Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Zarrir on December 17, 2016, 01:28:16 am
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Hi Valvefreaks. I was looking at the bellow Melvin Leibowitz 1961 design. So simple, 6watt per channel. My question is, can this be considered HIFI based on the current standards?
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Cork sniffing HIFI, probably not by todays standards, but to play normal ppl music, should do fine.
for my "HiFi" I used a 6sn7 driver, UL taped OT, but I used QuadSE 84's and SS rectifier, still wouldn't pass the cork sniff test though, but she rocked a pair of audio Nirvanas quite well!
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This was cheap "fidelity" even in 1961. Poor push-pull. NO speaker damping.
May be a fun project. May "bring out" (or add) things you never heard in your records. But far from a transparent playback amplifier.
Nicely drawn, though.
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http://www.r-type.org/articles/art-003h.htm (http://www.r-type.org/articles/art-003h.htm)
I know they were selling tubes, but still I doubt Mullard would have gone through all this effort way back when if it didn't matter, and they also demanded quality iron which they didn't sell.
Resolution is like a drug, you can't enough.
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My understanding is as follows. Until about 1962, OT's didn't have the full audio spectrum of frequency response. They had about 100Hz -to- 8K or 10K Hz, out of 20Hz to 20K Hz. However, that limited range is fine for most human voice and mid-range instruments.
Another factor is THD = Total Harmonic Distortion. This is a bit misleading as it includes all noise and harmonic additions not present in the pure signal input to the amp. About 2% THD is considered acceptable with 5% borderline unacceptable. SS amps have no OT to limit frequency response; none of the hiss & noise which tubes tend to have at least some of; and can have THD at tiny fractions of 1%. Despite the textbook specs, many people prefer the sound of tube amps, even though SS amps score better technically.
Some hi-end tube hi-fi amps like the Harman-Kardon Citation II do have very low THD. But they are said to sound sterile to some ears.