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#1 |
diyAudio Member
Join Date: Dec 2017
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Hi all. the wealth of info on various DIY audio forums drove me down the DIY path instead of the expensive gear path and its been amazing so far. I was lucky enough to realise spending hundreds/thousands on gear doesnt guarantee you'll find that sound you truly love. building and tuning something yourself to sound like your definition of amazing is the right way, and the feeling of doing it yourself excells anything an over-priced piece of gear will offer
I built this headphone amp which you can find it on this site. Initially I was just really happy that it worked when I flicked the switch but I soon realised it didnt sound amazing, not bad but not great either. Firstly I tried changing up the op amp to an LM4562, this refined the signature a lot but it was still the same sloppy amp. Today I upgraded the 4700uf caps to good 8000uf caps taken from an old pioneer amp... all i can say is holy ****! from the minor improvements I got from the op amp what could a couple of power supply caps do? the answer: a lot! The amp is finally alive, but I feel like I've barely scratched the surface of its potential. I have a nice collection of polystyrene caps left over from building this amp, and also some electrolytics Im not very knowledgeable on the electronics side of things so Im looking for advice on how (and if) I should add these to the circuit... in parallel with current caps or in series? etc. Im also wondering about the power transistors, currently BD139s. for such a simple amp this is really the only part left un-upgraded from the original design. Should I upgrade these? Last edited by laserscrape; 19th December 2017 at 04:18 PM. |
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#2 |
diyAudio Member
Join Date: Apr 2010
Location: Coffs Harbour, NSW
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After all that hassle to post in the power amplifier forum, we do have a separate headphone systems forum here:
http://www.diyaudio.com/forums/headphone-systems/ Hmm....ancient, massive overkill 8,000uF electrolytics for the power supply of an amp. with a tiny output? This seems like an act that that will be hard to repeat or for others to verify. Best see if you can replicate the sound with new parts too as those old used ones you have chosen probably won't remain in the form you like, for any significant period of time.
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If only I had listened.... Last edited by Ian Finch; 19th December 2017 at 05:42 PM. |
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#3 |
diyAudio Member
Join Date: May 2007
Location: Germany
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Can you post the schematics of that headphone amp?
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#4 |
diyAudio Member
Join Date: Oct 2004
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See post#1 for the schematic.
As long as you are adding capacitors, I would surely try and add a 4.7uf electrolytic between +/- on the op amps. I don't think the 8,000uf is total overkill, but now that you've experienced the results, it may be a good idea to shop for some newer parts for sure. |
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#5 |
Got Foam?
diyAudio Member
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BD139 is a fine output transistor for a HP amp. Try making a push pull with BD140 and use a better IC driver chip. I built this one by Wayne Kirkwood and it rmains the lowest distortion amp I have made or tested. There is also a nice design by ESP that uses BD139/140.
Simple Class A Headphone Amp Using THAT1646 Here is the Kirkwood HPA: You don’t need big caps or better BJTs. It’s all in the design and implementation. FFT:
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XRKaudio https://www.etsy.com/shop/XRKAudio |
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#6 |
diyAudio Moderator
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#7 |
diyAudio Member
Join Date: Oct 2004
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Also, I would take a .1uf film cap in series with a 15-25 ohm resistor, and place that parallel to both c11, and c12.
I do like that driver chip, very cool. |
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#8 | |
diyAudio Member
Join Date: Dec 2017
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Quote:
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#9 | |
diyAudio Member
Join Date: Feb 2013
Location: Electrostats or bust
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Quote:
ideal psu-has zero impedance across whole frequency range. this is not doable with just few wet capacitors. wet caps are good maybe up to 1khz, foil caps are much better, stable params. you "smoothened your power rails with 1000grit sandpaper", but you may try some more. ![]()
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BLOG. XMOS_U8/PCM5102A > LL1544A > 6H9C+gyrator > 2A3_SOV/JJ > LL1660 > STAX ![]() Last edited by hpeter; 20th December 2017 at 08:12 PM. |
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#10 |
diyAudio Member
Join Date: Oct 2004
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I wouldn't recommend going without a .01 to .1uf to ground on each rail as well, but the smaller electrolytic part from rail to rail has helped when I had used the lme49720/4556. This was in addition to 47uf parts nearby.
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