18Watt.com

Yeah i've read the same about the EF86's tending to be a bit microphonic but they work well in the vox's and have a listen to Josh at JMP's amp! sounds great and very touch responsive.

geoff 1965 wrote:Yeah i've read the same about the EF86's tending to be a bit microphonic but they work well in the vox's and have a listen to Josh at JMP's amp! sounds great and very touch responsive.

Thanks.

If you keep the amp build clean, and are careful in your tube selection, it's a lot easier to avoid the microphonics. My EF86 amps have the EF86 in the first stage, so I have no experience to share regarding other stages as he mentioned.

Theory is nice (in theory), but real world application is the only way to know what kind of noise you'll actually experience. There are some specific NOS EF86 tubes you can find with thicker glass (real RFT tubes for example) that are much less prone to microphonics than others. That's what I used on my combo version.

a couple more idea's ive seen regarding the EF86, one was a guy on youtube who mounted the tube socket on rubber gromets which he claims makes a big difference. the other is i recently bought a 1960's ex-royal air force amp on ebay for spares and all the components were absolute top quality! including 4 mullard ecc83's! and one thing i noticed was the cans that covered the preamp tubes were covered in a thick black matt paint which i'm sure is some kind of "screening" paint.

I use small rubber grommets too, sometimes. I did for the combo version. I don't know if it really makes a difference, but I figured it couldn't hurt.

I don't know if I would bother on my head version. I guess if they were in front of me within arms reach, but I wouldn't go down into my shop to get them if I forgot.

I really lucked out on my last 36w build. It's got an ef-86 channel and it's as quite/noisey as I would imagine one being. There doesn't seem to be any excessive noise and the tube I use (old national) seems to be just fine.

Sorry to be lax on the posts on here. I finally have this build up and running, but I have failed to take pics because I'm not done. I say that because the normal channel rips, but the trem channel is giving me grief.

I'm sure it's something dumb like a bad solder or whatever but when I have v3 plugged in for the trem channel, it makes crazy noises like a ray gun. When I pull the v3 tube and just run the normal channel it sounds like a million bucks.

Though I'm slowly working my way through it, have any of you guys had any crazy noises like that? Or any ideas on what to look for?

Update: No more crazy noises, but also no tremolo. Volume and tone are all good and I can use the trem channel just fine, but no tremolo. Sounds like maybe the noises was something dying? Should be noted that I'm using the "b" improvement layout http://18watt.com/storage/18watt_layout ... ents_b.pdf except I didn't move c15 on mine. All resistors are fine. The pots seem to test good. All the voltages on v3 seem to match close to Mark D.'s voltages on this chart http://18watt.com/storage/Voltage-Chart.htm but it's the lower of the two (170 and 112). I assume that the lower voltages are present when the tremolo is on?

Assuming you have used the 18 watt classic preamp: Two things to try. Swap the valve in V3. Some kick in better than others. The second is to have a higher plate voltage on pin 1 (if pin 2 is the screen connected to the trem). I have 190v as opposed to 145 on pin 6. Unfortunately I cannot recall how I achieved that. But probably to do with the value of R12 (Pedal Monkey 18 watt schematic). I have a note that I changed the value but not what it is now. It involved a few trials.

Dd

I updated my last post noting that I used the improved "b" layout
http://18watt.com/storage/18watt_layout ... ents_b.pdf

That's the same R12 which connects the plates and controls the voltages. The layout does not give values to the components so you need to see it on the schematic. In the classic it is 220k.

Dd

Totally had to have been something stupid. I reworked my v3 tube socket and we're all good now! I'll have some new pics of the finished product soon. very soon!

Good news.

Dd

Gorgeous work on this build. I love the lacing too. I've built a few amps with lacing and its not that much more difficult to do and it looks great. When I install GDS transformers in a Marshall 18W reissue, I usually reuse the factory lacing which is somewhat "light-duty" compared to authentic lacing but at least the job looks "factory" when its done.

Also, don't get too worked up over the supposed preferred filament wiring. Millions of amps have been built the way you did it and they sound just fine. I read an article a while back that discussed the theory of why "twisting" reduces noise and the basic tenet was that for audio frequencies, we don't even need to twist the wires - they just need to run side by side. So zip cord would probably work just as well although you'd never hear the end of it on the cork-sniffers forums!

Your lead dress looks great. Keep up the good work. You could work for Harry Joyce I think.

this one's for you Graydon!
no twist or zip cords,the amp is dead quiet no hum or hiss!
sorry purist's! notice the "phase switch" between the el84's

Very nice, indeed! Enjoy that puppy and post some sounds in the Hear It! section when you get a chance. We love hearing every build although we don't get that.