DIY audio blog for projects, schematics, PCB's, designs, electronics, mods


Diamond Buffer Headphone Amplifier

Here is a truly classical implementation of the diamond buffer. A headphone amplifier.
There isn’t much to be said about this topology. It’s pretty popular and is used in variety of applications. One application is buffering an opamp’s output so that it can drive low impedance high capacitance loads like a pair of headphones. Here is a schematic showing the diamond buffer as a current booster for an opamp:

The gain is set by the resistors R5 and R2. If you are using NE5534 the C6 capacitor is a must when gain below 3 is set. For more info on this read the 5534 opamp datasheet.

The buffer is biased in pure class A at about 300mA 30mA. That will give a plenty of headroom for plenty of voltage swing. To calculate the quiescent current use the following equation:

    \[ I_{q}=\frac{V_{cc}-V_{be}}{R}; I_{q}=\frac{15-0.7}{470}; I_{q}=30mA; \]

This amp will output a substantial amount of power so it must be used with care. Always switch it on with a volume pot set to minimum. It’s very easy to damage you hearing so be warned!

The PCB artwork is available for download HERE. You need two PCB’s for a stereo application.

**********THANK YOU FOR READING THIS ARTICLE**************


TPA6120 Headphone Amplifier – COMPOSITE TOPOLOGY


SSM2017 Line Preamplifier – High Quality Design


  1. Can this circuit be run from +/-9VDC (dual 9V batteries) satisfactorily for use with 16-32Ω/113dB/1mW IEMs? Also, what is the output impedance of the circuit?

    Thank you for your time, I realize your post is nearly a year old.


  2. Vencislav Simonov

    in theory you can run this topology from batteries. However I don’t think this is the most power saving solution in the world, as the quiescent current is quite high. The batteries will have their life drained quite quickly.

    The output impedance is very low. You can even use this circuit to power some high sensitivity 8 ohm speakers. I’ve tried this on my FE206E. However when used with speakers, the circuit will exhibit clipping at higher levels. With headphones your ears will be long gone before driving this topology to clipping so this is not a problem.

  3. Wow, thank you for such a prompt reply 🙂 I have bookmarked your blog. I am interested in experimenting with this circuit. Primarily, as an output buffer for something like my iMac or iPod. Leaving out the NE5532/4 voltage gain stage and using the diamond buffer section only to present a low impedance output to my headphones. My Mac/Pod play sufficiently loud enough as they are for my taste, so I figured to leave out the gain stage. Am I making any sense? LOL I have some rechargeable 9V (8.4V) to power the circuit with and can make a charge circuit for use with a 12VAC/1A wall wart.


  4. Vencislav Simonov

    I don’t recommend using just the buffer and dropping the op-amp. Running this in open loop will result in significant DC offset at the output. This will damage your headphones.

    You will also need a dual supply power that is +/- 15VDC. You can’t power this circuit up of a single supply.

    As I said it’s not meant to be powered by batteries. It’s a stand alone high current class A headphone amplifier.


  5. Hi Venci,
    I have decided to build this circuit as is but have a few questions. First, are there any pre-made pcb’s for purchase? Also, the values for C2-C5 are not mentioned or shown in the schema, what value should they be? Data sheets seem to specify a 22pF comp cap, any reason you selected 33pF? Finally, what are the heat sink requirements (if any)?

    I have designed a bipolar power supply for it using a 16VAC/1A wall wart with 78/7915 regulators and 1000uF filtering, will that be adequate? I can link the schematic to you for evaluation if you like. It’s on CircuitLab.

    Thank you for your time and consideration. Cheers!

  6. Vencislav Simonov

    you can use 22pF compensation cap but I suggest to input a square wave and scope the output just to make sure there are no oscillations. On the other hand you could simply increase the gain of the stage by setting R5 to higher value. Using 4.7k will result in much higher gain and improved stability on NE5534. In that case C6 can be omitted.

    The two large electrolytic capacitors are subject to variations. 1000uF/25V should be quite adequate.

    About the power supply – bare in mind that each channel will draw about 300mA of current all the time! That means you need the voltage regulators 7815 and 7915 mounted on heatsinks. There are large TO-220 heatsinks available over eBay and electronics stores. Also, I’d recommend power capacitors of about 4700uF/35V given the large current consumption.

    If you want to use this power supply then you should lower the current consumption by making R3/R4 – 1.5k This will give about 100mA of quiescent current per channel. This is still enough to drive 32 ohm headphones to dangerously loud levels without clipping. However the voltage regulators will still need some sort of heatsinking.

    Few words about heatsinking. If you set the current to about 100mA using R3/R4 – 1.5k then you will be just fine with two small heatsinks. If you can find some old Pentium 2 heatsinks you are OK 🙂

    PCB’s – no I’m sorry I don’t have for sale.


  7. Barny

    I see this is designed to be powered by DC +-15 volts, could/would this run off a +-12volt DC supply?


  8. GN

    Do the BD243/244 require heatsinks?

  9. Gautam


    Is the base of J1 connected to pin 6 of the 5534 (along with the base of J3)? I assume the volume pot is placed before the input, right? Do I need heatsinks for the transistors?

    Thanks and Regards

    • Hi,
      both J1 and J3 bases are connected to opamp’s pin 6. If you’d like to omit the heatsink you could adjust the quiescent current. That would result in much lower power dissipation.

  10. Gautam

    Thanks for your reply, just the part about the volume control was not addressed. Could you please answer that.


  11. WG

    Can you suggest some replacements for BD243/244?

    Can I use BD 135/136 or BD139/140?

    Thanks and Regards

  12. GN

    Is the schematic shown complete or is there something missing?
    I assembled this and it does not work I only get a loud hum in the output. Any ideas?

  13. ramani

    Hi, Can this circuit work using a opa2134 and bd 139/140 instead of 5532 and bd234/244 respectively without any other changes. Thanks.

  14. GN

    Hi, Please help me understand how you calculate that the quiescent current of your circuit is 300mA with R3/R4 as 470. How does it drop to 100mA if R3/R4 is 1.5K. The gain is 2 right (R2+R5/R2)? so I =15/470=32mA*2(gain) =64mA. If I use 1.5 K for R3/R4 then I=15/1500=10mA*2(gain)=20mA?. What am I missing?

    • Hi,
      thank you for the question. I’ve looked at the math again and my calculations are off by one decade. To calculate the quiescent current you solve for Iq=(Vcc-1*Vbe)/R=(15-0.7)/470=30mA

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Powered by WordPress & Theme by Anders Norén