High Voltage Hijinks

Asdrael said:
Looking good! One last and overlooked source of hum are the small ground loops you might have been the ground of the pot and the actual pot itself when it’s on a bare chassis. But if you are happy with it leave as is!
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Really? Haven’t crossed any thought for this as I trusted I’m all good by not soldering any leads on pots. But wouldn’t your suggestion need isolating pots from chassis with plastic washers and adding a strip wire through every pot or using a metal sheet with potholes? With current pots not possible ’cos of thread length. :/
 
I might have been unclear but in a nutshell: bolting pots into a raw chassis makes the pot housing connective to the raw chassis. Which is fine, unless you also run a ground bus between pot housings (common in powder coated chassis) - then you have a loop. And worse if you use a ground lead that should go on a lug to also “bridge” the lug and the chassis.

I can’t see the back of your pots there so I just thought I’d throw it in.

A minimal amount of hum will always be there anyway… big PT, heaters, etc.
 
Had rehearsals today and the amp worked as it should. Pedal board not so! Ride never ends, guess my wife loves this DIY thing too as much as I do!

Edit. Oh and yeah I left my amp there not to be seduced by changing V2 plate and cathode resistor values… Maybe in future I’ll clip first halves bypass cap away or reduce it down to 1uF. And cathode resistors could be around 3k and 47k ones plate. Now there’s 82k/1k+22uF and 82k/3K+22uF. But for now pedal board first before amp tweak!
 
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Quick question about parallel inputs (treble’n’bass) and signal splitting. Wise to do a splitter with a phase switch for separate fx chains between inputs to accommodate possible difference on count between phase flipping stages in pedals stacked?
 
JohnnyCreepy said:
Quick question about parallel inputs (treble’n’bass) and signal splitting. Wise to do a splitter with a phase switch for separate fx chains between inputs to accommodate possible difference on count between phase flipping stages in pedals stacked?
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Definitely wise to have a phase switch on the splitter.

That said out of phase can sound great in certain circumstances so it's worth trying both. Sounds good is good!
 
I have received the replacement bells for my power transformer so… I went at it.

In case you wonder how it looks inside:

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It wasn’t bad at all. Just have to be mindful of not pulling on the wires too hard.

Followed a long wiring session. I think I made it look pretty tidy in the end, even if I am not 100% decided on some of it (hence the longer than usual wiring for secondaries). Some stuff on the pcb and chassis could have been located a bit better but hey hindsight 20/20, learning as I go etc.

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Looking good from the top too! The theme is solid white. Or should I say heavy white? I have never seen transformers this heavy.

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I will do a trial run this weekend and hopefully it works. I have to wait for a few things before I finish the front grill too, then I ll take a lot of pics and record something.
 
So good news, bad news.

Good news is, circuit is sound, the relays and switches all work, nothing exploded, I am alive.

Bad news is, the schematic for the bias circuit I found was apparently wrong and I didn't check. I can't go cold enough, at most I am at like 80% dissipation with my tubes and turning the standby off, I got some red plating and I think a thermal runaway on a KT77 (I was late in shutting it down). I have to triple check my screen resistors and bias resistors to make sure no component suffered any damage, and switch out a couple of resistors on the bias circuit to adjust the range (modeling it on LTSplice right now, probably just lower the dropper and call it a day). Likely will have to buy tubes too, although red plating at sub 100% when I was trying to adjust bias is kinda shit. Might ask for warranty on that.

Right now, the amp stays more or less stable at 80% bias (too hot and with one tube likely shot) and already sounds awesome. I just have to invert 1 and 3 on the pots for depth and presence and rotate the bright switch around. Nothing out of the ordinary there ;) The shape switch I have put in for the gain channel works as expected but has a volume drop. Not meant to be switched by playing and logical looking at the schematic but hey, it's there.

So yeah, some LTSplice, an order or two and we should be good to go.
 
