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Update on Williamson Amplifier http://dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=1404 |
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Author: | Grover Gardner [ September 14th, 2019, 11:19 am ] |
Post subject: | Re: Update on Williamson Amplifier |
Well, it's been a bit of adventure lately. I ordered a new pair of Heyboer/Peerless trannies, this time with 50% primary taps to more closely duplicate the originals and allow for a "Gilded Lily" or "ultralinear" version of the Musician's Amplifier. They arrived in due time, but there was a problem: Attachment: Yikes! Here's the open-loop response: Attachment: Obviously they really screwed something up. Back they went, and after a lot of discussion, they wound a new pair: Attachment: That's more like it! |
Author: | Grover Gardner [ September 14th, 2019, 11:32 am ] |
Post subject: | Re: Update on Williamson Amplifier |
(Cont.). Here's a FR plot with a standard Williamson shelf network across the input stage (4.7K + 200pF) and 150pF across the feedback resistor: Attachment: Meanwhile, as a kindly fate would have, I found two original Peerless S-265-Q's on eBay within three days of each other, for a not-unreasonable price, so I can now directly compare the copies with the originals. Here's the same set-up with an original 265-Q: Attachment: Attachment: So you can see the Heyboers are not very far off at all. Sonically, the originals have a very silky top end, as you might expect, while the Heyboer copies are less refined but still very clean and musical. On the plus side, the Heyboers sound equally good in triode (11wpc) or "ultralinear" (22wpc) mode, while the Peerless give up a little bit of realism in ultralinear mode. It's "pretty" but it doesn't have that triode solidity and immediacy. Would I choose the originals over the copies? Yes, I would, but I'd be perfectly happy listening to the copies as well. And the originals very rarely come along. It was sheer luck to find the pair that I did. But if you have patience and persistence, they do turn up now and then, and they're worth getting if you can. Considering that the Sowter "Williamson" OPTs cost $900 plus shipping to the US, and the Hashimotos about as much if not more, it's not unreasonable to pay $300-400 for one. Meanwhile the Heyboers are about $450 a pair including shipping, and they make a swell Williamson amplifier. |
Author: | Grover Gardner [ November 12th, 2019, 12:13 am ] |
Post subject: | Re: Update on Williamson Amplifier |
Here's a schematic for the Heyboer Musician's Amplifier. This is quite an amp, if I do say so myself. Direct comparison with the original Peerless shows that the Peerless are more silky on top, and more liquid overall, but the Heyboers are punchy and crisp. I could live with either one. The "ultralinear" version gives up very little to the triode version, and yields a very robust-sounding 22wpc. I cannot recommend this new/vintage circuit highly enough. If you want a bit more power, use a good 6L6GC or, even better the new Tung-Sol 7581a, and the 5V4 rectifier with the 400-0-400 power tranny. This gets you a bit more punch and does not stress either output tube. Attachment:
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Author: | Pelliott321 [ November 12th, 2019, 8:01 am ] |
Post subject: | Re: Update on Williamson Amplifier |
Please explain the resistor/cap networks to ground |
Author: | Grover Gardner [ November 12th, 2019, 11:03 am ] |
Post subject: | Re: Update on Williamson Amplifier |
Pelliott321 wrote: Please explain the resistor/cap networks to ground Those are just power supply decoupling caps. They're stacked electrolytics with equalizing resistors across each caps. I drew them in that way to emphasize that you must have plenty of voltage headroom in the power supply capacitors. The original Musician's Amplifier used 600vdc electrolytics, which you cannot find anymore. |
Author: | ratbagp [ November 12th, 2019, 11:17 am ] |
Post subject: | Re: Update on Williamson Amplifier |
You could use DC Link film caps with 600 or higher voltage limits. https://www.mouser.com/ProductDetail/WIMA/DCP4I052507GD2KYSD?qs=sGAEpiMZZMv1cc3ydrPrF77Ed2j2AojdDai0LtMjM6g%3D The two 47 uf caps in series could be replaced by a single 25 uf and you wouldn't need the resistors. ray |
Author: | GaryB [ November 12th, 2019, 11:19 am ] |
Post subject: | Re: Update on Williamson Amplifier |
Grover Gardner wrote: The original Musician's Amplifier used 600vdc electrolytics, which you cannot find anymore. There are some currently manufactured 600v electrolytics that are available at places like Digikey and Mouser. Search for Nichicon LGN series capacitors and you'll find values ranging from 56uf to 220uf all at 600v rating. I haven't tried them but Nichicon typically makes high quality caps. |
Author: | Grover Gardner [ November 12th, 2019, 11:41 am ] |
Post subject: | Re: Update on Williamson Amplifier |
ratbagp wrote: You could use DC Link film caps with 600 or higher voltage limits. https://www.mouser.com/ProductDetail/WIMA/DCP4I052507GD2KYSD?qs=sGAEpiMZZMv1cc3ydrPrF77Ed2j2AojdDai0LtMjM6g%3D The two 47 uf caps in series could be replaced by a single 25 uf and you wouldn't need the resistors. ray Yes, you could. Even Solens would do the job. I haven't cared for the sound of the plastic caps I've tried but I'm always willing to experiment. |
Author: | Grover Gardner [ November 12th, 2019, 11:45 am ] |
Post subject: | Re: Update on Williamson Amplifier |
GaryB wrote: Grover Gardner wrote: The original Musician's Amplifier used 600vdc electrolytics, which you cannot find anymore. There are some currently manufactured 600v electrolytics that are available at places like Digikey and Mouser. Search for Nichicon LGN series capacitors and you'll find values ranging from 56uf to 220uf all at 600v rating. I haven't tried them but Nichicon typically makes high quality caps. Interesting, I'll take a look. The first cap at the rectifier needs to stay low, 8 or 10uF, to keep the rectifier from freaking out, but after that I haven't read anything that indicates that increasing the decoupling cap values a bit leads to any instability. I did increase them a bit to the values employed by Heathkit in their version of the Musician's Amplifier, the W-2, mostly because it's easier to implement. |
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