jcmusic Posted February 14, 2015 Share Posted February 14, 2015 -- and that output transformers do NOT need to be the size of welding machines to achieve very respectable low end response. Erik, how can you say that (see picture below) ? Just joking, of course. I've been getting amazing results with the little Hammond 125CSEs which can achieve very potent output all the way down to 25 Hz. Best regards--- Maynard Hi Maynard, Lets talk for a second about how you know/feel you can ahieve output levels down to 25 hz with this little amp. What is the output in watts of this amp? Are you just hearing it or have you measured it by means of spl? Jay Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted February 14, 2015 Share Posted February 14, 2015 (edited) Jay, I'm not sure which little amp you are referring to. The one pictured above, with the large xfmrs, puts out approximately 4 wpc with only a slight decrease even at 20 Hz. I've been using the Hammond 125CSEs in my budget amps which typically are 1 wpc or less and, at that power level, there is also a minimal decrease in output power at the bottom of the audio band. Output power is measured across a resistive load just before clipping, and the sine wave appearance at multiple frequencies is compared on the 'scope to the input signal. I also consider the square wave appearance as that shows a great deal about the amp and transformer capabilities. Spl is irrelevant as most speakers can't do much at 25 Hz (mine crap out like a rock below about 40 Hz). George Anderson did some terrific measurements of the 125CSE which confirm just how effective this little unit is if run way below its rated output power. I hope this answers your question!http://tubelab.com/articles/component-testing/budget-output-transformers/Maynard Edited February 14, 2015 by tube fanatic Quote Link to comment Share on other sites More sharing options...
jcmusic Posted February 14, 2015 Share Posted February 14, 2015 Maynard, Yes and no but, I'm good with what you said thanks... Jay Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted February 15, 2015 Share Posted February 15, 2015 (edited) And of course there are those designers -- Atma-Sphere, Tenor Audio, Transcendent Sound, and others, who view output transformers in general as a part best avoided completely. Check the bandwidth and power specs on this amplifier from Atma-Sphere (these are very highly regarded amplifiers), and then note that it not only does NOT use a small output transformer, it uses no output transformer, period. In a conventional (transformer coupled output) an OPT is needed for impedance matching between the very high plate impedances of output tubes (either push-pull or single-ended) and the much lower impedance of a loudspeaker voice coil. As in the case of those designers mentioned above, an ouput transformer is viewed as something of a necessary compromise - transformer-coupled amplifiers MUST use them in order to be capable of effective power transfer into a loudspeaker load. And so, we hear of builders and/or designers throwing out terms like "heavy iron" with a certain admiration. And that's fine; in some cases and in some circuits "heavier iron" may be a benefit, but in my view not necessarily so. Another criticism has to do with damping factor and generally higher output impedance associated with transformer coupling. In this, OTLs (amplifiers that designed to NOT require ouput transformers) can have an arguable advantage. Here's an OTL from Atma-Sphere: http://www.atma-sphere.com/Products/ An example of a neatly wired and dressed amp, also from Atma-Sphere: fun to watch http://www.atma-sphere.com Edited February 15, 2015 by erik2A3 Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted February 15, 2015 Share Posted February 15, 2015 (edited) Another criticism has to do with damping factor and generally higher output impedance associated with transformer coupling. In this, OTLs (amplifiers that designed to NOT require ouput transformers) can have an arguable advantage. Here's an OTL from Atma-Sphere: http://www.atma-sphere.com/Products/ No advantage seen in this example which specs show 7 ohm output impedance. Unless the loudspeaker load this amplifier is paired with has a very flat impedance curve there will be tonal shifting audibly larger than most typical SE Triode transformer coupled amplifiers (usually around 2 to 4 ohm output impedance is common). Now EQ compensation could be applied to any of these higher output impedance amplifiers if it was designed for the specific loudspeaker connected to this amplifier but otherwise it will color the tonal balance of the reproduction. Note also that no power output rating is specified for driving 4 ohm loads (which many speakers can dip down into this range) so one needs to be aware of this when matching loudspeakers to these OTL amplifiers because power output will be significantly lower than the 16 ohm ratings. My experience has also been that in a few amplifiers that I have listened to that have basically the same circuit design except the paralleling of output devices (for increased power output whether Solid State or Tubes) in the amplifiers there can be a loss in clarity so unless the extra power is needed the paralleling of output devices should be avoided IMHO. miketn Edited February 15, 2015 by mikebse2a3 Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted February 15, 2015 Share Posted February 15, 2015 (edited) Easy to read bold-face type - thanks! Atma-Sphere Is just one example -- the main point had to do with the need for an output transformer, which OTL amps don't require. Let me provide another example related to the output impedance question, if that would help: Paralleling of output tubes, whether single ended or push-pull parallel has been done for many years by skilled designers. We would likely agree that whether the practice should be avoided or not is, in my opinion, probably rather dependent on who one asks. http://www.transcendentsound.com/Transcendent/Mini_Beast.html Or the Atma-sphere Novacron http://www.atma-sphere.com/Products/#Novacron And the