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Old 21st February 2008, 02:20 AM   #11
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So if these are good for hifi they ain't going to be all that good for a guitar amplifier...
I agree with Kevin on this for most guitar amps. For the typical electric guitar amp transformer you need to cheapen it up a bit, quite a bit. Or, in true Tubelab style, crank up the applied power to one of these. Some of the characteristic sound in many vintage amps was obtained by using too small an OPT (especially Fender). However if you are building an amplifier for an acoustic guitar, or a 12 string, a very clean sound may be desired and a HiFi type OPT may be desired. The type of speaker used plays a big part of the sound equation too.

And as a corollary if they are good for guitar use they won't be all that good for hifi..
A typical guitar amp transformer loses about two octaves on the low end since the lowest frequency a guitar can produce is 82Hz. This is usually accomplished by leaving out most of the iron. In order to save cost there is usually no interleaving, thus killing off some of the high end. Some guitar amp transformers are pretty bad, and some can actually pass audio with HiFi specs, at reduced power levels. Several years ago I bought a bunch of surplus transformers from the closing of the ADA guitar effects company. They were "80 watt" P-P OPT's that weigh in at about 5 pounds each. They work so well that I have a pair in my 300B P-P amp. They are maxed out at 25 watts though.

Those 1700 ohms units are quite interesting as they might be a good match for some low rp tubes......certainly interesting for low power cathode follower amps!
I recently acquired some 7233's and I have some Russian 6S19P's on order. I was planning a small SE cathode follower, but didn't know where to find the OPT. Now I know. I need to run some simulations to determine the best choice. With a little creativity you can get 850 ohms, 1250 ohms, or 1700 ohms. Then I will order a pair. If the HiFi experiment fails I can always build a guitar amp.

So perhaps the guitar transformers are more conservatively specced for power, but since they are bigger will have better low freq response? Just a guess...
The Edcor XSE 15-8-5K caries a 70 Hz to 18 KHz rating. I measured 16 Hz to 46 KHz. This is the frequency response at 1 Watt. There are some saturation effects that prevent operation below 70 Hz at 5 watts. The 15 watt rating seems more like something that you would see in a guitar amp. Maybe the new line of transformers are just more realistically rated.
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Old 21st February 2008, 01:57 PM   #12
kevinkr is offline kevinkr  United States
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Originally posted by Geek
*the skeptics look at the new EDCOR with fear as they tap it with a stick*
I'm not a skeptic at all, I like all of the other edcor transformers and recommend them frequently for various projects. It's just that I have not had good luck with guitar output transformers made by vendors who specialize in good quality hifi designs - they need to take a different mindset which can be very uncomfortable if you are trying to make the best quality product.

Transformers for acoustic guitar amplification are another matter, good hifi transformers work well here.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 21st February 2008, 08:54 PM   #13
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Hi Kevin,

Originally posted by kevinkr
It's just that I have not had good luck with guitar output transformers made by vendors who specialize in good quality hifi designs - they need to take a different mindset which can be very uncomfortable if you are trying to make the best quality product.

Kind of like a winery that makes a really good red - the whites usually suck and vice versa?

Brian's a smart guy over there. I can't wait to try some and see.

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Old 21st February 2008, 09:06 PM   #14
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They certainly are affordable, do any oem guitar amp manufacturers use them? I wouldn't be surprised if they stared to...Strapping a pair of 6L6GCs to the 10 watt guitar tranny would likely get that special sound...
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Old 21st February 2008, 09:22 PM   #15
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Hi Boris the blade and Fuling

Many thanks for the information on the tax system and the Swedish group buy. For the moment I will work with what I have, and ask Edcor to deliver the package to Greeley, CO before I arrive myself.

my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!
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Old 22nd February 2008, 02:54 AM   #16
jlsem is offline jlsem  United States
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EDCOR Releases Line of Guitar OPT's
I was under the impression that's all they ever made.

"Those who abjure violence can do so only because others are committing violence on their behalf." - George Orwell
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Old 22nd February 2008, 03:04 AM   #17
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Originally posted by jlsem
I was under the impression that's all they ever made.

Try building with some of the CXPP's and you'll change that attitude real quick. or maybe not
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Old 22nd February 2008, 03:48 AM   #18
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Originally posted by Boris_The_Blade
They certainly are affordable, do any oem guitar amp manufacturers use them?
They were just released... literally.

I design for CKAmps.com and will be beta testing a couple for suitability.

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Old 22nd February 2008, 05:06 PM   #19
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All this talk that guitar amp transformers have to conciously be built "poorly" by hifi standards to sound good in guitar amps----

perhaps I could offer a different view and some counterexamples;

check out (and they have some nice eye candy on their site)


they use "hifi" tranneys made by us... and seem to like them pretty well.

check out www.allessandro-products.com

George has gotten (as I understand it) some killer reviews in Guitar Player magazine and has a super clientele list of some pretty accomplished musicians. Again--- good quality output transformers are what he gets from me.

One of the legends in the guitar amp world--- Alexander Dumble has the distinction of being the last customer Peerless built a new design vacuum tube output transformer for. It was rated at 150 watts. Was quite sophisticated with tri-filar secondary windings--- a lot of interleaving. Top end response past 100khz at minus 1 db.

here is a wikipedia entry on the famous Dumble amps


Also--- realize that SUNN amps used stock Dynaco output transformers and their amps "rocked" many a house over the years.

And lastly--- for another contemporary guitar builder using quality outputs--- in this case single ended outputs and with amps up to the 25 watt range check out;


and here is a quick review I found on the six moons site of one of Gordon's guitar amps;


the guitar market is larger and more variegated than to make universal statements about how the products are made or what qualities the designers of guitar amps are looking for when they buy output transformers for their creations.

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Old 22nd February 2008, 05:44 PM   #20
Trout is offline Trout  United States
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I guess my big question is has anyone actually confirmed that the Edcor guitar series transformers are lower quality in any way? Or are they just designed with a more suitable core & interleave for guitar use.

I have used a heck of a lot of Edcor XSE & XPP OT's in various guitar amps and have just loved the big full extended sound.

As MQracing mentioned, some of the most sought after amplifiers ever made used HiFi grade transformers. Trainwrecks and Dumbles command huge money in the current market.

I have also been running a couple of the new Hammond Guitar series OT's the past few weeks and they stand up great to the OEM's I have swapped out.

I feel Edcor has just realized that the DIY guitar amp market has and is growing, Combine that with their great prices and they can easily make this a viable product line.

I can still remember the first time I called Phyllis at Edcor to order some XSE's for guitar amp replacements, She in not so many words thought I was nuts!
Once the low cost SE guitar amps like the Valve Junior and the Champ 600 hit the shores and stores, guys went nuts modding them and upgrading the OT's to various brands. Edcor XSE's turned out to be a popular alternative in both quality and price.

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