Greetings to all.
Recently graduated from there this project will dedicate.
Yours faithfully.
http://sites.google.com/site/agalkaaudio/hobbi/-angel-pp-amplifer-pentode-ul-triode-c3g-s---el-34
Recently graduated from there this project will dedicate.
Yours faithfully.
http://sites.google.com/site/agalkaaudio/hobbi/-angel-pp-amplifer-pentode-ul-triode-c3g-s---el-34
The OPTs are Edcor 15W open frame style (XSE15-8-5K). The amp has been on now for 9.5 hours and bass response has lifted. Everything is new. It may just be a run-in/burn kinda thing. Using a test CD there is good bass to 40hz. My 6AS7 would go to 30hz with the same speakers etc. Also I can roll the preamp tube in the amp. Might be even better bass ahead. Mids though are ridiculous.
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Here is my first build, two mono amps on one chassis using KT88s and 6SN7s. I started this ten years ago, got the chassis assembled but hadn't started wiring anything underneath yet, and then we have to move. This and all my parts got stuffed in a box and shoved into a closet, and never came out. Recently I got inspired to get it out and finish it. Now I'm committed since I've put the picture out here. It will be a project for the winter.
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You're going to LOVE IT! -6SN7s are amazingly excellent low-level/driver tubes- nice high B+ rating to drive the KT88s to clipping before the 6SN7s even get close...
And those Sovtek KT88s are awesone!
Looks like you have separate pwr xfmrs for each channel- a fine idea. I built one similar but with one single big honkin' Hammond pwr xfmr. Turns out that when the transformer gets THAT large, it buzzes a little, just due to magnetic domains re-aligning, not loose laminations or anything. You're likely better off with two smaller ones, like you have.
Mine uses a pr KT-88s, 6SN7 driver, 12AX7 preamp with about 20 dB global feedback. Sounds sweet w/ or w/o feedback, a bit "tighter" with. At any rate, those KT88s are going to blow you away!
Good luck!
And those Sovtek KT88s are awesone!
Looks like you have separate pwr xfmrs for each channel- a fine idea. I built one similar but with one single big honkin' Hammond pwr xfmr. Turns out that when the transformer gets THAT large, it buzzes a little, just due to magnetic domains re-aligning, not loose laminations or anything. You're likely better off with two smaller ones, like you have.
Mine uses a pr KT-88s, 6SN7 driver, 12AX7 preamp with about 20 dB global feedback. Sounds sweet w/ or w/o feedback, a bit "tighter" with. At any rate, those KT88s are going to blow you away!
Good luck!
In addition to the projects of a different home, part of what stalled this for so long was that I got sick of listening to the commercial solid state amp that I had, and a few years ago bought a Fisher 400 through ebay to replace an identical one I had many years ago that I never should have sold. That sounded good enough that it was easy to leave this in the closet. But I expect this will sound better than the Fisher does. I hope it does blow me away. I've never heard an amp of this caliber, so I really don't know what to expect.
I looked at that big Hammond power transformer, but the lower voltage output of these units made it a little easier to get what I wanted. Plus now it's like two monoblocks on once chassis. This will be a class A push pull amp. I should be able to adjust the bias and also use EL34, 6550, and 6L6 tubes.
I also have a phono preamp chassis styled to match and completed to the same level this is. But I'll start with this.
I looked at that big Hammond power transformer, but the lower voltage output of these units made it a little easier to get what I wanted. Plus now it's like two monoblocks on once chassis. This will be a class A push pull amp. I should be able to adjust the bias and also use EL34, 6550, and 6L6 tubes.
I also have a phono preamp chassis styled to match and completed to the same level this is. But I'll start with this.
I share your story, sort of: I had a commercial solid-state amp that I thought sounded pretty fair. Got interested in using my sound card to rip my old LPs to CD, and in recording bits and pieces from our local classical FM station. I thought it might be fun to pick up an old tube amp, maybe something small- about 20 watts/ch or so. There was an old audio reseller nearby (Triode Electonics) that had an H.H. Scott 299B for sale. Slyly, they let me take it home for approval. Oh, WOW what a difference! Needless to say, I still have it...
Took me about six years part-time, entirely at my leisure (this IS a HOBBY, right?) to design and build my KT-88 amp. Started out as a 6L6GC AB2 design, wound up with KT88s. Glad I did!
