Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DummyLoad on July 01, 2020, 06:40:25 am
-
fun amp. much fun. still tweaking the dry/wet mixing network, but i think for now that's where it'll stay. very THICK and lush reverb on tap if desired. DO NOT bypass 6BQ5 (R9), you'll want to, every being in your core tells you to, but don't do IT - IT WILL HOWL like a banshee if you do.
i did not install R24 safety load resistor on the breadboard.
allen amps OT model TO-11S found it's way on another experiment. reverb driver OT is a heyboer unit sold by triodeelectronics. the rest of it is run-of-the-mill hammond iron.
quick calcs from telemetry state about 82mA total draw at idle. 5881 is burning at about 24W. i'll post a link to some BB pics later - for now all the gear porn y'all get is a schema.
--pete
-
Ciao Pete
As you have 3 triodes before the power tube (instead of two like in the standard Champ), don't you think you can use a Tone Control ?
Franco
-
have had time to evaluate after rewire of reverb mix pot wiring error that actually sounded much better than when wired correctly.
i wouldn't build this: it sounds like $#!t when turned up. considering scrapping the works.
--pete
-
Ciao Pete
As you have 3 triodes before the power tube (instead of two like in the standard Champ), don't you think you can use a Tone Control ?
Franco
probably. it might make it sound somewhat better, but i doubt it. the reverb circuit and dry/mix is off - sounds really good at low-mid volume with a wiring error, sounds horrible when cranked up as drawn.
--pete
-
I just snagged the TDR preamp and ran it in to a 6L6
EDIT- I added a mid-boost by making a switchable .002 in place of the mid cap.
Like K said, try a tone control, or two, before you go scrappin it.
This Champ Reverb thing comes up all the time. I would love to see you put it to rest.
You're almost home.
-
I'll post this for shooter, cause I know you know.
Here's what I mean by the mid boost wiring.
And now that I've fully hijacked your thread and I'm trying to goad you into finishing my schematic for me let me also say that I've been known to remove Ck from my output valve and put a little sticker on the back that says NFB is for wusses.
-
ha, just drill 3 more holes :think1:
I personally like my mids up not squelched :laugh:
sounds really good at low-mid volume
what if you knock those 22uf's down to 5-10?
guessing there's to much drive? or is it just 2 good sounds that can't live in the same house :laugh:
-
The 2 cascaded preamp stages (with only the vol pot for attenuation) is competing with 1 reverb recovery stage that has a very weak (compared to guitar pup) input signal. Add up the gains
-
this will cinch my ignorance;
each is 2 gain stages so they're in phase, any chance T3 adds a phase shift to put them outta phase at the mix :dontknow:
-
The 2 cascaded preamp stages (with only the vol pot for attenuation) is competing with 1 reverb recovery stage that has a very weak (compared to guitar pup) input signal. Add up the gains
found a loose grid connection on the 6L6 driver on the socket side of the proto adapter. that was creating gross distortion intermittently.
fiddling around with it some more - compensated for the added gain of 2 stages without TS - lightened the load on the reverb recovery - e.g., swapped out 100KL for 500K. now getting very strong reverb. need to tweak the reverb recovery amps coupling cap (smaller).
--pete
-
ok, that's a wrap for this one. sounds really good. not WoW good, but would be a nice 10W addition with a sweet sounding reverb. the 6BQ5/EL84 sounds really, really good in that application. and on a footnote, i have never been a big fan of the champ overdrive tone.
rev 2a & likely the last update, unless y'all have any other ideas you want me to give a whack at.
--pete
-
last revision before teardown. nice sounding amp.
enjoy!
--pete
-
Might also get more wet signal if you increase the grid leak resistor on the reverb recovery stage to something like 220k
-
Might also get more wet signal if you increase the grid leak resistor on the reverb recovery stage to something like 220k
doesn't need it IMO. full up on the reverb control & dwell control, the effect is so thick it's at the edge of screeching.
--pete