buzz

i have just bought a load of old british ecc82 valves. can i safely use one of these in the pi (v5) and / or reverb drive (v4) of my jcm800 4211.

i tried a couple at low volume in v1 and v2 with the expected results.....less distortion and a lot quieter (but quite nice all the same).

tried one in v3 for a short time and it got real hot!!!!!!!! (extra current draw ?????) albeit it sounded ****in fantastic...like classic vh brown sound. dont want to fry the amp tho'......i aint got eddies repair budget.....

any thoughts appreciated...............

Marshall Amps

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RickyLee

I am thinking you have the older first version Split Channel?

Is V3 the cathode follower (which means you have the older version)?

You can try it in the V5 phase inverter slot. You will lose quite a bit of output which could be a positive thing.

buzz

thanks for the reply.......mines an 88 so quite late......i thought that v3a was part of the boost circuit and v3b the effect return......v4 reverb and v5 pi ???

buzz

just noticed that the majority of the new 1w anniversary models run ecc82 as a power amp valve........e bay here we come if i cant use 'em............

RickyLee

Being you have the later version, you are correct.

I was tinkering the other day with the same tubes as well as 12AT7, 12AV7 and 12AY7 in my '88 2205 - mostly in V5. The 12AU7 in the phase inverter V5 was not too bad for me. My 2205 is just extremely loud. The 12AU7 in V5 allowed me to get the Master Volume up higher which allows more preamp signal into the circuit after the Master Volume getting rid of some of the fizz. If I run a 12AX7 in V5, I start bringing the MV up from 0 and at 1 it is loud. The physical interaction of the pot at that setting makes my amp sound harsher.

Try a 12AU7 in V2 as it might help your Clean channel.

RickyLee

I forgot to mention that V3A is a gain stage, V3B is the reverb driver coming off the reverb transformer. Then V4B is the reverb return coming off the tank and V4A is the last gain stage before the phase inverter. Would have been nice if one tube was for both sides of the reverb and then the other tube was both gain stages allowing more tube rolling options on the tone of the amp.

I have always wondered why Marshall set it up this way? Anyone know the reason for having the tube layout this way on the later version Split Channels?

paradox419

I run an ECC82 in V5 whenever it's absolutely necessary to lower volume. It's my opinion that anyone who hasn't tried it is cheating themselves out of tasting a new flavor. Some people will use phrases like "why neuter your amp" and "you bought the wrong amp", but in the real world you just have to turn it down sometimes. That ECC82 sounds so much better than any of the attenuators I've tried so far. I occasionally leave it in on purpose even when volume isn't an issue. It's never hurt my amp even though I've been known to open it up all the way and let it stretch it's legs for a good while.

I don't like it in V1 (too little gain).
I like it in V2 (I still prefer the 12AX7).
I don't like it in V3 (around 450 volts on pin 6 gets really hot).
I don't like in V4 (too little gain on both channels).
I like it in V5 (when needed and sometimes just because).

__________________
'88 JCM800 2205
1960A with WGS Vet30s X ET65s
'70s Lotus "LP Custom" with T-Top buckers
Boss SD-1 modded
Lots of other gear collecting dust

mickeydg5

I was wondering if someone would mention V3b reverb driver. I believe that reverb spot is designed around the 12AX7. Like Buzz had mentioned, putting a 12AU7 there may put too much draw through the circuit. I am curious, how did the reverb sound when doing this, different than a 12AX7?

buzz

it had the effect of lowering the reverb level....i usually run the reverb at 1-2 (best tank on any marshall IMHO) and with the 82 in it needed to be 6-7 for similar effect...wouldnt be happy having it run that hot all the time tho'

paradox419

That's exactly what I heard this morning when tryng the 12AU7 in V3 again. And now I've got a blister covering my thumb fom pulling the tube back out before it cooled down enough. Very very hot even compared to a hot 12ax7.

__________________
'88 JCM800 2205
1960A with WGS Vet30s X ET65s
'70s Lotus "LP Custom" with T-Top buckers
Boss SD-1 modded
Lots of other gear collecting dust

buzz

yeah........we got matching blisters.........have to call it 12au in v3 syndrome. glad i used my right hand to pull it or wouldnt be able to play for a week........