DIY headphone amplifier
 

"Arny Krueger" wrote in message
. ..
"Serge Auckland" wrote in
message

I bought a BTech headphone amp from Maplins, something
like £ 30.00

This one?

http://www.rock-grotto.co.uk/B-tech.htm

That's the one!

Uses the 5532 chip which drives my AKG
K270s and Koss Pro4AAs to quite sufficient level.

I find this to be an interesting application of this chip. It does have
has a lot of current drive capacity for a chip that is usually considered
to be for line-level and low-level use.

Interestingly, it's the same chip that Meridian use in
the headphone section of the 201 pre-amp.

5532s are used all over the place, particularly for pro audio.

At the price,
it didn't seem worth building one. With a simple
modification, I made it into a passive "pre-amp" with
separate headphone and amplifier volume controls to drive
small active 'speakers.

How does it sound? ;-)

Indistinguishable from the headphone output of the Meridian 201. That's the
only other headphone driver I have. The 5532 op-amp drives the 75 ohm AKGs
perfectly satisfactorily. On the Meridian 201, into a 200 ohm load, I
measured a maximum current of 30mA before clipping, ( 6 Volts) at which
point distortion measured 0.015%. Haven't measured the B-Tech. Just for fun,
I uprated the power supply smoothing capacitor and the output coupling
capacitors, but I can't say I heard any improvement. I removed the tone
control and used the thus liberated pot to act as a volume control on the
signal pass-through.

At the price, and with my cans, I can't fault it.

S.

DIY headphone amplifier
 

"Serge Auckland" wrote in
message
"Arny Krueger" wrote in message
. ..


How does it sound? ;-)

Indistinguishable from the headphone output of the
Meridian 201. That's the only other headphone driver I
have.

Well, technically about the same. The 5532 chip is the most significant
determining factor, given that the pots and switches are OK, which
http://www.rock-grotto.co.uk/B-tech.htm suggests is true.

The 5532 op-amp drives the 75 ohm AKGs perfectly
satisfactorily. On the Meridian 201, into a 200 ohm load,
I measured a maximum current of 30mA before clipping, ( 6
Volts) at which point distortion measured 0.015%.

That agrees with the specified performance of the 5532.

Haven't
measured the B-Tech. Just for fun, I uprated the power
supply smoothing capacitor and the output coupling
capacitors, but I can't say I heard any improvement.

Depends on their initial sizes. I've seen headphone amps that were bass-shy
with the as-supplied blocking caps.

I removed the tone control and used the thus liberated pot
to act as a volume control on the signal pass-through.

At the price, and with my cans, I can't fault it.

Life is good!

DIY headphone amplifier
 

"Arny Krueger" wrote in message
...
"Jem Raid" wrote in message

I'm thinking of making a headphone amp and have found
various sites with circuits.

I've also found the circuit diagram for the Grado RA1
amp, turns out to be a single chip of £0.50 value and a
few resistors, it gets great reviews and costs anywhere
between £350 and £400. It is in a mahogany case though.

http://www.geocities.com/rubin_jpk/r...RADO_schem.gif

I intend to make mine in a roomy Scottish Shortbread
biscuit tin we got for Christmas. I do also have an old,
smaller and thicker gauge but rather battered Smith's
Crisp's tin from the 1950's does anyone think that
vintage tins may perform better than new ones?


This is pretty ironic, given all the angst about the sonics one reads
about JR4556 chips. I must have read 1,000 articles suggesting that one
audio component or another could be "mind-blowingly" enhanced by replacing
4556 chips with something more highly thought-of by the author.

Of course, its just fine, but people like to bad-mouth parts that are
readily-available and cheap, even if they perform just fine.

If you've misplaced your soldering iron, just try one of Behringer's
offerings with a headphone jack. They are very fond of 4556 chips and
chips like them... ;-)

http://www.behringer.com/HA4700/index.cfm?lang=ENG


Well, thanks Arnie, Goodness! What a contraption, wouldn't know how to use
it even if I could afford it, I suppose it's one of those where you think of
a high number and then multiply it by ten.

Jem


--------------------------------------------------------
Dramatised - Photography Granularised - Photographs
Black and White - Prints Blue and White - Cyanotypes
http://jemraid.wikispaces.com/

DIY headphone amplifier
 

"tony broughton" wrote in
message
news:slrne4d5qi.1bi4.tonybDELETE_THIS_SPAM_BLOCKER ...
I made a nice headphone amp once from a pair of LM380's and a single
big 9V battery, in a round toffee tin about 6" diameter on a scrap
bit of veroboard. The circuit was super-simple and super cheap, can't
remember for certain but I think it just had a single cap on the
output and a couple of resistors and an input cap and that was it.
It even had a volume pot sticking out the side. The sound quality was
pretty good for the 2 pounds or so it cost me although I think it
hissed a bit.

