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opinions on williamsonish build?
opinions on williamsonish build?
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Old 22nd November 2019, 01:57 PM   #21
Lingwendil is offline Lingwendil  United States
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Quote:
Originally Posted by kodabmx View Post
With the voltage that low and 6000 Ra-a, you'll only get about 3W in triode out of it. You might just go pentode...
Is this in AB, or strict class A?

The speakers I currently use (karlsonator with dual 16 ohm faital pro 3FE25 wired in parallel for 8 ohm) can also use another set of drivers I have ( peerless TC9FD1808, 8 ohm) wired in parallel for 4 ohm. Would this be a bit better match since its a 3k load at that point? I've been wanting to pull a pair of the 3FE25 out to try in another project anyway, so it wouldn't be a big deal at all to swap over.
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Old 22nd November 2019, 03:21 PM   #22
kodabmx is offline kodabmx  Canada
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opinions on williamsonish build?
With 250V, 60mA, 6000 Ra-a, it's all Class A. With 300 Ra-a, it's Class AB with a limit of 2.2W class A. The total power barely goes up.
With 320V, 60mA, 6000 Ra-a, you get 4.5W watts, still all class A, and 3000 Ra-a will give you 5.25W, with a 2W class A limit.
Interestingly, if you use a pair of VPT12-4170 in series interleave, you'd get almost 15W with a 2.5W class A limit. Higher efficiency and lower DCR...

Did you say you have 6P43P? You'll get about 20% more power (with 6k load) from them than the 12AV5GA, and lower THD, too. If you go 3k load, they will make 8W, but 22W with the VPT12s (2k2 load)... 320V B+, 35mA OP.

Keep in mind these are only calculations, and I find in reality there is usually a mismatch.

Last edited by kodabmx; 22nd November 2019 at 03:27 PM.
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Old 22nd November 2019, 03:55 PM   #23
Lingwendil is offline Lingwendil  United States
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Hmmmm

I need to play with the power transformers I have on hand and see if I can't get more voltage out of them. They are industrial control types with a single multiple tap primary (480, 277, 240, 208, 0) and a 120 volt secondary. I'm running them backwards off of the the 277 volt secondary but with winding losses from the configuration I'm only getting ~270 volts after the rectifier. I'll try to maybe run from the 480-208 taps instead and see if the loss is any better. Maybe I can try a doubler off of the 0/208 windings even

I already have an EL86 pentode connected (my daily use one, even) amplifier that I plan to use with 6P43P triode connected once this project is finished, so I'll try to get something together that's reasonable here to use the 12AV5GA if at all possible.

If I had a hundred bucks to spend on iron I would be making an order from Antek right now
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Last edited by Lingwendil; 22nd November 2019 at 03:58 PM.
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Old 22nd November 2019, 04:11 PM   #24
kodabmx is offline kodabmx  Canada
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opinions on williamsonish build?
Or run it from 480-277 with a doubler even...
Ya... I'm waiting for a quad of VPT12-2080 myself... 100.64$CAD isn't bad for effectively a pair of 25W OPTs...
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Old 22nd November 2019, 04:45 PM   #25
Lingwendil is offline Lingwendil  United States
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I may have to try a pair of those at some point. Look like a quad wouldn't be too pricy from Arrow, free shipping over $50USD, and $17.33USD each-

https://www.arrow.com/en/products/vp...SABEgL8Z_D_BwE

I was considering these originally before money got tight again, wonder how they compare? 1.1 pounds, versus 14 ounces, otherwise they look pretty similar.

AN-0206 - 25VA 6V Transformer - AnTek Products Corp

Would be a good match with one of these power transformers per channel (secondaries in parallel) which is a good value at $28USD. All the iron for a pair of monoblocks for $91USD shipped isn't too bad at all. If building all on a single chassis you could go with a single 100VA like this one and you would even save ~$22. Shipping is pretty reasonable from Antek within the US, even for the four together it's only $13.50 priority mail.

I use a set of these on the EL86 amplifier with series connected secondaries, for roughly 4200k into 8 ohms, and have been very happy with them. They would probably have been a good choice too, for a pentode connected build at least. Maybe overkill on triode mode?


As it was I was only able to afford the pair of enclosures for this build with the birthday money I got in a card this year
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Old 22nd November 2019, 06:01 PM   #26
kodabmx is offline kodabmx  Canada
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opinions on williamsonish build?
I run the B+ for the just the 4 6P43Ps from a 100VA transformer, and it's at it's limit.

I've never tried the Antek because of the costs to Canada being crazy compared to Triad from Mouser of Digi-key but I'll bet they will be fine.

The higher the VA rating, the lower the DCR, and higher the efficiency. On low current it doesn't matter much, but when you try and push 1A through a 100R winding, if doesn't work very well (you lose power).

I use a pair of 25VA coils for 6P43P, a pair of 50VA coils will be used to build something with 12AV5GA I think, That, 6BQ6, or 6P36S, a pair or 100VA coils for the 36LW6 amp, and a pair of 250VA for the PPP 6P45S monoblocs. By the time you get to the 250VA coils, your paying almost as much as for Hammond, but the DCR is lower, and there are more choices for a low Z primary. If I build the monoblocs again, I'd use the 160VA version I think.
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Old 22nd November 2019, 10:24 PM   #27
Francois G is offline Francois G  United States
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Quote:
Originally Posted by kodabmx View Post
I run the B+ for the just the 4 6P43Ps from a 100VA transformer, and it's at it's limit.
The Antek AS-1T275 that Lingwendil referenced is rated at 180 ma for each of its two HV secondaries. What are you averaging in your 6P43Ps?
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Old 22nd November 2019, 10:32 PM   #28
kodabmx is offline kodabmx  Canada
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opinions on williamsonish build?
160mA @ 300V.

I based my calculation on this:
V (Peak) D.C. = 1.41 X Sec. V A.C.
V (Avg) D.C. = 0.90 X Sec. V A.C.
I D.C. = 0.62 X Sec. I A.C.

I also tend to oversize. Less voltage drop with a larger coil and there's a big difference between 280V and 300V in triode mode.

Last edited by kodabmx; 22nd November 2019 at 10:35 PM.
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Old 23rd November 2019, 12:50 AM   #29
kodabmx is offline kodabmx  Canada
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opinions on williamsonish build?
Thought you might find this interesting.

Ran the sims for 36LW6 trioded, B+ 300V, 80mA OP.

With VPT18-5560 in series (100VA) Pout=50W
With VPT18-13800 in series (250VA) Pout=75W.

The only difference is the DCR and regulation spec. VPT18-5560 primaries are 45R, VPT18-13800 is only 6R... That makes a 25W difference apparently.
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Old 23rd November 2019, 01:13 AM   #30
Francois G is offline Francois G  United States
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Very interesting! Thanks.
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