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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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17th Jun 2021, 9:10 pm | #21 |
Octode
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 1,518
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Re: Quad II Transformer woes!
I once tried an RS 100V line transformer together with a loan Vortexion 50W 807 PA amp into my Hi-Fi speakers. I expected it to just 'work', but it actually sounded amazingly good!
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18th Jun 2021, 4:26 pm | #22 |
Heptode
Join Date: Jan 2008
Location: Shrewsbury, Shropshire, UK.
Posts: 843
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Re: Quad II Transformer woes!
Interesting to hear about the output transformer problems.
I have a Quad II which I 'rescued' from a company that went under. The Quad is actually new, & appears not to have been used, & still in its original but tatty box. I've had it for around 40 years, & checked it out a few months ago. Unbelievably, the output transformer is o/c on one of the secondary windings! I'm wondering if perhaps the wire was never soldered to its relevant tag. But how did it pass a final test? I'm hoping to sneak the transformer past my wife into a warm oven at some point so that I can disassemble it. Incidentally Canford Audio used to do an HQ 100v line 'Music' transformer, which I have installed where I needed better quality speakers, & the results were very good. David. |
18th Jun 2021, 4:36 pm | #23 |
Pentode
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 201
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Re: Quad II Transformer woes!
Thanks for info David, I've just looked at their site and the HQ transformers look very affordable.
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Pete BVWS Member |
18th Jun 2021, 7:15 pm | #24 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,195
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Re: Quad II Transformer woes!
Hi Gents, it should be quite easy to wind a good quality 100v line matching transformer that would be of a similar size to, and used with the Quad. It could also be wound using an interleaving method. Given the presence of an additional transformer in the chain I would expect a marginal increase of distortion.
On a theoretical front, as isolation is no longer required, the transformer coul be an autowound type and more compact. Only a few thoughts, please discuss Ed |
18th Jun 2021, 7:25 pm | #25 | |
Dekatron
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,311
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Re: Quad II Transformer woes!
Quote:
Cheers, GJ
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http://www.ampregen.com Last edited by GrimJosef; 18th Jun 2021 at 7:34 pm. |
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18th Jun 2021, 10:02 pm | #26 |
Heptode
Join Date: Jan 2008
Location: Shrewsbury, Shropshire, UK.
Posts: 843
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Re: Quad II Transformer woes!
I am aware of the connections on this particular transformer, I had hoped that someone had simply miss-wired it, but not so!
I will take it apart some time, but unfortunately have more pressing issues at present. David. |
18th Jun 2021, 11:33 pm | #27 | |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,873
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Re: Quad II Transformer woes!
Hi!
Quote:
Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
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19th Jun 2021, 10:39 pm | #28 |
Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,878
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Re: Quad II Transformer woes!
Some interesting posts that were a wee bit off topic have been moved here.
https://www.vintage-radio.net/forum/....php?p=1382776 Cheers Mike T
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Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk |
20th Jun 2021, 3:09 am | #29 | |
Heptode
Join Date: Oct 2009
Location: Melbourne Australia
Posts: 901
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Re: Quad II Transformer woes!
Quote:
BTW, the 1961 Crowhurst book "High Fidelity Sound Engineering" is available on-line (just google search for it) and interesting to note how Crowhurst has summarised the preceding decade of knowledge on certain matters. |
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20th Jun 2021, 8:01 pm | #30 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,195
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Re: Quad II Transformer woes!
Hi Tim, from memory this part was a few turns of winding wire (10?) in a strip of SRBP and was perhaps 6mm in dia.
I believe it was connected between 2 winding sections and was just buried in the pitch Ed |
20th Jun 2021, 8:14 pm | #31 |
Pentode
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 201
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Re: Quad II Transformer woes!
If you scroll down almost to the bottom of this link, you can see Keith Snooks interpretation of the transformer windings including the resistor.
http://www.keith-snook.info/quad-ii-...amplifier.html
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Pete BVWS Member |
21st Jun 2021, 2:58 am | #32 |
Heptode
Join Date: Oct 2009
Location: Melbourne Australia
Posts: 901
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Re: Quad II Transformer woes!
Thanks. So the extra resistor 'loop' is in series with the innermost wound section of the feedback winding (P-Q). It's plausible that the additional resistance or leakage inductance (or both) provided by that 'loop' is balancing some high frequency characteristic.
It does seem a bit strange that the stated resistance of the resistor 'loop' is 0.36 ohm and the stated resistance of P-Q is the same as Q-S at about 0.55-0.61 ohm, and that each secondary winding section that comprises P-Q and Q-S are each comprised of 51 turns. Given the photo of the resistor 'loop' showing only a few turns on a small SRBP strip, I'd expect it to be a lot less than 0.36 ohm given that the wound sections total up to be 0.55-0.61 ohm. Maybe 0.36 ohm relates to the total L2 winding section that contributes to P-Q, and not just the resistor 'loop' itself. As such, it seems that the resistor 'loop' is more about its leakage inductance contribution than its resistance contribution. |