Hi Tony,
Nice, a custom design. All you need is a good metal shield and you are all set to go 🙂 Not necessary but they are nice when in a metal casing.
Interesting 230VAC only primary. I guess it saves a bit on construction costs not needing a dual primary too.
As a comparison, I bought a Triad (VPT100-5000) 500VA/50-0-50V toroid from Arrow, free shipping, for $105 CDN (~$84USD) + 13% tax. Excellent value but I was wanting something closer to 800VA, shipping can be a good portion of the cost. This is good enough for testing and most apps.
The triad is rated 115V/230V, my line is 121VAC, getting +/-75V, no load.
Take care
Rick
Nice, a custom design. All you need is a good metal shield and you are all set to go 🙂 Not necessary but they are nice when in a metal casing.
Interesting 230VAC only primary. I guess it saves a bit on construction costs not needing a dual primary too.
As a comparison, I bought a Triad (VPT100-5000) 500VA/50-0-50V toroid from Arrow, free shipping, for $105 CDN (~$84USD) + 13% tax. Excellent value but I was wanting something closer to 800VA, shipping can be a good portion of the cost. This is good enough for testing and most apps.
The triad is rated 115V/230V, my line is 121VAC, getting +/-75V, no load.
Take care
Rick
Hi Tony, I've also considered adding a transformer like this. Does it make sense to put this in its own metal housing and the power amplifiers in a different housing in order to minimize hum interference?
I'm waiting for a custom Toroidy transformer as well. A 800VA 230V prim and 4x40V sec supreme audio grade. The total cost incl shipping and taxes was around $370-380. That also inklues a 20VA 2x12V audio grade transformer.
The transformers metal case is stainless steel non magnetic. You still need some housing to reduce magnetic induced hum...
Does this matter that much? Doesn't a non magnetic material also reduce stray by presenting a short circuit winding to it? See the copper belly bands around many transformers.
Best regards!
Best regards!
Non-magnetic shields only work when they are thicker than the skin depth of the frequency to be rejected. So copper gauss bands generally only work on HF noise (EG treble) and not at 60Hz. Magnetic steel however works even at DC.
Dear Toni,
I have built SA2014 and I am listening to it quite frequently, however I have still difficulty with setting iddle current in the output stage. The right channel is working properly all the time. It is set to 40 mV through 2 emiter resistors, i.e. 42 mA per output device.
However the left channel iddle current is not stable. If I set it to 40mV per emitter resistors, it gradually rise up to 110 mV. If I set it to 35 mV then it gradually decrese down to 3 mV. The sound is allways excellent, does not matter what iddle current is there. I am not able to find out what is the reason. Maybe some part is damaged since I during testin I have made some stupid mistakes. Is there any idea what could improve this state?
Thanks a lot,
Ladislav
I have built SA2014 and I am listening to it quite frequently, however I have still difficulty with setting iddle current in the output stage. The right channel is working properly all the time. It is set to 40 mV through 2 emiter resistors, i.e. 42 mA per output device.
However the left channel iddle current is not stable. If I set it to 40mV per emitter resistors, it gradually rise up to 110 mV. If I set it to 35 mV then it gradually decrese down to 3 mV. The sound is allways excellent, does not matter what iddle current is there. I am not able to find out what is the reason. Maybe some part is damaged since I during testin I have made some stupid mistakes. Is there any idea what could improve this state?
Thanks a lot,
Ladislav
If I use the right IPS for the left OPS, the idle current is stable 🙂. So it seems that the problem is in IPS.
The only difference between these two IPS are the LED diodes in current sources. The LED is there instead of D1 and D2 in the original scheme.
In the "better" one there is green LED and R27 is 56 ohm (R7 is 150 ohm). In the worse one there is red LED and the T27 is 27 ohm and R7 is 82 ohm as originaly suggested.
The only idea in my mind is to change red LED for the green one and adapt the resistors R7 and R27 to set proper currents.
