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In the Forum: Melquiades Amplifier
In the Thread: Fun with transformers?
Post Subject: Re: “Easy come, easy go” sound...Posted by AnonymousUser on: 3/31/2006
Assuming that your questions are "honest" ones ( I have no reason to believe they are traps, like it happened to me before with a certain Mr. Thor), I will give you "honest" answers, hoping that our dialogue will be of some interest to the audiophile community.
Foreword : it will not be easy for you and me to meet on a common ground, because I have the feeling (sorry, I am new to your Forum) that you judge in terms of "sound emotions" , which is not wrong, after all, and I judge in terms of "amplifier structure" . My reasoning will be more clear after you see my answers, but, in any case, it is based on : make a good sound reproduction electrical device and the result will not be too far from the live one (exactly the same is impossible, I believe).
Your query a) : "speed" and "harmonic structure/pattern" .
By "speed" I mean the response of the amplifier to transients. I have some nice instruments in my personal laboratory but not all the ones I would like to possess (a matter of budget, family needs, etc.). I mentioned this characterisics for two reasons: a1) how could a circuit be faster that a driver stage of the concertina/williamson" type and a no-capacitor coupling between the terminals of the anode load of the second stage of the driver and the pair "Grid/cathode" of the power tube ? a2) I have a dozen people who said so, in different ways ( quoting some words: fast, dynamic, aggressive). These statements come close to your way of judging the reproduced sound, I think.
Sorry again, but I cannot supply measured data. I had a "slew-rate" meter software fitted to my former
PC, but, probably due to a mistake, it failed and also "burned" my computer. So, now, as stated, I can only rely on my observing the schematics and on other people's judgments. By the way, some of them are musicians, some skilled electronic engineers, and some both. Among the younger judges, my 19 year old daughter, who, exceptional case, likes Beethoven, Vivaldi, Pavarotti and Gershwin as well as Alicia Keys' songs.
Regarding the harmonic structure, I can only measure the THD with my HP 334A distortion analyzer, and I rely on the fact that, in Single ended amplifiers, the odd harmonics content is very weak, compared to the second harmonic one. The latter, as many people state, is well accepted by the ear.
I add to that something you might not agree with: although I know that, in an average size listening room (living room, TV room or other) 5 watts, with 95-100dB enclosures, are more than enough, I prefer to build a 30 W amplifier that showed 6,5 % THD at full output, and listen at moderate level ( 5-7 W ) in order to have 0,5 % THD, of which 0,05 % of nasty odd harmonics ( as found in bigger quantities in push-pull amplifiers). Have you had a chance to look at the "Simplex" "Duplex" or "King" (the latter is a 3X6C33C-B per channel, delivering 50W in single ended - see AudioXpress July 2004) schematics ?
Your Query b) By frequency discrimination I intend the difference in the signals' amplitudes transferred from the driver to the power tube, at different frequencies. In typical R/C couplings, this is due to the presence of the blocking capacitor, worsened by the Miller Effect. The same problem exists with the DCMB, but to a much lesser extent ( it depends of course on the circuit layout and components used).
Your Query c) This is the most difficult question. I think you are right with your "bass sensation feeling" and I am at a loss to give you a decent answer. All I can say is that it happened also to me to listen to a
couple of amplifiers with a "disturbing bass effect" . Let me add that this does not happen with my amplifiers ( I have built about 20 different ones), except in a couple of cases ( mainly due to a mismatch between power tube and impedance of the load, or uncorrect biasing and/or supply voltage) that I immediately discarded or solved .
Transparency : In my condition ( meaning age ) I must rely on two facts:
- other people's reactions ( to avoid polite statements I make listening sessions with two or even three
different amplifiers and get more genuine responses with preferences and corresponding reasons)
- Because the lisening sessions cannot be too long, I sit and listen myself , for hours, different kinds of
music, paying much attention to the "fatigue" or "boring" sensations. In some happy cases, the more
I listened, the more I wanted to, but most of the time I was "satisfied" but absolutely not "tired".
To conclude, I think you understood that I am particularly fond of the Single ended layout and have spent much time in boosting its qualities ( I particularly like the way it respects the slightest details of the music - some of my friends can listen to the fingers touching the instruments: pianos, and other).
Nice talking to you, Romy, but do not bother to criticize, if it is constructive.
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