I wondering if one can run two SUTs in series to achieve higher gain? I have a very nice sounding phono-stage using D3A > 5687 but even with a 1:20 Sowter SUT I am just getting marginally enough volume. I built it with octal mounted transformers and 1:20 is as high as they carry. I bought the 1990s which can be switched between 1:10 and 1:20. Si I'm thinking I could add another stand alone SUT and feed that output into my phono stage.
Thoughts?
Thoughts?
Wouldn't the reflected load be all wrong with two transformers wired in series? You must have an extremely low output cartridge?
jeff
jeff
A) you got two, right? Try It!! Build a mono cascade. Sure the 'stereo' imaging is flat but how is the spectral balance?
B) it is pretty sure to be short in highs or lows or both. Transformers do not "have an impedance" but frequency response and impedance go together in transformers and getting far off optimum will suck.
Find more electronic gain. FET, tube, chip, etc.
B) it is pretty sure to be short in highs or lows or both. Transformers do not "have an impedance" but frequency response and impedance go together in transformers and getting far off optimum will suck.
Find more electronic gain. FET, tube, chip, etc.
I would have to change the load resistor I am sure but that is easy. The phono-stage output is lower than I expected that is also for sure. The cart is a Per Winfield which has an output of 0.4mV. The frequency response sounds excellent so I believe my build is sound.
One would think a cart output of 0.4mV shouldn't need more than a 1:10 SUT (which gives 4mV) - however, Ortofon's recommendation for a SUT for the Per Winfield is their ST-80 SE ... which has a gain of 27dB (ie. 1:22).
This is only marginally higher than your 1:20 Sowter - so the volume problem would seem to lie with your phono stage? Does it have less gain than the standard 40dB (100x)?
Andy
Depends how "basic" your equipment is! 😀
You need:
1. something to generate a signal: I use a signal generator - but if you don't have one of these, maybe you can get an app for your phone which will generate a 1kHz tone?
If so then use a "3.5mm barrel plug to 2x RCA plugs" cable to take the output from your phone into your phono stage.
2. something to measure the output signal with: I use a CRO but a multimeter that can measure a few thousand mV, AC will do.
Output level / input level will give you the 'x gain' ... I can convert that to dB gain for you. Default gain for an MM phono stage is 100x = 40dB.
Andy
Sorry - 'Cathode Ray Oscilloscope'. 🙂
(So you can see the waveform on a gridded screen, instead of having to measure it with a meter.)
Andy
I asked my Idiot. The only well-modeled transformer in its poor selection is a beast, with many taps for the Idiot to whine about, but the Zs and ratios are not too-too-far-off, and we want the trend not the banker's answer.
Dyna OT run backward, fed from 1 Ohm and loaded with a bit less than nominal plate-size Z, gives the expected wide flat response with a loaded gain of 13.7 (16.4 unloaded).
Two of these in cascode, the I and Cs are wrong. We do get a higher step-up ratio but only mid-band (proving this was a balanced design favoring neither highs nor lows). The -3dB bandwidth is like 200Hz to 2kHz, bad pocket AM radio response.
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OK. Thanks. I do have an oscilloscope as well as two DMVs. When I try and measure the output of the basic frequency generator I get just a flat line on the oscilloscope and not the sine wave I expect. When hooked up to either DMV, I get 0.00mV. I'm not sure what I am doing wrong here.
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Hi, WntrMute2
Contact Jack Elliano ( Electra-print audio ) or Sowther and have a custom (proper) transformer wound. You can always select a different MC cartridge of similar quality. I think a series connection of 2 transformers will be a compromise.
Contact Jack Elliano ( Electra-print audio ) or Sowther and have a custom (proper) transformer wound. You can always select a different MC cartridge of similar quality. I think a series connection of 2 transformers will be a compromise.
Got some measurements. Used an online frequency generator set to 1kHz. Output to phonostage to 4.7mV. Output of phonostage 590mV. Used two DMVs not oscilloscope since I can't get a reading off of the frequency generator I have.
The typical D3a+5687 phono has about 30..34 dB gain.
With 1:20 SUT the gain it's just enough (with higher output MM cartridge), but in the lower side.
Using 5687 in two stage phono IMHO is mistake, no have enough gain.
If it works as the CF after the second stage, it's a perfect solution.
If you use D3a as pentode, achievable the 40dB gain, but (IMHO) the quality deteriorates compared to trioded.
With 1:20 SUT the gain it's just enough (with higher output MM cartridge), but in the lower side.
Using 5687 in two stage phono IMHO is mistake, no have enough gain.
If it works as the CF after the second stage, it's a perfect solution.
If you use D3a as pentode, achievable the 40dB gain, but (IMHO) the quality deteriorates compared to trioded.
D3A is wired as a triode. Using only one half of the 5687 in each stage. Friend with almost exactly the same setup has plenty of volume. Same phono stage, same cartridge, same preamp, 300b amp (mine) vs 2A3 amp his. Similar Altec speakers.
So your phono stage gain is 125x (590 / 4.7). This equates to just under 42dB - which is perfectly normal.
So I wonder what is going on, given you're not getting a sufficient sound level?
Andy