QUAD II ex-broadcast/Swedish Radio/SR

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Disco Volante

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My latest acquisition is a pair of above mentioned. They are equipped with a large multi-connector for power, input and output, clearly to be easily swapped.
They also contain what looks like a balanced-drive input transformer.
However, they came without the bottoms!

They're briefly mentioned here:
(for whatever reason I am not allowed to post in that thread)

I would like to keep this strange pair of Quads as they are (with new caps, etc of course), so my question is:

Does anyone have a pair of connectors or know what make they would be?

I have of course studied said connectors for any sign of a brand or name, and done some research on the 'net.

Here is a picture of the missing bottom-plate (the forum does not respond to my membership application)

Regards and happy tinkering
 

Conviction

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- That would be the common 12-pin Tuchel female connector called T2009. Still readily available!

- As far as I'm aware, Radiotjänst/SR didn't keep the bottom plates but hacked the units up. They used the "sleigh" (that you linked to) mounted in a designated wooden box in the bottom of the Goodman Eleganzia II stands. Great for maintenance/rapid swapping... not so much for conservation. But that was then.

Regarding the input/step-up transformer: is it a Unitran, a Jørgen Schou or that unbranded silver-y type? Weirdly enough they're usually wired 1:10. I think you should bypass it and restore the original grid input configuration. You probably won't be needing a 600 ohm input? Or how are you intending to use them?

Pics, please! I have a few ex-SR-blocs.
 

Disco Volante

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Thank you, this certainly clears up some of my bewilderment.

Interesting about the Goodmans, I was under the impression that they were used for monitoring with the stacked ESL57's I bought them with... But who knows what the story is? The ESLs are also marked Sveriges Radio.

Anyway, here's a few pictures. The input transformer seems to be of the unmarked silvery type. There's also an added RC network at the input.

I was thinking I'd have them work right next to the speakers (currently biggish TLs), and use the balanced drive to feed them, after I make a little extension-box for my Quad 33 preamp containing the transformers.

The feedback resistor is twice the factory spec at 1K, so the units would have a significantly higher gain and somewhat better stability, AFAIK...
 

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Conviction

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Interesting about the Goodmans, I was under the impression that they were used for monitoring with the stacked ESL57's I bought them with... But who knows what the story is? The ESLs are also marked Sveriges Radio.

Ah, yes, they were! Unfortunately I've never seen a photo of how/if they were mounted to the ESL's. Maybe you know? The image you linked showed that wooden Quad II box in the bottom of the Eleganzia II stands. The successor. I own a pair (with boxes) :)

Do you have the possibility to test the EL37's? Lovely tubes! Apparently, Kjell Stensson liked them better than KT66's. I guess SR kept quite the stock back then.

This is the SR Quad II schematic with the Unitran E10E input transformer:

QUAD_II_SR_modifierad.jpg



tumblr_pa4banJEYb1qeksnbo1_500.jpg

(from hififorum.nu)

If you want I can take better/high res photos of my Eleganzia II stands with the aformentioned Quad box.
 
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Disco Volante

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This is very helpful information indeed.
Unfortunately, I only have the single pair of EL37's. The other amp had broken KT77's in it (as in shattered glass).
So I've bought four KT77's and some matched pairs of EF86's.

There are no signs of amplifier mounts on the ESL57s, only some fixtures for a stacked mount on one of them. It's a bit of a motley crew I've gotten myself into. Long-term project is to restore the ESLs, but for now I'll spend some time with the amps, something that I'm quite familiar with. Restoring electrostatics are apparently very fiddly business, so maybe better for the long winter nights;-)
If anybody wants a pair of (probably well used) EL37s, I'd be willing to part with them...

Thank you very much, this was really very helpful.
 

Disco Volante

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Hmm, are those a pair of ex-SR Thorens TD124 in the middle of the picture? I own one since 1989, bought as a solitary mechanism, now with SME3009 and housing;-)
Lovely machines...
 

Tubetec

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Some interesting differences between the original Quad II and the Sverige radio version , they seemed to have rewired the o/p transformer to provide three ratios and tapped the feedback from the 4 ohm connection instead, where the original grounds that point and takes the feedback from the opposite side of that winding providing only two impedance ratios .

