Aftermarket 6v6 for my TC-50

[ffariasrey]

Hello guys!

So I read that putting 6v6 on the TC-50 reduce the amp power to half and gives a more vintage feel, which sounds perfect as I don’t need 50w and I tend to like vintage voiced amps.

Therefore, I decided to give the 6v6 a try. Unfortunately in my country I have no access to mesa tubes. I did found a shop that sells 6v6gt-str redbase TAD premium matched. My questions are: will this work as good as the mesa? Do these need biasing?

Thanks in advance for the help

Cheers,
Felipe

 

[bandit2013]

Yes, the TAD redbase is a 6V6GTA tube. Mesa had used those but with a black base as equivalent to STR417.

 

[ffariasrey]

Awesome. Will these need to be bias?

 

[bandit2013]

Awesome. Will these need to be bias?

Now that is the trick. Mesa amps have a fixed bias and is not adjustable. Contact your tube supplier and indicate to them what amp you are using the tubes in. Most tube suppliers should be able to pull a pair of tubes that will fit the Mesa bias range. When I have ordered non-Mesa power tubes, I always indicate the amp it will be used in. Plate voltage max 450VDC but that is at the center tap of the OT. I have not measured the plate voltage or current of the TC-50. I have been told by one of the members here that was a Mesa Tech stated the TC runs at 450VDC. So at the tubes I would expect an 8% to 10% drop in voltage on the plates. 28mA to 32mA current range. Depends on the tube. The 6V6GTA tubes I have from Mesa are a Grey code. The other 6V6S came out of a California Tweed and it has a color code of green. As for bias voltage, not specified as there are no schematics available to review. Screen voltage is also unknown. If I had a bias probe I would measure it for reference but I do not have that equipment. Sorry. If you are buying direct from TAD, they may be able to provide you with the tube to match the Mesa bias. Not sure it will help but the 6V6GTA is marked as "matched to STR417".

Here is one that references plate voltage with the 6V6 tubes.
https://boogieforum.com/threads/plate-voltage-tc-50.83017/

 

[ffariasrey]

Great feedback mate!

Just out of curiosity. Do you have any reccomendation for preamp tubes? I read on one of your threads that you like a higher quality 12AU7 in the FX Loop, how about the rest of the preamps tube? any brand preference?

Cheers,
Felipe

 

[bandit2013]

Great feedback mate!

Just out of curiosity. Do you have any reccomendation for preamp tubes? I read on one of your threads that you like a higher quality 12AU7 in the FX Loop, how about the rest of the preamps tube? any brand preference?

Cheers,
Felipe

If I ever stated a 12AU7, that would be in grave error. I know you can use that tube in the Mesa subway TT800 but not in any of the guitar amps that I am aware of. I believe what you are referencing is the 12AT7.

JAN/Phillips 12AT7 -WC would be the full name.

Has good tone characteristics. Use in V5 position on the TC amp (FX S/R).

With the TC-100 I kept losing volume. Amp did not seem to sound like a full 100W. Changed the Mesa 12AT7 to the JAN/Phillips 12AT7 and was overjoyed that TC-100 was much better than I thought it could be. Tried another JAN/Phillips 12AT7 in the TC-50. Yep. Sounded much better. However, I did not have the same volume loss with the TC-50 as I did with the TC-100.

As for the other preamp tubes, not much will change anything except for the phase inverter. The preamp is tightly tuned and compensated so there is not much to gain with using other 12AX7 variants. I much prefer the stock Mesa 12AX7 tubes in the TC (including the phase inverter). I have tried EHX, Mullard CV4004, Mullard 12AX7A (long plate), TungSol 12AX7, NOS RFT 12AX7A, NOS Ei CV492 (similar to NOS Mullard 12AX7), NOS Chinese Beijing square foil getter. Not much of a notable difference. The Mesa 12AX7 (JJ ECC83) is just fine. I still have the stock Mesa 12AX7 tubes in my TC-50 and TC-100. I may have changed one or two due to noise issues but that is about it.

