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 Post subject: Help with tubes Roadster
PostPosted: Sat Jul 12, 2014 9:48 am 
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Mark I

Joined: Wed Oct 23, 2013 3:52 pm
Posts: 24
Hello. I plan to retube my Roadster. I saw some retube sets on http://www.rototubes.com/Roadster-Trem-O-Verb/
I know that Roadster have fixed bias and they recomend Mesa tubes for Mesa amps. Do i need any additional moding or i can just install some of this sets and go play.


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PostPosted: Sun Jul 13, 2014 10:48 am 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1973
Location: North Carolina
From what I learned thus far with the Roadster.

V3 (tone stack triode) V5 (FX loop send) are cathode follower circuits. Either use Mesa (selected JJ tubes) or Chinese (have nickel plated clips on the plates). Russian made tubes will fail prematurely in the Cathode Follower circuits due to the voltage differential between the heater and cathode. An alternate is the JAN/GE 5751 which is supposed to be compliant with cathode follower circuits.

Somehow I believe that Mesa also selects their preamp tubes for matched triodes, otherwise there would be an out of balance signal to the power section (matched triodes are better served with Class A/B power amps, it probably does not matter much with the Simul Class circuits of the Mark Series amps but it does not hurt to used matched triode tubes there either).

I honestly prefer the Mesa tubes in the Roadster. I love the way the Mesa power tubes sound in this amp when saturated. They come close to the SED=C=6L6GC that I have used in the Mark V. I have experimented with EH EL34, TAD6L6GC STR, SED =C=, and KT77 (all of which I specifically ordered for my Mark V ) The TAD6L6GC-STR sounded great as well as the EH34's. I have not tried the newer set of SED =C= 6L6GC or the EL34 (in use with my RA100). I prefer the tone of the Ruby (Mesa Branded STR440 in the Roadster). Since I am not using the SED =C= 6L6GC at the moment (loaded the KT77 in the Mark V) I should give them a shot in the Roadster. I have also tried some of the different preamp tubes (EH, Tung Sol, Mullard reissue, Mullard CV4004, Preferred series 7025, and vintage Mesa Chinese tubes (which I think sound the best overall in my other amps). The Roadster seems to benefit tone wise with the Mesa branded JJ 12ax7a tubes. I did not notice much difference in gain structure, but I did notice more brightness with the Mullard reissue and a Sovtek LPS in V6. However, it became apparent that the tone I liked with the stock tubes was not the same with the different preamp tubes. My experience with the Mark V is quite the opposite, I did not like the Mesa JJ tubes, actually it is a fault with the power section as I believe it is running a much hotter bias than it should ( I have red plated many of the commonly bought tubes except for SED or Gold Lion KT77 ( I ordered them specifically for a fixed hot bias amp and so far no issues). Roadster and rest of the DR family, they run on the cold side as I recall.

The weak link is the rectifier tubes, not many available. I did try a NOS JAN 5U4G but it was a dud. I normally use either Mesa or EH 5U4G (same tube). I believe the Roadster would sound great with many of the 6L6GC tubes available since it has a moderate bias and does not run as hot as the Mark V.

If you were considering a different tube than a standard EL34, 6CA7 had some interesting character too them. (I would avoid the JJ 6CA7, many have had great success with the EH 6CA7). Also you can run the EL34B (lower bass response). As far as EL34 are concerned, the SED =C= EL34 are tops but much higher cost. Gold Lion KT77 are also a big expense. I like the EL34 (SED) the best.

The Svetlana (not true SED or Sevetlana from St Petersburg) are not too bad either (made by Reflektor, also makes Tung Sol, Sovtek, Mullard, etc...) I have been running them in my Mark IV for the past 2 years. Close but not close enough to the SED =C= tube. Tung Sol 7581 are also killer tubes (has more complex harmonics than the Svetlana). I have a quad of those, wonder what they would sound like in the Roadster ?

_________________
TC-50, shares the same cab as the JP-2C below
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (V30)
Mark V combo (MC90 )


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PostPosted: Wed Jul 16, 2014 9:20 am 
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Mark I

Joined: Wed Oct 23, 2013 3:52 pm
Posts: 24
Thank you for your reply. It was very helpfull for choosing type of tubes for me. My concern is can i put any tubes not only Mesa branded in my Roadster and just use it or non mesa tubes need some kind of biasing or moding the amp.


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PostPosted: Fri Jul 18, 2014 6:04 am 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1973
Location: North Carolina
If your amp is under warranty, best to use Mesa tubes. I have experimented with some of the preamp tubes and power tubes just briefly so I could compare the effect on tone. Tung Sol in V1 will tend to brighten up the amp as well as a Mullard Reissue. I did not care for the change in tone. Unfortunately, most of the power tubes I have available were ordered specifically for the Mark V so they were not as defined in the Roadster or RA100.

