I have collected most parts for this amp, actually the Alex Gendrano version shown below. Just wondering if any of the veteran sages on the forum have any advice as to changes they personally would make to the amp and/or PSU circuits.
Especially interested to hear about filter chokes and viable options. And, if there are reasons to change any component values, etc., it would be interesting to hear why.
Regards, Greg
http://diyaudioprojects.com/Tubes/KT88/
Especially interested to hear about filter chokes and viable options. And, if there are reasons to change any component values, etc., it would be interesting to hear why.
Regards, Greg
http://diyaudioprojects.com/Tubes/KT88/
Hi, I built that amp.
If you use motor run capacitors (ASC preferably) on the power supply, it sounds way better than the Nichicon electrolytic.
I omitted the 5H choke on the LC filter going to the 6n1p and replaced it with a 100R resistor (on some 6n1p, am getting oscillations and replacing the 5H with a resistor cured the problem).
I also bypassed all the cathode bypass electrolytic capacitors with polypropylene, and it seemed to help a bit.
Another change that I did which I did not submit at Gio's site is I replaced the cathode resistor of the 6n1p with an LM317 current sink, you can also try using two red leds to bias the 6n1p (both seems to sound better than the 1K resistor).
I have not updated the schematic at Gio's site, with the tweaks I did.
Look for Sherman and porkchop's thread on this forum, they described how they built this amp and the tweaks they did.
HTH,
AlexG
If you use motor run capacitors (ASC preferably) on the power supply, it sounds way better than the Nichicon electrolytic.
I omitted the 5H choke on the LC filter going to the 6n1p and replaced it with a 100R resistor (on some 6n1p, am getting oscillations and replacing the 5H with a resistor cured the problem).
I also bypassed all the cathode bypass electrolytic capacitors with polypropylene, and it seemed to help a bit.
Another change that I did which I did not submit at Gio's site is I replaced the cathode resistor of the 6n1p with an LM317 current sink, you can also try using two red leds to bias the 6n1p (both seems to sound better than the 1K resistor).
I have not updated the schematic at Gio's site, with the tweaks I did.
Look for Sherman and porkchop's thread on this forum, they described how they built this amp and the tweaks they did.
HTH,
AlexG
Here's how mine is currently configured:
My SE KT-88 configuration
More info on my page:
http://webpages.charter.net/porkchop/tubeamp/KT88_SET_amp.html
My SE KT-88 configuration
More info on my page:
http://webpages.charter.net/porkchop/tubeamp/KT88_SET_amp.html
I built Mikael's schematic but as monoblock power amps. I think you are on the right track with changing the power supply to the 6N1P. I had some motorboating in very bass-heavy passages when built per schematic. I decoupled the 6N1P with a simple RC network (can't remember the values off the top of my head) and the problem was completely solved.
I used Mikael's original component values for everything else. I used Auricaps for the coupling caps and motor run (ASC) caps for the PS filter. All in all it is a very good sounding amp.
I used Mikael's original component values for everything else. I used Auricaps for the coupling caps and motor run (ASC) caps for the PS filter. All in all it is a very good sounding amp.
porkchop61 said:
Porkchop, that is really nice! Thanks for the information. Believe it or not, I just purchased one on E-Bay, from a fellow who made this unit, based on Alex's schematic. It's this one, right here. We think we figured where the hum came from, and I believe he fixed it before sending it. I should get it tomorrow, or Tuesday. It will be interesting to give it a go, and see how she works.
alexg said:
I checked out the ebay link, the driver is 12au7, so it is not same as Mikael's circuit.
Though it is quite trivial to replace the driver with 6n1p.
When it comes in, which it hasn't, I'll turn it over and trace things and look at what is different. But I know that he actually based his amp on your project.
I'm not sure what is different, but he did state that he had to do some modifications. He is using SS rectification, and I believe you all used tube rectification, correct?
He stated that he has made five or six of these amps, and they are all based on this circuit, so he has made a few changes, possibly to experiment. I cannot answer this.
I'm also new at making amps, so I am on a steep learning curve.
alexg said:John, the amp that you got from ebay looks gorgeous.
With the transformers that the builder used, it should sound excellent. Pretty soon you will be tweaking it!
Probably not for a good while. He has a pair of monoblocks that I have already committed to purchase from him. He had completely built them and used them for about 8 months. However, he had another project, and had to rob Peter to pay Paul, so he removed the Edcor OP trans, and the Hammond chokes.
Anyway, the power transformers are there, along with everything else. And the power trans are Freed, that he got on E-bay a couple of years ago. He told me that they are more than adequate, and run so easily that they are always cool, and never warm up. Once I get those, I will be tweaking them and removing his SS rectification, and replacing it with tubes.
But it is the idea of monoblocks that is exciting, because they have seperate power iron.
I'm really getting interested in this SE thing. I have all kinds of PP amps, and receivers, including a Fisher 500C, Sansui 1000A, Bogen RPF 60, and about three or four others. Half of them have been checked out and brough up to date, and the other half is in the process. I have a very competant technician. He has two of my integrated amps right now.
However, all of them are PP. I've really been looking forward to the SE experience. So, when they arrive, I will be asking a lot of questions, for you guys. I'm even thinking on how I want to remake those monoblocks to look goregous eventually. Exciting stuff.
My Wharfedale Airedales are already excited about putting out some different sweet sounds.
Well, you guys are not going to believe this, but it's true! Blair, the seller, and I had been wondering what could have happened to the FedEx delivery to my house. When it did not arrive yesterday, Tuesday, he started checking back with FedEx, because the trace went to one spot, and then it stopped.
Come to find out the truck it was on caught fire and burned up completely, including my SE amplifier. This is simply amazing! What do you think the odds of something, such as this, actually happening, much less happening to you? One in how many million? I don't know, but if it can happen, it has happened to me in my lifetime.
Back to the starting boards, I guess. I'm going to have to get those two monoblocks and order the OP trans and chokes, or I may be without my first SE for a long time.
Rats!
Come to find out the truck it was on caught fire and burned up completely, including my SE amplifier. This is simply amazing! What do you think the odds of something, such as this, actually happening, much less happening to you? One in how many million? I don't know, but if it can happen, it has happened to me in my lifetime.
Back to the starting boards, I guess. I'm going to have to get those two monoblocks and order the OP trans and chokes, or I may be without my first SE for a long time.
Rats!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.