"WHAMMY" Pass DIY headphone amp guide

How does this amp fares against, for example, typical entry level 100$ head amps? I got a JDS Atom and my soldering iron is starting to itch.

Been waiting to answer a question like this. I don't get excited about amps very much or head-gear for that matter. So far in my years into head-gear, the value has not translated into that phenomenal sound I've been looking for. I stumbled upon the Whammy through a friend and I can safely say that the Whammy is totally worth the price and beyond. The main attribute that the Whammy offers is that it makes the music sound very life-like. I am looking back at some of the music that sounded meh with other amps, but the Whammy delivers a refreshing sound that I've never heard before. Great recordings will sound even better.

The right question is how does it fair against head amps that are more expensive? It's remarkably better in almost all aspects. (Perhaps not in the bass but tube amps do a better job at that in general, but can be fixed with closed back headphones)

I would suggest only using the OPA2107 op-amp. I've tried several $50+ op-amps, but it was obvious on first listen that this was remarkably better than the rest. This provided the life-like quality that I mentioned above. Soundstage is awesome.

This could all be had for about $270 including the chassis. Compared to my $400+ $800+ amps, the Whammy with the OPA2107 is sublime. Please build one.

PS I'm using HD 650's
 
Last edited by a moderator:
Discrete Chinese Opamp

Hi,

I have tried one of these Chinese discrete opamps. It sounds great but I am getting -25 mV on the left and 21 mV DC offset on the right. Does anyone know if the DC offset can be zeroed, and if so how ?

Thanks

Mark
 

Attachments

  • Discrete Opamp.jpg
    Discrete Opamp.jpg
    819.4 KB · Views: 642
Member
Joined 2011
Paid Member
Maybe you could disconnect the input bias resistors from ground (zero millivolts) and instead connect them to ((-1) x OffsetVoltage) millivolts. Two wrongs make a right and presto the offset is nullified.

Your circuit designer will probably want to add noise-elimination capacitors and range-limiting resistors / diodes and so forth, to go from the "here's an idea" drawing below, to a finished schematic.

What nobody knows is: does the offset vary with time ("drift") ?? If so then a fixed offset cancellation scheme is doomed, and you need an adaptive offset canceller (active circuit) instead. Or else an output coupling capacitor :) or an output transformer :p

_
 

Attachments

  • whammy.png
    whammy.png
    64.3 KB · Views: 634

6L6

Moderator
Joined 2010
Paid Member
mod_sonic - do you have any offset with a normal opamp?

Also, 21millivolts across 32ohm is a breathtaking 0.000013W of additional DC current that the voice coil needs to dissipate. If you have say, 300ohm cans then it's 0.0000014W

I'd put that squarely into the "who cares" column and instead listen to music. :yes:

:)
 
mod_sonic - do you have any offset with a normal opamp?

Also, 21millivolts across 32ohm is a breathtaking 0.000013W of additional DC current that the voice coil needs to dissipate. If you have say, 300ohm cans then it's 0.0000014W

I'd put that squarely into the "who cares" column and instead listen to music. :yes:

:)

6L6,

Yes I've done the V^2/R calc too and I totally agree with you it's 2/5 of not a lot :), which is why I have been listening to it for a while with no worries. However, out of interest, and in the pointless pursuit of perfection, I wondered if there was some simple way of zeroing the offset. Mark Johnson has suggested something I will take a look at.

Mark
 
General Questions

Hey folks, placed an order for an ACA1.6 recently. I plan on using my phone loaded with flac files as a source upon completion.
I am contemplating building the Whammy for use as a preamp and headphone amp.
Couple of question: How are the outputs to the ACA wired? They appear to come off of the “headphone” jack in a couple of pictures.
Would this combination of components make a reasonable sounding system with the right speakers?
Might one exercise patience and wait on the ACP+
 
I just asked about the ACP+ and how it fares to the WHAMMY just a couple of days ago... still waiting on more input. It might merit waiting for it, on that I cannot give feedback.

I have built the WHAMMY though, and can give praise and a bit of feedback:

Regarding using the WHAMMY as a PRE, the nicest route (IMHO) is to use a switching stereo headphone jack. The setup is exactly the same as the output diagram you find in the ACP+'s second page: you take the 'interrupted' outs from each of the headphone jack's channels into a 33 ~ 100 ohm resistor and those into the RCA connectors.

Ground can be taken from the jack as well.

I have this very same combo (with just the 1.5 ACA, not the 1.6) without the resistors (not exactly recommended as per Wayne's own comments in these pages) and I find it incredibly musical!

I love the Whammy and what it brought to my system. You can't go wrong with it.

Good luck! Hope this helps a bit,
Rafa.
 
Member
Joined 2019
Paid Member
Hi Rafa - Great to see you again. Maybe I just haven't been hanging out in the right threads :D

re: WHAMMY and ACP+. The WHAMMY was my first build, and I'm never giving it up. The ACP+ was my most recent build, and I'm never giving it up. :D

I did do a very small amount of back to back listening with both. Everyone has their own preferences, ears, brains, and headphones... So... grain of salt.

I'm still keeping both, but as a headphone amp, I lean ACP+ for my Meze Classics, and toward the WHAMMY for my Sennheiser models. I'm not one to do flowery language music descriptions, and I have no measurement gear. All I can say, it that I think the WHAMMY brings out a bit more of what the Senns can do, and the ACP+ brings out a bit more of what I love about the Meze's.

