I built a few prototypes with non-transformer filament supplies. The issues above ultimately lead me to only using power transformers. Its a lot easier
Taking the OTL VT Concept to the Next Level: NO Transformers
- Thread starter Mark (Basspig) Weiss
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I built a few prototypes with non-transformer filament supplies. The issues above ultimately lead me to only using power transformers. Its a lot easier
I built a few prototypes with non-transformer filament supplies. The issues above ultimately lead me to only using power transformers. Its a lot easier
Yes, it IS easier, but the object of this project is not to be easy, but to do something never done before.
Mark,
Are you referring to the 6P45s anode current? I usually find it specified maximum as 800 mA in pulsed mode in old russian data sheets.
I'm referring to the current curves on the data sheet, pages 2 and 3. Some of the curves reach 1800mA. The actual current will depend on the circuit operating conditions, of course.
Yes, it IS easier, but the object of this project is not to be easy, but to do something never done before.
If you mean, build an amplifier with no power transformers you're a little late to the party. Did you ever here of that KSS amplifier from about 15 years ago?
Yeah I did. They received some press and then disappeared. Whatever happened to them?
No, I haven't. To be frank, I stopped following the consumer audio industry in the late 1980s, cancelled my subscriptions to all the magazines. Heck, a few years ago, some guy was telling me about his "Wilson" loudspeakers. I had no clue as to what he was talking about. I knew Wharfdale, Bozak, Klipsch and more recent comers like Cerwin-Vega, but the name Wilson was not on my radar. Then I found out is was a new startup, only since 1992, which explained why I hadn't heard of them. Same goes for this "KSS" that you mentioned. Frankly, I thought it was impossible to get UL listing on any electronics that connect directly to the AC power line under the new rules that banned the American Five radios.
Not them- him. As I understand it he went to prison. Nothing to do with the amp as I recall, but my recollection is hazy.
I'm pretty sure that the KSS amp would not have gotten UL approval. I think he did wind up selling them with an isolation transformer... but the amp did run- I heard them a couple of times at CES. He ran his power tubes really cold. The envelopes were almost touching each other.
Now that I'm 'officially' in the amplifier repair business, I get to see quite a few amplifiers. I, too, thought that direct connect line powered amplifiers were a thing of the past, but I was mistaken. Case in point: a Mirage SS-1000 Sub Strata subwoofer. The amplifier is one of those 'digital' amps. The power supply connects directly to the line---there are no power or isolation transformers. This unit is made in Canada, and the woofer that it drives has a DC resistance of 29?. Quite an odd duck, when you consider that a typical 8? impedance woofer has a DCR of 6.4?. I suppose they get away with it because the woofer is enclosed and the terminals not accessible to the user. The inputs are isolated from the power supply by ferrite coils with wires looped through them to transfer power, where it is rectified on each PCB. Very unusual.. kinda reminds me of something Nikola Tesla might do, on a small scale.
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