Transformer Shootout- Hammond vs Magnequest vs Dynaco vs HW

for the DIY ST35, the Dynakit and every other PP EL84

Postby EWBrown » Wed Jan 10, 2007 9:45 am

I know, this topic has been dormant for a long time...

While doing some minor cleanup in the cellar, I stumbled across the old pair of HWTs that I had long ago replaced with Hammond 1620s, then later, stole the board out of that amp, to build up another into a Par Metal chassis.

Anyhoo, the HWTs surfaced (I had forgotten about them), and I couldn't remember their cockamamie color code, so I did some DCR measurements just to try to accomplish this.

First thing I noticed, the DCR on all windings was substantially lower than that of the Z565s, about 40% of that on the Dynacos. Where the CT to plate was aboput 190 ohms on the 565, it was about 76 ohms on the HWT. Similarly, the other plate and the UL taps read proportionally lower.

So, does this mean that they "cheaped out" and used less turns, or (very unlikely) used heavier gauge wire for the windings. All things considered, I'll have to go with the first chioce, less turns... cheep cheep cheep

Since I NEVER throw anything away which may have a possible future use, I suppose some day, they'll land in some "plinkertron" design which evolves out of too much winter cabin fever and bad home made beer... Yellow_Light_Colorz_PDT_09

If anything the end bells look pretty nice with their silver-gray hammertone finish, I'l probably take them off and use then on a couple of good working, but ugly-looking Z565s, which I yanked out of a junker SCA-35 some time ago. The HWs can get the cruddy looking, dented Z565 ends and get the "plinker" treatment at some future date... Yellow_Light_Colorz_PDT_21

BTW, HWT is (deserrvedly so) long sinve demised, it devolved itself out of existence, it's totally gone, flushed down History's Toilet, , along with the T-Rex, Dodo Bird, and Wooly Mammoth. It has rolled up its tootsies and joined the "choir invisible". It's not pining for the Norwegian Fjords, It is a DEAD parrot.... Yellow_Light_Colorz_PDT_07

/ed B in NH
Last edited by EWBrown on Fri Jan 12, 2007 9:27 am, edited 1 time in total.
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Postby sorenj07 » Wed Jan 10, 2007 4:58 pm

Well, I was wondering how the Edcor 7600-ohm 25-watt OPT's would stack up against these (pardon the pun)... if you ever pick up a pair, would you mind crunching the numbers please? Yellow_Light_Colorz_PDT_07
User avatar
sorenj07
KT88
 
Posts: 925
Joined: Tue May 02, 2006 2:39 pm
Location: Berlin

Postby EWBrown » Fri Jan 12, 2007 9:31 am

I haven't yet tried the Edcors, but I would bet a silk pajama that the Edcors would "stomp" the HWTs... Given that Edcor is still in business and Lucas's Folly HWT is extinct. or is that EX-Stinked Yellow_Light_Colorz_PDT_21

At the Big Output Transformer Shotout at the OK Corral, Magnequest brought a .44, Hammond brought a .38, and HWT showed up with a rubber knife. Yellow_Light_Colorz_PDT_05

The next unknown trannie company I'll be trying, is Trafomatic, in Serbia, I have a set of ST35 toroidals coming from them through Vista Engineering in NY State. Stay tuned...

/ed B in NH
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Postby mesherm » Tue May 01, 2007 2:55 pm

So Ed, did you ever get your toroidals from Trafomatic for an ST35?
If so, how did they sound?
I see them pop up on ebay from time to time and am getting that familiar "got to build something" itch.
User avatar
mesherm
KT88
 
Posts: 1232
Joined: Fri Aug 27, 2004 10:33 pm
Location: Alvin Texas

Postby sorenj07 » Tue May 01, 2007 10:32 pm

another OPT maker other than Sowter or Hashimoto/Tango that interests me is Korato out in Belgrade.

http://www.korato.com/product.php?id=105

anyone deal with them? Their transformers look sweet.
User avatar
sorenj07
KT88
 
Posts: 925
Joined: Tue May 02, 2006 2:39 pm
Location: Berlin

Postby EWBrown » Wed May 02, 2007 5:10 am

I did get the toroidals, there was a mixup, which eventually worked out big time in my favor. The original order was two OPTs and a power trannie, I ended upgetting four OPTs at a three-trannie price, then later on got two of the power trannies at a 10% discount, those arrived just last week. So now I have two complete sets, two stuffed and ready rev D boards, and all I need is some time... My projects are getting "backed up" like a toilet at a cheese factory.... Yellow_Light_Colorz_PDT_09

So I guess it isn't just five projects in progress (sort of), make that seven :o Yellow_Light_Colorz_PDT_02

/ed B in NH
Last edited by EWBrown on Wed May 09, 2007 5:06 am, edited 1 time in total.
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Postby parabellum » Wed May 02, 2007 12:20 pm

sorenj07 wrote:another OPT maker other than Sowter or Hashimoto/Tango that interests me is Korato out in Belgrade.

http://www.korato.com/product.php?id=105

anyone deal with them? Their transformers look sweet.



Korato was started as a two man operation by two enhusiasts. Now there is about 7 people in the company. They handbuild amps. Their transformers are apperantly made by Trafomatic by their specifications. Funny thing is that they are virtualy unknown in their own homecountry because noone there believes something of quality can be built there.
User avatar
parabellum
 
Posts: 195
Joined: Wed Apr 25, 2007 1:37 pm
Location: Bay Area, CA

Postby EWBrown » Thu May 03, 2007 6:40 am

FWIW, the Trafomatic Trannies look like those in this EL84 amp:

(It's not one of my amps, I just show this as an example of what the trannies look like, on mine, the label is on all three of them).

