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PostPosted: Sun Feb 24, 2013 9:05 am 
King of the Skip Monkeys
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simonlovell99 wrote:
hi, any swaps or px for the aura amp


Its not mine to swap with but let me know anyway and I will see what I can do.


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PostPosted: Sun Feb 24, 2013 10:20 am 
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Mr Panda wrote:
Apache - Are you up for general repair/improvement to hifi kit for other folks? I think the phono stage on my Audiolab 8000A has given up. I have no local repairers within 100miles so my options are either travel or posting anyway.........

:D


Let me see if I can get diagrams from t'interweb...

...Yes I can - thanks hifiengine.com! You'll need to log in before you can download diagrams here http://www.hifiengine.com/library/audiolab/8000a.shtml

No ground breaking technology there, but interestingly unusual, and carefully though out circuit topography. A few questions...

1) Is it just phono not working?
2) Both channels or just 1?

If you're happy to pay for a round trip of postage (~£30?) then I'm happy to take a look for you. No fix, no charge? However, before you do, check your source, cables etc. I've had a few things sent to me before which have been working fine, and the problem lay with other kit.


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PostPosted: Sun Feb 24, 2013 10:38 am 
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Update on the Quad now I've fired it up.

Balance control a bit fried - will probably wire it out if I cant find a replacement easily. The output of my modded CD player a little high for the Aux input, so will pull the card and add a bit of attenuation so I'm not at 'deafening' 3 detents in on the vol control!

Studying the schematics reveals that the 44 uses pretty conventional topography (with the exception of the brilliant tone controls) so I think I'll just bring it up to date componentry-wise as all of those caps are probably way past their best by now, and TL07X op-amps were never earth shattering. Perhaps I'll rework the supply with tracking regs so I have best chance of no DC offset throughout, and remove some of the coupling caps in the signal chain. Basically, just keep it 'Quad', but bring it up to how Quad would build it if they had today's tech.

The 405? Well, will start with PSU now I've bought the lovely low ESR caps - perhaps split the supply so it's separate left / right. Fit decent speaker posts as per later variants. I'll look into removing the current / voltage limiters* fitted to early 405's for use with ESLs and again, modern tight tolerance componentry.

*edit - a quick glance at the manual tells me it's easy! :-) They're great handbooks Mark!


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PostPosted: Sun Feb 24, 2013 11:09 am 
King of the Skip Monkeys
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apache wrote:
Update on the Quad now I've fired it up.

Balance control a bit fried - will probably wire it out if I cant find a replacement easily. The output of my modded CD player a little high for the Aux input, so will pull the card and add a bit of attenuation so I'm not at 'deafening' 3 detents in on the vol control!

Studying the schematics reveals that the 44 uses pretty conventional topography (with the exception of the brilliant tone controls) so I think I'll just bring it up to date componentry-wise as all of those caps are probably way past their best by now, and TL07X op-amps were never earth shattering. Perhaps I'll rework the supply with tracking regs so I have best chance of no DC offset throughout, and remove some of the coupling caps in the signal chain. Basically, just keep it 'Quad', but bring it up to how Quad would build it if they had today's tech.

The 405? Well, will start with PSU now I've bought the lovely low ESR caps - perhaps split the supply so it's separate left / right. Fit decent speaker posts as per later variants. I'll look into removing the current / voltage limiters* fitted to early 405's for use with ESLs and again, modern tight tolerance componentry.

*edit - a quick glance at the manual tells me it's easy! :-) They're great handbooks Mark!


Glad its all good - I had to sell it as a project due to the age. This system was used with ESL57's from new along with a Garrard 401, all of which I managed to get over the years except the ESLs...

The original Quad workshops were great. The stories were great too. One experimental speaker design had to be carefully dismantled as it started to induct off the earths magnetic field. They were always very helpful if you wanted to experiment and had a close relationship with KEF in later years.

I had the miserable task of clearing the factory after sitting in on the meeting that sacked up to 3 generations of Quad employees. In the mary celest workshop, I found a complete 34 system built from spares squirreled away under one of the desk. It hadnt been audited by IAG so I was allowed to keep it.

IAG then bought the TAG McLaren Audio intellectual rights some 10 years later so I went through the same nightmare - except that I was in the firing line. So, before IAG audited EVERYTHING, I was asked to gather all of the 3rd party manufacturers equipment together (REVOX, KRELL etc) and offer it out to the staff. Nobody wanted it despite its value (some £100,000+!) so I was allowed to purchase the lot for £1000.

