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Marshall Valve Question

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I have an AVT-100 which has an ECC-83 in the preamp section. Now I'm just thinking in advance for when I need to replace it, are certain makes better than others or will this not matter as it isn't a proper valve amp?

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I think its pretty unlikely you'll need to change it in a hurry. I think its maybe different from normal valves as well.

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No, that one little valve can make a huge difference in sound, as the pre-amp is where most of your distortion is coming from. The power-amp is merely there to round it off and amplify it to make a loud enough noise out the speaker. EEC83 valves are cheap enough, so I'd recommend buying a few different ones and experimenting. JJ/TESLA, GrooveTube, etc. They are all slightly different in design and thus so will you sound. In my Marshall JCM800 2203, the EEC83 in V1 makes the biggest difference to the sound of the amp.

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Guest redmeat

Changing the single pre-amp valve in a hybrid amp will make barely any difference to the sound. I know this because the a guitarist I once knew set about the same quest with his Marshall VS100R. I also once owned a Fender ROC-PRO 1000 years and years ago and went through the same thing.

Most of the pre-amp tone in hybrid amps comes from diode clipping. The ECC83s run at half, sometimes less, their normal operating voltage (this applies to the AVT amps as well) and their contribution is questionable, apart from the marketing angle. (See also: any "valve" equipment that has one ECC83 which glows with a little help from an LED) The good thing about this is that they will practically never need to replaced unless damaged.

According to Doug Randall from Mesa Boogie, you need a preamp section with at least 3 ECC83/12AX7s, running at the correct voltage, to make any worthwhile addition to the sound (compression, harmonic distortion etc)

Replacing one of the pre-amp valves in a all-valve pre-amp may affect the tone, but in my case and my friends, it made absolutely no difference whatsoever. To make things worse, the valves are so inaccessable they required the amp chassis to be dismantled by a tech just to replace them. This wasn't free.

I'd think twice.

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Originally posted by redmeat:

Changing the single pre-amp valve in a hybrid amp will make barely any difference to the sound. I know this because the a guitarist I once knew set about the same quest with his Marshall VS100R. I also once owned a Fender ROC-PRO 1000 years and years ago and went through the same thing.

Most of the pre-amp tone in hybrid amps comes from diode clipping. The ECC83s run at half, sometimes less, their normal operating voltage (this applies to the AVT amps as well) and their contribution is questionable, apart from the marketing angle. (See also: any "valve" equipment that has one ECC83 which glows with a little help from an LED) The good thing about this is that they will practically never need to replaced unless damaged.

According to Doug Randall from Mesa Boogie, you need a preamp section with at least 3 ECC83/12AX7s, running at the correct voltage, to make any worthwhile addition to the sound (compression, harmonic distortion etc)

Replacing one of the pre-amp valves in a all-valve pre-amp may affect the tone, but in my case and my friends, it made absolutely no difference whatsoever. To make things worse, the valves are so inaccessable they required the amp chassis to be dismantled by a tech just to replace them. This wasn't free.

I'd think twice.

Thought so. I was gonna buy a Roc Pro 1000 before getting the Marshall, was it a good amp?

Anyhow I'll just worry about valves when I get a proper valve beast in the future. I'd send the amp to Marshall anyway to replace the valve so they will know what to do with it! :)

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Guest redmeat

The ROC-PRO was a nice wee amp. It had the best reverb out of any amp I've owned and didn't break once. I wish I still had it sometimes.

Good luck fixing yr amp.

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AVT 150 Trouble

I've been having some trouble recently with my AVT150 - it powers up ok, but the footswitch is completely unresponsive and non of the channels appear to be working??

I'm reluctant to put it into R & B for repair coz they're changing a sh!t load!

Anyone had any similar problems with their Marshalls?

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I've been having some trouble recently with my AVT150 - it powers up ok' date=' but the footswitch is completely unresponsive and non of the channels appear to be working??

I'm reluctant to put it into R & B for repair coz they're changing a sh!t load!

Anyone had any similar problems with their Marshalls?[/quote']

i cant say what the problem is, but get in touch with marshalls repairs department, from everything i have heard they are brilliant. and if anyone knows how to fix your marshall, its Marshall ;)

David

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