Quote:
Originally Posted by alanb
I have one of these Headcase amps which I've actually had from new. As Pink Floyd says, it was designed by Tim de Paravicini and the circuit is apparently closely based on the Musical Fidelity A1 amplifier which Tim also developed.
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First off, apologies for calling it the ugliest amp on the planet you know I'm joking
I think Tim De Paravicini must have been on the magic mushrooms when he designed the PCB but other than that it's not a bad sounding amp.
Quote:
Originally Posted by alanb
The only change I've made to mine was to replace the volume pot because the original got very noisy and unreliable. I'm not surprised Pink went back to the original if it was working OK - an Alps doesn't fit in very well and the original had long legs which helped to lift the extension rod above the capacitors.
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The ALPS RK27 is actually a "better" fit than the original and all you have to do is angle it slightly on the board in order that the potentiometer con rod clears the PSU caps. If you look on the board you'll notice there are 9 pads so you can fit different pots with different pitches... if you're using an ALPS RK27 then you fit it in the front and back holes leaving the 3 centre holes unoccupied.... the original fits into the rear and centre holes...... the stock pot is a 47K log but you can replace this with a 10K log if you like.
Quote:
Originally Posted by alanb
* The capacitors on mine are 6.3 rather than 10 volt, and I can't discern any makers name.
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The stock caps in mine were 10V 1000uF "Hitano" types... 85C general purpose.
Quote:
Originally Posted by alanb
* The mains transformer is different but that's probably just what they could get hold of - there isn't any serial no. but I can't believe they were made in any real quantity.
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Do you have any pictures? it would be interesting to see the difference in the transformers... the one I have doesn't appear to be the original as there are some "funky" mods to the tracks around the transformer which I can only assume have been performed by a third party.
Quote:
Originally Posted by alanb
* Mine came with gold plated phonos
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Lucky you
Mine came with a quad socket which was nickel plated but I've since fitted a gold plated quad socket. As Rick says though, Nickel plated sockets are a lot more durable than your gold plated derivatives and there's no sonic advantage (or very little / if any) to be gained by replacing with gold. I replaced mine with gold as it was the only finish I could source at the time (required a bit of modding to get it on) the only reason I replaced the originals was the centre connecting screw had come loose and I couldn't be arsed filling the hole with epoxy and drilling it out etc. etc. a new quad socket is only about a quid so what the hell
Quote:
Originally Posted by alanb
* The mains switch on Pink's must have been added by an owner - the original design didn't have one.
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Yes. The original owner fitted the on / off switch.
Quote:
Originally Posted by alanb
* I notice on the latest picture there are a couple of resistors soldered to the headphone jack - these aren't present on mine but may be one of Pink's mods.
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I fitted these to act as a dummy load. Even with output caps I measured some DC on the output which disappeared when I connect a load (headphones) this is pretty normal with cheap non polars there will always be a small amount of leakage so to null the offset with no load (ie: headphones connected) I fitted a couple of 500 ohm resistors, one from sleeve to tip and the other from sleeve to ring..... this acts as a dummy load and is switched out as soon as you connect your 'phones.
Quote:
Originally Posted by alanb
Sonically mine sounds generally pretty good - on the warm side with a tendency (at least on my old 600 ohm Beyer 990s) to lose a bit of control in the very deep bass. I suspect this is down to the capacitors being well past their best as I don't remember it sounding this way from new.
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When I first listened to mine I thought it sounded pretty crappy to be honest but fitting new capacitors really did improve the sound a lot. I'd urge you to remove the old ones and replace them with brand new ones as soon as possible, they'll definitely inject life back into the old girl. It's well worth experimenting with different opamps as well..... I found the TL082 slightly shrill and uncontrolled, tried a few opamps and the best one (by far) is the LM6172..... totally in control, fast, airy, spacious and pretty much "spot on" in all departments. It's well worth fitting a Dil8 socket and experimenting with a few opamps
Quote:
Originally Posted by alanb
I'm half tempted to try to modify it - only my own enormous incompetence stands in my way.
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If you're in the UK I'll do it for you free of charge, no problems whatsoever, it's really very easy to desolder the caps and fit new ones and I really enjoy firing the soldering iron up so if ever you decide to take the plunge give me a shout.
Just one question for you Alan....... how's your volume control? I find it's not very responsive up until about the 2 o' clock position and then "wham!" it kicks in big style. You may be used to this action but I'm not and am more accustomed to a progressive increase in volume.... just wondering if this is unique to my particular amp or if it's the same with yours? It's not a problem and I can get used to it but I would prefer a bit more oompah across the dial.
Mike.
Quote:
Originally Posted by rickcr42
combined with the coupling cap at the output,also using what was good for the time but dated as far as the sonics go and would be the main upgrade path since it has the most influence on the amp sonics (everthing must go throught it)
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I actually fitted output caps into mine Rick, they weren't "stock"