last example here on this from me - very high power output transformerless amplifier again from Transcendent Sound with an a vanishingly low output impedance, and easily capable of driving 4 ohm loads: http://www.transcendentsound.com/Transcendent/Transcendent_Sound_BEAST_OTL_Tube_Amp.html Edited February 15, 2015 by erik2A3 Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted February 15, 2015 Share Posted February 15, 2015 All amplifiers have compromises and as a Output Transformer design is a compromise so is a OTL design a compromise and it's knowing the compromises that is important if accurate reproduction and understanding which loudspeakers might be a reasonable match to a given amplifier. The Transcendent amplifiers use negative feedback as a compromise for output impedance control. Does this cause audible problems versus an amplifier that doesn't use feedback as some SET Transformer designs? Maybe? http://www.transcendentsound.com/Transcendent/Amplifier_Output_Impedance.html I've listened to the early Transcendent amplifier design many years ago on Klipschorns and the sound was very good but not better or worse than a good 2A3 SET transformer coupled design IMHO. Like so many things in audio we single out a perceived weakness like Output Transformers, Negative Feedback, Solid State P/P or Se, Tube P/P or SE etc......and design around them and in the end we still have an amplifier with compromises and loudspeakers with compromises and in reality a Total Reproduction system from recordings to source to listening room that are full of compromises. Stereophony is an amazing and fascinating hobby..!!!! miketn Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted February 15, 2015 Share Posted February 15, 2015 (edited) Or the Atma-sphere Novacronhttp http://www.atma-sphe...ducts/#Novacron The 6C33 is a very nice tube which I have heard in the Lamm P/P transformer coupled design and is great option for OTL designs. Since I've not heard this amplifier versus the Lamm all I can really say is this will be a more expensive amplifier to maintain over the years (as many OTL designs will be) versus Transformer Coupled Designs due to the need to replace so many output tubes since reasonable designs require more tubes for a comparable power rating versus transformer coupled designs. miketn. Edited February 15, 2015 by mikebse2a3 Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted February 15, 2015 Share Posted February 15, 2015 My experience has also been that in a few amplifiers that I have listened to that have basically the same circuit design except the paralleling of output devices (for increased power output whether Solid State or Tubes) in the amplifiers there can be a loss in clarity so unless the extra power is needed the paralleling of output devices should be avoided IMHO. miketn Mike, I agree that using fewer devices is always the preferred route, but on occasion I do run pairs of output tubes in parallel and don't encounter any degradation in sound quality. The key seems to be placing the tubes very close together and using G1 and G2 stoppers to prevent any parasitics (which, as you know, can often occur above the audio band). Just my take on the situation-- Maynard Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted February 15, 2015 Share Posted February 15, 2015 My point in mentioning OTLs had really nothing to do with a statement about transformer coupling V.S. OTL amplification in terms of which is better. Of course every design is something of a dance of compromises. We were discussing the perceived merits of larger output transformers as opposed to their sometimes a bit misunderstood smaller counterparts. The OTL was an illustration of those that require neither a large nor small OPT of any kind. The designers of the amps for which I provided links know a good bit about this subject, and both have created very successful OTL topologies. The feedback issue is something also often brought up, but, as an owner and builder of both single-ended and PP amps, we should not discount some of the merits of judicious and careful use of negative feedback. Maynard -- I absolutely agree concerning the point you make regarding grid stoppers. Amplifiers can oscillate at such high frequencies to be virtually inaudible, yet still be undesireable. I own two OTL amplifiers, and will say that clarity is very much their forte.' Quote Link to comment Share on other sites More sharing options...
jcmusic Posted February 16, 2015 Share Posted February 16, 2015 My point in mentioning OTLs had really nothing to do with a statement about transformer coupling V.S. OTL amplification in terms of which is better. Of course every design is something of a dance of compromises. We were discussing the perceived merits of larger output transformers as opposed to their sometimes a bit misunderstood smaller counterparts. The OTL was an illustration of those that require neither a large nor small OPT of any kind. The designers of the amps for which I provided links know a good bit about this subject, and both have created very successful OTL topologies. The feedback issue is something also often brought up, but, as an owner and builder of both single-ended and PP amps, we should not discount some of the merits of judicious and careful use of negative feedback. Maynard -- I absolutely agree concerning the point you make regarding grid stoppers. Amplifiers can oscillate at such high frequencies to be virtually inaudible, yet still be undesireable. I own two OTL amplifiers, and will say that clarity is very much their forte.' Erik, Which two OTL amps do you own? Jay Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted February 16, 2015 Share Posted February 16, 2015 Jay - I own one Transcendent Sound SEOTL (single-end-output-transformerless - the first version, which has been replaced by another, apparently much better design. I also own two Transcendent Sound T16 stereo amps. I am going to rewire them for monoblock operation. The T16 has also been replaced by a new design. Quote Link to comment Share on other sites More sharing options...
