gyraf Headphone amp: heatsink?

Hello Forum!
I have build the gyraf HP-amp and its working fine and i really like the sound. Now i´m housing the hp-amp and i wonder if i have to deal with the heat of the voltage regulators and the transistors? They get hot, but i have no experience how much heat is ok...
sorry: for my bad englisch and the noobie-question.
merry christmas everyone!
Chris

In my street approach, if it gets too hot to hold on to it needs to be cooled...
BTW, why is there LEDs in this circuit instead of diodes?

I don't think heatsinks are ever going to hurt  [ unless not isolated ]
but in fact could save some aggravation come the time that you really tax them

LED=1.8V voltage drop

Need for heatsink depends on supply voltage from transformer, but usually it does well without.

Jakob E.

Thank you Jakob!
The hp-amp runs with the 18 volt and i use an 10VA-Transformer. So i guess i will try without and see what happens
Thanks Jakob for a great DIY-project!
Chris

So a diode would provide about 1/2 the voltage drop needed?
Just curious as I have seen this type circuit used in various output drivers, using diodes instead of LEDs...

yes, in stead of 2½-3 standard si-diodes.

Hi! Is it problematic if the leds have about 1,4v voltage drop?

Shouldn't be much of a problem, but have you measured them? Most standard red leds are 1.6-1,9V at rated current.

The LED (and it being the red type) was entirely decided on by listening to the driver back in 1990's.

Jakob E.

Thank you Jakob..
Yes I ve mesured something between 1,4v and 1,5v, it's a quite old stock of red leds (from the 80s or 90s)

  Is there a way to protect the headphones from too much voltage, maybe with 2 or 3V zeners between input and ground?

I built a version of this for my 51x rack - x3.
My little thread was here:

http://www.groupdiy.com/index.php?topic=53523.0

Initially I was concerned about heat from the transistors.  But I have used this a good amount of hours now including a 4 hour location recording session this past Monday and it works great.  The heat hasn't at all interfered with the function of the unit in the least.  Last I measured the temperature of the transistors they were up to ~150F - hot, but nowhere near their max temp.

I should add that I changed R1, 2, 3, and 4 to a value of 100R to try to lower the output to headphones and it seems to work fine.

http://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf
Do you mean R7/R8 here ?

saint gillis said:

http://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf
Do you mean R7/R8 here ?

Click to expand...

Yes-
sorry, I referenced a different schematic

Could this Headphone Amp be powered by +/-15V ?
Something to modify? Like 3K9 for R5 & R6 ?

Anything between +/-12V and +/-22V works fine irl, no mods necessary. But maximum output level will be different, off course.

Jakob E.

Nice!
  It is really a great headphone amp!

I ve included some in a monitoring station, I ve put a talkback mic (small dynamic capsule with small transformer) that came close to the headphone amps PCB, and I have a kind of big hum on the talkback when I use this internal mic, I ve tried to keep the mic away from the HP Amp PCB and the hum disappears, does it make sens?