dgta (and others),
I'm on my maybe 12th tube amp design, build and "tune" and so offer the following "opinion" from my own experience.
Once you get to a certain level of performance you are listening for pace rhythm and attack and imaging. To assess the "improvement", once at this level, it is necessary to do both channels as you are primarily listening for phase effects. You are passed the point where you can just do a single channel and try to compare it with the un-modified channel.
Cheers,
Ian
I'm on my maybe 12th tube amp design, build and "tune" and so offer the following "opinion" from my own experience.
Once you get to a certain level of performance you are listening for pace rhythm and attack and imaging. To assess the "improvement", once at this level, it is necessary to do both channels as you are primarily listening for phase effects. You are passed the point where you can just do a single channel and try to compare it with the un-modified channel.
Cheers,
Ian
I did not say, nor did I suggest, listening to single channel amps.
I did, however, imply that the vast majority of people claiming to hear such small differences, in fact can't. Therefore, it is my advice that those who believe they can, should check their ability by a double blind test. It may not be very ego-boosting to fail the test, but it saves you tons of time and money 🙂
I did, however, imply that the vast majority of people claiming to hear such small differences, in fact can't. Therefore, it is my advice that those who believe they can, should check their ability by a double blind test. It may not be very ego-boosting to fail the test, but it saves you tons of time and money 🙂
I agree - in general, plus the "you expect to hear an improvement and so you do" affect.
My post was meant as a general observation - appologies if you saw it as a negative comment to you personally - that was not my intent. The smiley sort of re-assured me that you had'nt taken it that way.
Cheers,
Ian
My post was meant as a general observation - appologies if you saw it as a negative comment to you personally - that was not my intent. The smiley sort of re-assured me that you had'nt taken it that way.
Cheers,
Ian
Hey,
I could hear a difference between the Solen and the orange drop. The Solen is the right direction but it doesn't go far enough. I make the changes between both amps at once and then listen. I'm a singer and voices are very important for me. It's now down to one voice sounding better than others on particular CDs.
Kevin
I could hear a difference between the Solen and the orange drop. The Solen is the right direction but it doesn't go far enough. I make the changes between both amps at once and then listen. I'm a singer and voices are very important for me. It's now down to one voice sounding better than others on particular CDs.
Kevin
Hi,
I cut the feedback a little and got the center back. I would no longer characterize the sound as harsh, but still a little too bright.
With an input of .007 volts at 1k without feedback I got 4.04 volts output. With the feedback in place I have .93 volts output.
I don't know if you are familiar with this music but with Aimee Mann its too bright. With Tori Amos it seems much better. I'm going to try some acoustic jazz and then a little night music next.
My Friend Rob at Tube Depot thinks the Solen's might be a bit bright. Not as bright as the orange drops though. He recommended metalized polyester. Specifically Mallory 150 series. Any recommendations there?
Kevin
So open loop gain is 55dB and closed loop gain 42dB, which means 13dB of NFB. 42dB gain is a bit high, perhaps you should increase the NFB either locally, globally, or both? 30dB is the norm for a pwr amp.
Your square wave looks just a tad fast, hinting towards a slightly bright sound. Perhaps you should tweak the coupling cap values before cap types?
SemperFi,
Yes! The amps are too bright. When you say too fast do you mean that the horizontal part of the square wave is too short? I've been playing with the feedback trying to warm the amps up and it didn't work. I was thinking about the cap values today. The original caps between preamp and phase splitter were .1uf orange drops. Too bright. I changed to .12uf Solens. The coupling caps between the phase splitter and outputs are .33uf Solens.
So would the cap values need to be larger? Like .22uf first and .47uf final? When I get the brightness fixed then I can tweak the feed back.
Thanks very much, Kevin
Yes! The amps are too bright. When you say too fast do you mean that the horizontal part of the square wave is too short? I've been playing with the feedback trying to warm the amps up and it didn't work. I was thinking about the cap values today. The original caps between preamp and phase splitter were .1uf orange drops. Too bright. I changed to .12uf Solens. The coupling caps between the phase splitter and outputs are .33uf Solens.
So would the cap values need to be larger? Like .22uf first and .47uf final? When I get the brightness fixed then I can tweak the feed back.
Thanks very much, Kevin
SemperFi,
Its too late to order caps for the weekend. If I parallel caps it has the same effect doesn't it?
Kevin
Its too late to order caps for the weekend. If I parallel caps it has the same effect doesn't it?
Kevin
Hey guys,
I think the difference between the orange drops and the Solens was more the value than the manufacturer. .1uf to .12. I have some Mallory 150 .22uf caps. And the original Mallory .47uf caps from the Mark VI boards. I'll try those tonight.
Kevin
I think the difference between the orange drops and the Solens was more the value than the manufacturer. .1uf to .12. I have some Mallory 150 .22uf caps. And the original Mallory .47uf caps from the Mark VI boards. I'll try those tonight.
Kevin
Hey All,
I have a question about resistors. In these amps there are 8 - 22 ohm 2 watt 10% CC resistors and 4 - 1k 1/2 watt 5% cc resistors. They are some of the only original parts left in the amps. These amps sat for quite a number of years and I have read that CC resistors can absorb moisture which affects their performance. Since they are all in the signal path I think its a good idea to replace them. It seems my options are CC or metal oxide for the 2 watt, which would sound better? I've read that metal oxide can be noisy. Are their any other options?
I have a question about resistors. In these amps there are 8 - 22 ohm 2 watt 10% CC resistors and 4 - 1k 1/2 watt 5% cc resistors. They are some of the only original parts left in the amps. These amps sat for quite a number of years and I have read that CC resistors can absorb moisture which affects their performance. Since they are all in the signal path I think its a good idea to replace them. It seems my options are CC or metal oxide for the 2 watt, which would sound better? I've read that metal oxide can be noisy. Are their any other options?
"Metal Oxide can be noisy" - I've heard that claim before but never suffered a noise problem when using them - certainly they won't be as noisy as Carbon Composition (CC) which are about the worst choice for noise performance.
I will use CCs in only one place - grid stop resistors.
I generally use all metal film except where their voltage rating is not sufficient and then I use either carbon film or wire wound.
I would replace any CC in a place where there is higher current, that is, anode loads and cathode bias resistors, it is the higher currents which "stimulate" noise in CC resistors.
There is a "subset" of guitar amp builders who will only use CC for that "vintage" sound, I'm not a believer although there is sound theory behind this. CC resistance value is slightly voltage (across them) dependent. when used for anode loads this imparts some 2nd harmonic distortion. A lot of SS guys in the HiFi world started fitting Rikken Ohm CC resistors in places like the feedback loop to deliberately add 2H distortion to mask higher order (and therefore more objectionable) distortions.
Just one mans views - others may disagree.
Cheers,
Ian
I will use CCs in only one place - grid stop resistors.
I generally use all metal film except where their voltage rating is not sufficient and then I use either carbon film or wire wound.
I would replace any CC in a place where there is higher current, that is, anode loads and cathode bias resistors, it is the higher currents which "stimulate" noise in CC resistors.
There is a "subset" of guitar amp builders who will only use CC for that "vintage" sound, I'm not a believer although there is sound theory behind this. CC resistance value is slightly voltage (across them) dependent. when used for anode loads this imparts some 2nd harmonic distortion. A lot of SS guys in the HiFi world started fitting Rikken Ohm CC resistors in places like the feedback loop to deliberately add 2H distortion to mask higher order (and therefore more objectionable) distortions.
Just one mans views - others may disagree.
Cheers,
Ian
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