jaencer said:
If the problem is that the OT primary impedance isn't high enough, you should put 8 ohm (or 16 ohm) speakers on the 4 ohm tap (as you had planned to do).
I don't know if the '16 ohms tap ' was just a typo, but would certainly make the problem worse, not better, I think.
If you have some spare speakers around, you can always put them in series to get to 16 ohms-or more- for some quick experiments.
Cheers
John
The solution!
Coldcathode and I have been talking via e-mail a bit, and I am posting this to update the community of our findings. I have messed around with this finicky little amp for quite some time now, and the solution was to abandon the original schematic all together. I was fond of it in the beginning (the original), but I remember how it sounded, and now i know that i only liked it because it was the first 'tube' sound i had ever really heard, and didn't know better.
Coldcathode designed the attached schematic for me a while back, but i hadn't tried it until today. -- please note that the tubes have changed to 6v6, and every single component has changed from the original; it isn't even the same amp --
SO
i ripped out all the old parts, and put the amp together exactly as per the schematic. the first time that i fired it up, i was using some 40 dollar jensen speakers in case there was a wiring mistake (there was on the left channel, which i fixed promptly). the crap speakers sounded so nice playing Diana Krall that i listened to her whole album on them, and then switched my new fostex f120a alnico speakers... I instantly have higher standards for music! :really-exited-super-happy-internet-smiley:. Anyway the amp is done, I wouldn't feel comfortable touching a soldering iron to it again-- so that says something
Coldcathode, i can't thank you enough. Thank you. Pictures are on the way.
Coldcathode and I have been talking via e-mail a bit, and I am posting this to update the community of our findings. I have messed around with this finicky little amp for quite some time now, and the solution was to abandon the original schematic all together. I was fond of it in the beginning (the original), but I remember how it sounded, and now i know that i only liked it because it was the first 'tube' sound i had ever really heard, and didn't know better.
Coldcathode designed the attached schematic for me a while back, but i hadn't tried it until today. -- please note that the tubes have changed to 6v6, and every single component has changed from the original; it isn't even the same amp --
SO
i ripped out all the old parts, and put the amp together exactly as per the schematic. the first time that i fired it up, i was using some 40 dollar jensen speakers in case there was a wiring mistake (there was on the left channel, which i fixed promptly). the crap speakers sounded so nice playing Diana Krall that i listened to her whole album on them, and then switched my new fostex f120a alnico speakers... I instantly have higher standards for music! :really-exited-super-happy-internet-smiley:. Anyway the amp is done, I wouldn't feel comfortable touching a soldering iron to it again-- so that says something
Coldcathode, i can't thank you enough. Thank you. Pictures are on the way.
Attachments
Jaencer,
I am happy that you enjoyed the amp, I myself have not had the time to build it. Actually, I thank you! in our conversations I thought back to my first build which happened to be the same original 5 tube amp. I too was slightly enthused with the sound from the original but since I had spent much time listening to some very high end SS stuff and had a little understanding of the "analog" world, (I am just old enough to pre-date the CD) my first impressions were not that great. It did however give me the courage (is it really courage or lack of judgement?) to venture further into tubes.
One of the nice things about SET is that it kind of "forces" you to look at your speakers and listening levels. I had for years thought that you needed to listen at "ear bleeding" levels in order to get the "feel" of the track. This is due to the fact that my SS stuff and rather "low end" speakers were just lacking all the "full-bodied, rich" sound of a SET tube amp. (sounds like a coffee commercial huh?). Once I acquired a decent set of speakers and a better (acoustically) listening area, I found that 1 or 2 watts of SET was more than enough to really enjoy my music. Careful attention to the basics of amp design; minimal components in the signal "path", careful choice of F3 points, trade off power for low distortion, adequate filtering and capacitance in the PS etc, make even a modest design like this, with modest components a real "listener".
My only hope is that you also went through some of the reading material I included along with the loadlines and calculations I provided. I learned here on this forum that there is a considerable difference between "building" an amp and "designing" an amp. You can't just throw a bunch of parts and pieces together and call that "designing".
I am happy that you enjoyed the amp, I myself have not had the time to build it. Actually, I thank you! in our conversations I thought back to my first build which happened to be the same original 5 tube amp. I too was slightly enthused with the sound from the original but since I had spent much time listening to some very high end SS stuff and had a little understanding of the "analog" world, (I am just old enough to pre-date the CD) my first impressions were not that great. It did however give me the courage (is it really courage or lack of judgement?) to venture further into tubes.
One of the nice things about SET is that it kind of "forces" you to look at your speakers and listening levels. I had for years thought that you needed to listen at "ear bleeding" levels in order to get the "feel" of the track. This is due to the fact that my SS stuff and rather "low end" speakers were just lacking all the "full-bodied, rich" sound of a SET tube amp. (sounds like a coffee commercial huh?). Once I acquired a decent set of speakers and a better (acoustically) listening area, I found that 1 or 2 watts of SET was more than enough to really enjoy my music. Careful attention to the basics of amp design; minimal components in the signal "path", careful choice of F3 points, trade off power for low distortion, adequate filtering and capacitance in the PS etc, make even a modest design like this, with modest components a real "listener".
My only hope is that you also went through some of the reading material I included along with the loadlines and calculations I provided. I learned here on this forum that there is a considerable difference between "building" an amp and "designing" an amp. You can't just throw a bunch of parts and pieces together and call that "designing".
Remove PSU resistor somehow?
I've done a lot with this amp since the last post-- after all i listen to it a big percentage of my life. There was some hissing, so I replaced all the components, and it solved it. I tried swapping the rectifier tube from 5y3 to 5U4, and they are VERY different. The 5u4 is much stiffer sounding. 5u4 is better for fostex F120A speakers, 5y3 is better for bookshelf speakers.
BUT: I would like to be rid of the resistor on the power supply. So there is some voltage that needs to be wasted. Here is my proposal:
- I know that the voltage drop on a 5u4 is much higher than the drop on a 5y3. So I've already lost like 20volts by switching rectifiers.
- The first capacitor after the choke can be removed (the 15uF), and then the 15H choke will be more reactive and voltage should drop some more (but how much I don't know).
- The 600ohm resistor can be replaced with another choke. Maybe one around 10H with a couple hundred ohms DCR?
It just seems silly to have all these nice components like a 15H, 16ohm choke and then throw in a 600ohm series resistor to ruin it...
One more idea: What if i were to buy a lower voltage transformer? Like a 275-0-275 V ? Or other?
I've done a lot with this amp since the last post-- after all i listen to it a big percentage of my life. There was some hissing, so I replaced all the components, and it solved it. I tried swapping the rectifier tube from 5y3 to 5U4, and they are VERY different. The 5u4 is much stiffer sounding. 5u4 is better for fostex F120A speakers, 5y3 is better for bookshelf speakers.
BUT: I would like to be rid of the resistor on the power supply. So there is some voltage that needs to be wasted. Here is my proposal:
- I know that the voltage drop on a 5u4 is much higher than the drop on a 5y3. So I've already lost like 20volts by switching rectifiers.
- The first capacitor after the choke can be removed (the 15uF), and then the 15H choke will be more reactive and voltage should drop some more (but how much I don't know).
- The 600ohm resistor can be replaced with another choke. Maybe one around 10H with a couple hundred ohms DCR?
It just seems silly to have all these nice components like a 15H, 16ohm choke and then throw in a 600ohm series resistor to ruin it...
One more idea: What if i were to buy a lower voltage transformer? Like a 275-0-275 V ? Or other?
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