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In the Forum: Melquiades Amplifier
In the Thread: Fun with transformers?
Post Subject: Re: Ari Polisois’ Direct-Coupled SimplexPosted by AnonymousUser on: 3/30/2006
Rob and Romy the Cat,
Thank you for inviting me to discuss this subject. Allow me to reply only to the main points raised, due to the present overload of work. However I will try to answer, later, to any specific question on the subject.
First : - My philosophy on sound reproduction valve amplifiers ( my knowledge on solid state is very limited and I rely on my son, who is a young electronic engineer, for help) is very simple : it is based on the logical statement that what is simple is easier and what is easier generates less mistakes.
Therefore, I wrote an article for Valve e-zine, some years ago, after patenting (just an elementary certificate named here, in France, "Certificat d'utilité") my D.C.M.B. system, also described as absolute direct coupling all-the-way of the musical signal path. Some objections were made on this statement because the signal crosses a set of capacitors in the power supply. Sorry, there is not much I can do about that, except suggest to use batteries or some other electric power source not using capacitors.
At the beginning I used prestigeous output transformers, such as the Plitrons, designed by Menno van der Veen and Brian Sowter's OPTs, but when a friend of mine asked me to design a high power amplifier ( 50 Watts ) to drive his Greek-pi AR enclosures ( wonderful but very stiff) and specified he wanted it in single ended layout and DCMB, I realized I could never find a SE output transformer to handle such a power.
Second - I revised my magnetic circuits knowledge (dusty because it went back 30 years before, when I studied it at the Ecole Central de TSF of Paris, with an excellent teacher : Lucien Chrétien.
After reading several books ( I could mention them but I do not know if I am allowed - in another Forum a long message I had written was rejected because I mentioned a good author and his book and I got discouraged and frustrated , I understood why there is a gap in the SE output transfomers and the consequences of this compromise. From there I imagined several solutions and experimented them, until I came close to a good one, the SC-OPT (presented at the AES Convention held in Barcelona May 2005).
Third - Life is hard for individual researchers. After drying my savings to achieve acceptable results and obtain the corresponding patents) I received some justified objections, both on the Direct Coupling Modulated Bias System ( see www.audiodesignguide.com - bottom of the banners list, and Glass Audio 17 novel projects and Plitron's site ) mentioning Loftin and White's amplifier, and on the SC-OPT . In reality, some solutions look similar on the paper (schematics) but not in practice, and this was my case. A small detail sometimes makes a huge difference.
Fourth - What DCMB has achieved ? a) simplicity b) speed c) no frequency discrimination d) wider frequency range e) suppression of the PSU noises ( I owe this claim to a Canadian friend who noticed it first), f) single point idle current adjustment and g) (under experiment) possibility of modifying the sound stage.
Regarding the OPT, just one, big, step forward : you can now build SE amplifiers with unlimited power (better said : up to the physical limits of an output transformer) as opposed to the 10 max 30 Watts currently accepted.
Sorry for this long story but it explains what follows :
I cannot issue any certificate on the quality of the sound. I have, of course, testimonials, but I am not ready to repeat them ( in the past I quoted them several times, but the skepticals remained such ).
As a consequence, those who want to check the DCMB and spare some time and money, as well as curiosity or faith, are welcome to send me an e.mail at A2BElectronic@wanadoo.fr and I will do my best to supply more information and advices.
Alternatively, they can build the 1940-1960 models of amplifiers, changing one or two components here and there, to refine the sound. Just make sure that the qualities claimed for these products are real and not "commercial".
PS - The SC-OPT works satisfactorily only with low internal resistance valves ( lower than 250 ohms).
There are however two more generations under test, based on alternative solutions, that are expected to solve the problem to such a degree that even penthodes will be suitable for single ended layouts.
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