Old or new output transformer?

Cycline3 · 21st August 2007, 03:44 AM

OK, here's my problem. I have a pair of output transformers from an EICO HF87. Many of you know -- they are excellent quality. I built a tube amp around them back in the 80s and the power transformer (50s era) has failed. I want to build a new dual mono amp for my main stereo... and my problem is... do I use the excellent, yet getting very old transformers OR risk going with a new hammond/edcor/whatever? I have a hard time thinking I'll get a better output transformer than what I have, but in putting in all the hours of work into a new amp, I'd like to think it is going to be fairly reliable. Any thoughts? My gut is telling me to use the old ones, my common sense is telling me to use new... alas...

DigitalJunkie · 21st August 2007, 04:19 AM

As long as the wiring,etc. on the old ones isn't brittle and falling apart... I'd go ahead and use them.
They shouldn't fail,unless the bias fails,or some other 'catastrophic' event,-which could damage a new tranny (and/or tubes) just as easily as an older one.

my .02 anyways..

planet10 · 21st August 2007, 05:58 AM

Go ahead use the old ones... even with new ones it is a good idea to do the build so that different transformers can be swapped in.

dave

SY · 21st August 2007, 01:13 PM

I'll be the contrarian. The Eico opts (made by Chicago Transformer) are pretty good, but they have their problems. The severest one is a fairly substantial side-to-side imbalance at high frequencies (note the 1nF cap in the original circuit to try to fix this). On the bass end, the Eico transformers are very good, and much better than competitive Dyna or Acro units.

But if I were taking the trouble to scratch-build an amp, I'd go new, both for reliability and performance. With modern opts, you get new and better insulation, new and better core material, and new and better winding techniques. I would guess that $200 would get you a pair of new opts that would blow away the Chicago iron.

arnoldc · 21st August 2007, 03:06 PM

Like James

Cycline3 · 21st August 2007, 05:12 PM

OK.. a little more info:

I don't use the EICO circuit at all. So referring to the original amp in ref to the transformers may not apply. The transformers are physically in excellent condition - the wiring and insulation is in some of the best condition I've seen on vintage parts. So in that case, they are good to go. As for sound - I won't write them off as easy to best, they are excellent and I've got a lot of WOWs from friends and audiophiles (with lots of experience with gear) alike. Plus, they impress me and I count the most! So it does in some extent boil down to - I am not sure I'll get better iron from new parts but I want this thing to last another 20 years. I suppose I could breadboard and test old iron vs new for sound quality before I build the final amp... and I suppose I'll have to consider it. I do appreciate everyones comments and hope we get some more opinions on here to help me decide. Thanks everyone.

planet10 · 21st August 2007, 05:43 PM

Quote:

Originally posted by SY
I would guess that $200 would get you a pair of new opts that would blow away the Chicago iron.

I'd still go ahead and use the old iron. You should always design to accomodate the option of replacing the iron later -- even if it is brand new iron.

It also depends on how much you total build is going to cost.

dave

richwalters · 21st August 2007, 06:15 PM

Bit awkward this one...... if the transformers were manufactured to class A then alone materials enamel etc are expected to last 20 years continuous slog. If overheating and stress as taken place then times up ! Judge for yourself.. ??
However the catch as Planet 10 mentions always recon for Murphies Law. Modern-day replacements from good vendors can out perform old ones and put budget aside.
Another 20 yrs from now will see only a few types of popular tubes about.

richj

HollowState · 21st August 2007, 06:29 PM

I agree with the others, use the old transformers since you like them and say they aren't dried out. To help assure their safety, consider putting an appropriate sized slo-blo fuse in the B+ feeding the center to protect them from a catastrophic tube failure.

anatech · 21st August 2007, 07:36 PM

Hi SY,
Well, you know I have an Eico HF-87 that usually sounds great. What transformers would you consider using as replacements?

Oddly, I found the very high frequencies the best on these. Very clean.

