OPA2134/IRF510 Schematic... - diyAudio
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Old 11th August 2014, 05:00 PM   #1
ammel68 is offline ammel68  United States
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Default OPA2134/IRF510 Schematic...

I found a photo of a commercial design, that uses a OPA2134 along with a pair of IRF510's for the output, that I would like to build and try.

As seen in the photo, there's also a pair of LM317T regulators which I assume are used as some type of CCS for the 510's.
All the through-hole resistors appear to be the same value.
C3 & C4 appear to be Wima caps. perhaps used as coupling caps. on the inputs?

Can someone, who understands this circuit, please draw up and post a schematic of it?

Thanks...
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File Type: jpg IRF510_Headphone.jpg (198.9 KB, 329 views)
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Old 11th August 2014, 06:51 PM   #2
JoeB83 is offline JoeB83  United States
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I don't know anything about this circuit, but I don't see how it could be an effective headphone amp. I'd guess it's part of a larger system, maybe it's some sort of voltage or current regulator (can be accomplished with an op amp & 317s)? Just shooting in the dark here. Do you have any other pics?
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Old 11th August 2014, 07:06 PM   #3
jcx is offline jcx  United States
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the 1st question for headphone amp projects should always be "for which headphone?"
they vary by orders of magnitude in Z, sensitivity, required I,V

MOSFET buffers can waste a lot of Vsupply - whether that matters depends on what the particular model of headphones you want to drive need

lots of various project amps have been posted over the years


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Old 11th August 2014, 08:11 PM   #4
ammel68 is offline ammel68  United States
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Quote:
Originally Posted by JoeB83 View Post
I don't know anything about this circuit, but I don't see how it could be an effective headphone amp. I'd guess it's part of a larger system, maybe it's some sort of voltage or current regulator (can be accomplished with an op amp & 317s)? Just shooting in the dark here. Do you have any other pics?
Here's a photo of the interior:
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Old 12th August 2014, 05:05 PM   #5
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Should be similar to what's been discussed in this thread, opamp + Class A MOSFET follower w/ LM317 CCS, either inside or outside the feedback loop. Pretty standard stuff in DIY about a decade ago. Not especially efficient, obviously (a push-pull output could deliver twice the current, not to mention the possibility of transitioning into AB), but simple, easy to bias and doing well in terms of distortion.

Here's how a basic Szekeres (just the buffer) will fare with and without a CCS.

Instead of the MOSFET, it basically is also possible to use a BJT, a Darlington - or even another LM317 (there's a thread on that somewhere in this forum).
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Old 12th August 2014, 11:09 PM   #6
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Don't think that it's as simple as what you see on the top of the board. I see one surface mount resistor on the top, which means there could be a plethora of other surface mount components on the bottom.
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Old 14th August 2014, 04:32 PM   #7
ammel68 is offline ammel68  United States
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Quote:
Originally Posted by sgrossklass View Post
Should be similar to what's been discussed in this thread, opamp + Class A MOSFET follower w/ LM317 CCS, either inside or outside the feedback loop. Pretty standard stuff in DIY about a decade ago. Not especially efficient, obviously (a push-pull output could deliver twice the current, not to mention the possibility of transitioning into AB), but simple, easy to bias and doing well in terms of distortion.

Here's how a basic Szekeres (just the buffer) will fare with and without a CCS.

Instead of the MOSFET, it basically is also possible to use a BJT, a Darlington - or even another LM317 (there's a thread on that somewhere in this forum).
So, are saying I'm better off building a Lehmann design, which uses BD139 and BD140 output devices, instead of using MOSFET's?
If not, can you point me to some designs that you consider to be very good?

I'm not really interested in building designs that are considered "out of date".
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Old 14th August 2014, 04:55 PM   #8
jcx is offline jcx  United States
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you still haven't said which model headphone - need the Impedance and Sensitivity numbers to even pick a power supply V

and "universal" isn't an option in headphone amps with orders of magnitude sensitivity range
some headphones and some amps won't work together well - high sensitivity headphones will hiss and be using a tiny, often poorly matched high attenuation setting on the volume pot with the "wrong" amp
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Old 16th August 2014, 02:16 AM   #9
ammel68 is offline ammel68  United States
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you still haven't said which model headphone - need the Impedance and Sensitivity numbers to even pick a power supply V
SENNHEISER HD 580
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Old 16th August 2014, 03:34 AM   #10
jcx is offline jcx  United States
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the HD580 is speced as 300 Ohms and 97 dB/mW so 11 Vpk, 36 mApk would drive them to 120 dB SPL - that's fairly loud, really only "needed" for reproducing live event listening level transient peaks

some op amps can do that without buffering, even more if you parallel the outputs "A47" style

if you want well documented projects there are lots of options, some even with kit suppliers

the O2 project claims to be good enough with cheap parts


I like DSL driver CFA op amps instead of unity gain buffers, they certainly outperform any less than a dozen parts discrete buffers I've seen anywhere within the op amp's I,V limits


even if you want Class A I believe a few DSL driver op amps have enough internal output stage bias to drive HD580 to over 100 dB SPL before leaving Class A - and still control the distortion to below audible, i.e. distortion alone below human hearing threshold in quiet after leaving Class A

and they have enough extra current output capability that even ccs pull down is practical up to full Class A for HD590
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