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| Romy the Cat's
personal site dedicated to advanced audio and evolved music reproduction
techniques
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[quote user="drdna"] It will be a little project to modify the amplifier, but it may be educational. To optimize the Moondog circuit for the NOS 2A3 tubes, so they will give their best, I plan to buy a new OPT with primary impedance around 3.5-4K. [/...
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Romy, I did some models using a 400V supply and a 6K OPT load. It's easy to get 4 watts output in this configuration, but using a 2K cathode resistor results in higher distortion and a weak transfer curve. Plate dissipation is around 11 wa...
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[quote user="Paul S"]Adrian, I agree that SETs generally have issues such as you describe, and moreso the small ones, especially at the frequency extremes, and at saturation, which tends to occur all too soon, IMO. But I have not sourced t...
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Not to mention the "overload"!Jim, I have never seen that before.I happen to like the 2A3 a lot; nice tone and great bass. I only quit on it because of the power limits.Congratulations.AC or DC heaters?If you haven't yet tried the Sovtek 2...
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[quote user="drdna"] I also use the 6SN7-2A3 DHT for my system (except subwoofer). Did you use the Electrocubes for the coupling capacitors? Was the internal wiring regular copper?
The coupling capacitor is critical, of course.
Also, I will say t...
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[quote user="Romy the Cat"]Can you post or explain the topology of your 6SN7-2A3?[/quote]The amplifiers I use started from a kit I bought, the Moondog, so here you can see the basic topology. It is very simple. The first stage here can be eliminated,...
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Dealing more with Sun Audio SV-2A3 kit it amassed me how bad the kit was. The guys made very cheap, in fact I hardly believe that this company has anything to do with Japan – it looks more like K-Mart level of amplifier. I heard a number of very posi...
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Romy, don't be so sure the amp is 2-stage. The ECC99 is a twin triode (mu=22, Rp around 2k) so the two sections could be cascaded, paralleled or the second section used as a CF or several other possible topologies.
Their 2A3 is rated up to 40W pl...
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You will be happy to hear I have got the new 2A3 tubes. I have spent the evening listening to them all. Some very interesting results! I will be posting soon...
Adrian...
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[quote user="Romy the Cat"]BTW, I run today the Chinese 2A3 and they were much better then Sovtek tube, much-much better, in fact I was very surprise how bad the Sovtek were.[/quote]Having received a bunch of tubes, I have spent some time liste...
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[quote user="drdna"]
Having received a bunch of tubes, I have spent some time listening….[/quote]
Yes, it looks like the Sovtek 2A3 are remarkably bad, even I with my stinky Tannoy was able to get it. Regarding the rest of your comments I ha...
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First, Adrian, Thanks for your feedback on the newer designed 2A3 tubes... very interesting. I've looked at all 3 of these brands before but have not as of yet purchased any (I have a large collection of 45 and 2A3 of various NOS US brands...
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Just some additional thoughts on the new generation of 2A3 tubes. The only ones I would seriously consider are the Kron Enterprises, the Sophia Electric, and the Emission Labs tubes. If I did not hear these side by side over an extended period of ti...
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I am not sure what rectifier the 2A3 SET uses. Mine uses the GZ37. The best regarded is usually the Mullard NOS. I have used that for years.
Recently I was on the kick of listening to the vibration of tubes and I came across a dirt cheap tube fr...
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[quote user="floobydust"]If you do some modeling you're running about 15.5 watts of dissipation on the plate and pushing over 4.5 watts output. Running the higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load results in hig...
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[quote user="floobydust"][The Moondog amplifier has] a higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load.[/quote]
[quote user="Romy the Cat"]...the most proper operation of this tube will be at 275V on plate and 4.1K ...
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KM:
It will be a little project to modify the amplifier, but it may be educational. To optimize the Moondog circuit for the NOS 2A3 tubes, so they will give their best, I plan to buy a new OPT with primary impedance around 3.5-4K. Will that be s...
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[quote user="floobydust"]As Romy pointed out, having high gain is not the same as power. If you're only barely cracking the volume control on your amplifier or preamplifier then it should be obvious that you have more gain than you need. If you're p...
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Adrian, Fair enough... it's not about power or gain in your case, just making it sound as clean as possible. Well, if you go back to my earlier post on findings, I list the basic operating values. Just to recap them here:Plate supply ...
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[quote user="floobydust"]Plate supply = 350 voltsOPT Primary impedance - 3.5K
Cathode bias resistor = 866 ohm
Cathode bypass capacitor = 50uF
Grid resistor to ground = 249
You need to select a new OPT.... I would suggest the H-20-3.5U.[/quote]I b...
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So what's wrong with the 6SN7, apart from the high prices fetched by good ones? If building a 2A3 amp for personal use, it seems a likely choice. I do not know the 6E5P, but I do love the tone of the 6SN7, and I especially like it driving...
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It turned out that I end up with 4V tubes for MF channel and am running my YO186. The 2A3 tubers I kind of have left on peripheral of my interests. It is not the 2A3 tubes are “bad”. I did not go deep with 2A3 and did not try their expensive sin...
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First of all, this not an attack on NOS tubes and it is all meant to be just sort of fun and educational. I happened to have all these 2A3 tubes side by side for comparison, so why not? I also have done the same thing with other tube types like 6SN...
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Adrian, Thanks for a most interesting post. I can't fully respond to this as I don't have the new tube brands you have. I posted earlier regarding my personal findings with the EML 45 solid-plate versus NOS however. Ultimately I found that...
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Gee, now that I read my post again after yours.... that last bit didn't quite say what I was wanting to say (I hate when that happens). I was really referring to people being "brand specific" as my example of the 45 showed that you can't always...
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[quote user="Paul S"]So what's wrong with the 6SN7, apart from the high prices fetched by good ones? If building a 2A3 amp for personal use, it seems a likely choice. I do not know the 6E5P, but I do love the tone of the 6SN7, and I espec...
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[quote user="drdna"] Well, and I have a dozen of them sitting here next to my desk while I am building my Milq amp s-l-o-w-l-y so I guess I will discover my audio intelligence level sometime after the New Year.[/quote]
That is so cool that you...
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It sounds like a lot of the circling has to do with which 2A3 "sounds better", outright. In any case, I'm guessing everyone would agree that it is specious to argue about which 2A3 sounds most like some internally-estab...
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If I say that it was horrible with San Audio 2A3 driven with buttery biased 6E5P then I really meant it. I got home today tune it on and it was so bad that decided that it shell not use it as is. Even though it an experimental amps but still it...
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[quote user="drdna"]
Having received a bunch of tubes, I have spent some time listening….[/quote]
Yes, it looks like the Sovtek 2A3 are remarkably bad, even I with my stinky Tannoy was able to get it. Regarding the rest of your comments I ha...
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