The ugliest headphone amp on the planet?
Jan 22, 2006 at 9:01 PM Post #62 of 100
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.

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.

There are a number of differences between the pinks and mine

* The capacitors on mine are 6.3 rather than 10 volt, and I can't discern any makers name.

* 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.

* Mine came with gold plated phonos

* The mains switch on Pink's must have been added by an owner - the original design didn't have one.

* 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.

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.

I'm half tempted to try to modify it - only my own enormous incompetence stands in my way.

Alan
 
Jan 23, 2006 at 11:31 AM Post #63 of 100
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.

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.

There are a number of differences between the pinks and mine

* The capacitors on mine are 6.3 rather than 10 volt, and I can't discern any makers name.

* 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.

* Mine came with gold plated phonos

* The mains switch on Pink's must have been added by an owner - the original design didn't have one.

* 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.

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.

I'm half tempted to try to modify it - only my own enormous incompetence stands in my way.

Alan



I'm just off to the dentist Alan but I will reply to this, in full, when I come back.. there's a reason for the resistors on the headphone socket which I will go into when I come back.
 
Jan 23, 2006 at 6:42 PM Post #64 of 100
Quote:

* 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.


At a guess they are a bias path for the output caps which are unloaded until connected to a headphone or line input if used as a cable driver instead of headphone amp.Something usually missing in the DIY arena but should be there so common for commercial amps

Quote:

* The capacitors on mine are 6.3 rather than 10 volt, and I can't discern any makers name.


I was wondering about that one and thinking "I wonder what the turn on surge voltage is ?" then thinking maybe even 16 volts would be better if the power supply is an instant on" rather than slow turn on type.Maybe nothing,maybe something.

Quote:

* Mine came with gold plated phonos


I have some 20 year old (or more) gear that uses nickel plated jacks and not once has jack reliability been an issue.Gold is nice and definately looks good but to me personally better heavy nickel plating than lightweight gold plating and if the gold is consmetic only keep it.not saying that is the case here (the more likely answer is not) but just commenting on a practice I hate because it is meant to fool folks into spending more for nothing gained.

Quote:

* 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


likely.Parts were a lot harder to source back then and you took what you could find then made it work.
icon10.gif


Quote:

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.


could be a combination of limited current drive to the base of the "current pump" output transistors (the opamps used were SOTA at the time but a bit dated now) 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)
 
Jan 24, 2006 at 12:45 AM Post #65 of 100
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.


First off, apologies for calling it the ugliest amp on the planet you know I'm joking
wink.gif
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.


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.


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.


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


Lucky you
tongue.gif
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
wink.gif


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.


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.


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.


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
smily_headphones1.gif


Quote:

Originally Posted by alanb
I'm half tempted to try to modify it - only my own enormous incompetence stands in my way.


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)



I actually fitted output caps into mine Rick, they weren't "stock"
 
Jan 24, 2006 at 1:23 AM Post #66 of 100
Quote:

I actually fitted output caps into mine Rick, they weren't "stock"


That IS interesting.I realise the Op-amp used was an FET input type so with low inherent DC offset but that discrete stage leaves a lot of area for a huge DC offset to enter if there is no DC balance trim considering none of the parts look to be precision matches (also common then due to parts availability).What is the "pre" coupling cap offset measurement loaded into a 1K resistor ?
 
Jan 24, 2006 at 7:08 PM Post #67 of 100
Quote:

Originally Posted by rickcr42
That IS interesting.I realise the Op-amp used was an FET input type so with low inherent DC offset but that discrete stage leaves a lot of area for a huge DC offset to enter if there is no DC balance trim considering none of the parts look to be precision matches (also common then due to parts availability).What is the "pre" coupling cap offset measurement loaded into a 1K resistor ?


Haven't measured it Rickster but I did measure the offset at the output before fitting the o/p caps and it was pretty darned high.

This amp gets stranger and stranger.. with a log pot it's nothing.... nothing.... a little bit..... a tiny bit more...... WHAM! I tried a linear law pot and it was pretty much "WHAMMO!" immediately which makes me wonder if this amp was designed to use a linear pot instead of a logarithmic type... I really haven't had time to experiment with it but will definitely get to the bottom of the pot thing before the end of the week. It's not a problem but it's not behaving as it should with a log pot (very little until 3pm them "wham")
 
Jan 24, 2006 at 9:22 PM Post #69 of 100
Quote:

Originally Posted by PinkFloyd
First off, apologies for calling it the ugliest amp on the planet you know I'm joking
wink.gif
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.



It's OK - I'm not offended - it's very much a thing of its time visually as well as electronically

Quote:

Originally Posted by PinkFloyd
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.


I'm using an Alps "Blue Velvet" 100k log pot - it's being used with some valve electronics which don't take kindly to low input impedences!


Quote:

Originally Posted by PinkFloyd
The stock caps in mine were 10V 1000uF "Hitano" types... 85C general purpose.


The capacitors in there are nameless - but they're 2 cm tall, which is a fair bit bigger than the 1.25 cm of the panasonics - and explains why the extension rod is fouling them.

