Mark wrote: ↑Wed Oct 07, 2020 12:47 pm
Thanks for your feedback Marcus.
The test is to put your guitar though a looper and switch between the two settings. That will provide the greatest evidence of the difference in timbre. It has been my findings that most people have a poor memory of timbre.
Personally, I find if I’ve owned the piece of equipment for quite a while then I’ll know it. Otherwise, I won’t be so sure. I video everything these days. It has really surprised me. Changes that I thought were barely noticeable were quite apparent when playing back a recording.
My two cents worth.
Mark yes you're correct, I didn't have the time to go through all that today though.
I know this amp well though and had played it for a while before quickly swapping the resistor. For me it made a noticeable change instantly, not huge as I said but enough to say I like it better. I have not felt/heard the same thing with different resistor makes swaps , but lets not go down that road again
norburybrook wrote: ↑Wed Oct 07, 2020 12:58 pmI know this amp well though and had played it for a while before quickly swapping the resistor. For me it made a noticeable change instantly, not huge as I said but enough to say I like it better.
In a simulation I see a small increase in gain, and the balance changes slightly. We're talking 10ths of a dB, though. The bias will shift a bit too, I think.
norburybrook wrote: ↑Wed Oct 07, 2020 12:58 pmI know this amp well though and had played it for a while before quickly swapping the resistor. For me it made a noticeable change instantly, not huge as I said but enough to say I like it better.
In a simulation I see a small increase in gain, and the balance changes slightly. We're talking 10ths of a dB, though. The bias will shift a bit too, I think.
Whatever it did I like, and it was subtly noticeable to me, and you know what I'm like with these things
Cool, yeah what bothered me a little about the Tweedle Dee when I built it years ago was the break up felt a little hard to me. I just kind of assumed that it was because I was using new production output transformers. I guess maybe the LNFB has more of a compressing effect with the 10 meg resistor. As far as component makes and little tweeks, I will agree that usually the perceived effects may be slight, small percentages, but you start to add up all the small percentages and to me, it can make the difference as to whether an amp is OK or really great. RIP Eddie.
CW
Been away for a while and got back to see this. Made the mod and as Marcus described, smoother into distortion and distortion comes on way earlier than before. Definitely more gain than before and I'm liking it a lot. This amp seriously rocks with a LP! Thanks Charlie for the update.
Well after reading Charlie’s post about the one mega resistor that should’ve been a 10 meg, I decided to change it out today and give it a listen. I did not perceive anything different but I do have a question. After changing this should I readjust my phase inverter trim pot? Also here is a link below to a YouTube video I did giving you a listen on what this sounds like. Probably best if you don’t listen to it through your iPhone speaker but true headphones. It’s just a room microphone that the phone has that’s capturing the recording. Let me know your thoughts.
Adding to post. I did check some voltages and the 21 volts that was on the 1 meg Going to pin 7 of the phase inverter is now 3.6 volts. I also noticed that there now seems to be a ground buzz when my hand is not on the bridge. Tried a different cord and 2 other guitars. Still there. Any thoughts appreciated
I fixed my grounding issue , now on to another question
With this new resistor arrangement, the max phase inverter
AC swing is 1.6 volts using 1000 hertz Input. That is The most you can get end to end. Would this resistor change have this affect , along with only 3.5 volts at pin 7 of the phase inverter
Charlie Wilson wrote: ↑Mon Oct 05, 2020 1:38 am
Well, six years later and I think a made a mistake with regards to one of the component values in the Tweedle Dee. After talking to Jelle a while ago and staring at my own photos I now believe that the grid leak resistor on the PI is a 10 meg rather than a 1 meg.
CW
Charlie,
Was the 21.58V on V2b7 measured on the actual amp or your own build? With the resistor change, I'm getting 3.58V. I'm sorry, I didn't measure before the change (I measured way back when i originally built it and can't find them) but if I remember correctly, it was around the same as the layout (21.58V).
I have the same voltage on v2 pin 7 after the resistor swap. Also,
My previous voltage was 19. In addition , I noticed that you cannot adjust the phase inverter to have any imbalance of more than 1.6 volts. Did you try to adjust your inverter yet?
I have the same voltage on v2 pin 7 after the resistor swap. Also,
My previous voltage was 19. In addition , I noticed that you cannot adjust the phase inverter to have any imbalance of more than 1.6 volts. Did you try to adjust your inverter yet?
Hey Delmar,
I tried to set by ear and didn't measure. Really didn't have enough time so I'll spend some more time tomorrow. I am interested to hear if this matches the original amp.
What are you guys getting on pin 8 of the PI? I have more to add but I am curious about the cathode voltages on pin 8 and the other side of the 4k7 resistor.
CW
After talking to Jelle a while ago and staring at my own photos I now believe that the grid leak resistor on the PI is a 10 meg rather than a 1 meg.