The only difference between these two IPS are the LED diodes in current sources. The LED is there instead of D1 and D2 in the original scheme.
In the "better" one there is green LED and R27 is 56 ohm (R7 is 150 ohm). In the worse one there is red LED and the T27 is 27 ohm and R7 is 82 ohm as originaly suggested.
The only idea in my mind is to change red LED for the green one and adapt the resistors R7 and R27 to set proper currents.
The green LED is mandatory! The red LED has a different throughput voltage and another temperature curve!
Use exactly the same type of green LEDs and the recommended resistor values as shown in post #2028
Have fun, Toni
Use exactly the same type of green LEDs and the recommended resistor values as shown in post #2028
Have fun, Toni
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Many thanks!!!
I changed mentioned resistors and it is stable now. Now I will enjoy from the music without any wories about imperfect construction.
I changed mentioned resistors and it is stable now. Now I will enjoy from the music without any wories about imperfect construction.
Listening experience
After quite a long listening of various kind of music I want to express my opinion on the sound of ASTX SA2014 amp.
I have built my first amp in 1986 and since then approximately another 10 amps. Those that I had built and I was satisfied with the performance I have accomodated into the appropriate box. (A75 from Nelson Pass, then my variation of supersymetric topology based on Pass findings, Mr. Dudek DPA222, Hypa 17 from Mr. Stranka, Hybrid amp from Mr. Vzaichenko, another one CFA from Mr. Dadod). My reference amp up to now was HYPA 17 - that is blameless topology with JFET at the input and tripple bipolar output stage. So here is my direct comparison between these two amps.
At very low and low volumes SA2014 sounds more lively, bit more exciting music. No one of them is disturbing if used for background music. So minor preference for SA2014, here. At moderate volume level I could not find any difference. Definitely the blind test would not be the case for the comparison. At high volumes was the biggest difference. SA2014 is playing deeper bass and quite often I feel that I should remove my speakers (Troels Gravessen Ellam Flex 3W) for another ones with bigger bass cone. It plays very well controlled bass, real pleasure to listen to. If I go to even higher volumes (not normal, very rarely) then Hypa 17 seems to be more friendly to my ears. SA2014 is probably playing as it should be but acoustic pressure from the tweeter is bit earlier sending me out from the listening room.
Final conclusion - it the best amp I have ever listen to. I would even argue with my friend, that SA2014 outperforms his expansive Accuphase amp. I recommend to build it for everybody, who wants to hear reference amp.
Ladislav
After quite a long listening of various kind of music I want to express my opinion on the sound of ASTX SA2014 amp.
I have built my first amp in 1986 and since then approximately another 10 amps. Those that I had built and I was satisfied with the performance I have accomodated into the appropriate box. (A75 from Nelson Pass, then my variation of supersymetric topology based on Pass findings, Mr. Dudek DPA222, Hypa 17 from Mr. Stranka, Hybrid amp from Mr. Vzaichenko, another one CFA from Mr. Dadod). My reference amp up to now was HYPA 17 - that is blameless topology with JFET at the input and tripple bipolar output stage. So here is my direct comparison between these two amps.
At very low and low volumes SA2014 sounds more lively, bit more exciting music. No one of them is disturbing if used for background music. So minor preference for SA2014, here. At moderate volume level I could not find any difference. Definitely the blind test would not be the case for the comparison. At high volumes was the biggest difference. SA2014 is playing deeper bass and quite often I feel that I should remove my speakers (Troels Gravessen Ellam Flex 3W) for another ones with bigger bass cone. It plays very well controlled bass, real pleasure to listen to. If I go to even higher volumes (not normal, very rarely) then Hypa 17 seems to be more friendly to my ears. SA2014 is probably playing as it should be but acoustic pressure from the tweeter is bit earlier sending me out from the listening room.
Final conclusion - it the best amp I have ever listen to. I would even argue with my friend, that SA2014 outperforms his expansive Accuphase amp. I recommend to build it for everybody, who wants to hear reference amp.
Ladislav