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| Romy the Cat's
personal site dedicated to advanced audio and evolved music reproduction
techniques
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I was playing lately with the Single-stage Melq and the DHT amp driving MF channel. It turned out that the Sun Audio VT-2A3 was very simple kit and it 2-3 hours to make it working. There is a lot in this kit that I do not like and some revisions will...
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While I would agree that modern construction should be much more robust than that of 5-6 decades ago, actual machining and manufacturing costs today are significantly higher than they were back then and there is much less of it going on. Look a...
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Adrian, Romy, et al, Okay, I don't take any of it as an attack... so none of that bothers me.... I'm fine with it... again, it's a view on what you heard based on your test scenario, nothing more and I certainly welcome the review. Now tha...
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[quote user="floobydust"] Question: the 0.75 ohm resistors in the filament lines on the 2A3. Is it your intent to drive them from a 2.5VAC transformer or a 5.0VAC transformer. Voltage drop considering the 2.5amp filament requirement would result in i...
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Very good, floobydust. They are exactly my thoughts about the “period tubes” as well. In addition to that I think that factor that call “Holly Ignorance” did take place with some vintage tubes. They might not have too high demands for the quality of ...
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[quote user="floobydust"]The 2A3 can be almost as quiet, but ONLY in the dual-section paralleled types. I adopted a split balance technique. It only works with cathode bias due to the topology but it is effective. You also need a good quality filamen...
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In context of the recent changes in my playback regarding the electricity and the consequential effects:
http://www.GoodSoundClub.com/TreeItem.aspx?PostID=9252
I have revised and reinstated my interest in the DHT experiment. In addition to a...
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[quote user="drdna"] So, my thought was that below 35 hz, there are many ways of thinking about amplification. Some might say SS amplification is helpful due to power demands of horn loaded 18" woofers. To use 6C33 might be a trade off but I do not k...
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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 these problems back to...
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Thanks Adrian, Have you also had a chance to listen to some NOS 2A3? I'd be interested to see how they compare to the new issues. I've managed to collect quite a number of NOS 2A3 tubes over the years, brands I have include RCA, Sylvania, ...
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[quote user="Romy the Cat"]However, you need to find out how much power and how much gain you need for you subs and your room. Borrow for someone any 6C33C and measure how far the 6C33C will be from class A2 at a level of max tolerable bass in your r...
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[quote user="Romy the Cat"]I was thinking about this: how come that driving 6C33C (in fact driving anything one can imagine) the 6E5P was very fine but driving 2A3 it was dull like hell. I opened the amp and tested all – everything was perfect but th...
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Some of the more powerful SETs (including some of the Gm70s, I think) run parallel output tubes, and some go into A2. I know parallel output can work at line levels, but no experience I can recall with parallel output at high levels.My Wright 2...
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I know – it idiotic even for my site but it us what it is. I do not think that I can generalize my observations as I have not a lot of experience with DHT tubes but one thing that I have been observing for the last week is really arouse my curios...
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I run the driver tube at 170V @20mA. I don't think you need to run this tube at high current. It is very linear with wide signal swings at this bias. I can get roughly 70Vrms out of it. Output stage clips first, driver continu...
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[quote user="Romy the Cat"]
[/quote]OK, now, after mach thinking, consulting and very little actual listening I have finally conceptualized my next move with powering Macondo MF channel. Considering that I have some extra space Melquiades’ ...
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Adrian, Romy, (Dima), First, I most certainly agree that the textbook operating point for the 2A3 is not optimal and can be improved on, hence my own design from a few years ago. If you are sticking with a 2.5K load, you will simply not ge...
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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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From my view, I would add a dedicated filament transformer for the DHT. It's clean, simple and a known performer. I'd also be inclined to drop the support of a 6A and stick to a 2A3 only. Alternately, if you have no need for a center-tap on the DHT ...
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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="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="drdna"] I think this 2A3 must have a specific set-up to sound its best. You have not found it yet. To begin with and familiarize yourself with the sound of it, I suggest sticking with the topology that has been tested by amplifier design...
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[quote user="drdna"]You want a suggestion for a good 2A3? Get Ricardo Kron's (KR Audio Enterprises) KR 2A3. Very rugged, overbuilt. There is no comparison between this tube and all other 2A3's, and I tried many of them. The sound is more dynamic, the...
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I have run each of these for long periods and can validly comment.My power amp circuitry is a 6N1 based Mu Follower driving a 2A3 in turn driving a 3K Tamura amorphous core OPT.The 6N1 tube is a special military type that is not freely available.Ther...
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Romy, That gets you where you want.. good transfer curve, low distortion and about 2.7-watts output. 2A3 should last a long time. One question and one comment:Question: the 0.75 ohm resistors in the filament lines on the 2A3. Is it your in...
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Yes, the last 3 pics are of the "dead" 2A3. Saying it warms up could mean two things... it literally gets warm and nothing else as it may have leaked air. Or it could mean the filament lights up (and assumes getter flashing still intact which i...
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[quote user="drdna"] How about using the 6C33C for the low midrange-woofer, the 2A3 for the upper midrange, and the 45 for the tweeter? I suspect if each circuit can be optimized, that they can do their best within each frequency range. [/quote] Hm…....
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[quote user="Romy the Cat"]I do not know what you mean by “specific set-up” and what San Audio did is very orthodox use of 2A3 and I did not change it. The only change that I made (and I do not know at this point if it was a good change) was the chan...
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The problems I've had with small DHTs have had nothing to do with tone, which has been SOTA in some cases, IMO. The cheap-o Wright's 6SN7/2A3 pairing is excellent with respect to tone and even with respect to "authority", within its limits...
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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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