now a days. It is what it is, the final art of creating a simple product has been lost. For some reason I think part of it is the dual getters but there is more to it than a meager internal feature. SED claimed that they could no longer resource the quality of glass that was required to make the tubes. As the story goes, it was the end of the line for that part of the production and I would assume the cost to drop the production was probably less than retooling. So what ever the reason it does not need to make any sense. With some of the Mesa amps, the tubes really made a difference as I found it hard to find similar gain characteristics that had that 3D quality. Odd thing though, the Roadster loaded with Stock power tubes sounded much better as it had its own 3d gain character that I could not get from the Mark V unless I had the =c= in it. What does come close is the Tung Sol 7581A. I had tried the non A version and they were great for a while until the tone shifted. Even after I burned many hours on them (4 to 5 months if not longer) I was pleased they lasted longer in my Mark V than the stock tubes. Never red plated them. Quality was there in spades just like the SED. Note that even the Mark IV was able to get a red tint on the plate seams with the SED but you had to really drive the amp hard. The Mark V seemed to eat tubes right from the start. Thus far the long term survivors in the amp was the SED, Tung Sol and the TAD. Everything else had a very short life. (one last note, the KT77 and all other EL34 never had this issue at full power but now stated in the download manual it is better to use variac power with EL type tubes). I still have both quads of SED tubes and they still sound awesome. I have recently adopted the Mesa STR440 tubes as they have their own character to them but had to adjust the bias resistor to use them (kept the amp from red plating but it was not just limited to the Mesa tubes either, perhaps there was an issue with that one part and as it got hot the bias shifted, not really sure, odd thing I was red plating the center pair using 45W mode and variac power). I basically replaced the one 82k resistor with a 91k but may go and try a closer value to the stock part eventually. I do not want it adjustable as it only applies to the 6L6 bias and would not affect the EL34 bias all that much based on the circuit design. I measured the bias voltage before and after and did not see any change but could have been due to limits of the meter. A scope would have been a better choice to use). No matter. I did not see any benefit in having an adjustable bias pot with this amp.

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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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PostPosted: Tue May 16, 2017 6:42 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
I finally got around to the Acid test. No I did not take acid. :shock: I wheeled in the OS Recto 412 cab with original speakers. I found the V30 with the Mark V to have been more brutal and accentuated the ice pick to breaking glass tone. WOW, my ears must have been deceiving me as I was in heaven. The mod does make a huge difference. The horizontal or vertical 212 cabs have nice deep tone which make them sound huge. The 412 cab is a bit different and can be extremely bright once you get the amp to the sweet spot. The mod does not kill the top end by any means, it is present and abundant but the lower mid peak as well as more roll off on the upper harmonics is more enjoyable on all voices of the Mark V channel 3. Woot Woot... :P

Jan/Phillips placed in V4 puts the boogie back into your boogie (Mark V that is). CH1 and CH2 remain the same. The reverb may be slightly different but still sounds the same. Not louder so no worries there.

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Current amps:
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Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Tue May 16, 2017 2:56 pm 
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Mark II

Joined: Tue Nov 14, 2006 8:17 pm
Posts: 113
I'm officially a believer! I put a Jan/Phillips 12at7 in the V4 position and ....wow! Channel 3 on Mark IV, 45 watts(variac), in Triode is just pure heaven. This is the heavy Mark tone I've been looking for. With a moderate V (nothing boosted or cut more than half way)on the EQ and the mids at around noon there is a character to the sound that is incredibly pleasing and organic/natural. The difference is huge, more than I ever would have expected from changing 1 preamp tube.

I was having a hard time before the change, switching back and forth from IIC mode and Mark IV mode, never quite finding what I was looking for. It would either get ice-picky or too scooped sounding as I got closer to what I wanted to hear. Now I'm a very happy Mark V owner.

Thank you APEMAN and Bandit!


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PostPosted: Tue May 16, 2017 4:01 pm 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 157
Location: Good ole England
Thanks for the low down Bandit. Is a shame that had to happen with the =C=. Would have liked to have tried them, heard lots of good things. Nevermind. Look forward to hopefully being able to try the TAD 6L6's.

Roll on the weekend so hopefully I can try get another couple hours in the garage. Rock on you good people.

_________________
Mark V/V4 AT7 Combo
2 x 12 Vertical Cab
Danelectro Fab Overdrive
Dunlop Cry Baby Wah

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85
Jackson Dinky XL with Duncan designed???
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PostPosted: Tue May 16, 2017 5:35 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
Organic, that is the best term that defines what CH3 become with a change in one preamp tube.

