The Amp Garage

Rip out everything and make him a 1987/2204 thing. Only use transformers if the PT has enough power.

The ma rating on those new tubes was as tested per industry standards for the spec on those tubes which is not how your amp run's them . Hi Steve, The sound wat pretty good from the new tubes. It sounded louder then the old tubes as well. What do you think, the bias of the amp should be modded as t...

You have too much negative bias voltage that's keeping you from idling the outputs hotter. We need to sink more of that unnecessary voltage to the chassis, to do such the value of R23 needs to be lowered. First type placing another 56K 1/2 watt resistor across R23 and set the bias pot to the middle...

pdf64 wrote: ↑Mon Sep 27, 2021 1:44 pm Rather than the now typical 1ohm value, those are 10ohm cathode current sensing resistors. Are you sure you not looking at 200mA, rather than 20mA?

Yes I red 200mV, so 20mA

You have too much negative bias voltage that's keeping you from idling the outputs hotter. We need to sink more of that unnecessary voltage to the chassis, to do such the value of R23 needs to be lowered. First type placing another 56K 1/2 watt resistor across R23 and set the bias pot to the middle...

Hi All, I've got a Marshall, I want to bias, but the range is way to insufficient for my new JJ EL34II tubes. I can only get it to approx. 20mA What is the best wat to extend the range? Please find schematic and picture below. https://www.drtube.nl/schematics/marshall/9005.gif https://www.audioasylu...

ChopSauce wrote: ↑Fri Sep 10, 2021 6:57 am That or a MOSFET follower, which has the side bonus to drain the caps.

This is what I looking for, do you have a solid design for this application? I have a irf820 or lnd150 which I can use.

I'd still tame that birds nest in the chassis. Shorter wires lower capacitance, crosstalk and potential oscillation. Yes for sure, but this is only a test setup. If i’m happy with the sound I want to build it in a pedal. I didn’t know the long lead, etc. Would cut so much treble and punch. The idea...

The long guitars cables were a big part of the problem. Thanks! Now I'm using shorter cables and ended up with 0,68uf cap on the first cathode. Little less bottom. 22/25uf will be on a switch in final version for sure. I now have one 220k into two 1M master volumes. I will try removing the 220k as w...

So the ‘out’ is feeding a remote power amp? If so, how long is the cable between them? Correct, I run it throug a Marshall 9005 or 18 watt EL84 poweamp. Cable is 3 mtr. I've ran it side by side through my vox AC30CC2X as well, the amp's preamp had way more brightness, presence and punch. Could it b...

Stevem wrote: ↑Wed Aug 18, 2021 3:38 pm Do you have a scope to detect if you have a oscillating problem that would be making for phase canceling?

I don’t have a scope, but do you suggest phase canceling by wires overlap? I can poke arround with the wires. Funny thing is, it’s dead silence with all this wire…

xtian wrote: ↑Wed Aug 18, 2021 3:19 pm Remember that any length of hookup wire adds capacitance. It may be that you've got so much wire running around that you've dulled the top end.

You can increase the value of the 120p bright caps.

I’ve tried this, but the effect is to little. This circuit should be ver bright on it’s own, right?

Maybe switch over to 12 VDC power supply. And get your heatersupply from there. I do the same.
+ to pin 4, - to pin 5 and you're done. leave pin 9 unconnected.

BTW love your design, looks great.

I made a Suhr PT15 clean channel in a box, very similar.

Hi guys! Fairly new here. I'm working on a cool project. I wanted a Top Boost channel to use as rhythm channel and a more overdriven channel for solos. Please see below pictures for schematic and photo of my test preamp. The preamp and switching works fine, no hum or noise, but I can't get a good br...

Hi, I want to use below schematic as basis. Top boost Preamp only with a 500k volume pot. Is it possible to load another tone stack and volume to the cathode follower? and switch 'channels' at the volume pot taper only? Thank you, Jim schematic: https://el34world.com/Hoffman/files/Hoffman_AC30.pdf