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I see two crossovers and an amplifier of some sort.
The HiFi chat, build and modification thread!
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Ah! Yes that will be the electrostatic bit then
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10,000 volts give or take a volt or two. At least thats what they were in the Quads.
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Late to this party and I'm going waaaaaaaay back in the thread, but Apache, have you tried rolling any other op-amps in your headphone amp, or any other bits you've modified for that matter?
I was messing about with some headphone amps a while back and as many op-amps are pin compatible and run at the same voltage range you can swap them straight over. I tried several, including the pricey Burr-Brown OPA627, but my favourite, in my headphone amp at least, was the LME49710 (single channel) and LME49720 (dual). Some say the metal can TO99 versions sound better than the plastic DIP versions as well.
Late to this party and I'm going waaaaaaaay back in the thread, but Apache, have you tried rolling any other op-amps in your headphone amp, or any other bits you've modified for that matter?
I was messing about with some headphone amps a while back and as many op-amps are pin compatible and run at the same voltage range you can swap them straight over. I tried several, including the pricey Burr-Brown OPA627, but my favourite, in my headphone amp at least, was the LME49710 (single channel) and LME49720 (dual). Some say the metal can TO99 versions sound better than the plastic DIP versions as well.
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I'm not a fan of swapping out parts in a finalised design, though I can see advantages in designing around a particular part's strengths. I do know that swapping op-amps can make things sound 'different', but in general (assuming a competent design) the designer will have done his homework.
Headphone amps are an awkward one, as there are very few op-amps which are happy driving low impedance loads (in fact I can only think of one off the top of my head). With many, you will see a rise in THD when you start driving into less than ~ 600 ohms. There are ways around this, such as current splitting across several op-amps, but this is well beyond most of the cheap sh*t you see on eBay.
There's a great blog I would suggest for any budding designer (or part time enthusiast!) to read. http://nwavguy.blogspot.co.uk/
And a superb book proving beyond shadow of doubt that if you're clever you don't really need to go beyond NE5534 / NE5532 to build effectively zero distortion kit. 'Small Signal Audio Design' by Doug Self.
You mention the LME49720. Give the LM4562 a whirl. It is way cheaper than the LME, and guess what? It's the very same (and I mean exact!) chip. Compare the datasheets! It's performance is marginally better than the NE5532, but the design you pop it into had better be good or you won't see any difference in overall performance. I always have LM4562's in stock for a theoretical upgrade in stuff using bipolar op-amps in a decent design, and when audiophiles seem to want to junk the NE5532s in favour of something more fashionable on the audio forums.
I'm not a fan of swapping out parts in a finalised design, though I can see advantages in designing around a particular part's strengths. I do know that swapping op-amps can make things sound 'different', but in general (assuming a competent design) the designer will have done his homework.
Headphone amps are an awkward one, as there are very few op-amps which are happy driving low impedance loads (in fact I can only think of one off the top of my head). With many, you will see a rise in THD when you start driving into less than ~ 600 ohms. There are ways around this, such as current splitting across several op-amps, but this is well beyond most of the cheap sh*t you see on eBay.
There's a great blog I would suggest for any budding designer (or part time enthusiast!) to read. http://nwavguy.blogspot.co.uk/
And a superb book proving beyond shadow of doubt that if you're clever you don't really need to go beyond NE5534 / NE5532 to build effectively zero distortion kit. 'Small Signal Audio Design' by Doug Self.
You mention the LME49720. Give the LM4562 a whirl. It is way cheaper than the LME, and guess what? It's the very same (and I mean exact!) chip. Compare the datasheets! It's performance is marginally better than the NE5532, but the design you pop it into had better be good or you won't see any difference in overall performance. I always have LM4562's in stock for a theoretical upgrade in stuff using bipolar op-amps in a decent design, and when audiophiles seem to want to junk the NE5532s in favour of something more fashionable on the audio forums.
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And on another subject, finished repairing a basket case of an Audiolab 8000A today. Looking like it had been dropped on its back panel at some time as I had to replace all the input sockets. Then found that the volume pot had come apart internally, meaning that right channel volume was no longer proportional to the position of the knob! THEN found several caps in the MM and MC pre-amps had gone high impedance leading to some pretty weird tonal shifts! Now all that's sorted, I must admit it's a pretty fine sounding bit of kit, with superb low end detail and power (compared to my Rotel pre / Quad 405 power combo. It's a little ratty looking, but I may hang onto it for a while. Might try it as a pre with the Quad...
The Rotel 810A underneath is freshly repaired and re-capped and is for sale. There's an 820BX and a NAD 3220PE coming soon too when I fix them!
And on another subject, finished repairing a basket case of an Audiolab 8000A today. Looking like it had been dropped on its back panel at some time as I had to replace all the input sockets. Then found that the volume pot had come apart internally, meaning that right channel volume was no longer proportional to the position of the knob! THEN found several caps in the MM and MC pre-amps had gone high impedance leading to some pretty weird tonal shifts! Now all that's sorted, I must admit it's a pretty fine sounding bit of kit, with superb low end detail and power (compared to my Rotel pre / Quad 405 power combo. It's a little ratty looking, but I may hang onto it for a while. Might try it as a pre with the Quad...
The Rotel 810A underneath is freshly repaired and re-capped and is for sale. There's an 820BX and a NAD 3220PE coming soon too when I fix them!
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To run an older 8000a as a pre/power you need to move a couple of resistors (if you havent already). From the factory, the pre-outs were in operable. Never did find out why.