Nikolas Topaloglou Posted February 16, 2015 Author Share Posted February 16, 2015 What is your opinion about De Havilland aries-845 amplifiers?? Quote Link to comment Share on other sites More sharing options...
jcmusic Posted February 17, 2015 Share Posted February 17, 2015 Jay - I own one Transcendent Sound SEOTL (single-end-output-transformerless - the first version, which has been replaced by another, apparently much better design. I also own two Transcendent Sound T16 stereo amps. I am going to rewire them for monoblock operation. The T16 has also been replaced by a new design. Erik, Have you heard the new design vs yours? Are is this just what you have read or been told? I have always wanted to try one of those OTL amps I just never got to it, and now I am really happy with my system but still very curious!!! Jay Quote Link to comment Share on other sites More sharing options...
pite Posted February 17, 2015 Share Posted February 17, 2015 I'd came up with a technical explanation - white paper explaining, the relationship between efficiency and power... pershaps, I should dig it up and post it for fellow Klipschers. Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted February 17, 2015 Share Posted February 17, 2015 Jay I have not heard any of the new Transcendent OTL amps. Rozenblit is a sharp EE and a designer who is constantly working and experimenting. His newer models depend on a different output tube than the earlier versions and despite what others have said about the greater number of tubes required, there are those who, once they tried an OTL, will never return to transformer-coupled designs. Each to his or her own. For those, the cost of ownership is not really an issue. He also designed a model I am particulalrly interested in that, like his new preamp/headphone amp, uses 300B triodes. It is a very low power amplifier, and uses AC current on the filaments (DC can't be used here), but Rozenblit managed to get around the AC filament hum problem in a way that I think is particulaly smart. The majority of amplifiers I own are not OTL designs. Quote Link to comment Share on other sites More sharing options...
dubai2000 Posted February 17, 2015 Share Posted February 17, 2015 And - much as I like Rozenblit's pre-/amps - he is pretty good at suggesting that his latest designs are always superior to his "older" work. Be that as it may, the GG/SEOTL (old version) and his phonostage are certainly outstanding products. Whereby I also believe (contrary to him) that some better parts do have positive effects on his designs (which obviously speaks for his designs!). One day I might actually try his new 300B based preamp...... . Wolfram Quote Link to comment Share on other sites More sharing options...
jcmusic Posted February 17, 2015 Share Posted February 17, 2015 Jay I have not heard any of the new Transcendent OTL amps. Rozenblit is a sharp EE and a designer who is constantly working and experimenting. His newer models depend on a different output tube than the earlier versions and despite what others have said about the greater number of tubes required, there are those who, once they tried an OTL, will never return to transformer-coupled designs. Each to his or her own. For those, the cost of ownership is not really an issue. He also designed a model I am particulalrly interested in that, like his new preamp/headphone amp, uses 300B triodes. It is a very low power amplifier, and uses AC current on the filaments (DC can't be used here), but Rozenblit managed to get around the AC filament hum problem in a way that I think is particulaly smart. The majority of amplifiers I own are not OTL designs. Ok thanks Erik!!! Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted February 17, 2015 Share Posted February 17, 2015 Jay, sure! Wolfram: I think he says the new designs are better because he really believes they are -- which of course is a subjective judgement. I have built quite a number of TS products, and have had the opportunity to experiment with a variety of "upgraded" (ie more expensive passive components, and my opinion was not the same as yours. I did not find differences that warranted the greater cost. That's not always been the case, though, with other preamps and amps I have built. I don't choose parts based on cost. I make judgements based on performance in specific circuits, providing that a part is correct in terms working voltages, etc. Were I to do otherwise, I would be compromising my own sense of what is important in creating a component. BTW: I know that he does appreciate well made parts, such as with the usual culprit (coupling capacitor). I would say any designer is pretty good about reflecting faith in his/her new product once it has been thoroughly tested. That confidence has been rather well-illustrated over the years on this forum. Quote Link to comment Share on other sites More sharing options...
Nikolas Topaloglou Posted February 20, 2015 Author Share Posted February 20, 2015 Well, do you have any experience with De Havilland aries-845 amplifiers?? Quote Link to comment Share on other sites More sharing options...
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