-Chris

21st August 2007, 03:44 AM	#1
Cycline3 diyAudio Member Join Date: Jul 2007	Old or new output transformer? OK, here's my problem. I have a pair of output transformers from an EICO HF87. Many of you know -- they are excellent quality. I built a tube amp around them back in the 80s and the power transformer (50s era) has failed. I want to build a new dual mono amp for my main stereo... and my problem is... do I use the excellent, yet getting very old transformers OR risk going with a new hammond/edcor/whatever? I have a hard time thinking I'll get a better output transformer than what I have, but in putting in all the hours of work into a new amp, I'd like to think it is going to be fairly reliable. Any thoughts? My gut is telling me to use the old ones, my common sense is telling me to use new... alas...

21st August 2007, 05:58 AM	#3
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Go ahead use the old ones... even with new ones it is a good idea to do the build so that different transformers can be swapped in. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

21st August 2007, 01:13 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I'll be the contrarian. The Eico opts (made by Chicago Transformer) are pretty good, but they have their problems. The severest one is a fairly substantial side-to-side imbalance at high frequencies (note the 1nF cap in the original circuit to try to fix this). On the bass end, the Eico transformers are very good, and much better than competitive Dyna or Acro units. But if I were taking the trouble to scratch-build an amp, I'd go new, both for reliability and performance. With modern opts, you get new and better insulation, new and better core material, and new and better winding techniques. I would guess that $200 would get you a pair of new opts that would blow away the Chicago iron. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

21st August 2007, 06:29 PM	#9
HollowState diyAudio Member Join Date: Aug 2006 Location: Taxland, New Jersey	I agree with the others, use the old transformers since you like them and say they aren't dried out. To help assure their safety, consider putting an appropriate sized slo-blo fuse in the B+ feeding the center to protect them from a catastrophic tube failure. __________________ "The supercomputer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required." ~ Professor of Electrical Engineering, New York University

21st August 2007, 07:36 PM	#10
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi SY, Well, you know I have an Eico HF-87 that usually sounds great. What transformers would you consider using as replacements? Oddly, I found the very high frequencies the best on these. Very clean. -Chris __________________ "Just because you can, doesn't mean you should" © my Wife

21st August 2007, 04:19 AM	#2
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	As long as the wiring,etc. on the old ones isn't brittle and falling apart... I'd go ahead and use them. They shouldn't fail,unless the bias fails,or some other 'catastrophic' event,-which could damage a new tranny (and/or tubes) just as easily as an older one. my .02 anyways..

21st August 2007, 03:06 PM	#5
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	Like James

21st August 2007, 05:12 PM	#6
Cycline3 diyAudio Member Join Date: Jul 2007	OK.. a little more info: I don't use the EICO circuit at all. So referring to the original amp in ref to the transformers may not apply. The transformers are physically in excellent condition - the wiring and insulation is in some of the best condition I've seen on vintage parts. So in that case, they are good to go. As for sound - I won't write them off as easy to best, they are excellent and I've got a lot of WOWs from friends and audiophiles (with lots of experience with gear) alike. Plus, they impress me and I count the most! So it does in some extent boil down to - I am not sure I'll get better iron from new parts but I want this thing to last another 20 years. I suppose I could breadboard and test old iron vs new for sound quality before I build the final amp... and I suppose I'll have to consider it. I do appreciate everyones comments and hope we get some more opinions on here to help me decide. Thanks everyone.

21st August 2007, 06:15 PM	#8
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	Bit awkward this one...... if the transformers were manufactured to class A then alone materials enamel etc are expected to last 20 years continuous slog. If overheating and stress as taken place then times up ! Judge for yourself.. ?? However the catch as Planet 10 mentions always recon for Murphies Law. Modern-day replacements from good vendors can out perform old ones and put budget aside. Another 20 yrs from now will see only a few types of popular tubes about. richj

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