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In Reply to: RE: The last 26-26 DC 45 amp schematic .... posted by kyle on January 24, 2015 at 08:00:22
Kyle,Willie's earlier schematics showed a Hammond 274X with a 134 Ohm DCR high voltage winding. Likely, ..... that is what he used.
The 274BX, with about an 80 ohm DCR winding, will work FINE, especially if yours is a later one and has the 115 and 125 primary taps - use it on 0-125 VAC input !!
An unused 6.3 VAC winding will not be very much of a factor in overall VAC output with the lightly-loaded high voltage secondary winding. PT is working in a loaf mode.
Over Christmas 2014, Willie's unique / original build inspired me to design a 26-26-45 amp, ( without the cap couple ), and I gave it an absolutely over-the-top KICK-ASS, easy-to-implement power supply.
I did not bother to build it, ( 'am more interested in optimized two stage amps ), but ..... I would be happy to post my schematics IF anyone is interested and / or thinking of doing a 26-26-45 amp. I believe it is a solid design.
One day, later in the year, I hope to drive to St. Louis ( 225 miles one way ) and visit Willie, so we can A-B our various DIY amps on his MLTLs, and have some FUN !!
Jeff Medwin
Edits: 01/24/15Follow Ups:
Somewhere in his thread, he mentioned better iron. I'm surprised you haven't suggested Magnequest OPTs.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
Yeah, I'd use my M.Q. DS-050s, ( and "rob" my 1/2 12AT7 - 6AQ5 triode connected DC two stage amp ), ... which I am unwilling to do !!
Output iron is not that big of a deal-breaker here IMHO, but me getting RID of the amp's one cap couple, is what "I" honed-in-on doing in December.
Jeff Medwin
9H of inductance won't get you much bass, which is clearly reflected in the specifications for the Hammond 125 series transformers.
Just curious C.B. Have you ever used a Hammond 125ESE ?
Willie
Yes, I used them in some bread board circuits some years ago, but ended up getting rid of them on eBay in the end.
Don't get me wrong, if you don't care about bass and just want to experiment, they work well!
My experience with the new version of the 125ESE has been totally different.
First off the new 125ESE are almost twice the size of the originals they can actually handle 15 watts..
On my GPA 604's there's plenty of bass. ( Due to reworked Xover and Wiring).
All that, and just as you said " to experiment, they work well".
I just don't want anyone to write them off as not "hifi" enough to listen to.
Willie
If you rework your speakers to complement an output transformer with sub-par inductance, that will help mask the issue, but it will make other amplifiers with better iron sound bass heavy.
Hello,What the heck are you talking about? The discussion was on Hammond's "Classic 200-Series" power transformers. Was your post meant by you to be part of this thread?
Please explain or delete it, and I will do likewise. Thanks !
Jeff Medwin
Edits: 01/24/15
You said output iron wasn't a deal breaker
..
Ohh, OK, it isn't !!
I could build an amp and, (as my friend Dennis Fraker likes to say), put a doorbell transformer on it, and it can outperform 95% of the tube amps out there.
Outrageous?? Not really. Do you know how to do that ?? You may !!
Jeff Medwin
I was beginning to think this was going to be a constructive discussion until I scrolled down some.....
nt
Here we go again.
maybe you can jeff... but in that same amp if you replace the doorbell transformers with hammond or mq iron it will be significantly better.
really though.. I think the doorbell transformer thing is a myth.. and I briefly scrounged for doorbell transformers after reading that line in the past too....
what core material do you suppose they use on those doorbell transformers? suppose they interleave the coil for good doorbell frequency response?
would the doorbell transformer need new leadouts?
is it possible that those doorbell transformers, with their super charged leadouts... could they possibly have an effect similiar to that which you've mentioned of octal pins? that is, an added solder joint vs a noval socket? solder joints add up!
A doorbell transformer , if it's an EI transformer will have a split bobbin and no airgap . Hence distorted bass and no top-end . If it's a toroid , it will have no airgap and play ok in the HF but have distorted bass unless cap-coupled . Add a choke for the anode load , plus a cap and the costs go above what you'd pay for a basic output transformer . You could scrimp and use a cheap PSU choke as anode choke and a line matching transformer but this is purely an acedemic excercise in attempting to save money rather than build something decent-sounding , especially when there are those inexpensive Edcor transformers out there .
Al
Well said. Awfully "straight" and thoughtful answer Al, loved it !! I just like to rile the conventional-thinking audio guys up some, every now and then, helps me maintain my image and lack of credibility, gotta remain consistent, otherwise its no FUN !! :-)
Jeff Medwin
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