From memory I managed to get:

Revox system (CD, Tuner amp

B&O Beosound (still have that)

Krell FPB350M x3

Wilson Audio 'Puppy' speaker system

Krell KAV 300i integrated amp

Krell MD20 top loading CD

Kenwood DAB car radio cassette (1997 pre production model!)

Plus lots of separates left over from the Audiolab days.

Even found some Audiolab surround processor prototypes that showed Audiolab were on the ball in 1998 just before they were bought by TMA.

Was given by the CEO a set of JBL4333B and some large tower speakers that I forget the name of.

When I finally left, I bagged an AV192R with the video processor option, a couple of DVD32Rs/ AV32R and some amplification - that all went on ebay while I went on a 6 month hiatus...


After all that I am left with the B&O system and a prototype AV32R


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PostPosted: Sun Feb 24, 2013 1:14 pm 
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Some nice kit there Mark.

Would be interested to hear the 'earth magnetic field induction' story! I spent a few evenings in the shed attempting to receive and plot Schumann Resonances (to do with EM resonance in the earths atmospheric 'cavity' due to lightning. You can detect lightning anywhere on the planet - but you also 'hear' ULF submarine transmissions too. I downloaded ULF spectrum analysis software to look for them, and think I may have seen them, but there is so much other low frequency mush out there from the power grid and data transmitted on the grid that its hard to see.

Anyway, I digress - I'll post up pics of my progress as I go.


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 Post subject: Here we go...
PostPosted: Sun Feb 24, 2013 6:43 pm 
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First up, reduction of gain of the Aux input. The gain is 1.6 as standard on both the Aux and Radio cards, but the Aux card differs in having a voltage divider on the input (roughly 4:1) possibly as a mod for CD players coming out back then? Anyway, I reconfigured the gain to unity so now it's merely a buffer. While I was in there, I figured I'd swap all of the old 5% carbon resistors for 1% metal film (matched by hand for good channel matching). Don't have any top notch single op-amps in at the mo, so didn't change / bypass any caps until I change the op-amps and null any DC offset.

Image

Next up was that balance control, I've bypassed it until I find a replacement, and while I had access to the main board, I swapped out all the old electrolytics for new Silmics (decent, but not stupid cost).

I think the muting relay is getting a bit lazy as one channel stayed off for a few seconds... That's for another day.

Image


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PostPosted: Sun Feb 24, 2013 9:17 pm 
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Well my NAD T-585 multiformat player finally stopped working after a repair only last May....

Just replaced it with an ex-demo Cambridge Audio Azur751BD unit from the Danish sales outlet, for less that Richer Sounds has it on sale for ... which is awesomely good. So it picked a good time to die on me.

But before I consign the NAD to the great tip in the sky.... Is there anyone who could conceivably use the parts from it- there's a new laser in there... I think it's a software-related error - it just won't start up and the display was playing up before it froze up completely.

Also looking for an OK-sounding pair of bookshelf speakers for the bedroom system... (Thanks to this place and others I now have : Living room system, kids games-room system, wife's workroom system and shop system... and bedroom system missing loudspeakers)


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PostPosted: Sun Feb 24, 2013 10:57 pm 
retrobike rider / Gold Trader
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apache as a complete nivice to the inner workings that's all very interesting, thanks for taking the time to post it 8)


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PostPosted: Mon Feb 25, 2013 2:00 am 
P.o.T.M. Winner / MacRetro Rider
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Thanks for that. Had a rummage around this evening and traced fault to output wiring from LP12 turntable, which is still original. Loose wiring at (female) plug ends. Guessing the best option is to rewire/solder on male plugs which will go straight into amp without need for additional cables :?

Thanks for help.

apache wrote:
Mr Panda wrote:
Apache - Are you up for general repair/improvement to hifi kit for other folks? I think the phono stage on my Audiolab 8000A has given up. I have no local repairers within 100miles so my options are either travel or posting anyway.........

:D


Let me see if I can get diagrams from t'interweb...

...Yes I can - thanks hifiengine.com! You'll need to log in before you can download diagrams here http://www.hifiengine.com/library/audiolab/8000a.shtml

No ground breaking technology there, but interestingly unusual, and carefully though out circuit topography. A few questions...

1) Is it just phono not working?
2) Both channels or just 1?

If you're happy to pay for a round trip of postage (~£30?) then I'm happy to take a look for you. No fix, no charge? However, before you do, check your source, cables etc. I've had a few things sent to me before which have been working fine, and the problem lay with other kit.


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PostPosted: Mon Feb 25, 2013 8:56 am 
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No worries - might be best to just buy a new cable if you're not confident with a soldering iron. There's probably lots of reasonably priced third party cables out there.


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