Quote:

Originally Posted by PinkFloyd
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.


I'm taking some pictures later on this evening (the battery on my camera was flat)

Quote:

Originally Posted by PinkFloyd
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.


That's a very generous offer - I may well take you up on it.

Quote:

Originally Posted by PinkFloyd
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.


Now that is odd - mine works pretty much as you'd expect - put I did get some odd effects when I hadn't soldered the pot in properly.

Alan
 
Jan 24, 2006 at 10:19 PM Post #70 of 100
Looking at the pictures more closely the transformers look the same, except thay mine doesn't have a cap, and yours has, for some strange reason, been fitted the other way round - which might explain the funky wiring!

Alan
 
Jan 25, 2006 at 12:01 AM Post #71 of 100
Quote:

Originally Posted by alanb

Now that is odd - mine works pretty much as you'd expect - put I did get some odd effects when I hadn't soldered the pot in properly.

Alan



Mine is working fine as well but it just doesn't have the gradual increase in volume I'm used to, it's the same with 3 different pots I've tried and "could" be the gain but I haven't got around to experimenting as yet:

8am low
9am low
10am low
11am a bit higher
12pm medium low
1pm medium
2pm medium
3pm medium +
4pm high
5pm ear shattering

Hard to explain but not as progressive as any other volco I've used... doesn't really matter as I rarely listen at medium / high levels.

Quote:

Originally Posted by alanb
Looking at the pictures more closely the transformers look the same, except thay mine doesn't have a cap, and yours has, for some strange reason, been fitted the other way round - which might explain the funky wiring!

Alan



Yours has got different feet and a different head socket too, seems they bunged in what they had on the shelf. Mine also came with a red LED whereas yours has got a green LED. Have you got any high resolution pics of the rest of the PCB? It would be interesting to have a good look at the entire amp.

attachment.php


DSCF2356.jpg
 
Jan 25, 2006 at 8:30 PM Post #72 of 100
I think the feet might have been replaced at some time in the 19 years since it was new - I think mine are HomeBase stick on specials
icon10.gif


The socket and everything else in the pictures is original though.

I've got a couple of pictures of the whole board - It's probably more sensible if I mail them to you as they are pretty big and probably of (very) limited interest.

The other thing I've noticed looking back is that the original capacitors in yours had their legs bent in a Z to offset them from the holes thus making the gap between them wider and allowing the extension shaft to pass between them without fouling, wheras mine didn't. More magic mushrooms at work during board layout I suspect.

Alan
 
Jan 29, 2006 at 8:18 PM Post #73 of 100
Quote:

Originally Posted by mrarroyo
It would be funny if after you modify it then it becomes your favorite amp.
biggrin.gif



As it turns out, you were pretty on the ball with that comment as this "is" now my favourite amp!!

I managed to get to the bottom of the volume control gremlin thanks to David White asking me "have you checked the value of the resistors from the wiper of the pot to ground?" I hadn't bothered checking and assumed they were 47K..... they were not 47K, they were 200R !! no bloody wonder the pot had a strange action to it!

After replacing the 200R with 47K (you can see them in the picture they are the black resistors) the difference was night and day! This is one extremely awesome sounding amp...... full of balls, grunt, drive and so so so "musical" all through the audio spectrum....... It'll take somebody to pull the headphones off my ears, that's how bloomin good it is.... totally awesome sound
smily_headphones1.gif


DSCF2489.jpg

47K resistors (black)

I've also removed the TLO82 and replaced it with an LM6172 which is a truckload better sounding especially with regard to space and air around instruments. Generally a little prima donna of an opamp but not in this amp, she just plugged and played with no complaints at all... excellent stuff!

DSCF2493.jpg

LM6172 (superfast chip)

After I heard just how totally superb this amp sounds it was back in with the ALPS RK27 (50K LOG)

DSCF2494.jpg

ALPS RK27 potentiometer (Groovy)

So excited was I with this DRAMATIC improvement in sound I decided to really pull out the stops and fit a brand new gold plated headphone socket. Also fitted a 1K dummy load between sleeve and tip and sleeve and ring of the head socket.

DSCF2534.jpg

New head socket with 1K dummy load.

£42 well spent??? You bet!!!! Just a case of tarting up the enclosure now and this will be numero uno in my rig... (seriously it is that good) Thank god Dr. White mentioned the wiper to ground resistors else I'd have been none the wiser...... Rock on baby!!!

DSCF2523.jpg


DSCF2518.jpg


DSCF2515.jpg

Full frontal.

DSCF2505.jpg


DSCF2498.jpg
 
Feb 5, 2006 at 5:16 PM Post #74 of 100
Coming on nicely. I was going to spray paint it black but the grey primer looked pretty good against the rest of the amp so I am just applying clear lacquer over the grey primer. The MDF was a bugger to seal and it sucked up a good 10 coats of UPVA / Water mix so this is a very time consuming process I'd have been quicker just veneering it, having said that the grey does look pretty nifty in real life
smily_headphones1.gif


attachment.php


attachment.php
 

Users who are viewing this thread

Back
Top