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I have RCA 2A3 gray and black double plate tubes. I am thinking of purchasing the new Sovtek 2A3s as future replacements. One tube enthusiast said the new Sovtek does not sound as good as the 2A3s. Any other opinions?
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Thanks Jack. I have four RCA 2A3 double black plates with the RCA 2A3 double gray plates as well. Please read '2A3 Operating Parameters' listed below. Fixed vs cathode bias. Jim
I have both RCA & Sovtec 2A3's. I used to think that the RCA's were in a different league. However I decided to store my RCA's and use the Sovtecs while I built another amp. Well after about 200 hours of playing the Sovtecs suddenly bloomed. Overnight they had far more extended bass and sweeter top end with a fuller midrange. Recently I compared them against the RCA's and now find I prefer the Sovtecs. That probably goes in the face of opinion.
Try the Sovtek at 45 operating points.Very nice.
There is no other 2A3 or 300B tube in current production or RCA double plater that can compare with the Sovtek if in 45 mode (250V, 1.5K resistor)Enjoy!
Is it because of running them at the 45 load (5K primary) vs a 2A3 load (2K5)? Doing so might lower the distortion a bit.Just wonderin' aloud.
-Steve
I read this before on the web. How does the amp on Angela Instruments' wob page look for this. "A Simple SE 45/2A3 Amp for First Time DIYers" @ www.angela.com.Also, any thoughts about underdriving a 300B or 245.
... 300B or 845.
The Sovtek 2a3 has a bight clean sound more like its brother Sovtek 300B, but it certainly misses something, that magnetic subtlety of the RCA double plate.
Doc, your responce is the same as the other gentleman explained to me. I will continue to purchase RCA 2A3 double plates, Jim
Interesting. I designed my DIY 2A3s to operate at 275 volts (plate), -56 volts (grid) and 2.3 vac (filament). I calculated the % 2nd-harmonic as follows:
%2nd-harmonic distortion = Imax+Imin/2-Io= X then X/Imax-Imin(X)100This was calculated from the RCA 2A3 plate curves. As the operating points are changed, the output distortion can double with, for example, a 5 volt change in grid bias under some conditions. My design is fixed bias with a regulated B+ supply. I have not an idea if this fixed bias will sound better, but does stabilize the tube. Another interesting specification is that the RCA Technical Series RC 15 Receiving Tube Manual dated 1947 states in PP 50% more power out is available at 50% less distortion with fixed bias! Jim
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