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In Reply to: What make a transformer good ? posted by Rune on February 21, 2007 at 02:35:00:
Ha !!You are really barking up the wrong tree.
Start to read up on Power Supply Iron, and read all my posts specifically on Low DCR, Low C, and Low HY .......... 'cause without it, you are OTL.
Follow Ups:
it helps makes my box go BANG BOOM! --and I likes that lots.
You likes low 'HY' in your OPT? I'm kinda head scratchin' here...
Hi Thomas,To clarify, I was talking about power supply iron, not final output stage iron.
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When your only solution is a hammer, every problem looks like a nail ;)
But uncalled for.Without the hammer and nail, nothing holds together optimally on music playback. You should TRY it like I just did, rather than post up here without a clue.
The triode amp STARTS with the best possible power supply, err, hammer and nail !!
Respectfully and not ill-intentioned,
Because on July 24, 2006, you wrote *I am really only low DCR experienced.* and per Low C, Low Hy, you wrote: *I think it is not yet time for early adaptors to move, based on forum writings, may take a year or more to sort it out, if ever.*
Hi Ron,That was my truth and my perception seven months ago, but its not accurate now.
I have, since then, accumulated parts to do Low HY, Low C and Low DCR supplies so that I could obtain direct experience. The problem was, I've been busy with work and didn't have a SE amp to experiment with.............'till this past weekend.
Now, I HAVE the direct experimental and listening experience, at last!!
I have a good audio friend in KC, MO area that I amp-mentor named Greg. He has had this 245 SE amp that I help him design, powering his lovely RCA MI-1443 Field Coil high frequency drivers mounted on large RCA 90 by 40 horns, all sitting atop Altec 515 Bs in very large bass reflex boxes.
The system uses my 5687 LINE level passive-biamp at 600 ohms Z, with a Peerless output trannie and Daven bridged T pots and an absolute phase reversal switch mechanism installed. The biamp line-passive crossover point is at 400 HZ. Greg's DIY H.F. amp has two separate supplies, and is a two-stager for transparency sake...a symmetrical Type 76, trannie coupled into a 245 ( globe ).
Our experimenting ONLY encompassed his 245 output stage B+ supply Ron !!
He had been using a multi-tapped Signal Transformer DU1/2 power trannie ( a 500 VA stable monster ) with only about 3 ohms DCR, into four TV damper diodes as a full wave tube bridge. Choke input, L1 was 1/2 of a 8 HY Lundahl choke ( 4 HY @ 18 ohms ). C1 was a 100 uF round oil cap, L2 was a 8 HY Lundahl choke, wired as a CMC choke ( two 4 HY 18 ohm windings as CMC ). C2 was another round 100 uF oil cap, into a Plitron 2.5K or so output trannie.
I performed systematic changes and listened to each change to assess its worth. Everything I did was as a result of my understanding of Low C, Low HY, Low DCR supplies, as I have presented it from others up here in the Forum last year.
The output stage B+ supply I ended up with for friend Greg's amp, was this : ( L1/C1/L2/C2/L3/C3 )
Same Signal 500 VA PT and a 5U4GB hybred Graetz full-wave bridge rectifier, L1 is Triad C-56U, 35 mHY @ .75 ohms DCR @ 2A., C1 is a 10 uF round oil, as used by my first amp mentor, Mr. Fulton of Fulton Musical Industries, L2 was a Triad C-40X, .32 HY @ 10 ohms DCR @ 600 mA., C2 was a 40 uF ASC oil from Michael Percy, L3 is another Triad C-40X, and C3 is another Percy 40 uF ASC. ( I didn't get a chance to apply Mills MRA-12 bleeders after C2, to ground, but its on my to-try-next list ).
Also, since the importance of GROUND wiring in SE amps was fully explained in prior posts, I decided Greg's existing ground wiring was woefully inadequate, so I added TWO sets of paralleled clip leads to EACH run in the triple pi filters, and we both listened to that.
What did it sound like??
Fabulous Ron, one of the best amplifier and system transformations I have ever experienced in 40 years of audio experimenting. The amp played better in EVERY parameter, particulary better in its ability to play dynamics with real freedom that we both loved, and it could untangle difficult simulaneous multi-event musical information in a way that thrilled and almost at times even scared me. It WAS playing like a good audio friend of mine says: " a gated 200 watt amp ", with real gusto, verve, and yet with unbelievably great nuance. I never have had such an easy success in all my years of doing audio. IMHO Ron, this experiment and listening experience has way foreshadowed any "DCR-only" stuff I have done or can recall. This B+ output stage supply....... just had it all.
Net result is Greg and I are very enthused and Greg is going to rebuild his 245 SE amps, from a two chassis stereo 245 SEer with separate power supply chassis and umbillicals, to a pair of mono SEers, with ALL the wiring proper and parts placement intimate and well thought out, as per prior Forum suggestions. Ron, no longer will I use umbillicals in my gear.
Oh, one other BIG BIG BIG improvement came when we significantly dropped the OP-POINT on the 245s so that they more closely reflected a Golden Ratio percentage ( 62% ) of the Manufacturer's suggestions. It went from VERY STRAINED sounding at Manufacturer's suggested op-point, to TOTALLY RELAXED and LUCIOUS sounding, just lovely to hear.
Amazing thing to me was ALL of this we covered on-Forum, last year and maybe early this year. Even though I listened to different changes, the amp really was the sum of ALL that we did and it was certainly synergistic. BTW, on his Altec 515's, we found that the ripple was NOT audible, even though it measured very very high at 1.09 VAC on a Fluke 8060A, so I now think output stage ripple is NOT much a factor at all, ESPECIALLY when compared to the overall sonic benefits we both heard from Low HY, Low C and Low DCR. Really, there was "no contest" as to how good this performed. Pretty cool audio news, eh Ron !!
So, Really, YES !! Thats my report.
Jeff Medwin
Greg and I have since the above report, converted the front end B+ supply of the two Type 76s to a similar Low HY, Low C, Low DCR supply, with excellent overall amplifier results.We have decided to eliminate the small L1 and C1 used in my above post ( 35 uHY and 10 uF oil ), and we settled on simply what remains, as the best-sounding configuration for both supplies. i.e.: L1 is .32 HY at 10 ohms, C1 is 40 uF ASC oil, and it is just the same parts, repeated as L2 / C2.
Not stressed sufficiently in the above report is that we found out, from our listening comparisons with this type of supply, that the wire gauge was critical. We did this experimental configuration with clip leads, and I recalled Dennis saying how important it was for the grounds in a SE amp to be substantial. So, I added, in parallel, a second set of clip leads at every point in the filter system, and it was quite a bit better.We eventually settled upon three clip leads in parallel, until Greg rebuilds it all, losing his umbillicals, into two mono chassis with short heavy wire paths.
Heavy wire from the tube rectifiers forward, through L1/C1/L2/C2, is an absolute necessity to properly hear the benefits of this type of supply!! Its great !! We love it. I owe Dennis a debt of gratitude for sharing this with me, and for allowing me to post it up here publically on the Forum mid-2006.
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