trinityamps.com

I am working on an amp with an Ef86 channel that is borrowed directly from the TC-15's.

But- due to the fact that it is a larger amp running fixed bias among other things- it does not have as much drive as I had hoped. Not nearly as well paired pre/poweramp as the TC-15.

So I'd like to increase the gain a bit either modifying the existing circuit- or running it into an available triode on the 12AX7 next to it.

I am looking for good voxy overdrive- which this thing has a bit of... just not enough. Any suggestions?

Hope this is OK with Stephen
here's a link where some guys more knowledgeable than I talk about different values for the ef86 stage.They are pretty similar to the tc-15 values

http://music-electronics-forum.com/t907/

here are some more ideas from another forum



I would be interested in any findings or experiments.

Thanks! I think I happened upon that conversation at music-electronics a while back and thus forgot how to retrace my steps.

Some pots to adjust the screens could be interesting.

Have you tried any of these ideas? I will def. post what I find/try. It may not be something that one would want to try in the TC-15. I think the TC-15 sounds great as is. Never know though.

Your welcome
I haven't tried any yet
just got my Tc-15 up and running
may try some in the near future
after some break in time
looking forward to any ideas

To me it looks like there's some confused information in those forum posts. For example in the one they're talking about increasing EF86 stage gain, without considering the fact that a typical AC15 style EF86 preamp stage already has more gain than you need (so it has to be attenuated down) and that as you increase gain, you also increase microphony problems. A btter idea may be to bias the EF86 into its more non-linear operating zone. The other guys are talking about increasing bass, but with increased bass you also get more woofy low end and mushy distortion. Anyway, there are some more ideas in this thread from 18watt.com http://www.18watt.com/modules.php?name= ... c&p=221528 HTH

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Great tones come in small glass jars!

Thanks Zaphod
If I understand right (for a more linear not gain)suggestions are to lower the 2.2M resistor value(pin 1) to around 1M -1.5 and the 330k(pin 6) to around 200-150k?

I'm getting nice results using a modded BD2 and the ef86 channel.

Zaphod- always brilliant info. Thanks.

I did notice increased microphonic problems as I attempted to use my limited knowledge and experience to increase the gain. But I guess that's not really what I want to do anyway.

Have you tried any of these yourself? Any favorites stick out at you?

Currently I have the exact same arrangement as the TC-15 except a slightly higher resistor value for Rs (2.6M). I think I tried 1M (Rs) and 220K (Rp) at one point... which I think was better. I am currenlty letting a friend borrow the amp- but I'll be trying out some new arrangements as soon as I get it back.