Fluidic, sustenance, and commanding also comes to mind. Not thin stale or lifeless. It really is not all that bad without the change, and many 12AX7 tubes will aid in the frequency response that may have a bit more top end roll off but they do not seem to help with the lower mid to center midrange that seems to be getting notched out. I never really thought the Mark IV mode was exact but with the change in V4 to a 12AX7 it gets farther from the Mark IV and way closer to the JP-2C. The IIC voice sound great too. Extreme is also reveling and screams JP-2C CH3 of course with some limitations. If you want the shred mode you may need a grid slammer pedal or other external OD with adjustable tone control. Since I have the Grid slammer, need to see what it will do up front. Before the Mod, the Grid slammer helped greatly as it introduced the mids that were missing and balanced out the tone on CH3.

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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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PostPosted: Wed May 17, 2017 2:26 am 
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Mark III

Joined: Tue Nov 08, 2011 10:48 am
Posts: 230
Hey there, yesterday I had my first rehearsal together with the band. 12AT7 in V4. As expected with the new massive CH3 it was harder to cut thru the mix, but after some preamp tweaking the sound was just perfect. I usually tend to dial in too much bass and low end when playing alone in lower volume situations so I have to adjust when playing out loud :D It is astonishing how much reserves the amp has to offer even in the settings - it sounds massive without the need to bring anything to its maximum.

If it comes to front end pedals I have to admit I sold all my ODs after I sold my Recto, the one I kept and still use from time to time is the mesa tone burst. Its a great pedal that works more like a preEQ. You can set bass and treble separately as well as the gain and output, which makes it very usable as a boost. By dialing out a little bass and treble while increasing the gain and output you get a very pleasing mid boost without the common tubescreamer mid-spike - very organic!


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PostPosted: Wed May 17, 2017 6:08 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
With the change in one tube alone, I am overjoyed on the result. At least it is not a permanent mod and can be returned to stock with a twist, pull, push (if you can get the tube in that easily) push and twist. It is only like changing a light bulb when the bulb is hot but you can wait for things to cool down.

Now I have no desire to use other tubes than the Mesa STR440. Hmm, I do have many to go through and wonder what............too much to do.

I have both grid slammer and Flux drive and have tried both (independently) on the JP-2C and the Mark V. The grid slammer effect on CH3 of the Mark V had the same qualities of the JP-2C without any effects. It did help with some of the brittle tone but did not correct for it. Flux drive was similar as that too picked up the lower midrange but also added more distortion. IMHO, I ran each into the JP-2C only to discover there is more to that amp and in either case the additional pre gain or OD was just as pleasing to the ear with out them in use. Do I like it with or without, even if it is not needed. I need to revisit the grid slammer on the V after the mod.

Everything is subjective. If you want more bite (assuming you want the effect brighter) use the Mesa 12AT7, fundamental is there but more crispy. I prefer the warmer tone of the JAN 12AT7. Speaker choice will also determine to what level of cut you may get in the mix or if you will drown. I would suggest this if you find your amp too brittle for enjoyment, or if you want your Mark V to sound like the JP-2C but only effects CH3 as CH2 and CH1 are unaffected.

Need a recording of before an after. That may prove more convincing that the written word unless you listen to it on a cell phone or cheesy internal PC speaker that only does beeps and buzzer sounds effectively.

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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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PostPosted: Fri May 19, 2017 5:54 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
I spent a little time comparing the cascaded gain stage of CH3 on the Mark V to the similar gain stage on the Mark IV (schematics for both amps). There is a minor difference between the two amps in this region. Mark IV circuit on the lead tube gain stage has a small capacitor that ties the cathode to the grid which may form a positive feedback loop to increase the gain saturation of the stage. The second tube gain stage does not have this capacitor which may explain why this amp does not get so brittle in character and retains more frequency range in its output. The Case of the Mark V is similar to the Mark IV but on the second gain stage the cathode to grid capacitor is present. My assumptions if correct this additional positive feedback may contribute to higher order harmonics that contribute to the brittle tone. I am no tube expert but since the feedback is connected to the cathode to grid it cannot be negative feedback as that would require it to be connected to the plate vs cathode on a common cathode circuit. Positive feedback is not a common thing to do as this may result in loss of gain control. Typically there is an intrinsic capacitance that between the grid and cathode as well as between grid to plate and plate to cathode as part of the model used for simulation purpose and to understand the tube characteristic. I am only assuming this to be a form of positive feedback but it may be a means to increase the intrinsic capacitance between cathode and grid for a change in tone control. Since the signal at the cathode will be in phase with the signal on the grid, I am to assume it is positive feedback. Signal on the plate will be inverted.

