Sensitivty of V1

[tubetek]

Benoit-
I think You've hit the nail on the head. I usually use solid/PTFE wire on all my builds/mods. I haven't completed my first Express yet, (in progress) but when I recently modded a Bassman head with a TW inspired preamp I did have to go to stranded wire on V1 and V2 to tame microphonics. This circuit is, by design, on the ragged edge of stability.
Good luck, Dart...You'll get it. (and, sorry you missed the show!)
tubetek

PS: Dart; Have you tried Breckenridge Small Batch 471 Double-Hopped IPA?
Out of Colorado, I believe...Inspiring!!!

[Allynmey]

I do use mostly solid core wire. I use both solid/teflon and solid/PVC. I use solid/PVC on 'wrecks, and solid/Teflon on komet style builds. I really like solid core wire for the neatness factor also. I don't think "skin-effect" is an issue with such small gauge wire.

[dartanion]

I haven't even seen the Brek beers anywhere in the SF Bay Area, so no I haven't tried it yet. I am an IPA fanatic and brew a few varieties of IPAs with my standard having about 300 IBUs Not for the faint at heart!!

I had to move on to a customers build, so I still haven't had a chance to tinker with the Liverpool. I plan to wire up my Express along with the customer's build, so I think I'll be using stranded on the socket connections as an experiment.

I have been using solid core PVC wire in more my recent builds, but this one has been the most troublesome. Oh well, I'll get it soon...I hope.

[LeftyStrat]

Although the pics of Francesca are pretty hot glue free, the pics of ginger show liberal use of the glue gun. My first thought is that this was to hold things in place.

My first build was incredibly microphonic, I could tap on the wires around V1 with a chopstick and almost induce oscillations. In the process of getting some wires to stay where I wanted them to with a dap of glue here and there, it seemed to reduce the microphonics.

So this is complete speculation, but perhaps one of the ways Ken brought an amp under control was a few strategic drops of hot glue.

[dartanion]

Here's a couple of photos of Jim K jamming through the Liverpool while it's on the bench.

[DerStever]

I havent tried gluing the wires down - am using a mix of solid and stranded based on Nik's boards and yeah there are microphonics with some tubes - I found some that work ok as they are so I'm good for now - will try the glue effect later.

I did however change the solid core going from V1 pin 2 to the volume wiper to a shielded cable - which really didn't do much but it is insurance.

I also went completely to metal film resistors with three exceptions 2K7 didn't have that in stock so its carbon film, and the two 100k plates on the pi are carbon film. The hiss is reduced and little if any change in tone to my ears.

However the biggest and bestus change was using a NOS Mullard 12AT7 in the PI ala Fender AB763 and alot of others. I'm using all Mullard OS tubes cause I like the British vibe in my amps - but this really tamed some of the noises, hisses, and I think gives you more headroom with the ability to still goto Pluto if you want to.

I got my 2nd Gold Alnico and put the 1st in a 2x12 OB Fender Twin II cab which has a piece of plywood over one of the speaker holes - sounds pretty good by iteself. My Maple cabinet got the new speaker which isn't even broken in yet and it sounds great. Put the two of them together and its sonic Nirvana (not the group).

Now to build a single ended mini-wreck like allyn's ... it never stops does it?

[Rick]

I don't know about caps and such being microphonic, but poor solder joints sure as heck are, I thought I had microphonic tube problems on my first amp for 2 weeks, and it was a poor rotating solder joint. I've been much more meticulous about soldering ever since, it's absolutely necessary. Even blackened tube pins can cause scratchiness, I polish them till shiny now. I use shielded audio cable for all input jacks and the volume control signal wiring. That has led to an almost complete cessation of amp bugs.

Oh, I wasn't questioning that these things can cause noise in the circuit, but rather questioning whether noise introduced in a way other that what I described (i.e. vibrations being picked up by the tubes themselves) was microphonic or something else altogether. I was under the impression that it was a fairly specific term.

OK, I neglected to agree that V1 is sensitive in most amps and especially TW Express in my experience. I have cured it with a good triple mica Shuguang tube with low microphonics of all things.

I was thinking that a cold solder joint might have the properties of a semiconductor junction because I have seen where it has acted very microphonic like.

[tubedogsmith]

The deal is to tame the microphonics not completely eliminate them. You can do this with lead dress, glue, chassis deadening material such as rubber strip insulation, and purposely selected tubes.

[LeftyStrat]

The deal is to tame the microphonics not completely eliminate them. You can do this with lead dress, glue, chassis deadening material such as rubber strip insulation, and purposely selected tubes.

Agreed. This got me to thinking. I remember the quote from Ken that some amps that he couldn't tweak to sound good enough, he would disassemble and not sell. I use to think that meant he couldn't get it under control. Now I think it might be the opposite, that some amps may have come out too stable.

Reeling in an unstable amp is probably a lot easier than trying to "untame" a polite one.

