Mullard ecc88 tube-any uses in guitar amps ?

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6FEETUNDER
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Mullard ecc88 tube-any uses in guitar amps ?

Post by 6FEETUNDER »

Hello All

I have an opportunity to pick up some nos mullard ecc88 tubes and was curious if anybody here has tried them in an 18 watt or any other amp for that matter.Also would like to know what the gain factor is,I cannot seem to find it on any datasheets.

Thanks

Pat
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Phil_S
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Post by Phil_S »

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krx
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Did you try Google? Lots of results there...

Post by krx »

It's a TV tube meant for use in cascode circuits:

http://www.tubezone.net/pdf/6dj8.pdf
http://www.duncanamps.com/tdsl/show.php?des=ECC88

It would not be suitable for a classic 18 Watt circuit.
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Post by zaphod_phil »

And a cascode gain stage can be used as a kind of substitute for a pentode gain stage, and even sounds quite similar to one.

www.geocities.com/keirkegeerd/alex_kenis-cascodes.pdf

But it's a little bit off the beaten path.....
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Post by kedsinger »

And the amplification factor is only 33.
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Post by zaphod_phil »

However IIRC, in a cascode stage the combined gain goes up to something in the same ball park as an EF86. So they really do make a decent substitute for a pentode.
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Post by 6FEETUNDER »

Sorry for the delay in responding.Dam car trouble has kept me off the computer.

Thanks for all the replies everyone,it is much appreciated

Pat
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Post by dotfret »

Even later than usual with this response -

There was a range of Russian amps called "Red Bear" that were produced about 1992. The V1 on those amps was a 6n1p, which is quite similar to the ECC88, if you ignore the way a 6n1p eats heater current.

The remaining parts of the Red bear designs are quite orthodox, using 6n2p (like a 12AX7, but different pin-out) and 6L6/5881 types for the output stage, so it might be worth looking if you really want an example of how to use them in a guitar amp.

Addendum - remembering this sent me out to look for schematics, and all I can find are of the later range that was marketed by Gibson - they don't use 6n1p, V1 is 6n2p in those.
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Post by dgriff »

Hi, sorry to hijack this thread, but does any body have any opinions/experience with ECC85 's instead of ECC83's? Im just wondering because I have a couple of Mullards from '50s radio sets.
Dave
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Post by dotfret »

If you build a small preamp, like the MacTube, you can try those strange double triodes out quite quickly -

http://www.dogstar.dantimax.dk/tubestuf/mctube.htm

You might find some interesting things this way - some valves are not worth modding an amp to use, but very satsifying as an alternative sound in a stomp box. Make sure you have enough oomph in the heater supply, so you can try the hungry valves, or use two 7 pin triodes instead of a duoble triode with a noval base. You want about 650mA to run a pair of EC92, for example. High heater current types do tend to be low noise.

Things I have found interesting include ECC40, 12AD7, 12BZ7, and a lot of 60s valves designed for computer use (these can often be very nice, but a lot turn out to be noisy).
ECC85 are not worth the bother, in my opinion, but lots of valves can be experimented with until you find a "sweet spot" that gives a nice sound. Unfortunately, you often find that the sweet spot varies from one valve to another, even if they are the same type.

Merlin Blencowe's "Designing Valve Preamps for Guitar and Bass" is a good way to learn about preamp design. Most of that material can be found on his website - http://www.valvewizard.co.uk

You can also find that book on this page -
http://astore.amazon.co.uk/wy4couk-21?node=3&page=1
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Post by Freddy »

The HiFi guys will pay pretty good money for those tubes. I sold a bunch of mullards and amperex like this on Fleabay last year and got some pretty good bids.
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