If you are not concerned about warranty and are really eager to experiment with different tubes, the Roadster is more forgiving than the Mark V due to a cooler bias. Typical power tubes will work well. When you order tubes, some places allow you to specify what tubes the amp will be installed in, and if it is a combo or not. Groove tubes with gain factor ranging from 4 to 7 are acceptable. The lower the number the earlier the distortion would be. Some tubes vendors rate them in terms of low, medium or high distortion levels, stay in the middle range and indicate your amp make and model. Not sure if specifying a Combo will make much of a difference but I assume they will be more stable in the mechanical aspects (less vibration of the internals). I think the next time I order tubes I will indicate a combo amp. I have gotten some noisy tubes in the past, vibrations were not noticeable at higher volume but at low volume the tubes sing (vibrate and rattle, this is more prone for EL34 and associated narrow bottle tubes that are similar )

There are tubes that hold up better than others. TAD are not bad at all, SED expensive but hold up well, Gold Lion are good but cost more than the SED tubes. Some of the Reflektor branded tubes (Tung Sol, EH, Sovtek, Mullards, and Svetlana) are also good. It can be hit or miss when it comes to tubes and quality. Generally using a source that selects tubes and sorts them for quality of sound and mechanical stability (Mesa and Groove Tubes). Also finding a good source for a good matched duet or quad. I generally use "the Tube Store" or "tube Depot" for the other brands of tubes. Just my opinion and I will restate it, I found the Mesa tubes to have the best overall sound quality in the Roadster. The Complex harmonics are present when saturated in CH3 and CH4. So my Roadster will only get Mesa tubes. As for preamp tubes, I believe the Mesa 12ax7 are match triodes. If you decide to use other brands, it should be required to get a matched triode for the PI tube (V6). Having all of the preamp tubes with matched triodes would not hurt (except your pocket book). You could probably use most common tubes available for V1, V2, V4, V6. However Russian tubes will fail in V3 and V5 due to cathode follower circuits (JJ or Chinese Shuguang {with additional chrome like clips on the plates}). If you get a bad tube and something happens to the amp, your warranty will not cover you unless it is a Mesa tube (not sure about GT).

You do not need to modify anything in the amp at all. No bias change needed as long as you stay in the mid range. Always good if the resource you are using will match the tube for the amp requirements based on its bias data they keep on hand.

A reminder on the Rectifier tubes, stick with the exact same type tube. 5U4GB. Mesa or EH have these available.

_________________
TC-50, shares the same cab as the JP-2C below
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (V30)
Mark V combo (MC90 )


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PostPosted: Thu Jan 12, 2017 4:00 pm 
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Single Recto

Joined: Mon Mar 09, 2009 5:16 am
Posts: 1256
I really love the Winged C 6L6s in my Roadster head and Mark V head. I feel they are a slight upgrade over the stock 6L6s. However, as we all know, they have stopped making the Winged Cs. So the quest to to find a similar replacement for me


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PostPosted: Sun Jan 15, 2017 8:23 pm 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1973
Location: North Carolina
I have been searching quite a while for a suitable replacement for the =c= 6L6GC. What does come close is the Tung Sol 7581A (at least for the Mark V).
TAD 6L6GC-STR are a bit different but sound great. I actually liked those more in the Mark V than the SED =C= 6L6GC. What I did not like about them was the plastic base, the center guide pin can break off easily. If you get them, use a silver Sharpie to mark where the key on the center pin is on the side of the plastic base. Forget about the Svetlana tubes as those will not last long in the Mark V. For the Roadster no issue as the bias is not the same.

_________________
TC-50, shares the same cab as the JP-2C below
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (V30)
Mark V combo (MC90 )


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PostPosted: Sun Jan 15, 2017 8:54 pm 
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Single Recto

Joined: Mon Mar 09, 2009 5:16 am
Posts: 1256
bandit2013 wrote:
I have been searching quite a while for a suitable replacement for the =c= 6L6GC. What does come close is the Tung Sol 7581A (at least for the Mark V).
TAD 6L6GC-STR are a bit different but sound great. I actually liked those more in the Mark V than the SED =C= 6L6GC. What I did not like about them was the plastic base, the center guide pin can break off easily. If you get them, use a silver Sharpie to mark where the key on the center pin is on the side of the plastic base. Forget about the Svetlana tubes as those will not last long in the Mark V. For the Roadster no issue as the bias is not the same.


I would have thought the longevity issue was due to the fact that it's enclosed in a smaller head cabinet, as opposed to be a bigger one which may help ventilation


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