Raoul Duke wrote: ↑Sun Apr 13, 2025 12:07 am
Ok, played the amp more today and it’s pretty stable, but sounds like I need a little bit more upper mods. Did some digging around here and found a build thread from about a year ago called “Holy Agressive!!!!” where the idea of using a Marshall-style treble peaker was proposed; which sounds like something I’d like to try. Here’s a cut and paste from GlideOn’s post:
“It's likely however you really rather like this full, rich sound but just desire a bit more mid-shaping. Some teeth to it all.
To take a page from Marshall, try implementing a "Peaker."
I found that 220k/330pf value compliments the more "Fender" aspects of a Trainwreck quite well, while injecting just enough of a Marshall attitude into it.
If it were me, I would try it a V2 after the .1uf before pin 7 of V3.”
So my question is given his suggestion for implementation - should the peaker go across the .1uf cap or from the pot side of the .1uf cap down to the 1M on the left of the LTP V3 in place of the white jumper wire in Ron Worley’s layout - which goes on to pin 7?
Also thinking of putting a 33k grid stopper on V1a just to reduce hiss. The hiss isn’t THAT bad - just not sure how much is normal I guess - so trying to drop some of it if I can.
Any and all suggestions are appreciated!
Looks beautiful congrats!
Which EL84s did you end up using? Did you try several different ones?
I went with JJ's in mine but wish I had tried several other brands for comparison while I had it.
Thanks Guy!
I have a well-used but still strong set of Apex matched JJs in there now, but I’m always looking. I have one last set of matched NOS 6P14P Saratov tubes sitting on a shelf that I plan to try in there - maybe tomorrow - or once I sort out my treble peaker idea.
Those 6Ps are funny tubes; IME amps either love them or hate them. They sounded great in a Matchless DC30 I used to have, but didn’t sound good in my AC30 - which I had been saving that last set for. A friend of mine tried a set in his 1974 RI and pulled them out for JJs in less than a week. I know Dr Z swears by them and uses them in all his EL84 models. The Z-Wreck Jr I recently traded (for a ‘78 Marshall 2204) sounded great with them for sure.
All the lore about KFs seemingly bottomless source of golden era tubes and how he’d roll through sets upon sets to find the right ones for a particular build makes me feel that anything I do is pretty arbitrary - but I trust that if the amp is built right; something available will sound good to me - I just have to be patient and find it, lol.
I wouldn’t be unhappy to keep those toasty JJs in there for awhile if I had to honestly.
Over the past couple days I’ve made a few small changes:
First: I put that 220k/300PF treble peak in in place of the jumper from the .1uf cap to the eyelet for pin 7 of the PI. Cleared things up nicely.
Next: I swapped out the set of well-used JJ EL84s for my last set of 6P14Ps. This circuit does seem to like them. Another small but noticeable improvement.
Last: I tried a bunch of different preamp tubes and settled on a Tungsram in V1, a Yugo Ei in V2, and a Telefunken in V3. Sounds good today - we’ll see tomorrow, lol.
One other thing I may try is the 820R from V1 pin 2 to the volume pot. I have to get some 820Rs in first though - and trying to understand exactly what it does.
So a month later after some break-in time I decided that I needed to tame the “swirl” I get on top of single notes some and dial back the gain just a bit; so today I tried the following “adjustments”:
- Added a 22k grid resistor on V1A
- Installed the 820R on V1B grid to volume pot
- Decreased the V2 grid feed resistor (R7) down to 100k from 150k
Happy to say that these changes have helped. Less swirl and more manageable gain, no negative impact on the overall tone or feel. Now I’ll play it for awhile and see how it goes. Two other adjustments I am thinking about are increasing the PI tail resistor and using a balanced 12AX7 in V3 (which I will try anyway as it’s pretty easy). All of these ideas were taken from various “tame your TW build” threads here - which are an education to read for an inexperienced and untrained feller like me, lol.
Going to do some more research on how the tail resistor affects things before I make any decisions on this. Still learning…
That sounds like a useful option, thanks xtian! I may try that.
Just for clarification: I was thinking the tail is the 39k that goes to the presence pot (R11 in the schem/layout) and that R13/1k is the cathode resistor. Do I have them reversed in my cranium? Still learning what everything does.
