Liverpool swirl sound

[lions den]

I posted a clip on my Liverpool build thread and swirl is the best description of a sound I'm trying to get removed from the amp.

I don't have a scope so looking to see if voltage readings would help point me in the right direction.

So far I've tried a 12at7 in the PI slot, lowered neck pickup on guitar.

Any thoughts on readings or other component things to check on? I'll try to add the clip to this thread to make it easy to reference.
Thanks
Sean

[oh7hhi]

I had a same kind of swirly overtone in my 18 watt TMB - amp.
I got rid of it by installing a snubber circuit in OT primary. No loss of highs, only that swirly "zing" was gone.
Here's the link: http://www.guitarplayer.com/article/smo ... -ride/5505

[lions den]

Thanks for the link. I remember skimming through that article in Guitar Player, will give this a try and see how it works.
thanks again,
sean

[Structo]

Hehehehe, there are some that strive to get that swirly sound that is often associated with blackface Fender amps.

[gary]

el84 fizz is discussed a lot on 18watt.com. My best anti-fizz measure was removing the bypass cap from the el84 cathode resistor. Not sure whether the Liverpool would like this!

[lions den]

Tom, yeah at times it's a cool effect and it's not there unless I'm holding a single note for a long time. I could live with it where it is today.

Gary, thanks for the suggestion, I'm going to try a bunch of things and see what impacts what.
Thanks
Sean

[jeff12]

Not sure what you can try in the amp, but I know speaker selection makes a big difference in the sound. With a Weber Blue Dog ceramic with pre rola doping I don't hear as much fizz from the amp as when I use a Tone Tubby hemp cone ceramic. With the Tone Tubby the fizz is very obvious where when using the Weber I have to listen hard to hear the fizz. It is still there with both speakers, just less noticeable. Maybe a combination of small changes together will provide the answer?

[gary]

conjunctive filter, zobel filter, cut control are other options

[ampgeek]

Here is a good thread that discusses/resolves a similar issue with an 18 watt plan. Looks like the OP solved the problem with the Ruby mod.

I can't think of any obvious reasons why it couldn't also be tried with a Liverpool.



http://ampgarage.com/forum/viewtopic.ph ... sc&start=0

Good luck!
Dave O.

[Lindz]

That buzz thread listed above was mine. The Ruby mod helped but did not kill the swirlies on my amp. I really struggled with bad swirlies and tried a whole host of things to get rid them.

Ruby mod - helped somewhat using zeners rated 2 volts over my idle voltage
big cathode bias cap - did not help but I liked the sound so I have 1000uf on my amp now (18 watter not TW - fyi).
Zobel filter on the OT- did not seem to help noticeably, but left it on
Guitar player article snubber - did not seem to help, removed it

What really got rid of 90% of it on my amp was a diode clamp across the Cathode resistor - found a 2009 thread by Chuck H over at the music electronics forum that pretty much described my issues to a "t "- and his diode clamp described half way through the thread worked like a charm on my amp. Night and day. Still a tiny bit of swirl but as many have said this actually sounds cool. I think that is part of the charm with el84's getting driven hard

http://music-electronics-forum.com/t10833/

Also this thread by Zaphod http://www.ax84.com/bbs/dm.php?id=254498 would likely have a similar effect though I have not tried the diode in series like his description.

[ampgeek]

Ooops....sorry for the repitition!

And thanks for the updates regarding this topic. I took on a 6 month work assignment in HI and am just getting back at that 18 W build. I will be revisiting your experiences in the very near future.

Cheers,
Dave O.