Does anyone know this amplifier ?
I got it with a heatsink a few years ago and was told that it was an elektor class a headphone amp that could also deliver around 10 watts into 8 ohms.
Anyone recognice it ?
An externally hosted image should be here but it was not working when we last tested it.
I got it with a heatsink a few years ago and was told that it was an elektor class a headphone amp that could also deliver around 10 watts into 8 ohms.
Anyone recognice it ?
Class A, discrete 10 Watt in 8 Ohm.
I do not remember this Elektor headphone amplifier.
What are those 4 ouput transistors?
BD139/BD140?
I do not remember this Elektor headphone amplifier.
What are those 4 ouput transistors?
BD139/BD140?
A headphone-amp that provides 10W output? That's a little unnecessary. Why don't you email elektor with the PCB-number and see if they can help you?
/U.
/U.
I have build this Headphone amp too.
And somewhere i have the orignal article ...
But 10W is to mutch for this headsinks ...
And somewhere i have the orignal article ...
But 10W is to mutch for this headsinks ...
I remember this amp. 10 W with these transistors is a bit weak but if the supply voltage was +- 15 volts it's possible to get a couple of watts from the amp. Beware of the thin traces from the output.
Why do you ask?
I have the article somewhere in my collection. If you could tell me when it was published it would help me.
Why do you ask?
I have the article somewhere in my collection. If you could tell me when it was published it would help me.
Elektor did that design in 2 versions, the first one was part of their 80s discrete modular preamplifier design.
Second version was identical but doubled output devices, also BD139/140.
Bias was 0.1 amps.
I still have both articles.
Second version was identical but doubled output devices, also BD139/140.
Bias was 0.1 amps.
I still have both articles.
I soldered those trannies on today, the originals were fried/stolen a few years ago, i still have the heatsink that came with the amp when i got it from a forum member of a swedish hifi forum.
It originally used BD139/140, the ones there now is similar ones but are drivers from a broken poweramp.
It was the previous owner that said the thing could deliver around 10 watts in 8 ohms while it operated in class A driving 32ohm headphones.
I believe its either the 1983 mag 4 headphone amp, the mag 7 1984 mini crescendo, the mag 1 1986 AXL amp, the mag 9 1986 or the mag 10 1986 mini stereoamp.
Board number EPS83022-7 if it helps.
It originally used BD139/140, the ones there now is similar ones but are drivers from a broken poweramp.
It was the previous owner that said the thing could deliver around 10 watts in 8 ohms while it operated in class A driving 32ohm headphones.
I believe its either the 1983 mag 4 headphone amp, the mag 7 1984 mini crescendo, the mag 1 1986 AXL amp, the mag 9 1986 or the mag 10 1986 mini stereoamp.
Board number EPS83022-7 if it helps.
It does nearly 10 watts in class AB.
With 4 BD139/140 per channel i managed to get 2 watts in class A and keep the devices alive.
Sound on a K1000 isn't bad
The board number stands for 1983
I can post a picture of the 2 device version i built, same as yours.
I used it on efficient loudspeakers, amazing what such a little amplifier can do.
With 4 BD139/140 per channel i managed to get 2 watts in class A and keep the devices alive.
Sound on a K1000 isn't bad
The board number stands for 1983
I can post a picture of the 2 device version i built, same as yours.
I used it on efficient loudspeakers, amazing what such a little amplifier can do.
I find the sound suprisingly good with just a cd-rom drive as source.
My output transistors are: 2SD669A ond its complement 2SB649.
If anyone have the issue with this amp, i´d like a scan of the info sheet and schematic.
My output transistors are: 2SD669A ond its complement 2SB649.
If anyone have the issue with this amp, i´d like a scan of the info sheet and schematic.
Maybe i should add that i run it with a pc power supply, also i have it hooked up to a pair of old 4 ohm speakers.
With a + / - 15 V DC supply, the amp should infact be able to put out 10 Watts into 8 Ohms, though into 33 Ohms it would be 2.5 Watts and 'just' 0.25 Wats into 330 Ohms.
I recall this circuit though never built it. I am sure the circuit would have been repeated in their Summer Ckts, and books...
I recall this circuit though never built it. I am sure the circuit would have been repeated in their Summer Ckts, and books...
Tekko said:
What is the question ?
The 2-device version was published in 1983, the 25volt rails version with 4 output devices in the 1992 Elektor Personal Hifi book.
Using MAT02 for the differential instead of the BC550C's is a big improvement, and separate LM317/337 regulation.
Here's an old board>
Attachments
Hi Tekko, the 10 W figure comes from my memory of the first article. This was in 8 Ohm as said but in Class AB as also mentioned. The amp was biased to run in Class A for the headphone impedance.
/UrSv, The member who sold it to Tekko...
/UrSv, The member who sold it to Tekko...
UrSv, i guess it pleases you to see that the amp is still in one piece and working.
What does the two pots next to each other do ? The standing ones is volume and the two in the middle of the transistor forest is bias, but the remaining two i dunno, offset ?
What does the two pots next to each other do ? The standing ones is volume and the two in the middle of the transistor forest is bias, but the remaining two i dunno, offset ?
A blast from the past for me....
Just browsing and I thought I recognised your board layout - I built one of these (must have been around '83) together with a discrete preamplifier from ETI (remember Electronics Today International?
).
Just dug it out of the garage - as you can see - poor quality components used throughout!
I remember etching the board in my parent's back garden and stripping the paint off the door with Ferric Chloride (an accident).
I have long since lost the articles, and the peak-level indicator board appears to be missing, but I wonder if it still works...
NB. The piggy-back board is just a delay relay for the preamp (RH side of board) and I think the paint spots on the transistors was for gain matching.
Just browsing and I thought I recognised your board layout - I built one of these (must have been around '83) together with a discrete preamplifier from ETI (remember Electronics Today International?
).Just dug it out of the garage - as you can see - poor quality components used throughout!
I remember etching the board in my parent's back garden and stripping the paint off the door with Ferric Chloride (an accident).
I have long since lost the articles, and the peak-level indicator board appears to be missing, but I wonder if it still works...
NB. The piggy-back board is just a delay relay for the preamp (RH side of board) and I think the paint spots on the transistors was for gain matching.
Attachments
Yeah, this enclosure was superb for audio projects - I remember getting all the bits from Maplin Electronics (or Maplin Electronic Supplies as they were then).
Tricky getting decent metal enclosures these days in the UK - everything seems to be made out of ABS plastic, or to fit the 19" rack system - really expensive too!
Plz anyone - any recommendations?
I'm stuffing boards for a Zen v4 (Penultimate) at the moment, so I'll probably use Al sheet and hardwood and build a case around the heatsinks.
Next project will be something along the lines of the SL10 or NS10 - this enclosure would have been ideal for these 🙁 .
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