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Hi, I made a few passive preamps.One uses 2 Alps Black Beauties 100K left and right.The other uses 2 50 K pots,Bournes,that are stepped pots.They make little clicks whe rotated. Which way would you go? I don't know if I could tell the difference.Which is the better pot to use.The Alps have never made a click or pop or been lubed.Thanks for any input.....Mark Korda
Follow Ups:
I build my own gear so don't use a preamp. I just put the added gain stage at the input to the amp. I replaced the Precision Electric 100k attenuators with 100k Goldpoint stepped attenuators in one amp I built and was using regularly. The difference was not subtle so I ended putting them in each amp I build: three more so far.
hi Palustris, I made another passive preamp using Goldpoints but it was transformer implemented. I saw a simple article in AudioXpress.One thing bothered me.It was an outcry from Mark Levinson I read; Keep transformers out of the signal path! I made it in a Dyna PAM metal chassis.It sounds good but Levinsons statement put a psychological hex on it.Thanks Palustris....Mark Korda
Ninety percent of tube amps have a transformer in the signal path. Only the rare output transformerless amps don't have a transformer in the signal path. Some amps use a driver transformer to drive an output tube that generates considerable grid current and some use an input transformer.
BTW: nice preamp
Exactly!
And did Levinson also condemn the step-up transformers which many moving coil cartridge users seem to prefer, I wonder? I'd have to see his actual quote to better understand the context. Perhaps it had something to do with the implementation of the particular transformers recommended in the AudioXpress article that he was opposed to. All transformers certainly aren't equal in 'sound quality', something Levinson certainly had to have been aware of.
I'd love to listen to music without transformers, capacitors, etc. in the signal path, but I could never afford to pay the Rolling Stones to do an acoustic set in my living room.
Hi Palustris, Are the 10 percent of tube amps you mentioned something like the Julius Futterman amps? I have some older literature called Tube God.I think Harvey Rosenberg put it out. He was an editor for Listener mag.,Art Dudley was the main guy for that mag.I can't spell magazine...-Mark
Yes, the Futterman amps are exactly what I was referencing and the ten percent was really just a wild guess; probably more like 5%. Rosenberg (New York Audio Labs) marketed Futterman style amps for a while. I believe that Atma-Sphere Music Systems is the only current builder of output transformerless amps and they are very well respected by those that use them.
There are really only two different types of OTL amplifiers, the Futterman type, formerly produced by companies such as Futterman, NYAL, Prodigy, Counterpoint, KSS, and Sans Pareil (I think that's a model name, not a company name), and going back in time, Luxman. All of those are basically Futterman amplifiers with some modifications to his original patent. Then there are OTL amplifiers that use a circlotron output stage, and to my knowledge, there is only Atma-sphere in that category. The Futterman circuit places capacitors in series with the output, in order to keep DC out of the speakers. The circlotron output stage places PS capacitors in parallel with the audio output. I've owned 2-3 different Futterman amplifiers and for the past 30 or so years I have been using Atma-sphere amps to drive ESLs. There is another company out of N or S Carolina that made OTLs; they were a major player, but my mind has gone blank on the name. I think those were circlotron types also. Then also BAT makes or made circlotron amplifiers but with a transformer coupled output.
Edits: 11/24/24
That's the name of the other company that produced OTL amplifiers with circlotron output stages, I think. They are out of business, so far as I know, but the amplifiers are still in use.
Hi Shovel,The Mark Levinson comment was not from the AudioXpress article and project.It is somewhere in my stack of stuff. I'm glad you explained the transformer issue.In the article were mentioned 2 different transformers and where you could buy them.I'll dig it out tonight with some more info...-Mark
If so, you might try switching to "Classic", as indicated by the red arrow in the first picture above. With that view, it makes it much easier to see that you're responding to Lew's reply, and not to mine, as shown in the second picture (below). I nearly didn't see this, so the Classic view might save you some grief in the future if you're wondering why a person isn't responding to you.
Hi Shovel, after I read your note I put the transformer implemented passive preamp back in my bedroom set up.Electroprint was the name of the transformer co. Jack Eliano was the head and article writer.I have not found the article yet but I do have it.There were 2 transformers recommended.There was a nickel core and a more expensive silver core.I opted for nickel. There were plenty of specs in the article.I will find it...-.Mark
Hi Palustris, here is the front....Mark
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