Transformer brand question

[keaster]

Just looking through some amp circuits for something cheap to build and came across this

I was going through the parts to get an idea of how much it would cost to build and was shocked at the price of the Hammond transformers. I've used Edcor before and found something that I think would be a close match.

Hammond 1608A $117
Edcor GXPP10-8-8K $26.10

So why so much difference in price?

 

[GloBug]

The Edcor is 1.75 lbs.
The Hammond is 2.5lbs.

The Hammond is ~%30 bigger.

Generally the bigger the iron, the better the bass.

Lot's have folks have been using Edcore because they are cheaper though, they seem to be happy.

You can save a little bit with the Edcores but generally speaking you get what you pay for.

Get the Edcores, upgrade if you want later or save the Hammond purchase for another project.

 

[scott17]

You will get a better frequency response from the Hammond unit in comparing the two units you mention. A closer and better match for the Hammond unit is the Edcor CXPP25-MS-8K. Superior frequency response and still less expensive.

EDCOR Electronics Corporation. CXPP25-MS-8K

 

[kmaier]

Well, agree on iron opinions so far.... better iron costs more, period, and you should be careful as this is a budget design (low parts count and cheap) with feedback. In my view, why bother (I built the original referenced Dyna circuit from the original (Dyna) brochure over 45 years ago, it's not that great), you can add one tube and do so much better (for a stereo amplifier).

Regards, KM

 

[scott17]

You will get a better frequency response from the Hammond unit in comparing the two units you mention. A closer and better match for the Hammond unit is the Edcor CXPP25-MS-8K. Superior frequency response and still less expensive.

EDCOR Electronics Corporation. CXPP25-MS-8K

This Edcor PT would also be a good substitute for the Hammond PT:
EDCOR Electronics Corporation. XPWR172-120/220

 

[DavesNotHere]

I would do the 25W edcor or even a 50W for more power headroom.

but I would change the coupling caps : .1 to 1 uf and the bypass on the output from 47uf to 330Uf as that will give you better power bandwidth gain at lower frequencies. and the classic designs are set up this way.

 

[Richard Ellis]

Another observation here............" 0.25 Watt resistors unless otherwise noted".

No, no, use some One-Watt resistors, don't be cheap....someone wanted to cheapen things......Rules of thumb, Over design...don't run it any-where near the limits, overbuild! Besides 0.25 watt resistors can be so small to work with....1W are better.

_________________________________________________Rick............

 

[keaster]

Now that the topic has turned to the amp circuit....is it any good?

 

[rmyauck]

This might be more appropriate with close to 25% UL taps.

EDCOR Electronics Corporation. CXPP25-MS-8K/23%

Also look at the Z-565 clones out there say ones from:

Z565-48 17.5(35W) Watt Triode USA Dyna Clone Output Transformer for Dynaco MADE IN USA

If you have the budget.


Broskie's looks like it is a well liked PP design for diy P2P wiring.


http://www.diyaudio.com/forums/tube...-circuit-referenced-tubecad-journal-site.html

Use Dave Gillespie's EFB mod on it for great sonics.

http://tronola.com/html/dave_s_lab.html

More info at diytube.com under ST-35

For example:

http://www.diytube.com/phpBB2/viewtopic.php?t=4654

Randy

 

[rmyauck]

George's tubelab simple EL84 PP board is another great way to go and you can get a kit of board parts for it.

http://www.diyaudio.com/forums/tubelab/195626-board-availability-13.html

 

[Miles Prower]

Now that the topic has turned to the amp circuit....is it any good?

For what it is, it's not bad. You won't get uber-premium performance from it, but it'll sound pretty good.

That floating paraphase splitter isn't as good as an LTP or cathodyne (unequal harmonic distortion between phases, residual AC imbalance) and I'd like to see lighter plate loading for the 6SL7, as this loading comes a bit close to the rp. However, it's a simple design and you could do a good deal worse in that regard.

 

[roline]

The cheapest iron that I know of are the NSC041318 8K-8 AT $22 EACH. I used a set on my first Compactron amp design because of it being close to Christmas and delivery was delayed on the big iron. The elves did not want to miss being able to stuff it in a stocking... It was completed in time for the elves to break it in to "Dark Side of the Moon", that should have no negative effects on the long term stability of the Amp or the Elves...
The amp was designed for ~30 watts in Triode mode, so the iron needed to be and was upgraded this Christmas, 35 watt iron chosen with Z11 silicon steel. They were $65 each delivered.
A little louder and improved authority on the base, we also replaced the 6U10 driver with 6AC10's..
You can see in the pic that the 8k-8 outputs are dwarfed by the 10lb'r power transformer.

For a DIY, in-expensive 6L6 Dynaco like design, I did a Kegger inspired PCB. The cheapest output tubes were the 6P3S Russian 6L6's at $4 each. I used it to play with different feedback schemes, output transformers and B+ voltages. I tried poly and PIO coupling caps Ul and triode mode. For the lowest cost, 6P3S tubes in triode mode (no UL taps) with the NSC041318 8K-8 iron ~25watts/channel.
For UL, I replaced the outputs with Hammond 1650H 40watt with UL tap and tried both UL and triode mode. My favorite version was with boosted B+, Svet-6550=C='s in triode mode with 1650P iron, not the cheapest version, but I was surprised how well the 6P3S tubes sounded on a diet of 360V.
The PCB was designed to fit on a 8.5x11 sheet to allow for toner transfer PCB fabrication in the sink for DIY folks.
The NSC041318 iron is used in a 25 watt Fender Amp and can be found from several vendors online.