butwhatif wrote:Cool, do u have a cable or anything in the loop, or is it just direct? and, is your scope on the 'hot' term of the return level pot? I would keep a grid input r/c but you can mess with the elements in the stage to try to get the recovery amp square or close. As u know, any element in the loop has a capacitance, and also the return level setting can affect this. I have a trimmer in one of my amps as a return pot, which I have found the sweet spot on, and i leave it alone.
When I measured, there were no cables in the loop. Just putting a send cable without even returning anything can cost you some highs, for just the reason you mentioned. Its no wonder the real dumblelator has bright switches going and coming.
Both traces are off the hot (CW) terminals. Now that I know what is happening it is good that I have options if I need to mess with the grid r/c values. I think I am going to first try some bright caps on the masters, although in the past, this has not given me what I wanted. I tried some caps today on the OD entrance network and that had promise. I just need a bit more definition. I had this thing sounding like a Marshall 18 watter by using some high value caps across the 470k OD entrance. Kind of interesting, but not Dumble. It was a lot more touch sensitive though with the cap, which I liked. Back to reality. On the OD entrance, I am at least going to return the 47p back to the 470k from its current postion across a 180k. I may also reduce the 180k to 120k which should help a tiny bit too, but thats another thread. Anyway, thanks for the help.
butwhatif wrote:Cool, do u have a cable or anything in the loop, or is it just direct? and, is your scope on the 'hot' term of the return level pot? I would keep a grid input r/c but you can mess with the elements in the stage to try to get the recovery amp square or close. As u know, any element in the loop has a capacitance, and also the return level setting can affect this. I have a trimmer in one of my amps as a return pot, which I have found the sweet spot on, and i leave it alone.
When I measured, there were no cables in the loop. Just putting a send cable without even returning anything can cost you some highs, for just the reason you mentioned. Its no wonder the real dumblelator has bright switches going and coming.
Both traces are off the hot (CW) terminals. Now that I know what is happening it is good that I have options if I need to mess with the grid r/c values. I think I am going to first try some bright caps on the masters, although in the past, this has not given me what I wanted. I tried some caps today on the OD entrance network and that had promise. I just need a bit more definition. I had this thing sounding like a Marshall 18 watter by using some high value caps across the 470k OD entrance. Kind of interesting, but not Dumble. It was a lot more touch sensitive though with the cap, which I liked. Back to reality. On the OD entrance, I am at least going to return the 47p back to the 470k from its current postion across a 180k. I may also reduce the 180k to 120k which should help a tiny bit too, but thats another thread. Anyway, thanks for the help.
Good work, seems that many sounds are achievable with one of these builds, but i've always been partial to the classic d sound. the bright switches for the loop never worked for me, they always wrecked the tone, too much top, you'd have to have some poor quality stuff in the loop ever to use one. Is yours non-hrm? I am using 470k as entrance, and no caps. Not sure exactly what you have there but sounds like u r on the track. The scope makes it easy to see. Check subbing the tube first. If your voltages are up to snuff and all else good, one thing you can do is reduce the series 220k to the (recovery) grid -not sure what value, and if it's smaller also divest or lessen the cap. Shorting this out was the right direction. Keep the 220k grid leak. This will give your top end back w/o changing anything else.
butwhatif wrote:
Good work, seems that many sounds are achievable with one of these builds, but i've always been partial to the classic d sound. the bright switches for the loop never worked for me, they always wrecked the tone, too much top, you'd have to have some poor quality stuff in the loop ever to use one. Is yours non-hrm? I am using 470k as entrance, and no caps. Not sure exactly what you have there but sounds like u r on the track. The scope makes it easy to see. Check subbing the tube first. If your voltages are up to snuff and all else good, one thing you can do is reduce the series 220k to the (recovery) grid -not sure what value, and if it's smaller also divest or lessen the cap. Shorting this out was the right direction. Keep the 220k grid leak. This will give your top end back w/o changing anything else.
I like the D sound too, although it has been a challenge to get it right for single coil guitars which is currently all that I play. Overall, I am pretty happy with the current state of the amp, especially now that I have some options on getting more note definition. It helps that I took a break from this amp for a couple of months while I put an 18 watt build through its paces. Going back to the D amp, I immediately noticed it needed more clarity all the way around. Also, all along, I was never satisfied with my clean channel - wrong xover points and lacking sweet harmonics. I had started with the HRM circuit, and added the BM PI at some point. I just this month went to the BM front end which really helped my clean sound and seems to have given the OD a bit more bloom too. I finally have the eq on the front end like I want it (no wonder the 250-500p, .02, .02 tonestack shows up in so many great amps). Also the lowered plate values seem to give up some nice overtones I was missing before. Ok, I am derailing my own thread here, but I learned what i was set out to learn, so again thanks to all for the help. I should probably look for some resources on how to better use my scope. I really want to know more about how to use it for frequency analysis, epecially as I cant afford a spectrum analyzer. The square wave tip was right on
