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Deleted member 50971
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The Fisher is fun, and I have a couple FM tuners that I run into it, as well as play some vinyl through it. Not necessarily transparent hi-fi, but it works well for what it is.
A series resistor will affect the FR. Not recommended. Better to get a suitable amp in the first place. Muscle amps from the 1980s-90s should work well. Big Haflers, Krells, dBx, et al…..Acoustats and SLs used the same split xfmr arrangement with similar impedance. Very high at low frequencies and less than an ohm at 20 khz. I could have told you the EAR would be less than good on either. I've never had hands on with Wolcott. Big mosfet amps and tube amps usually work. VTLs, ARs, C-Js. The best thing I've found for them is class D amps. With some large bipolar amps I've found adding a .5 ohm or 1 ohm power resistor in series will make the amp happy. If you intend to make it permanent you can just put it in series with the high frequency transformers.
Looks very respectable! Frankly, I can't think of a commercial offering that even comes close.I've been following a couple of DIY project at a Swedish site by a competent designer that I know and if I just had a bit more space and interest I would probably have tried to build one of the projects, just for fun:
The tube power amp (more measurements will come):
The tube pre amp including a separate RIAA tube amp:
Agreed. I have not seen such good performance for tube gear, but I also have not looked around very much either. Nevertheless, it is probably among the best you can get.Looks very respectable! Frankly, I can't think of a commercial offering that even comes close.
Positron vacuum tubes never did catch on.SS amps usually have lower distortion due to higher feedback, which in turn is available because of their designs' higher open-loop gain (often because complementary devices are more readily available).
I have a very vague memory of some very exoteric materials research for complementary tubes but my comment was poorly worded. I meant complementary transistors, of course, but obtaining matched p- and n- devices is still challenging. Mobility and all that jazz...Positron vacuum tubes never did catch on.
Still farrrr better than it was in the bad old days of quasi-complementaryI have a very vague memory of some very exoteric materials research for complementary tubes but my comment was poorly worded. I meant complementary transistors, of course, but obtaining matched p- and n- devices is still challenging. Mobility and all that jazz...
At 12k the 509 ought to be good!McIntosh MC 3500. reviewed in Electronics World in the late 1960s. Measured THD under 0.1 % from 20-20kHz at full power, 350w.
McIntosh MC 275. My own unit measured under 0.1 % THD at 75 W, 20-20 kHz both channels driven when tested at one of Mac’s amplifier clinics in the 1970s.
Luxman 3045. Tested in the 1970s.
Marantz 9 and 8B also met the under 0.1% THD 20-20kHz at rated output ppower benchmark.
The EAR 509 also has very low distortion based on tests. Around 0.1% THD at full power. It is probably the only currently produced valve amp that is is the same class as the old Lux or Marantz or McIntosh amps.
You're right, although a lot of mega-buck tube amps measure pretty awful.At 12k the 509 ought to be good!
Stereophile tested the Dynaco ST-70 (version 2) in 2004. Thomas Norton's results are a bit different. His level sweep only goes down to 100mW, but at that level he measured a THD+N of 0.09%, with the result obviously dominated by noise. The wideband SNR @1W/8ohms was 60dB.Here is the current Dynaco STA-70 version 3
https://stereo-magazine.com/archive/articles?tx_archive_pi1%5Baction%5D=download&tx_archive_pi1%5Barticle%5D=68836&tx_archive_pi1%5Bcontroller%5D=Archive&cHash=ef9ea05d15a2e49ba5313e38e4aae02c
At 50 milliwatt, 0.008% THD and SNR 81.2 dB
I doubt there's too much difference between version 2 and 3.
Same basic design. Both use proper solid-state rectifiers. V2 uses a 6GH8A input tube, V3 uses an EF86. It's hard to find anything that would indicate radically lower noise, especially seeing the innards of the V3. As I said, it's a competent design.Why?
well -- not in this section of space-time, no...Positron vacuum tubes never did catch on.
I couldn’t see any details of the output transformer or the schematic.I've been following a couple of DIY project at a Swedish site by a competent designer that I know and if I just had a bit more space and interest I would probably have tried to build one of the projects, just for fun:
The tube power amp (more measurements will come):
The tube pre amp including a separate RIAA tube amp:
It is there in a link in the below post but I am not sure you can reach the documents if you are not a member of the forum.I couldn’t see any details of the output transformer or the schematic.