Ive owned a pair of II's and ESL57 for close on 30 years , they still hold up well against the best today.
When I refurbed my amps I only had to swap out a couple of the higher resistance values and the cathode cap/resistor . Yours look in pristine condition so they might not need much done . My ESL's I got with a HF panel not working , when I looked at the frequency dividing network under the transformer I found a ceramic disc cap had one leg adrift , soldered it up an they worked fine again . Some guys make a big fuss over replacing the HT unit but I found removing the years of accumulated dust and swabbing down the wire insulation with isopropyl to be sufficient . One of my bass panels had the cover removed on the front , I used layer of cling film taped to the edges of the panel , never any problems since.

I find an aireyness in the high end of the ESL's that gives a huge sense of depth to the sound , the other thing is as they radiate in a figure 8 patern front to back they dont tend to excite room resonances in the same way as regular boxes , there is no cabinet after all .
I'm looking forward to hearing your impressions once your up and running .
 

Disco Volante

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Ok, so I've got two ESL57's cleaned up and plugged in (to a Quad 303). They were really just dusty, that's all. No signs of arcing or any debris inside the dustcovers. One bass had a small tear in the dustcover on back, I taped it up for now. They look like untouched original units inside. A very small amount of paint flaking inside one tweeter panel.
Not too impressed with the sound though, it's like there's a 12kHz low-pass filter in there. No lack of bass, however, lots of fat rubbadub. The ingenuous tone-controls on the 33 preamp came into good use for this first listening test.
Not really getting the almost religious revelations I read on the 'net. I guess my other speakers aren't too bad :)
They do tend to wake up a bit after about an hour, so maybe it's time to order some of those nifty psu pcb's from onethingaudio. Would the treble be going first if the PSU's are weary?
The dipole radiation pattern is very interesting. I guess they would be quite sensitive to room placement, so I will be experimenting with that...
 

Tubetec

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Theres some extra info here ,

It does seem the response droops a bit above 10khz but should come back up around 16khz , maybe check the resistances in the crossover , its possible they may have drifted out of spec . Bear in mind the panels will hold charge for hours , so best leave them powered off over night before getting stuck in with a meter . I'd suspect if the bass panels are working as they should your EHT supply is ok . You could try REW to measure , even if its just for comparative purposes between the two speakers .
 

Conviction

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I've also found the 57's to be a little dull in the upper registers. I've never heard a restored pair though, only originals (cleaned) but with confirmed healthy psu:s. My hearing is almost perfect, so there's no internal roll-off happening 😅

The mids are fantastic though. Perfect for nearfield listening and editing. I imagine that's one of the reasons why they stayed in service at Radiotjänst/SR for so long.

The Eleganzia II:s are similar, at least to my ears. The roll-off below 40Hz is quite steep and there's also a significant roll-off above 15kHz.
 

Tubetec

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I guess in the modern era some equalisation could be applied to flatten things out a bit at the top end .
The low end is determined by dimensions in the same way any open baffle speaker , trying to boost lows wouldnt be effective below 40hz in any case as the lack of acoustic load would mean the speaker couldnt really get a grip on the air , it would also increase the chances of flashover or arcing .

The lack of cabinet resonance does give a wonderfull quality to voice and solo instruments , a kind of acoustic transparency you could call it . I love how old jazz records sound through the Quad system , try Chet Bakers 'Jazz in Paris' broken wing or maybe Miles Davis's 'on the corner' sessions box set if you like more experimental/free form stuff .
 

Disco Volante

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Posting a few measurements for your enjoyment;-) Not quite hi-end by modern standards, quite some troughs and hills. The first (orange/red) is left and right speaker, s.no. 7250 and 8444, respectively. Second measurement is me adjusting the tone controls on the Quad33, using the 7250 left speaker. The black curve sounds quite good;-)
If anyone is interested, I can upload the .mdat too...
Having listened to quite a few records lately (Miles Davis too), I find them very agreeable, quite relaxed and transparent, though the bass from my largish transmission lines is hard to beat: low, exact, firm..
BTW, the distortion curve is outstanding, so that might explain the agreeable nature.

Staying on topic, there are some differences in component values between the schematic posted by Conviction and the original schematic as per Keith Snooks website. R4 is 1K (680R) and R2/3 is 680k (1M). My specific samples are standard Quad-spec units, except for the higher feedback resistor (R11 at 1K) and the RC-network protecting the input transformer from DC..
Screenshot from 2021-07-16 07-20-47.pngScreenshot from 2021-07-16 07-21-44.png
 

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