Thunderchief Breadboard Report

JimRayden · October 21, 2005, 04:49:33 PM

Oh yeah baby yeah! That's what I call a solo sound. Excellent harmonics. This one goes into the box and on the board permanently.

A question also, I can notice a bit too much treble when I run it into my tube preamp, could it be because I had to use 470n instead of the 680 as the bypass cap on the first two stages?

I haven't played a 100W Super Lead but I can't imagine anything sounding any better than this thing through a clean amp into good speakers.

----------
Jimbo

RDV · October 21, 2005, 05:02:47 PM

Got .68uF?

RDV

JimRayden · October 21, 2005, 05:57:38 PM

I'm in Europe, but I guess I can parallel some up to form 680-ish.

----------
Jimbo

JimRayden · October 22, 2005, 05:29:12 AM

I don't feel like wiring up a gain pot, I don't even think it needs one. But what's the difference between controlling the gain before (guitar vol) and after the first stage?

---------
Jimbo

JimRayden · October 22, 2005, 12:06:18 PM

Hmm, the decay seems to be relatively short though, there fore it also doesn't clean up with the guitar volume well. Is that a common drawback of JFET amp simulation or should I choose another type of FET's?

---------
Jimbo

Jered · October 23, 2005, 04:33:13 AM

When you say decay, are you talking about sustain? If so, you might not have the circuit biased properly. Check your voltages.
Jered

Johan · October 23, 2005, 07:02:37 AM

..since its rog's design, its not a fault, but if you want it to be even more like a plexi, there should be a 470k on the second FETs gate to ground ( on a plexi it goes to the other channels volume pot, wich when turned down means ground..)
it will reduce the overall gain a bit, but perhaps becoming more accurate sounding..
johan

JimRayden · October 23, 2005, 12:58:50 PM

Quote from: Jered on October 23, 2005, 04:33:13 AM
Â When you say decay, are you talking about sustain? If so, you might not have the circuit biased properly. Check your voltages.
Jered

Yes, it decays wierd and cuts off suddenly at the very end. I just checked the bias again, it's as close as I could get with resistors (about 49% of the supply

).

And Johan's mod didn't help either.

I just measured the pins and the gate of the third stage shows -0.45, while ROG lists this calue as 0.08V. Hmm, I must have some bug somewhere...

----------
Jimbo

JimRayden · October 24, 2005, 04:04:14 AM

Bump.

Anyone? There must be a rational solution to the gating. My guess is the funky third stage feedback-loop-thing thingy...

-------------
Jimbo

JimRayden · October 25, 2005, 01:43:10 PM

Bump.

Or can you recommend anything similiar sounding (besides a BSIAB)?

---------
Jimbo

Johan · October 25, 2005, 01:56:56 PM

..did you use a verified layout or did you make your own?...it isnt impossible the problem is coused by hf-oscillation...stages feeding back between eachother..it hapens in the reall ones sometime when someone has poked around a bit, so why not in an emulation?...

johan

alteredsounds · October 25, 2005, 02:41:27 PM

JUST about to build one! Is it that good?

Johan · October 25, 2005, 02:53:16 PM

Quote from: alteredsounds on October 25, 2005, 02:41:27 PM
JUST about to build one! Is it that good?

..there are soundsamples at ROG, I think it sounds accurate..I will builld one myself in the next couple of weeks, but match values to my 1975 SuperBass ( including tonestack ) so I can get THAT sound at home too...

johan

JimRayden · October 25, 2005, 03:11:09 PM

Oh thanks Johan, I poked around the breadboard and accidentally moved something right, so it sounds great now.

Hmm, the Lead Channel mod (250uF cap under the first stage) doesn't give me enough boost to bother wiring up another stompswitch. Any other boosting mods for the circuit?

---------
Jimbo

News:

Thunderchief Breadboard Report