I strongly recommend both. Note, I do not have my WHAMMY set up for pre-amp duty and have never used it in that capacity. I also have never tried different op-amps. That holds a lot of appeal for some. I plan to try it at some point, but I just haven't gotten around to it, and I think it sounds great "stock".

I suppose in summary, is that I'd highly recommend giving the ACP+ a shot. For those who would like to know if one is "better" than a WHAMMY. I can't answer that... sorry.

:cheers:
 
Member
Joined 2011
Paid Member
I think you'll be pleasantly surprised if you experiment with different bias currents in the WHAMMY output stage, assuming your output transistors are adequately heatsinked.

I don't know whether the schematic in post #2 of this thread is current and up-to-date, but it does mention the idea:

_
 

Attachments

  • post2.jpg
    post2.jpg
    107.3 KB · Views: 839
Hi Rafa - Great to see you again. Maybe I just haven't been hanging out in the right threads :D
This is a great welcome indeed! Thanks a lot! No, you haven't been on the wrong threads, I ended up on the wrong side of "ridiculously busy" this last few months and have been swarmed up with work and taking care of my dad who fell ill. Good news is he is doing much better, and I am slowly returning to catching up on my reading and hobbies!

I came back to learn of the ACP+ which was really great.

Your answer makes perfect sense thanks! I have the Sennheisers myself. As I read it (and hearing Mr. Pass' talk at the Burning Amp), the ACP+ is kind of 'tailored' for 30ohms. The Senns, with their 300ohms, probably are better paired with the WHAMMY.

That said, I use it mostly as a PRE and I love it. I did try a couple of op-amps, but I have an itch to try the 2107 which everyone in this thread appears to favor!

I am not brave enough to follow Marks suggestion of playing with bias current. In electronics, I'm kind of a 'paint by the numbers' type of builder. I do what is plotted. I don't have the knowledge to experiment.

That part of the thrill I use experimenting with the case designs and looks, which is more close to my area of expertise. :)

It's nice to be back and reading the great experiences of others! Big hug,
Rafa.
 
Member
Joined 2002
Paid Member
Hi Rafa, sorry your dad's been ill (but happy to hear he's doing better.) :cheers:
I have an old pair of Grados at home somewhere so when I built my
Whammy, I used 60mA bias. I don't view it as experimentation at
all, given Wayne included this info on the schematics, but rather as an option
of the design. Since you're using Sennheisers you should be fine with
a lower current setting.

The ACP+ is pretty neat; I hope you get a chance to build and try one sometime.

Dennis
 
I am not brave enough to follow Marks suggestion of playing with bias current. In electronics, I'm kind of a 'paint by the numbers' type of builder. I do what is plotted. I don't have the knowledge to experiment.

Have you checked which resistor values you used for your build? ….maybe it is 10 ohm ("high" bias)? ….I guess no fun to reduce bias...

It is about 1W in each output transistor if about 15V over each of the transistors. A normal "clip-on/screw on" heatsink should be able to handle that.

Will check what is supplied in the kit...….I have not built it yet…...but have the kit.....
 
This is a great welcome indeed! Thanks a lot! No, you haven't been on the wrong threads, I ended up on the wrong side of "ridiculously busy" this last few months and have been swarmed up with work and taking care of my dad who fell ill. Good news is he is doing much better, and I am slowly returning to catching up on my reading and hobbies!

I came back to learn of the ACP+ which was really great.

Your answer makes perfect sense thanks! I have the Sennheisers myself. As I read it (and hearing Mr. Pass' talk at the Burning Amp), the ACP+ is kind of 'tailored' for 30ohms. The Senns, with their 300ohms, probably are better paired with the WHAMMY.

That said, I use it mostly as a PRE and I love it. I did try a couple of op-amps, but I have an itch to try the 2107 which everyone in this thread appears to favor!

I am not brave enough to follow Marks suggestion of playing with bias current. In electronics, I'm kind of a 'paint by the numbers' type of builder. I do what is plotted. I don't have the knowledge to experiment.

That part of the thrill I use experimenting with the case designs and looks, which is more close to my area of expertise. :)

It's nice to be back and reading the great experiences of others! Big hug,
Rafa.
The OPA2107 sounds great. The LM833 sounds about the same as it though, imo. The most revealing/neutral sound op amp wasn't an audio opamp at all, but a video op amp I was experimenting with, trying to coax out oscillation (unsuccessfully), the AD812.
 
... I tried some different OpAmps: An Analog Devices AD823ANZ which is the most expensive part of my BOM and I didn't quite like how 'raspy' it is. I tried a Ti LM833 which, at 1/10th of the cost sounds much better. Then I placed a Ti OPA2134PA which sounds just fantastic! The best of the three. Stupidly, I have not yet tried the RC4580 which came with the parts KIT and is specifically listed as best for 'headphone amplifiers'. So I'll probably take some time today to try that...
Best regards,
Rafa.

I wrote this back in December. Since then I did try the RC4580, still the OPA2134PA was much, much better. For me, the difference was significant, specially using it as a PRE (but with headphones as well).

If the 2107 is not all that different from the LM833, I may just not spend the $30 they go for and live with what I have already, which is just fantastic! :)

I do have the 10 ohm resistors there, which is what comes with the KIT. So yeah, I would not go with higher voltages than that. I'm OK with 60mA.