Project files: PassHP headphone amp
October 24, 2017 20 Comments
What is it?
It’s the project files for the PassHP headphone amplifier from last week’s post and judging by the number of views since then they are eagerly awaited 😀
As mentioned last time, this design is a clone of the one from here and my version consists of a mono amplifier board and a stereo PSU board instead of the original “all-in-one” design.
How big are the boards?
The amplifier boards measure 2.95” x 3.0” (app. 75 x 76 mm.) and the PSU board measures 2.0” x 5.05” (app. 51 x 128 mm.).
What is the status of the boards?
Both boards are in version 1.0 as the prototype seems to work well and I couldn’t be bothered to make any cosmetic changes 😉
Does it use any special/expensive/hard-to-find parts?
Well, the recommended 2SJ313/2SK2013 output transistors are a bit hard to find, but there are plenty of substitutes available. This is a fairly simple design, so otherwise no problems.
Anything else I need to know?
- Resistors: I’ve used RN60-type resistors which are rated 0.5W, but that probably isn’t necessary – at least not for all the positions.
- Heatsinks: The heat sink profile is the one Fischer calls SK104 but there are many substitutes. The power dissipation isn’t great so even the small 25mm high version should suffice, but if you want to use bigger ones for cosmetic reasons that should be just fine 🙂
- Transistors: I’ve used 2SJ313/2SK2013 output devices because I had them, but if you don’t then I recommend using IRF610/9610 or one of the other substitutes mentioned in the diyaudio build thread. The 2SJ/2SK pairs are now either very expensive or very fake (and sometimes even both!), so using parts that are still in production should be safer.
- Optocoupler: In theory this is also substitutable for something else, but in all honesty I don’t know exactly how the optical bias-system works so it’s probably best to stick with the standard 4N35.
- Gain: The default gain is app. 6 but that can be lowered or raised by tweaking the value of R4. In theory you should recalculate the BW-limiting capacitor across the resistor if you change the value, but in practice you’ll probably be fine unless you make major changes. My prototype version has a gain of 3 (R4 = 2k) and I haven’t observed any problems.
- Opamp: My version uses a single-channel opamp which gives a bit more choice. Start out with something like the OPA604, OPA134 or LME49710 and then experiment from there if you want to change the sound.
Most opamps have a max. supply voltage of +/-15V so as a starting point I’d recommend this as the supply voltage. If you want more voltage swing use the OPA604 which is good up to +/-22V. - PSU voltage adjustment: Just as in the original you can use LEDs to raise the output voltage of the supply above the regulator voltage (although I’ve ditched the resistor option). Using 7×15-regulators and green/red LEDs should give you around 17V output whereas using 7×18-regulators and LEDs should bump that to app. 20V. If you just want the regulator voltage as the output, remember to jumper across the LED pins and omit the capacitor.
Downloads:
Download design files here
Related information:
You really should chew your way through the diyaudio-thread for information about the amplifier. As mentioned this version was mostly because I did not like the original form factor. If you just want a functioning amplifier then I strongly recommend that you buy one of the “real” boards from Wayne Colburn via DIYaudio (or wait a few weeks for when the boards show up in the diyaudio store).
Note: Always read the “intro post” for additional important information about my designs.
Thank you for sharing ! =)
Wonderful!! Thanks for sharing the project. Where could I get the pcbs?
Hi Jordi, you can send the gerber files to itead, Seeed Studio or any other board manufacturer and they should be able to make PCBs for you 🙂
Hi theslowdiyer, thanks for the answer, I did so, waiting for the PCBs 🙂
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Hi, Whammy Project and PassHP version are similar or different ?
It’s basically the same circuit (the differences are what is described here). It just wasn’t called the “Whammy” amp until after I published my version.
So, the sound quality of two PCB will be same ? I really love your design, which have different PSU I can use my PSU version.
I have done a comparison of the original board and my version, but if you build them using the same components I’m pretty sure they will sound almost identical.
Thank you so much for your work.
Hi what cable do you use for Signal ?
I normally use silver-plated 22-24AWG wire with teflon (PTFE) insulation, but you can use pretty much whatever you like 🙂
I plan change opamp to discrete opamp like Ticha 992enh or Burson V6 Classic Single opamp. Do you think it better than classic opamp ?
Sorry, I have no experience with either of those two.
What opamp you like most for this version ? I try to use opa828.
I liked the sound with the OPA604, but I didn’t test other opamps in this particular amp design. Do your own experiements and hear for yourself 🙂
Hi where resistor affect sound quality in schematic ? I plan to upgrade high quality audio resistor for your amp.
I suggest you check out the diyaudio-discussion on this amp for more practical experience. Personally I would not spend a lot of money on exotic resistors, but just use “standard” 1% metal film types. I think you choice of opamp is going to impact the sound much more, so if you want to experiment then do it there 🙂
Hi, can I use 4 battery 9V for this amplifier ?
No, it draws too much power for that.