Image

THis particular amp uses four EL84s and two ECC83 / 12AX7s.

I may have posted this or a similar photo earlier, but I was too lazy to look for it Yellow_Light_Colorz_PDT_09 Yellow_Light_Colorz_PDT_02

The toroids are potted in a red compound inside the metal covers, the leads come out in a neat bundle. Mounting is a single 8mm (?) bolt.

The leads' color coding is definitely not US standard, they do supply a schematic and lead identification sheet..

The power trannie has dual 120VAC windings, so these are a neat solution for those who want to build an ST35, and live in 240VAC / 50Hz countries. The other solution being the Hammond 37* series, with the "universal" primary windings.

/ed B in NH
Last edited by EWBrown on Wed May 09, 2007 5:08 am, edited 1 time in total.
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Heathkit transformers

Postby leadtower » Thu May 03, 2007 2:44 pm

I have a half a dozen Heath UL transformers from old amps. They were used for a PP 12A6/12V6 ouptut tubes. Does anyone know if they can be used in the ST 70? I looked on the Heath site and they are listed as 7K pri/8/16 sec.
BTW very nice amp EW.
leadtower
 
Posts: 200
Joined: Tue Mar 30, 2004 8:39 pm

Postby erichayes » Thu May 03, 2007 3:35 pm

The impedance is close enough for government work, but you'll have to throttle back the B+ to keep the power within their limitations (6V6s are good for up to 45 mA, but only at 250 VDC).
Eric in the Jefferson State
erichayes
KT88
 
Posts: 987
Joined: Fri Jan 23, 2004 9:01 pm
Location: McKinleyville CA

Ultralinear 6V6

Postby Gingertube » Fri May 04, 2007 12:57 am

leadtower,
Don't know if your still watching this thread but I've just posted a stunning (if I say so myself) 6V6 Ultralinear design to another forum. Those Output Trannies would be ideal.
IF interested check it out here:
http://www.diyaudio.com/forums/showthre ... did=101047

Its a Ultralinear plus balanced shunt local feedback design which I have found works really well. I've built 4 amps (1 ECL86, 2 6V6 and 1 EL84) and modified a Chinese EL34 push pull (To Triode Mode KT77) to this basic cicuit now was extremely happy with all of them.
Cheers,
Ian
Gingertube
 
Posts: 245
Joined: Thu Oct 05, 2006 10:27 pm
Location: Adelaide, South Oz

Postby EWBrown » Fri May 04, 2007 5:33 am

The 12A6/12V6 OPTs would be perfect with 6V6s (5V6 and 12V6) and some of their compactron equivalents (look under recent "Plinker of the Day" postings.

Also 6AQ5s (5AQ5, 12AQ5), 12AB5s, and even 6BQ5 / EL84s, all of which like to see around 7 to 8K P-P primary impedance. Though the 6BQ5s should be run at a lower B+ (320VDC or less)and output power, keep it 12 WPC or less to be safe.

12AB5 isbasically a 6AQ5 or 6V6 inside a 9 pin miniature envelope, with the same pinout as a 6973. These are available for low cost,and are decent tubes.

The ST70 voltages and currents would assure a very short lifetime for these trannies :o

I didn' t build that nice looking , nor have one, that is one of Boris's designs, he does some nice work! Mine will have more of my normal "Russian war surplus" look to them...
The normal cost for a set of these toroids is a little bit less than the PA774 and two Z565s from TubeZOne or Triode, my main interest is to try them out and see how they sound, and hold up over time.

/ed B in NH
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Postby parabellum » Tue May 08, 2007 3:51 pm

I just became aware of another possible affordable source of toroids. http://www.trafco.co.yu/ They are supposedly cheeper then Trafomatic. Both serbian.

I'll eventually do some more digging to find more details.
User avatar
parabellum
 
Posts: 195
Joined: Wed Apr 25, 2007 1:37 pm
Location: Bay Area, CA

So, whats the consensus??

Postby GrooveGrinder » Sat Sep 29, 2007 3:15 pm

All very interesting.... but I didn't come away
with an understanding of which is the best
tranny for the Dynas'!
Maybe its time to update this thread.
Lotsa folks would like to have some clarity before
starting a project.

Is there a consensus, at this time, as to which
is the best choice??

Thanks
GrooveGrinder
 
Posts: 40
Joined: Thu Sep 27, 2007 11:05 pm
Location: SoFla

Postby Ty_Bower » Sun Sep 30, 2007 7:44 pm

I'm not sure there is a single "best" output transformer for the DIY ST-35.

I've got a set of Hammond 1620 in mine, and you really can't beat the performance at their price level.

I think the original Dynaco Z-565 sets a very high standard, but you can't exactly buy them anymore. Prices for eBay donors runs high. Plus, there's no 4 ohm tap, which might be an issue for some.

I've seen the transformers that Eric Hayes has. I believe they were designed as a replacement for the Z-565, but with superior performance characteristics. He offered some for sale a while ago - I don't know if he is still selling them now. I haven't yet heard them myself, but the old test reports I saw were very impressive. I betting they're a contender in the "price-no-object" category.

I recall reading the Magnequest transformers were excellent, but they too are now out of production.

I don't think you can go wrong with the Z-565 reproductions sold by Triode Electronics.

Did I miss any?
User avatar
Ty_Bower
KT88
 
Posts: 1494
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

PreviousNext

Return to stereo 35

Who is online

Users browsing this forum: No registered users and 8 guests