Sound?
First I want to say thanks to everyone on this forum that helped me out. Particularly Mikael Abdellah whose schematic I used with only a very small modification, Frank, Sch3matic, SY, Dave (Planet10) and lots of others. This wouldn't have been possible without this forum! Thanks everyone.
So far I've only tested it with a cheap speaker. Input is from my preamp connected to a CD player. When the other one is finished and I have some proper bases I'll bring 'em up and test with better equipment.
First of all the amp is absolutely quiet. No hum or buzz whatsoever from the speaker, even with my ear inches away. Second the sound, even with my cheap test speaker is pretty amazing. Bass extension is excellent, highs are crisp and the midrange is very good. Diana Krall, even in mono sounds great.
Nothing exotic in the construction. 1/8" aluminum top plate sanded with 320 grit wet/dry sandpaper and sprayed with a couple coats of clear gloss acrylic. Power iron is a Hammond 273BX and a Hammond choke (8 henry) filtered with ASC oil caps. A .22uF Auricap coupling cap between the Svetlana 6N1P driver and the Valve Art KT88. Rectification courtesy of a 5U4-G (which looks great too).
The best part may well be the James 6123HS output transformer. I had a difficult time deciding between the James and a Hammond 1628SE but I am very happy I went with the James, even though it meant painting the Hammond iron to get some sort of match.
I'm anxious to get started on the twin so I can listen in stereo!
First I want to say thanks to everyone on this forum that helped me out. Particularly Mikael Abdellah whose schematic I used with only a very small modification, Frank, Sch3matic, SY, Dave (Planet10) and lots of others. This wouldn't have been possible without this forum! Thanks everyone.
So far I've only tested it with a cheap speaker. Input is from my preamp connected to a CD player. When the other one is finished and I have some proper bases I'll bring 'em up and test with better equipment.
First of all the amp is absolutely quiet. No hum or buzz whatsoever from the speaker, even with my ear inches away. Second the sound, even with my cheap test speaker is pretty amazing. Bass extension is excellent, highs are crisp and the midrange is very good. Diana Krall, even in mono sounds great.
Nothing exotic in the construction. 1/8" aluminum top plate sanded with 320 grit wet/dry sandpaper and sprayed with a couple coats of clear gloss acrylic. Power iron is a Hammond 273BX and a Hammond choke (8 henry) filtered with ASC oil caps. A .22uF Auricap coupling cap between the Svetlana 6N1P driver and the Valve Art KT88. Rectification courtesy of a 5U4-G (which looks great too).
The best part may well be the James 6123HS output transformer. I had a difficult time deciding between the James and a Hammond 1628SE but I am very happy I went with the James, even though it meant painting the Hammond iron to get some sort of match.
I'm anxious to get started on the twin so I can listen in stereo!
rdf said:
Glad to hear you got them! My amp is connected ultralinear also.
The Hammonds I received had a very poor level of finish with some spots and runs. The bolts holding the bells on appeared to have been cut to length with wire cutters. Even if I had gotten black James transformers I probably would have repainted the Hammond iron.
You are right about the James units. The quality of the finish is superb and based on my limited listening so far the guts must be equally well done.
resident said:
I didn't want to post it in the photo gallery until I have the other one done and real bases built.
Yes, I used 2 conductor shielded wire from the input jack to the first tube. It is just a spool I picked up at Radio Shack. I like it because the shield is stranded copper instead of foil like some brands. It is easy to twist the shield into a thin wire and to solder.
Mikael Abdellah said:Really nice job!
I'm glad you like the amp. I think it's a great amp, and I can't understand why no one had made a simple schematic like that before me.
Mikael,
Thanks again for the schematic. I think I mentioned when I first saw it that I had been planning on building a single ended design with ECL82 tubes. But when I saw your schematic it was only a bit more involved than the ECL82 and I knew it would be a nicer amp. I'm glad I built it. It sounds great.
Today I drilled the top plate for the second monobloc. I should have everything mounted and wired up in a couple days. Then I have to decide on the wood for the bases. Maybe cherry.
I also put the scope on the completed one for some preliminary testing. At 1 KHz it appears to be making about 8 watts before clipping! That's a bit more than I expected. I haven't yet tested output at other frequencies.
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