Which preamp Tubes for a JCM 2205?

[Australian]

I have bought matched Svetlana Winged C's for the 2205.

Now I am wondering if I just buy all 12ax7's to replace the rest of the tubes in the amp?

Do I need a different kind of 12ax7 for a certain V1, v2, etc?

 

[big dooley]

you may want a lower gain type in V2.. this helps keeping the normal channel a bit more clean... a 12at7 is a good example... it works in the PI (V5) as well, but thats a more personal taste... i'm running a 5751 in the PI of my JVM

 

[Darrenw5094]

you may want a lower gain type in V2.. this helps keeping the normal channel a bit more clean... a 12at7 is a good example... it works in the PI (V5) as well, but thats a more personal taste... i'm running a 5751 in the PI of my JVM

What does a 12AT7 do in the PI instead of a 12AX7?

 

[big dooley]

that's hard to describe... first i've never tried a 12AT7 in the PI... i used a 5751 instead... i tried the 5751 in the PI of my DSL but didn't like it... when i had my JVM for a while i tried it again and stupidly enough i liked it way more then the 12ax7 that was in there... it just gives a different feel....

there was quite a story i've read on a certain website about different tubes in the PI...

 

[Darrenw5094]

that's hard to describe... first i've never tried a 12AT7 in the PI... i used a 5751 instead... i tried the 5751 in the PI of my DSL but didn't like it... when i had my JVM for a while i tried it again and stupidly enough i liked it way more then the 12ax7 that was in there... it just gives a different feel....

there was quite a story i've read on a certain website about different tubes in the PI...

Maybe it's time for a Who, what, when, etc thread on Phase Inverter options.

 

[big dooley]

yes, maybe, but it's a difficult subject to discuss...
i think it's better to experiment with it rather discussing what's the best solution... it's all in the players taste

that's why i alway's advise to experiment yourself to find out what you like best... especially with the PI

 

[MartyStrat54]

I have bought matched Svetlana Winged C's for the 2205.

Now I am wondering if I just buy all 12ax7's to replace the rest of the tubes in the amp?

Do I need a different kind of 12ax7 for a certain V1, v2, etc?

The signal path in a 2205/10 is a lot different from conventional circuits. I am posting this up as a courtesy from the Preamp Tube Thread. Remember, a 12AX7 is a twin triode and has an A and B side.

Normal Channel: V1A and V2A and V2B

Boost Channel: V1A and V1B and V3A

Reverb: V3B and V4B

Effects Return: V4A

Phase Inverter: V5

 

[ReWind James]

There are (at least) two different versions of the circuit.

Most of the above can not be taken as fact without knowing what year/version of the circuit your amp has. If you pull V2 out and you only loose the clean channel, but still have the boost channel, it's the later version. If you loose both channels with V2 out, you have the earlier version. The changes seem to have happened around 1986.

In the later version, you can piggyback a resistor on top of R15 to clean up the clean channel in a much better way that changing to a different tube does (which only lower the OUTPUT of the clean channel). The R15 trick will sound more like rolling back your guitar knob on the clean channel.

Schematics:
earlier version
http://www.drtube.com/schematics/marshall/4210.gif
later version
http://www.drtube.com/schematics/marshall/2205prem.gif

 

[ReWind James]

btw - to answer the original question:

My 2205 likes, or rather insists on having Sovtek or Chinese tubes in V1/2/3. I have JJs in the rest. The amp would hum squeal and pick up German radio with any JJs in V1. TungSols sounded good in those positions too, but were a tad noisier and with less gain than the Chinese tubes and Sovteks.

Of course it likes old Mullards and Telefunkens too but not as much as the Chineese tubes. ...and those NOS prices, ouch!

 

[roylfukes]

Just wondering what tubes you went with in your 2205. I've got a 1989 and thinking about experimenting with some different ones.

 

[NewReligion]

My favorite 2210 is a Oct 1989 model. You speak about running the amp with pre-amp tubes pulled in order to check the signal path. Will this damage the amp with the Pre-amp tubes out while ON?!? In addition V1 is the 12AX7 tube closest to the input jack side, correct? Thanks.

David