Getting desperate looking for OPT

Mullard 5-20.

After refreshing my memory, it turns out the transformers I used were the CXPP30-MS-6.6K. The thread that discusses my issues with Edcor are here and here.
You make my day, You actually compare Edcor and Hammond and Hammond won!!!! Now I am excited about the Hammond 1650T. I think I can live with 1.9K primary. I can live with $150ea.

PartExpress is $175ea, free shipping. Mouser is $148 BUT only has one.

Ha ha, go Canada!!! all of a sudden, it's Hammond and maybe Plitron in the future.
 
That's cool. I've been reading Pak's posts here for a decade. Look forward to reading yours here in 10 too. Do post what you come up with.

;)
I don't think so, I move from guitar amps to SS power amp to this in the last 5 years. I don't stay in one area that long. Even in my career, I jump to different field in electronic from job to job. From designing digital scope front end for LeCroy, to Exar designing analog IC, to frontend of Ultrasound medical scannel for Seimens, to mass spectrometers, to defense contractor for military........... Never stay in one particular specialty. Too boring to stay in one field for years.
 
Yep, what's life without new challenge? I was a musician before I was 25. Here are two recordings of my street jam in 1978 almost 40 years ago in post #59 http://audiokarma.org/forums/index.php?threads/how-to-calculate-gain-and-draw-loadline-for-tubes-with-cathode-resistors.797692/page-3

I don't think this is anything to sneeze at 40 years ago. I won 4 times #1 in talent quest in Hong Kong before I turn 21. I dropped music stone cold in 1979 and never looked back. I was part time photographer in the mid 90s doing wedding and product shot for like 4 years and I dropped it stone cold, never look back.

Life is an adventure, don't want to be the best, just want to be better than a lot. Then move onto other adventure. Here are some of my photography work.
Henry L.jpg Jerome and Karisa L.jpg HD L.jpg Lazer lens L.jpg

These are pre-photoshop days, everything in one shot, all real lighting, no touch up. Unlike the photography now a days that you don't even know what they are doing. One shot, on film or transparency, all or nothing. I still have my complete set of Hasselbrad with 3 lens, all the lighting equipment at home, just store them in the garage. Still have a few guitars like a 75 Les Paul, a 97 American Standard Strat and a 2001 AS hard tail Strat. Don't know why I bought the two Strats, I just did.


Life is an adventure.
 
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I just got reply from SAC Thailand, they don't have the P-2220N just the C-core version and much more expensive. As expected, the shipping is horrendous. This is the email and the picture they send me, I just screen capture the reply and the picture they sent:

SAC reply.JPG

Well, that's a dead end.

Looks like Hammond 1650T is the only choice now. I did the load line for +B=400V, I lower the power dissipation on the tubes to preserve them a little better. As expected, since the 1.9K composite loadline cut to the right of the Vg2=0V curve that is quite horizontal, lowering the +B just take the load line shift horizontally to the left and won't reduce the output power much. For +B=400V, I get 46.2W output with the first 13.3W in pure class A. Now I have to power the Antek 400VA transformer up and maybe taylor the voltage to +400V.
 
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Mullard 5-20.

After refreshing my memory, it turns out the transformers I used were the CXPP30-MS-6.6K. The thread that discusses my issues with Edcor are here and here.
Hi Kevin

I gone through both of your threads, the second one is very interesting, the UL wires are reversed. Now I have to watch out on this.

When I got the Dynaaudio OPT from Max, I did not know which of the 5 wires is which, I ended up measuring the resistance between the wires and after some measurement, I managed to sort out the order of each tap. Like the correct UL tap with the plate wire should have lower DC resistance than the other UL tap. I better do this measurement before I wire up the transformer.

I can see why you don't like Edcor on top of the sound is not as good as Hammond, this is bad. Did you actually have to pay to ship it back?

I bookmarked your two threads, I need to re-read your thread when I get to that point, I am not there to really understand about your tuning, still have a lot to learn on this. I barely manage to choose the transformer and tubes on paper. I am sure in real life testing, there are a lot more to learn than on paper.

If you have other threads that is of interest, please give me the link, I like to read people's experience, how they solve the problems.

BTW, I downloaded your schematic for reference.

Thanks

Alan
 
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Hi

I know I have been talking about this here. I am desperate to find a little more reasonable priced OPT with primary impedance between 2K to 2.5K to do the first run prototype for me design. I really don't want to spend over $700 for a pair of good OPT on the first try. The only one that is reasonable is Edcor that is $110 each. But through communication with Edcor, I am not too confident with them. I have not managed to find anything in between Edcor and the more exotic Lundahl/Sowter or even Plitron.

Only other a little more reasonable is SAC from Thailand:
View attachment 1057888

Hammond has the 1650T that is 1.9K primary and it's $148 each + shipping. 1.9K is pushing it. More importantly, from things I read, Harmond is not exactly an upgrade to Edcor!!!!

I am output of ideas. Anyone have anything else? Or any more encouraging things to say about Edcor to make me feel better in buying the Edcor?
Alan - From the list you showed, you are looking for a 100w, dual secondary transformer. That's going to cost. How about trying a 50w, single secondary tranny? It will be cheaper and should be able to prove out your design with it. I have used both Edcor SE and CXPP trannies and I like them. Now they only deliver 20Hz-20kHz but do you really want a transformer that goes out to 175kHz ? Seems excessive.
 
Alan - From the list you showed, you are looking for a 100w, dual secondary transformer. That's going to cost. How about trying a 50w, single secondary tranny? It will be cheaper and should be able to prove out your design with it. I have used both Edcor SE and CXPP trannies and I like them. Now they only deliver 20Hz-20kHz but do you really want a transformer that goes out to 175kHz ? Seems excessive.

I am not looking for dual secondary OPT, I don't think there's one. Yes, I am looking for 100W or over. I think I am leaning towards Hammond 1650T 120W 1.9K primary OPT.

Higher frequency response is important for taming the GNFB, one wants to push the polls as high as possible beyond 20KHz.
 
1650T is dual secondary.

Why are you building a gNFB amp?
cheers,
Douglas
Ha, I just notice it has a feedback secondary.

I have not cast anything in stone, GNFB works for my SS amp, so I assume it's going to work. It lowers the output impedance, extends the BW and lower THD. So in the first pass, GNFB is good.
 
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Ha ha, Hammond just confirmed they do more interleaving than just the UL taps, that they actually have to have two secondary to accommodate the interleaving.
 
What I meant is with UL tap, by default, it has at least 4 sections already as there are 4 winding from the top tap, UL, CT, UL and bottom tap they have to pull wires out. From the description in Hammond, I strongly they have more sections than the minimum 4 sections.
 
Hammond has two secondaries so that turns aren't wasted when a 16 ohm isn't used. A normal secondary will only be half used with 4 ohm loads, leading to increased i^2r loss the Hammond wiring uses much more of it, and as a result, performance is better. Unless you have 16 phm speakers, it's best to wire it just for 4 and 8 ohm loads. Sowter does something similar with their transformers.

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sec3.gif
 
What I meant is with UL tap, by default, it has at least 4 sections already as there are 4 winding from the top tap, UL, CT, UL and bottom tap they have to pull wires out. From the description in Hammond, I strongly they have more sections than the minimum 4 sections.

Your understanding of how an OPT is wound is lacking a wee bit. Why not start with something easy, and examine what is inside of a Dynaco A470. If you can make use of that information, I can show you what is inside some significantly more complex and higher performance winds I happen to have winding cards to. Speaking of which, what output TX's *DO* you have the winding card to?
cheers,
Douglas
 
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