Power tubes is where most of the change will take place. The Stock Mesa STR447 (EH EL34) actually sound great after about a week of use. I prefer those over others I have tried when comparing the effect on all three channels. If I only cared about distortion, and had no care about the clean, Tung Sol EL34B, EH 6CA7 are great sounding in TC-50 or TC-100. Sure, the Gold Lion KT77 was awesome too.

 

[ffariasrey]

If I ever stated a 12AU7, that would be in grave error. I know you can use that tube in the Mesa subway TT800 but not in any of the guitar amps that I am aware of. I believe what you are referencing is the 12AT7.

JAN/Phillips 12AT7 -WC would be the full name.

Has good tone characteristics. Use in V5 position on the TC amp (FX S/R).

With the TC-100 I kept losing volume. Amp did not seem to sound like a full 100W. Changed the Mesa 12AT7 to the JAN/Phillips 12AT7 and was overjoyed that TC-100 was much better than I thought it could be. Tried another JAN/Phillips 12AT7 in the TC-50. Yep. Sounded much better. However, I did not have the same volume loss with the TC-50 as I did with the TC-100.

As for the other preamp tubes, not much will change anything except for the phase inverter. The preamp is tightly tuned and compensated so there is not much to gain with using other 12AX7 variants. I much prefer the stock Mesa 12AX7 tubes in the TC (including the phase inverter). I have tried EHX, Mullard CV4004, Mullard 12AX7A (long plate), TungSol 12AX7, NOS RFT 12AX7A, NOS Ei CV492 (similar to NOS Mullard 12AX7), NOS Chinese Beijing square foil getter. Not much of a notable difference. The Mesa 12AX7 (JJ ECC83) is just fine. I still have the stock Mesa 12AX7 tubes in my TC-50 and TC-100. I may have changed one or two due to noise issues but that is about it.

Power tubes is where most of the change will take place. The Stock Mesa STR447 (EH EL34) actually sound great after about a week of use. I prefer those over others I have tried when comparing the effect on all three channels. If I only cared about distortion, and had no care about the clean, Tung Sol EL34B, EH 6CA7 are great sounding in TC-50 or TC-100. Sure, the Gold Lion KT77 was awesome too.

So, I found Mesa's 6V6. They sound really good on my TC-50. They made the clean channel better, more fender-ish and vintage feel, which suits my playing. A bit creamier with rounder high frequency. Maybe not as aggressive and raw compared to the EL34, but still enough gain for me. Maybe a bit more compressed but I don't tend to use massive amounts of gain. Plus the wattage is more manageable. Definitely keeping these on the TC-50.

I stll need to find a decent 12AT7, I have only foun Tung-sol so far, which I don't know if will do the trick. For the preamp I guess JJ 12ax7 are good enough.

Thanks for the help!

 

[bandit2013]

The TungSol 12AT7 is what Mesa is using in the TT-800. Not a bad preamp tube. I have not tried it in the TC amp though. Depending on your location, NOS JAN/GE 12AT7 are readily available and do sound great in the TC. It will not be a major change as this is the FX loop circuit. A good quality tube there does make a difference. The Mesa branded JJ ECC83 will work. Actually it does not matter which 12AX7 you use in the TC series. The preamp design is so well compensated that I have tried several current production and NOS tubes and could not make much of a change in its character. If you are trying to tune the amp to sound different, the only means is with the power tubes, phase inverter tube and the FX send/return tube.

 

[ffariasrey]

I'll try to get the 12AT7 that you mentioned for V5 and I guess that for rest of the preamp tubes I'll buy JJ's.

 

[bandit2013]

If you can't find the NOS 12AT7, the Tung Sol 12AT7 should do just fine. The Send circuit is a cathode follower which can be hard on tubes. The preamp in my Mesa TT800 bass amp is mostly cathode follower circuits which surprised me. The Tung Sol 12AT7 can take the abuse as will the JAN/GE 12AT7.
Mesa stopped using the Chinese 12AT7 due to instability or other problems. It was original tube used in the TT800 based on the images I have seen.