Fischerman,
I'm working on an amp too that I just can't get right. Like you, I've rewired the thing several times and just can't get it to give up the magic like other amps that I've built. I've spent way too much time on it and think I will shelve it for a while....
When I scrape up some spare change I think I will throw a set of new iron in it too.
John
Tuning an amp with an O'scope
Moderators: pompeiisneaks, Colossal
Re: Tuning an amp with an O'scope
Dumb questions:
Do you have a hi-cut control?
When you mean clean power and drity preamp, do you mean unscaled preamp and scaled power amp?
Buzz/fizz is usually due to too much gain in the highs and squarewaving.
Do you have a hi-cut control?
When you mean clean power and drity preamp, do you mean unscaled preamp and scaled power amp?
Buzz/fizz is usually due to too much gain in the highs and squarewaving.
-
Fischerman
- Posts: 819
- Joined: Thu Dec 07, 2006 3:47 pm
- Location: Georgia
Re: Tuning an amp with an O'scope
No Hi-Cut but I have a post-PI Tone control in there...it's just two treble bleeds using a dual pot.
Clean power amp and dirty preamp means the amp is still at full power but the MV is turned down. However, my Standby switch just connects the OT center tap and screens to their respective PS nodes...so I can actually scope the preamp while the power tubes aren't doing anything at all (and I can crank the MV full-up). It doesn't affect the preamp voltages that much if the power tubes are running or not. But I checked it in all kinds of configurations just to make sure the problem never went away and it doesn't. Fully cranked with no scaling and MV full-up...or scaled with MV down or anywhere in-between...no change.
I already shelved this thing once...then I recently broke it back out and made the new preamp board. I think I'm gonna shelve it again but it's not getting any new iron. These are the Heyboer Express trannies and it sounds bad at low volumes so I'm pretty sure it's not the trannies. Besides, I've swapped out perfectly good trannies trying to improve tone several times before with other amps and it's usually a waste of time and money IMO.
I've got all the parts for my first ODS prototype so I'm ready to dig into that.
Clean power amp and dirty preamp means the amp is still at full power but the MV is turned down. However, my Standby switch just connects the OT center tap and screens to their respective PS nodes...so I can actually scope the preamp while the power tubes aren't doing anything at all (and I can crank the MV full-up). It doesn't affect the preamp voltages that much if the power tubes are running or not. But I checked it in all kinds of configurations just to make sure the problem never went away and it doesn't. Fully cranked with no scaling and MV full-up...or scaled with MV down or anywhere in-between...no change.
I already shelved this thing once...then I recently broke it back out and made the new preamp board. I think I'm gonna shelve it again but it's not getting any new iron. These are the Heyboer Express trannies and it sounds bad at low volumes so I'm pretty sure it's not the trannies. Besides, I've swapped out perfectly good trannies trying to improve tone several times before with other amps and it's usually a waste of time and money IMO.
I've got all the parts for my first ODS prototype so I'm ready to dig into that.