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-   -   4ch signal splitting heaphone amp (http://www.diyaudio.com/forums/chip-amps/235445-4ch-signal-splitting-heaphone-amp.html)

themadhatta 5th May 2013 02:19 PM

4ch signal splitting heaphone amp
 
so i am still new to audio diy and have a few ideas buzzing around my head, i got some free sample from ti the other day and included was the opa4132, now what i was thinking was 2 ch's for bass and the other 2ch's for mids and highs, is this possible to do, or would there be a need for some kind of crossover to split the signal before its amplified so the right signals go to the right ch's.....was just something playing on my mind

Fast Eddie D 6th May 2013 02:18 PM

First, there is a headphone section on this forum, where your post belongs.

Second, the 4132 is rated 40 mA short circuit current. Furthermore, it is rated for 600 ohms minimum load. Its performance will likely drop off sharply with typical 32-100 ohm headphones. Have you ever heard a headphone amp that consisted of a single op amp per channel? (You probably have if you ever listened to the headphone output on a component CD player or cassette deck.) It usually leaves a lot to be desired, although I don't have specific knowledge of a 4132 in this application. Parallel op amps can make a nice headphone amp, though. Two parallel 5532s make an OK headphone amp; 4 is better. 6 works really well. Note that the op amps are being run outside of their specified parameters even with 6 in parallel.


Third, you will definately need a crossover if your application calls for low frequencies and high frequencies to be reproduced separately.


Are you planning to make 2 way headphones?

Fast Eddie D 6th May 2013 02:34 PM

Your 4132 would be better suited for the active crossover part of your headphone amp. Conversly, you could use them with a buffered output to drive the headphones.

There are a lot of headphone amp circuits available here and on the web. They are not all equal by a long shot. I prototyped 6-5532s in parallel per channel and Death of Zen headphone amps (will likely build both at some time). Both were excellent. I am sure that there are many headphone amp configurations that are equal to or better than these configurations.

If you must drive low impedance (32-100 ohm) headphones from a single op amp per channel, you will likely get better performance running them off a lower voltage supply (like +/- 9 volts) instead of the typical +/- 15 volt supply.

themadhatta 6th May 2013 06:30 PM

i have built a few amps with opa2132pa's they seem to be highly regarded in the forums and other sites, and this was just an idea i had that was in my head, seems like i could be done, looks like i have lots more to learn then i will prob attempt it at some point i will draw up my idea for the heaphones and amp for them and try them when i aint such a noob to it all, my next project is a modified cmoy as i have built a few of them now

Fast Eddie D 6th May 2013 09:38 PM

Quote:

highly regarded in the forums and other sites
That doesn't really hold water with me.

But I will say this, you have more expertise here than you have on all the other forums put together, in my opinion.

Quote:

looks like i have lots more to learn then i will prob attempt it at some point
There's a lot of headphone amps that are noob friendly. Pick your poison.

Quote:

my next project is a modified cmoy as i have built a few of them now
If you think the cmoy amp is good, you will be blown away if you build a halfway decent headphone amp. Try two 5532s in parallel off a +/- 9 volt supply. It's more than twice as good as cmoy.;)

Cmoy is best off a lower supply voltage, like 18 volts split. But 6-5532s in parallel off a +/- 15 volt supply will drive any headphones you want. It's dirt cheap and simple too. If you built a cmoy successfully, you will have no problem with this.

themadhatta 7th May 2013 11:25 PM

6x 5532s hmmm sounds like fun, where can i find a schem/pcb layout??, one of my cmoys i have soldered sockets in the places of caps, doing some of my cap testing to see what give me a good sound and see what the different cap types do to the sound, ordered some elna cerafines and some nichicons for the power caps and some mundorf and wima for the outputs just experimenting and getting myself some what familiar with audio electronics now

Fast Eddie D 8th May 2013 04:55 AM

Mine was a prototype so it was built on a breadboard. I intend to build it on a universal op amp PCB board from Rat Shack. You can whip up a custom PCB board if you like.

Schematic is so simple it's self expalanatory. 6 5532 non inverting amps with gain of 3, use 0.1% feedback resistors, 10 ohms in series with each output, parallel them up. Provide conventional DC ofset nulling for each amplifier. Take usual bypass and DC blocking precautions. It couldn't be simpler.

themadhatta 8th May 2013 03:44 PM

i found a basic schematic for a 5532 amp so am going to make it and modify it and see what happens, and i have a lm386-4 thats a 1w output that i am going to do something with

Fast Eddie D 8th May 2013 04:06 PM

Try two in parallel first.

I've heard of people using the 386 as a headphone amplifier. It's not ideal, but it has obvious advantages; simplicity being the premier advantage. It does not have real good power supply rejection, so test it with a 9 volt battery to establish a benchmark.

Look at this. 5532 parallel headphone amp You can extrapolate this circuit to as few or as many iterations as you desire. This is the real deal.

Fast Eddie D 8th May 2013 04:14 PM

Also look at the pdf refernced here. http://www.diyaudio.com/forums/solid...el-ad811s.html Figure 6-37 might prove useful. There is also a master-slave circuit you might find useful.


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