PRE-AMP TUBE FUNCTIONS

[tonejam]

I'm totally confused by the description of the preamp tube functions in this amp, particularly as each half of a tube can have a separate function.
For example, V1A is "channel 2, 3rd gain stage". I assume channel 2 refers to the blues/burn channel. But then, V2B is "1st gain stage cln, 2nd stage O.D." Does this refer to BOTH channels? Can someone provide a clearer explanation of what's going on? It would really be appreciated.
Thanks, Bill.

 

[EtherealWidow]

Alright. This may be a bit "blind leading blind" stuff here, but I'll try it anyway. They split the triodes in the tube so that they can indeed perform two separate things. One tube can do different things for both channels depending on how it's wired. Also, the Express' are a bit weird in that the V2 tube is actually the input stage. At least, that's what a Mesa rep told me when I asked. So if you buy that kit from Doug's Tubes, you should switch the V1 and V2 to make sure they're in the correct order. In other words

- V1 Tungsol 12AX7
- V2 High Gain JJECC83
- V3 Penta 12AX7
- V4 Shuguang 12AX7 9th gen
- V5 Sovtek LP/LPS

On any other Mesa, do as it says. But with the Express', Put the Tungsol in V2 and the High Gain JJ in V1.

 

[tonejam]

Thanks for the info.
I'm not intending to buy new tubes. I'm looking for an explanation of what each half of each tube does. An explanation which is easier to follow than the manual, which I find confusing.
Can anybody help?

 

[MrMarkIII]

The guitar signal goes to V2A first. The signal probably goes through the tone controls at this point, but I don't have a schematic. The next stop is V2B. Then V1B or V1A, depending on the channel selected. Then V3A. The other half of V3 (V3B, that is), boosts and buffers the signal coming back from your effects.
V4A & B is the Phase Splitter, aka the Phase Inverter, or Driver. This tube takes all the sound generated so far and sets it up for the power tubes to do their magic. V5A & B handles the reverb in 'n' outs. Labeled or not, V6 and V7 are the 6L6 power tubes.

"... V2B is "1st gain stage cln, 2nd stage O.D." Does this refer to BOTH channels? ..."

Yes, each tube is really two, two, two tubes in one, and the jobs they do split up or seem to back track over each other.

 

[tonejam]

Thanks, that's exactly what I wanted to know! Thanks for taking the time to explain it.
Bill.

 

[Big Foot]

Alright. This may be a bit "blind leading blind" stuff here, but I'll try it anyway. They split the triodes in the tube so that they can indeed perform two separate things. One tube can do different things for both channels depending on how it's wired. Also, the Express' are a bit weird in that the V2 tube is actually the input stage. At least, that's what a Mesa rep told me when I asked. So if you buy that kit from Doug's Tubes, you should switch the V1 and V2 to make sure they're in the correct order. In other words

- V1 Tungsol 12AX7
- V2 High Gain JJECC83
- V3 Penta 12AX7
- V4 Shuguang 12AX7 9th gen
- V5 Sovtek LP/LPS

On any other Mesa, do as it says. But with the Express', Put the Tungsol in V2 and the High Gain JJ in V1.

I thought that made sense but to make sure I emailed Doug. Here's what he said....

Here's how our Mesa kit evolved because all we ever owned is a 1982 MKIIB and a Blue Angel and have never played any other Mesa!!! Maybe folks don't realize it, but our recommendations come about over time through the anecdotal stories of our Mesa(or other amp) customers who experiment with different tubes. They talk on forums and share their experiences. All of a sudden I realized folks were ordering those same 5 tubes so we decided to do a one click kit! That's the whole story. I've read criticism on the Boogie Forum about how that's all we recommend like Eurotubes recommends all JJ's. Whatever! Ignorance is bliss, I wouldn't even bother responding to stupid comments like that. It's always been up to the customer what tubes work in which spots. Who says they have to go in any order? But we've never been a fan of all one preamp tube, we wouldn't recommend all EH 12AX7's anymore than all JJ ECC83's. There's something about the dynamic of a mix of preamp tubes that works the best.

So, I don't own an Express, I've never played an Express...........all I can tell you is that you can put the Tung-Sol in any spot that is not a cathode follower.

Don't forget to share your experience with us for the next customer, and do feel free to share our email on the Boogie forum with those who just don't seem to get it.

So my next question is... Does anyone know if V2 in a 5:50 is a Cathode follower?
Thanks
Don

 

[Big Foot]

OK, I guess I'll just talk to myself then..... according to Chris at Mesa Customer Service V3 is in a Cathode Follower Circuit. So, swapping the tubes for V1 & V2 is OK just don't put the Tungsol in V3. Thanks for the tip EtherealWidow... can't wait to try it!

 

[vbf]

If anyone with the 5:50 tube set from Doug's swaps the V1 and V2 as discussed, please post your results and thoughts.

 

[Big Foot]

I swapped the Tungsol w/ the JJ in V1 &V2 at band practice last night... OMG! What a difference. Much more articulate, better bass and I'm sure I'll be discovering other things as I continue play through it that way. Thanks EtherealWidow for helping me find my tone!

 

[vbf]

Thanks for letting is know. I'm gonna swap mine tomorrow.

 

[Big Foot]

I'd like to know if your opinion will be simular to mine after you try it. Please let us know.

 

[vbf]

OK, I swapped the Tongsol (V1) and the high gain JJ (V2) with each other and the amp sounds more crisp. I didn't notice an increase in bass but it' definitely still quiet and the gains are fabulous. Being as this is my first tube amp I may not have as good an ear for the differences as some others of you but I definitely a crispness in the amp as compared to before the switch.