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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.
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Best measuring tube amp
- Thread starter gruefellow
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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…..
Some are reasonably priced on the second hand market.
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Here is the current Dynaco STA-70 version 3
At 50 milliwatt, 0.008% THD and SNR 81.2 dB
Marantz PM-10, bridged HypeX nCore NC500
At 50 milliwatt, 0.080% THD and SNR 77 dB
Accuphase A-47, pure Class A amp
At 50mW 0.050% THD and SNR 75 dB
Cambridge Edge A, Class XD
At 50 mW, 0.010% THD, SNR 71.4 dB
Bryston 4B3, Class AB
50 mW, 0.050% THD 61.2 dB
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At 50 milliwatt, a 93 dB/2.83V efficient speaker will hit 81 dB if you are 6 ft away, have the speakers near a wall and are listening to two speakers. In your mind, this is like -24 on a calibrated home theater receiver.
This shows that the Dynaco at 0.05W out measures HypeX NC500’s that are bridged (albeit a Marantz PM-10 which may have music tuning), a reference class A amp, reference class AB amp, and an exotic Class XD amp.
@amirm , I know it is apples to oranges when comparing THD from a website where we have no idea how they measure, but how would a AHB2 or LA90 do at 50 milliwatt with your tests?
Clearly the solid state amps outpace the Dynaco’s once you get to 5W, but the criticism of the LA90 and AHB2 has always been power. I wonder if they beat tubes even at 50 mW.
@SIY, @B&WTube
At 50 milliwatt, 0.008% THD and SNR 81.2 dB
Marantz PM-10, bridged HypeX nCore NC500
At 50 milliwatt, 0.080% THD and SNR 77 dB
Accuphase A-47, pure Class A amp
At 50mW 0.050% THD and SNR 75 dB
Cambridge Edge A, Class XD
At 50 mW, 0.010% THD, SNR 71.4 dB
Bryston 4B3, Class AB
50 mW, 0.050% THD 61.2 dB
—-
At 50 milliwatt, a 93 dB/2.83V efficient speaker will hit 81 dB if you are 6 ft away, have the speakers near a wall and are listening to two speakers. In your mind, this is like -24 on a calibrated home theater receiver.
This shows that the Dynaco at 0.05W out measures HypeX NC500’s that are bridged (albeit a Marantz PM-10 which may have music tuning), a reference class A amp, reference class AB amp, and an exotic Class XD amp.
@amirm , I know it is apples to oranges when comparing THD from a website where we have no idea how they measure, but how would a AHB2 or LA90 do at 50 milliwatt with your tests?
Clearly the solid state amps outpace the Dynaco’s once you get to 5W, but the criticism of the LA90 and AHB2 has always been power. I wonder if they beat tubes even at 50 mW.
@SIY, @B&WTube
Oh well, 3500 Euros for an updated version of an amp that cost $69.99 back in the day.
Yes, tubes and high voltage caps are expensive now, but still……
Not sure what measuring technique Stereo Magazine uses, but it is possible that the reported 50 maw distortion numbers for the SS amps are noise limited, and not a true measure of the distortion.
Yes, tubes and high voltage caps are expensive now, but still……
Not sure what measuring technique Stereo Magazine uses, but it is possible that the reported 50 maw distortion numbers for the SS amps are noise limited, and not a true measure of the distortion.
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:
The tube power amp (more measurements will come):
The tube pre amp including a separate RIAA tube amp:
faktiskt.io • Visa tråd - GDS-projekt: rörförsteg - LEVERANS!!
www.faktiskt.io
charleski
Major Contributor
Looks very respectable! Frankly, I can't think of a commercial offering that even comes close.
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.
Positron vacuum tubes never did catch on.
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...
Still farrrr better than it was in the bad old days of quasi-complementary
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At 12k the 509 ought to be good!
You're right, although a lot of mega-buck tube amps measure pretty awful.
charleski
Major Contributor
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.
It's a competent result for a tube amp, and shows how commercial tube offerings haven't really progressed over the past 4 decades. But easily outclassed by modern SS designs. I wouldn't like to speculate on why Stereo Magazine got such radically different results (though they cite the same max power), but I doubt there's too much difference between version 2 and 3.
Why? The ST-70 is like the Porsche 911. Same in name, but not really the same. Same fundamental rear engine, flat 6 topology.
The Dynaco brand is like Polaroid, it’s gone through different owners. The Version 2 and Version 3 are made by two different companies. Panor made version 2. Radial Engineering made version 3.
The SFS-80, VTA-70, and ST-70 Version 1 are all Dynaco ST-70 variants
Review and Measurements of Dynaco ST 70
This is a review and detailed measurements of the vintage Dynakit Dynaco Stereo 70. It is on kind loan from a member who bought it used online and repaired it. Previous owner hand upgraded it but could not get it working. Given that it is 60 years old, one can forgive the rust and dust...
www.audiosciencereview.com
VTA ST-70 Review (Stereo Tube Amplifier)
This is a review and detailed measurements of the Bob Latino's take on Dyna ST-70 stereo tube amplifier. I believe (the kit?) costs US $1,430. This unit was bought used for around US $900. The polished stainless steal case looks very nice. The three transformers give it substantial weight...
www.audiosciencereview.com
Sonic Frontiers SFS-80 Review (Vintage Tube Amplifier)
Sonic Frontiers SFS-80 Tube Amplifier: A "new" benchmark to beat from 1992 Up next on testing gear that would be impossible to ship safely... the Sonic Frontiers SFS-80 tube amplifier. 70 lbs, all concentrated in the transformers. Believe it or not, Sonic Frontiers is a company we all know...
www.audiosciencereview.com
charleski
Major Contributor
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.
mhardy6647
Grand Contributor
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well -- not in this section of space-time, no...
I couldn’t see any details of the output transformer or the schematic.
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 think the tranformer is this one:
Hammond Audio Transformer 1.9K OHM 280 WATT 1650W, 424,08 €
Hammond Audio Transformer 1.9K OHM 280 WATT 1650W in Audio transformers, Hammond, Classic Tube Transformers, Push Pull - Ultra Linear up to 280 Watts.
www.don-audio.com
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