One important note about the schematics and actual circuit board assembly. Just because a component is shown on the schematic does not mean it is actually on the PCB assembly. Sometimes designers leave component footprints in place in a particular circuit but may not be populated in the final assembly as it may have been deemed not necessary. Only way to confirm is to find the part reference designator on the PCB to confirm it is in the circuit. Also since I am uncertain its actual function (positive feedback is assumed) do not go looking for it as it may not even be there. I was just trying to correlate the differences between the Mark V and the Mark IV, and at one time I had both amps but preferred the Mark V over the Mark IV for its features and simplicity to dial in the CH1 and CH2 separate from each other. Mark IV shared common tone controls on the RHY1 and RHY2 that made some settings difficult to obtain for a good 3 channel amplifier. Still the Mark IV was better than the Mark III at channel separation (also needed a decoder ring to decipher the difference between clean and blues and everything else as the tone controls were common on all channels.).

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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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PostPosted: Sat May 20, 2017 1:43 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
Well I tried to capture the differences in a recording. Did not turn out so great but some of the differences you can hear. The top end frequencies seemed to have eluded the microphones for the most part but general tone is there. I may have had the bass dialed in a bit too rich. Also had some issues when switching over to the Extreme mode as the inputs were getting clipped so the mixer preamps were adjusted to compensate. I left the EQ as is. I did a little post eq that affected the entire recording. Also did a bit of compression when mastering the mix as the original signals seemed a bit on the low side. I did mark the sections with comments to identify the CH3 voices and where the JP recording starts. What you are missing is the feel, the recording is close enough but not quite the full experience.

https://soundcloud.com/user-353100000/markv0001wav

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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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PostPosted: Sat May 20, 2017 3:52 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
Keep in mind this is the first time I used the mixer for recording the guitar. The Sennheiser e609 need far more adjustments on the pre EQ settings than did the Audix D2 regarding the mixer. Actually the D2 by itself sounded the best. D4 was similar but deeper in tone. First time to use the Drum mics on guitar cab. Perhaps they were right that they will sound great as they are already pre eq'd to eliminate the low mid drone you normally get with acoustic drums. I am not too fond of the SM57 but I do have one. Thought the Sennheiser was better now I think I prefer the Audix D2.

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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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PostPosted: Sun May 21, 2017 9:40 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
It may be harder to hear the differences in the recordings but if you jump around with your cursor and click on the sound wave you can year the similarities in a different way than having to listen to the entire thing... Also the levels during recording were not managed properly. A DAW would have made things a bit easier. The in the room experience was more revealing than the recording. I believe the master control was at noon on the Mark V as I was using the FX loop. Probably what I should have done was record one voice with two different tubes and not adjust the settings on the mixer or master volume on the amp.

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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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PostPosted: Sun May 21, 2017 10:48 am 
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Bottle Rocket

Joined: Thu Jan 05, 2017 9:15 am
Posts: 7
Although it's not "perfect"... your clips do a great job at showing the difference. 12AX7 and 12AT7 in v4 differences (to me) are most noticeable in IIc mode, still prevalent in IV mode and not-as-much in Extreme. As you say, bouncing between related clips is really the way to compare these. But the JP2C clips on the end = yum!!!! There's really something a bit different there. I think there's a JP2C in my near future.

Thanks for do this!!!


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PostPosted: Sun May 21, 2017 11:26 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2399
Location: North Carolina
To do this justice and make it more apparent, the Vertical 212 or the Horizontal 212 is more forgiving than the OS Recto 412. I was also running the amp below its awesome point where the differences are definitive. In order to accomplish this I would have to use the attenuator in order to record using mics. That in itself does roll off the top end to some extent. Best advice is to just get a 12AT7 Jan type and hear for yourself. Also an SPAX7 in V1 helps too and aids in some of the harshness you may get running Crunch with the gain maxed out which was my way of getting similar tone to the Mark IV mode without getting that thin sound that CH3 seems to create. Also the brittleness of the Tweed setting on CH1 is reduced a tad. Only other solution is a Mullard 12AX7 long plate in V1 but that will also alter tone. Have not tried it in the amp since the V4 swap. Wonder what that will sound like.

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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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PostPosted: Mon May 22, 2017 2:07 pm 
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Mark I

Joined: Fri Jan 24, 2014 2:31 pm
Posts: 26
Forgive my lack of knowledge on this topic; but wouldn't using a different pre amp tube than a 12AX7 in the Mark V damage the amp?


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