I'm sure class A P-P will be fine, but consider this: If you go AB2 with the bias set to the recommended value in the spec sheets (50mA as I recall) then the amp will be entirely class A push-pull until you get to about 16-20 watts, at which time it will begin smoothly transitioning toward class B. -this is the "A" of class "AB". So really, most of what you're listening to is class A anyway, and only the peaks will be running AB2. For "normal"(??) listening levels, it'll still be class A P-P. Not really any audible difference, and the amp will run A WHOLE LOT cooler. Your KT88s will thank you.
As to the sound... Well! I'm just not gonna say. It'll be a surprise. You're gonna love it.
Took me about six years part-time, entirely at my leisure (this IS a HOBBY, right?) to design and build my KT-88 amp. Started out as a 6L6GC AB2 design, wound up with KT88s. Glad I did!
I'm sure class A P-P will be fine, but consider this: If you go AB2 with the bias set to the recommended value in the spec sheets (50mA as I recall) then the amp will be entirely class A push-pull until you get to about 16-20 watts, at which time it will begin smoothly transitioning toward class B. -this is the "A" of class "AB". So really, most of what you're listening to is class A anyway, and only the peaks will be running AB2. For "normal"(??) listening levels, it'll still be class A P-P. Not really any audible difference, and the amp will run A WHOLE LOT cooler. Your KT88s will thank you.
As to the sound... Well! I'm just not gonna say. It'll be a surprise. You're gonna love it.
One switch and one resistor seperates you from triode/UL mode if the tranni has the tap.
I used two switches per channel on an amp and could select pentode, triode, UL.
They all have merits and problems. Music type comes to mind! <<<power and party's
I would use a switch and give yourself a choice..I did after resoldering components a thousand times..wore out the soldering iron tip stripped the chassis screws<<worn out..Because I did not want to degrade the signal..
The switches might need replacing..
Used fixed bias and could use EL34, KT66, 6L6, Etc
then again just the switch or you will be forever trying different things..You don't know what you're missing....for ten years...I would not be able to sleep
Then again just to rub it in...your in the sweet shop.. and you could have 4 different amps built by now all different on a shelf ...try me try meeeee...LMAO
Regards
M. Gregg
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Here is a thought for you...You never heard an amp of this caliber...well you never will cuz you are ten years older..and this is going to eat away at you; how would it have sounded 10yrs ago when your hearing was better then than now!
Zoidberg Futurama!
LOL..how will it sound in another ten if it stays in the closet!
Ah well, perhaps its better..if you have never experienced it you can't miss it can you...
Sorry I can't resist..if you keep it in the closet long enough you can construct a brand new antique..it will be worth more,, LOL
Regards
M. Gregg
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Yes, thank you. And I think all or at least most of Hammond's output transformers have UL taps. I'll wire it for triode operation. I've lost my desire for high powered amps and am more interested in maximum quality.
This amp will sound better than a Fisher 400, won't it? Please tell me I'm right. Right? Right.
This amp will sound better than a Fisher 400, won't it? Please tell me I'm right. Right? Right.
Schematic? I looks like something I have planned to build within the next decade. I love 6SN7
I don't know if the board has policies about what can be posted. Most of the circuit came from Glass Audio publication. The power section could be said to have been modified to bring it to class A operation, or could be said to be based on a well known commercial design. The final circuit is my own combination of other people's ideas. I'm still drawing it, and some parts values may need to be tweaked after building and testing. Can such a thing be posted?
Best thing to do is start a new thread in the forum if you are not sure about the schematic ...as long as you have drawn what you are posting (not copied or scanned) put it up and let the moderators make the decision. They will just remove it if it has issues..Then again you will be commited to have to build it in 6 months or so...no pressure honest!
Regards
M. Gregg
Here is the schematic for the KT88/6SN7 amp. I had looked at different schematics for a long time and nothing seemed to be just what I wanted. This drawing takes ideas from three other schematics. I had originally wanted a fixed bias, but I went to a self bias here. Some parts values may need to be adjusted once it gets built and tested, but this is what I will start with.
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You can find the schematics here:
http://www.diyaudio.com/forums/instruments-amps/190738-hundred-buck-amp-challenge-128.html