But that wasn't as good as my very first stereo "hifi" amp made in an
oblong biscuit tin. Two ILP HY50's (who remembers?), two HY5 pre-amps,
separate power supply in an ally box, tape loop, tone controls,
volume, balance, inputs for tape, tuner, record deck, aux, tape out,
hand-etched f/glass pcb drawn using airfix paint as etch resist and
drilled
with a stanley hand-drill. That amp lasted about 5-6 years and saw some
really great parties too!

John

I built several amps with ILP's products. Ian Leonard Potts was the lab
technician at my old University, and started ILP Electronics as a sideline.
Hope he's well.

S.

DIY headphone amplifier
 

"Serge Auckland" wrote in message
...

But that wasn't as good as my very first stereo "hifi" amp made in an
oblong biscuit tin. Two ILP HY50's (who remembers?), two HY5 pre-amps,
separate power supply in an ally box, tape loop, tone controls,
volume, balance, inputs for tape, tuner, record deck, aux, tape out,
hand-etched f/glass pcb drawn using airfix paint as etch resist and
drilled
with a stanley hand-drill. That amp lasted about 5-6 years and saw some
really great parties too!

John

I built several amps with ILP's products. Ian Leonard Potts was the lab
technician at my old University, and started ILP Electronics as a
sideline. Hope he's well.

S.

I worked for him between 1979 and 1982 as an engineer. He was a demanding
boss and I found it impossible to satisfy his design demands and feel proud
of the results. For example, the HY120 (100W/8R) had a target parts cost
(electronics, PCB, heatsink, potting, packaging) of less than a pound. No
adjustments were allowed for biasing. The target distortion figures were met
with oodles of feedback. Output transistors could go outside their safe
operating area with realistic loudspeaker phase angle swings.

I believe that ILP got involved in high frequency lighting ballasts and this
may have pulled the original company down. However, he has resurfaced as ILP
Direct outside Ashford.



Graham Holloway
WPS/Accuphon Audio

DIY headphone amplifier
 

I worked for him between 1979 and 1982 as an engineer. He was a demanding
boss and I found it impossible to satisfy his design demands and feel proud
of the results. For example, the HY120 (100W/8R) had a target parts cost
(electronics, PCB, heatsink, potting, packaging) of less than a pound. No
adjustments were allowed for biasing. The target distortion figures were met
with oodles of feedback. Output transistors could go outside their safe
operating area with realistic loudspeaker phase angle swings.

Ouch! I shudder to think what the parts cost of the HY50's was (50p?)
I always wondered if the HY5 was just an encapsulated 741 with a
feedback circuit, or even just a couple of BC107's.

The truly amazing thing is that I never succeeded in blowing the
HY50's up, I'm quite sure the volume levels I used to use would have
done their very best to drive the output transistors outside their SAO.
Plastic 2N3055's perhaps?

They didn't sound too bad though, mind you, it was hardly a
critical audience! The basic concept was great for a schoolkid
who didn't know much about electronics (practical electronics R.A Penfold
superhet tranny radio project notwithstanding) building his first stereo.

Later on I went to a uni interview at Nottingham and in the computer lab
I was astonished to see an HY50 mounted on the back panel of a PDP8 CPU!
I have no idea what they were using it for but when I saw it I
immediately told the interviewer "Hey! I've got some of those!".

Tony

DIY headphone amplifier
 

I built several amps with ILP's products. Ian Leonard Potts was the lab
technician at my old University, and started ILP Electronics as a sideline.
Hope he's well.

Yes, I have fond memories of those amps and wish him well if he
ever reads this.

Tony

DIY headphone amplifier
 

As a teenager, yeah, I made a nice boxed power amp with 2 ILP HY60
modules, but I don't remember an HY50. Must be before my time! This
was in the late 80s.

The HY50 was an earlier version, I got mine around 1977 or 1978
as far as I can remember, they used to be advertised in practical
wireless and perhaps ETI (I think ETI was going then). The module gave
a claimed 25 watts per channel RMS and if memory serves THD something
like 0.04% was claimed at 1 kHz. I actually bought them 2nd hand off a
friend at school who had used them in his home-made disco rig but had
then progressed to building his own more powerful amps with 2N3055's
(which sounded truly dreadful, especially with motorola piezo tweeters).

The HY50 looked really spacey too because it had semi-radial fins unlike
the later amps that had vertical fins that looked rather more boring.
This was also before ILP brought out the toroidal transformers,
the power supply they provided used a "real" laminated transformer,
actually I think that transformer was actually of quite good quality,
at least it was satisfyingly heavy!


They also had a higher-power one that RS also sold, called something
like MOS-240, which used MOSFETs. Never got hold of one of them to play
with!