Asdrael said:
I just have to invert 1 and 3 on the pots for depth and presence and rotate the bright switch around.
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I also did this stupid mistake, but with both channels treble and bass controls. Didn’t fix it as some of the tone stack components are soldered into pot lugs.

Tomorrows gonna be another rehearsal day and having a second real play with my rebuild amp. Last time there I had planned to completely fix my pedalboard and go through cold solder contacts etc in every pedal etc, but I’ve done only one. There’s been -20 to -26 celsius degrees out so workbench in garage has suffered from lack of warmth as lift door insulation isn’t so great. Maybe next week I’ll get shit done, who knows.
 
Okay, routing drone master (rat) to treble ch and megalith (fuzzface) to normal was awesome. I used bypassed Malekko delay as a buffer before splitting signal to dirt pedals and yeah it was awesome. Noticed some thin and weird phased sounds when turning tone knob on rat, but tone turned completely to CCW was the trick.

I think I found how to doom more and with clarity. :D

Now I’m having many parallel things to figure out how to make my pedals and signal chain routing work with delays etc. Couple mute boxes, volume pedals and buffers/splitters are needed!
 
JohnnyCreepy said:
Okay, routing drone master (rat) to treble ch and megalith (fuzzface) to normal was awesome. I used bypassed Malekko delay as a buffer before splitting signal to dirt pedals and yeah it was awesome. Noticed some thin and weird phased sounds when turning tone knob on rat, but tone turned completely to CCW was the trick.

I think I found how to doom more and with clarity. :D

Now I’m having many parallel things to figure out how to make my pedals and signal chain routing work with delays etc. Couple mute boxes, volume pedals and buffers/splitters are needed!
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Oh yeah... I'm on the same road brother.

Splitting, multiple amps, true stereo setup with different panning for the various amps. I feel like that's the way forward for heavy guitar. At least for me.

I just have a couple of PPCB splitters at the moment so I can (eventually) triple amp... I NEEEEEEED one of these though:

1768158682883.png

Or maybe two lol. It might be cool to parallel some preamps into the different power amps for example.
 
Hal Harvey said:
Oh yeah... I'm on the same road brother.

Splitting, multiple amps, true stereo setup with different panning for the various amps. I feel like that's the way forward for heavy guitar. At least for me.

I just have a couple of PPCB splitters at the moment so I can (eventually) triple amp... I NEEEEEEED one of these though:

View attachment 109199

Or maybe two lol. It might be cool to parallel some preamps into the different power amps for example.
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I’ve browsed forum talks about using dual inputs in one amp, but most of the discussion is about multi/stereo amp setups. Guess I just need to experiment and plan how to make this thing workable for me.
 
I noticed that much of what is used in the thread for building amps are metal film resistors. I have been doing a lot of reading and research into carbon film vs metal film, especially in the case of marshall style amps. I recently pulled apart my dirty Shirley build and replaced all the metal films with carbon film. I left the metal film in the effects loop circuit for lower noise.

What a difference the carbon film made. I don't normally buy into to mojo, but the sound is not only more pleasing in an old school way, but the feel is better under the fingers. No more metal film for me. The noise floor difference was negligible. The amp felt more stiff and clinical before and now its more how I remember old amps I played 25-30 years ago.
 
That’s interesting. Are you talking about all the resistors, only specific ones, or the ones outside the power line? I’m using metal film for 0,5W and MOX above currently.
 
Asdrael said:
That’s interesting. Are you talking about all the resistors, only specific ones, or the ones outside the power line? I’m using metal film for 0,5W and MOX above currently.
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I'm using 2w metal oxide on the power line and 5w wire wound on the power tubes still. Basically everything else is carbon film. It gave a more tactile feel under the fingers. It's hard to explain without using lame words like woody, chewy, organic, liquid and syrupy. The notes feel more alive, more dynamic. The drive is more pleasing too. Again, this is in the weeds nerd stuff, but it has a more vintage vibe overall. This only in a marshall style circuit though, perhaps one wants a really modern more clinical vibe in a different circuit.
 
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