[tubedogsmith]

The deal is to tame the microphonics not completely eliminate them. You can do this with lead dress, glue, chassis deadening material such as rubber strip insulation, and purposely selected tubes.

Agreed. This got me to thinking. I remember the quote from Ken that some amps that he couldn't tweak to sound good enough, he would disassemble and not sell. I use to think that meant he couldn't get it under control. Now I think it might be the opposite, that some amps may have come out too stable.

Reeling in an unstable amp is probably a lot easier than trying to "untame" a polite one.

eggsactly!!!

[Fischerman]

I remember the quote from Ken that some amps that he couldn't tweak to sound good enough, he would disassemble and not sell.

Well, I guess I can't feel too badly that my Express doesn't sound good enough (although I imagine 'good enough' is relative).

[Tubetwang]

If you want to save yourself a LOT of frustration by trying to find the "perfect" tube which is not microphonic, wire a 33k 1 watt resistor directly on to pin 7 of V1. It also kills any oscillations the amp may be having. The standard value for virtually every other amp on the planet is 68k but 33k seems to work just fine and does NOT suck the tone out of the amp ...

Just my 2 cents ....

More info can be found here:
http://www.aikenamps.com/

Go to TECH INFO then "Grid Resistors - Why Are They Used?"

gcenker...you are the man!!!...

i've been wanting to stop a radio broadcast on my new Express build for a few days now...searching for a cure...reading like crazy...

That 33K one watt trick worked for me. No more radio!!!!!!!!!

I can honestly say that this Wreck is an amazing amp. Ken knew what he was doing.

Starting a Liverpool tomorrow.

Thanks again...

[Lonely Raven]

The deal is to tame the microphonics not completely eliminate them. You can do this with lead dress, glue, chassis deadening material such as rubber strip insulation, and purposely selected tubes.

Agreed. This got me to thinking. I remember the quote from Ken that some amps that he couldn't tweak to sound good enough, he would disassemble and not sell. I use to think that meant he couldn't get it under control. Now I think it might be the opposite, that some amps may have come out too stable.

Reeling in an unstable amp is probably a lot easier than trying to "untame" a polite one.

Mine must be too polite. Out of my collection of vintage pulls, NOS, and a couple dozen modern tubes...I've only had a couple that were microphonic. Hell, I keep cranking the amp up more to get that bloom-to-feedback effect like Geetarpicker does in his youtube videos....I don't think mine is "on the ragged edge" enough...it's just too damn tame!

Although tonight I think I finally found my "mix" of modern tubes!

I'm running one of those EH 12AX7 (with the yellow printing) in v1...and I usually hate those in other amps...and JJ in v2 and v3, then Russian made Winged C EL34 power tubes.

Damn I heard stuff out of my guitar I didn't know was possible!

It's still not as harmonically rich and bloomy as I'd like...I'll have to figure out what to do for that.

But only 2 microphonic tubes so far...

I guess I just lucked out on my first build to not have any bigger issues!

[LeftyStrat]

The deal is to tame the microphonics not completely eliminate them. You can do this with lead dress, glue, chassis deadening material such as rubber strip insulation, and purposely selected tubes.

Agreed. This got me to thinking. I remember the quote from Ken that some amps that he couldn't tweak to sound good enough, he would disassemble and not sell. I use to think that meant he couldn't get it under control. Now I think it might be the opposite, that some amps may have come out too stable.

Reeling in an unstable amp is probably a lot easier than trying to "untame" a polite one.

Mine must be too polite. Out of my collection of vintage pulls, NOS, and a couple dozen modern tubes...I've only had a couple that were microphonic. Hell, I keep cranking the amp up more to get that bloom-to-feedback effect like Geetarpicker does in his youtube videos....I don't think mine is "on the ragged edge" enough...it's just too damn tame!

Although tonight I think I finally found my "mix" of modern tubes!

I'm running one of those EH 12AX7 (with the yellow printing) in v1...and I usually hate those in other amps...and JJ in v2 and v3, then Russian made Winged C EL34 power tubes.

Damn I heard stuff out of my guitar I didn't know was possible!

It's still not as harmonically rich and bloomy as I'd like...I'll have to figure out what to do for that.

But only 2 microphonic tubes so far...

I guess I just lucked out on my first build to not have any bigger issues!

Play with the wiring going to the tone controls. You want the lead to the treble to be "floating", and bass and mid running parallel about two mils apart. If you search the forum, there is a post by Jackie Treehorn where he found that manipulating the leads to the tone controls made his amp come alive.

Hang, I found the thread:

https://tubeamparchive.com/viewtopic.ph ... highlight=

[Lonely Raven]

Wow, and to think I tried so hard *not* to make it run away...this whole lead dress to dial in tone is scary on a whole new level!

I'm going to have to re-read that thread and maybe try out some of those suggestions...