I always wondered what they were like, by the time they came out
I'd got more into micros and software than building amps which was a shame
in a way, although I built some nice amps a bit earler using
2SJ34/2SK133 hitachi horizontal topology power fets (I might have got those
part numbers wrong), they were attractive for home build because the
circuit only required a small signal transistor driver and you didn't
have the thermal runaway problems of bipolars (thermally self-limiting),
making them pretty simple to build into an amp and easy to set up.
Those Hitachi power-fet's were pretty expensive though - I seem to
remember getting on for 8 or 9 pounds per device, I bet those
ILP MOS modules didn't have those inside.

Tony

DIY headphone amplifier
 

"tony broughton" wrote in
message
news:slrne4t1te.26e5.tonybDELETE_THIS_SPAM_BLOCKER ...
I worked for him between 1979 and 1982 as an engineer. He was a demanding
boss and I found it impossible to satisfy his design demands and feel
proud
of the results. For example, the HY120 (100W/8R) had a target parts cost
(electronics, PCB, heatsink, potting, packaging) of less than a pound. No
adjustments were allowed for biasing. The target distortion figures were
met
with oodles of feedback. Output transistors could go outside their safe
operating area with realistic loudspeaker phase angle swings.

Ouch! I shudder to think what the parts cost of the HY50's was (50p?)
I always wondered if the HY5 was just an encapsulated 741 with a
feedback circuit, or even just a couple of BC107's.

The truly amazing thing is that I never succeeded in blowing the
HY50's up, I'm quite sure the volume levels I used to use would have
done their very best to drive the output transistors outside their SAO.
Plastic 2N3055's perhaps?

They didn't sound too bad though, mind you, it was hardly a
critical audience! The basic concept was great for a schoolkid
who didn't know much about electronics (practical electronics R.A Penfold
superhet tranny radio project notwithstanding) building his first stereo.

Later on I went to a uni interview at Nottingham and in the computer lab
I was astonished to see an HY50 mounted on the back panel of a PDP8 CPU!
I have no idea what they were using it for but when I saw it I
immediately told the interviewer "Hey! I've got some of those!".

Tony


PDP8 ! Boy, that's going back a bit. Earliest I encountered was a PDP
11/34A. Had about 512kB of memory spread across 2 boards, AIR. State of the
art for its day. Many hours spent adding / removing NPG jumpers from the
backplane. Happy days ...

I too built disco gear from ILP modules, and also marvelled at their
outstanding robustness. Can't say that I recall ever blowing one either,
despite subjecting them to some horrendous abuse.

Arfa

DIY headphone amplifier
 

"tony broughton" wrote in
message
news:slrne4t3c0.26e5.tonybDELETE_THIS_SPAM_BLOCKER ...
As a teenager, yeah, I made a nice boxed power amp with 2 ILP HY60
modules, but I don't remember an HY50. Must be before my time! This
was in the late 80s.

The HY50 was an earlier version, I got mine around 1977 or 1978
as far as I can remember, they used to be advertised in practical
wireless and perhaps ETI (I think ETI was going then). The module gave
a claimed 25 watts per channel RMS and if memory serves THD something
like 0.04% was claimed at 1 kHz. I actually bought them 2nd hand off a
friend at school who had used them in his home-made disco rig but had
then progressed to building his own more powerful amps with 2N3055's
(which sounded truly dreadful, especially with motorola piezo tweeters).

The HY50 looked really spacey too because it had semi-radial fins unlike
the later amps that had vertical fins that looked rather more boring.

But cheaper and proprietry, incorporating "T" slots so that square nuts
could be slid into the extrusion, avoiding the need to drill and tap.


This was also before ILP brought out the toroidal transformers,
the power supply they provided used a "real" laminated transformer,
actually I think that transformer was actually of quite good quality,
at least it was satisfyingly heavy!

The toroidal transformers were actually better performers and they were
capable
of very low acoustic noise.



They also had a higher-power one that RS also sold, called something
like MOS-240, which used MOSFETs. Never got hold of one of them to play
with!

I always wondered what they were like, by the time they came out
I'd got more into micros and software than building amps which was a shame
in a way, although I built some nice amps a bit earler using
2SJ34/2SK133 hitachi horizontal topology power fets (I might have got
those
part numbers wrong), they were attractive for home build because the
circuit only required a small signal transistor driver and you didn't
have the thermal runaway problems of bipolars (thermally self-limiting),
making them pretty simple to build into an amp and easy to set up.
Those Hitachi power-fet's were pretty expensive though - I seem to
remember getting on for 8 or 9 pounds per device, I bet those
ILP MOS modules didn't have those inside.

Tony

Yes, Tony, they did. ILP paid around £3 a pair as they had (maybe still
have)
the buying power. The current MOS240 type now uses Semelab parts. The
BDY64's and 65's in the HY120 were around 12p each. Small signal TO92's
were around 0.2p each.
This was mass production for a world-wide market.


Graham Holloway
WPS/Accuphon Audio