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In Reply to: RE: hum no fun posted by drlowmu on November 11, 2015 at 08:29:38
!
The Mind has No Firewall~ U.S. Army War College.
Follow Ups:
You THINK you have the amplifier resolved. Not so, IMHO, from your supply's description and my experiences.
Jeff Medwin
I built many SETs with 45, 2A3, 300B, 845. I built some 45 SETs including direct coupled one.
After listening to A-08, again and again, my friend and I concluded that there's something strange with 6Moons, or their taste is strange, or their speakers are differently strange or strangely different.
Since A-08 was in kit form, we checked the wiring again and again. I even let other DIYer friend to check the wiring, just in case.
The sound is exaclty opposite to 'lively', we even thought that this may be the Japanese voicing. Or we talked about there is something we did not know at all about SET sound.
I think now simply that the review is exaggereated with pretty look. Do not blindly believe the review. Yes it makes sound, but I'd rather go for Jeff low DCR chokes, for similar gambling.
The Yamomoto A-08 we used had exquisite parts. It was a FACTORY built unit, and it was neatly wired, for sure.The Yamomoto tube sockets, as one example, were lovely, and it has C-Core Output trannies, power and chokes as I recall. The speaker wire's binding posts are special also, very nice feel with a fine-thread so tightening is progressive to the touch. Lovely.
If you look at the A-08 schematic on line, you will see they specify " RN65 " resistors, vintage American military spec types I presume these to be. Where they use an RN-65, for - say, the plate resistor or cathode resistor of the front-end tube, I would now very carefully (and expensively ) employ TWO closely-matched Caddock MK-132s or TF-020s, and such resistors' end-result is HUGE in "tone, transparency and purity".
The Yamomoto sounded gray and artificial to us both, narrow band like a bad AM radio station signal playing through a cheap radio. It missed playing one octave higher and lower, versus my prototype's implementation. Also, it was TOTALLY outclassed in dynamic contrasting, and taking control of the large ALTEC A-4 speaker system. This is due to what holds almost ALL other SET amps back,
(1) poor internal wiring,
(2) high DCR chokes ( above 20 Ohms ) , and
(3) high amounts of capacitance in the power supply.
For example, the A-08 sports a "typical" / undesirable 10 HENRY ( about 80 to 100 Ohm ) choke in a C1/L1/C2 filter, ugh. Its DOA, by design, or should I more properly call it mis-design. I used L1/C1/L2/C2 - 10 Ohms and 8 Ohms for L1 and L2, 500 mHY and 1.8 HY respectively. Low Stored Energy Supply, aka LSES.One other thing, the A-08 used an electrolytic, (as I recall) to bypass the Rks. And noisy zeners on the Pentode's extra grid. No good. However, I used about EIGHT carefully chosen Rk bypass film capacitors in parallel - across each Rk, to ARTFULLY get the amp to play wide-band and with proper musical intent.
Yes, Yamomoto-San, ( had he been in front of those ALTEC A-4s ), may have rolled over and simply puked, if he heard the A-B. But maybe, he would learn something too, to apply into the future.
This amp build has been FUN so far, and I look forward to retrieving it from those A-4s, 55 miles away, and getting it playing on my now-silent A-7s, fifteen feet away. !! Need to finish re-wiring those A-4 woofers first, ( wanna' hear them properly ) that task coming-up this Sunday I hope.
Each ALTEC 210 bass horn weighs 440 pounds, unloaded, and each ALTEC 515C must be about 30 pounds, two per bass horn, so, we need to move about 500 pounds when loaded, just to access the enclosure's rear woofers' panel. Ugh.
Jeff Medwin
Edits: 11/24/15 11/24/15 11/24/15
Hi Jeff,
In fact I tried your low DCR concept in some different ways. I could feel the change in dynamics, etc.
But please use gentle and considerate words, or others may only see your definite writing and stick to that wording and may try to criticize it. You know what I mean. I've seen this before and feel sorry to see this again.
If you can offer the simplest combination of power tranny and chokes with proposed circuit, that will help, both you and others who are curious after all these years that you've been suporting that idea.
Cheers,
Chul
Hello Chul,I much respect the fact that you are a musician, pianist.
I do not mind others criticizing me.
I speak about what "I" hear and what "I" think.
There was plenty written previously herein about Flywheel, and LSES and one can peruse a Hammond catalogue and come up with decent alternatives, with a little effort, the use of PSUD and by listening.
In recent years, I more and more modify the leads of all power supply magnetics, ( see photo above ) to play back music's awesome peak instantaneous currents.
I still do not use chokes much over two pounds in weight, and over 2 HY or over 10 Ohms DCR. In 2015, I may employ LSES over a Flywheel, and in true LSES style, it will have L1 equal L2,..... but NOT always. Fastest settle is not my key PSUD priority ( as was written by John Swenson, John Hasquin et all ), smooth settle is the priority.
I still use 50 uF as the largest cap size, and typically use a lesser uF amount on C1 - than on C2. In 2015, I use WIMA DC LINKS as a main supply cap, and bypass it with four to eight smaller value, higher quality film caps, selected by ear, for full musical expression. Bypassing main film caps I find is a "must", in all C locations for decent full-frequency playback results. It must be done by listening and its an ART form IMHO, like musical expression on your piano.
Let people experiment on their own, by listening, and come up with a circuit they are happy with, and proud of to call their own.
Most important of all, do what pleases you and have fun in the hobby. If YOU like your results, that is ALL that matters. Have FUN.
Jeff Medwin
Edits: 11/25/15 11/26/15 11/26/15
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