I own a parallel single-ended 2a3 amp; the two tubes are not in antiphase (pushpull) configuration. Parallel single-ended puts out more power, and because parallel operation reduces output impedance, the turn ratio of the output transformer can be reduced. But, it is quite hard to get good balance in output from the tubes, and one ends up doing most of the work after a while. I had that happen with my amp.
There is no practical way for an amp to be switchable between single-ended and pushpull operation, the circuits are fundamentally different and the output transformers must be different in design to optimize performance.
it is so unclear as to what is being compared here except that it is two different amps.
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sns,
I can understand race control wanting the race and the season championship to be decided by actual racing, hence the bending of the rules and conventional practice. What they should have done, to be fair to all the drivers, and to conclude the race with a lot of green flag racing to the end, is red flag the race and let everyone pit and get fresh tires. Hamilton would have been in the lead, as he should be, and Verstappen, if he stayed close enough, would have DRS after two laps would have been able to attempt a pass. I think Masi botched the call by not doing this.
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Nonoise,
I agree. Of all the possible alternatives, the one chosen by Masi made the least sense. If there was not enough time for ALL the backmarkers to come around the leaders before the restart, he could have left them all in place, including the four between Verstappen and Hamilton. That would have made for an interesting race because Verstappen would be able to clear them relatively quickly, which would have given him a chance to pass, but not given him such an easy path to a victory that was unearned.
I still think red flag and either a standing restart or a safety car restart with more than one racing lap remaining would have made the most sense.
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Charles1dad,
Thank you for pointing out the Manley PSET-PP amp that can operate both topologies,. I do wonder, however, if it can really deliver optimal performance for both types, particularly because of the specific demands for a good SET transformer. Because the full DC current drawn by the output tube must flow through the primary of the output transformer, the transformer must be designed to handle this current without core saturation. This requirement is usually met by an air gap in the magnetic circuit, which results in reduced inductance which can be compensated for with more iron and more turns in the primary. These compensatory measures would not be as desirable for PP operation.
I do wonder if this type of convertible amp is somewhat like an amphibious car--it can be both a car and a boat, but it does neither very well.
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With the Manley, which sounded better in the setup you heard--the pushpull or single-ended setting?
I am pretty much agnostic when it comes to best topology. I've heard quite a number of very good amps employing all sorts of approaches. Between my pushpull 45, pushpull 349 and parallel single-ended 2a3 amps, my favorite is the pushpull 349. There are things I do like about the parallel SET amp, but the fullness of the 349 amp carries the day.
Among all the amps I've listened to in a familiar system, my favorite is a custom-built output transformerless amp--the sound was extremely vivid and lively, without having an unnatural edginess to it. My next favorite is a pushpull 252 amp (a real Western Electric 59A amp) that was also extremely lively and full sounding. I heard the 252 amp side by side with the Audio Note Kageki (the parallel SET amp that I own), and by comparison, the Kageki sounded thin and drab. The best SET amp I heard was an Audio Note Gaku-On. The Gaku-On sounds good with just about any speaker I heard it playing; .
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The 349 is now quite rare and expensive, although there is a reasonably priced drop in alternative (6V6?). The amp also runs 348 as input and driver tubes. Both types now sell for somewhere around $1600 each for used tubes that test “strong.” My stereo amp runs four of each type. The only good news is that the tubes are run gently so they seem to last forever. The amp is essentially a stereo rebuild of a Western Electric 133 amp. It has the correct input and output transformers for that amp type as well as some other vintage parts.
The sound of my 349 amp is similar to a 6L6 amp. I generally like that tube and KT 66 tubes as well.
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The meshplate triode tube I am familiar with is the EML 2a3. I ran a quad of these in my Audio Note Kageki amps (parallel single-ended). I like their sound. The soundstage was gigantic, open and enveloping. If someone thought it was a by hyper-realistic (in a technicolor sort of way), I would not disagree. A friend thought it sounded a touch phasey; I would sort of agree, but, image placement was precise, so it was not truly out-of-phase sounding.
The most exotic meshplate I've heard is a meshplate 252. This tube is so rare that I know someone who was offered a trade of a pair of solidplate 252 plus $20,000 forin exchange for a pair of meshplate 252s. The offer was declined.
By the way, the Western Electric 59As (the amp that runs 252s) is a terrific sounding amp. I could never afford the amp, and even if I had one, I could not see running it very often because of the crazy cost of its tubes.
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I have not heard the Heathkit amp, but, I've heard a number of amps with Peerless trannies, and I am a big fan of the KT66 (and similar sounding 6L6) tube so I bet the amp is quite nice. A good modestly powered tube amp feeding Quad 57s makes for a terrifically musical and enjoyable setup.
If it sounds like crap on YouTube, guess what: everything SHOULD sound like crap on YouTube.
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Jond,
I like vintage iron too. My pushpull 45 runs Accrosound To 330 trannies, my pushpull 349 runs Western Electric 171 iron (input trannies are Western Electric 618).
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If the idea is that one should not buy products from a country that ranks lower than one's own, based on whatever social metric, this would be problematic for those countries that rank high. You could scarcely buy anything non-domestic if you lived in Denmark or Finland, for example, but the world is your oyster if you lived in Nigeria or Myanmar.
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charles1dad,
A nice concise history of what happened. I would add that another aspect to the story. When stereo came around, the need to find room for two speakers, instead of just one, meant that smaller speakers gained in popularity. These smaller speakers, particularly of the air suspension (sealed box) variety were inefficient and required higher powered amps and this favored solid state over tubes.
Mozartfan,
There are many pentode/tetrode tube amps running pushpull that are extremely musical and great sounding with horn systems, fullrange driver systems, and multiway systems utilizing fullrange drivers. You cannot generalize from hearing only something like the Defy 7 and certainly not by "listening" to YouTube videos. I have heard terrific 6L6 and KT66 amps and some of my favorites are 350B and 349 amps (the favorite of the amps I own runs the 349 tube). I also own a pushpull 45 amp (triode tube) and a pair of Audio Note Kageki (parallel 2a3 SET). All of these amps sound good. My all time favorite amp is an output transformerless amp that is a custom built amp, and a pushpull Western Electric 59A amp (252 tube) which is something I could never own as a pair is well into six figures. Even with tubes that I don't particularly like (KT88, KT120, KT150), there are examples of amps that run them that I found to be decent. I know that there is a strong desire to come to conclusions about various aspects of design or parts choice, but, it really is not that simple to do. The more I hear, the LESS I am able to draw definitive conclusions in these areas, although I do see rough tendencies. As to such rough generalizations, I do like quite a few speaker designs that use fullrange drivers in multiway systems (e.g., Cube Audio Nenuphar Basis), a small handful of true single driver systems (Charney Audio, Voxativ), but mostly, I like horn-based systems.
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I agree with Atmasphere--most tube amps, both single-ended or pushpull, benefit from driver tubes with more oomph than the 12AX7 or 12AU7, which often means a 6SN7.
By the way, Atmasphere is being quite diplomatic by not mentioning the type of amp he manufactures and sells, which are output transformerless (OTL) amps. If you think your full-range driver system sounds incredibly alive and vibrant with your typical single-ended triode amp, wait till you hear it with a good OTL amp.
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I have heard many good SET amps, OTL amps and pushpull tetrode/pentode amps (what mozartfan refers to as KT amps). For the record, I’ve gone from a very good SET amp (Audio Note Kageki) to a pushpull 349 amp. It is simply not the case that one never goes back from SET amps. There are no absolutes. I don’t understand what appears to be a compulsion to declare one thing the best.
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