Tube Layout

Does anyone know the tube layout for the preamp section? I assume the (3) stock Chinese tubes are all 12AX7. Which one is the phase inverter?

I'm going to swap out the stock tubes for some higher quality ones.

Thanks!

Not Sure, obviously the most important one is the one with the Shield on it.
The tubes say 12AX7A on them.

I swapped out my preamp tubes with JJ 5751s (all 3 of them). The Chinese ones that came with my GM36 were all 12AX7B...never ran into 'B' tubes before. The 5751s have a little less gain than the 12AX7 tubes, and I think it warmed up the sound a tiny bit. The whole amp is now running JJ's in the power and preamp sections. Liking it so far.

I changed all the tubes this morning - swapping out the stock tubes with Mullard EL84 and tung sol 12Ax7. The meister in much warmer in tone now. I was having difficulty reigning in the high end for the heavier gain channels but the new tubes have made a huge improvement.

That's good to hear. Keep us posted.

So far my JJ's in the power section and JJ 5751's in the preamp section are working for me.

Wish there was a way to have some really good before and after clips.

What I might do is when I retube this monster I'll play a section and put it on my timeline's looper.

Get both my Audix i5 and Sensheizer 609 on my Egnater cab.

Warm up the amp, do a recording in a couple of different channels.

Leave timeline on so as not to loose the loop.

Change tubes.

Repeat.

Tie them together so we can hear a side by side comparison.


I'm anxious to swap out! But in my head, there's SOOO mnay electronics in the amp, it would seem that there's just too much in the signal patch to make much of a difference.

Now in my simple little Two Rock Studio Pro 22......maybe a bit more drastic of a change?


Love this thread! Tubes are fun!

I thought about doing a before and after comparison, but as it turns out my amp was making a crackling noise for the first 1 to 2 minutes coming out of stand by. After putting in my other tubes, that noise is gone. I did some research and learned that a bad tube can cause the crackling noise I heard. So I'm just going to leave it as it. But I will find some time to record my setup so we can all compare.

Awesome, thanks man, that'd be awesome!

I'm a JJ fanboy so bear that in mind. I used to be a Fender guy and my main amp was a Hot Rod Deville 212, I've owned a few of them. A few Hot Rod Deluxe too, as practice amps. Great amps. And made even better (my opinion of course, this stuff is SO subjective) by swapping out the stock Groove Tubes with JJ's. Not a dramatic improvement, but worthwhile IMO. The JJ's always sound less harsh, more musical, than the stock tubes.

A couple years ago I became a H&K convert (after drooling over Alex Lifeson's H&K rig for years) and I bought a TM18 head. I thought the stock Chinese tubes sounded fine, but per my usual routine I replaced them with JJ's, and again I noticed that slight improvement. I keep the stock ones handy as spares.

As of last week I am the proud owner of a GM36, and am currently in an evaluation phase, putting it thru its paces to see if it can replace my TM18 and G-System rig. So far so good. If I decide to keep the GM I will likely swap out the tubes, and it'll probably be JJ's but I'd also like to try TAD tubes someday. Isn't that what H&K uses in their main amps?

From what I understand,,, the one on the right nearest the input jack with the cover on it is the V1, then left is the V2 and finally the V3 phase inverter.

I have 2 JJ ECC83/12AX7's coming for V1 and V2 and a ECC81 12AT7 for V3. All matched Triodes and balanced.

Will advise !