Please search through the thread. A number of people have done some comparisons of other options both in terms of other projects, but also in of parts you can swap out/experiment with to make it suit your tastes.
You will find that as an active voltage gain stage, this is a top contender especially given that you can "fine tune" the basic presentation to your tastes by easily swapping the OpAmps in the front end of which there are literally dozens of options to try. The back end will drive just about any headphone out there (or even small speakers!). Because of these qualities, it is very capable as an awesome preamp because it provides some sweet sounding voltage gain. In that you get a 2-for-1 with this project: an HPA and a Preamp.
--Tom
I have built many different headphone amps and Whammy is by far the best sounding to me and the only one I have that seems to sound truly excellent with all my various headphone types. Those are closed, open, dynamic and planar in the mid-price ($300 - $600) range. It did take experimenting with quite a number of different opamps, both monolithic and discreet to get to that magic point.
Whammy may make do as a good preamp but Wayne's BA2018 line amp sounds better to me on loudspeakers than Whammy. Conversely, the BA2018 with the large outputs does not sound as good as Whammy when driving headphones.
Some similar class-A with linear power supply commercial products might be the Flux FA-10 ($750) or the RebelAmp ($500). But they won't give you the option of tailoring the front end the way Whammy does, or using your choice of resistance/brand of input potentiometer, or adding a nice, quiet filtered AC inlet.
You would need to bias the output at 83mA for 1W or 100mA for 1.5W to stay in class A*, all the heatsinks would need to be larger, that could be a challenge with the current PCB design unless you build from scratch; or, leave it as is and run it in class A/B.
* You leave class A at twice the bias current, W=IxIxR. Your headphones are 38 ohms.
That's always possible. if you move the output devices to the case heatsink, make sure you also move the gate resistors, connect them directly to the gate legs, the source resistors can remain on the board, change them for 5R9, that will give you slightly more than 1.5W.
If you move the regulators, add some extra decoupling close to the output, 10uF will be more than enough.
I purchased one of these cases with the same intention, at the moment, it's mounted on a piece of plywood.
If you move the regulators, add some extra decoupling close to the output, 10uF will be more than enough.
I purchased one of these cases with the same intention, at the moment, it's mounted on a piece of plywood.
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You could increase heatsink size if you want, but remember that unless you are listening at literally hearing-damage levels you will be using only a couple mW on even the loudest passages. The Whammy can happily swing a lot voltage into 37ohms, so with 17V rails (normal "LED reference") you will get deafening SPL.
I'm running 80mA output bias and 22v transformer, with led configuration. Regulators are clearly the warmest of the lot, mostly because of the 22v trafo.
The regulators are clearly the warmest of the bunch. I used the 80mm heatsinks instead of the 50mm stock ones in an hifi 2000 2U case, which runs fine for over a year.
I did some measurements with audio precision. With the lowest thd op amps I ve tried, highest harmonics pops at around -110dB at full output voltage. (Since you seem to be interested in numbers)
I'm so happy with my whammy right now, the jds Atom headphone amp (100dollards) stays in a drawer after a blind test comparison ( kind of expected, but its measurements are somehow better), and I have no itch to try something else, for a change
The regulators are clearly the warmest of the bunch. I used the 80mm heatsinks instead of the 50mm stock ones in an hifi 2000 2U case, which runs fine for over a year.
I did some measurements with audio precision. With the lowest thd op amps I ve tried, highest harmonics pops at around -110dB at full output voltage. (Since you seem to be interested in numbers)
I'm so happy with my whammy right now, the jds Atom headphone amp (100dollards) stays in a drawer after a blind test comparison ( kind of expected, but its measurements are somehow better), and I have no itch to try something else, for a change
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Being the curious type, I rigged up a 40ohm load for the whammy and measured it.
At 1% distortion (I.E., just starting to clip) it's happily pushing 4.94Vrms into 40ohms, for a real 610mW.
The least efficient headphones in your group are (from what I can find) 87db/mW.
For every doubling of power you gain 3db, so that series would be 87db/1mW, 90/2, 93/4, 96/8, 99/16, 102/32, 105/64, 108/128, 111/256, 114db/512mW, at which time you will be doing permanent hearing damage in a time less than a typical Beatles song, and the amp is still not clipping. You don't listen that loud, nor do you really ever want to.
Yes, it's possible to increase the power. But honestly, why? It's not going to make it sound 'better'... If you want to find happiness with this project, try a bunch of OpAmps and see which one delivers the most smiles.
At 1% distortion (I.E., just starting to clip) it's happily pushing 4.94Vrms into 40ohms, for a real 610mW.
The least efficient headphones in your group are (from what I can find) 87db/mW.
For every doubling of power you gain 3db, so that series would be 87db/1mW, 90/2, 93/4, 96/8, 99/16, 102/32, 105/64, 108/128, 111/256, 114db/512mW, at which time you will be doing permanent hearing damage in a time less than a typical Beatles song, and the amp is still not clipping. You don't listen that loud, nor do you really ever want to.
Yes, it's possible to increase the power. But honestly, why? It's not going to make it sound 'better'... If you want to find happiness with this project, try a bunch of OpAmps and see which one delivers the most smiles.
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Thanks 6L6, I think that your measurements were done with the stock 10ohms output resistor.
Also I fully agree, it's very subjective in the end and it's rare to be able to tailor your system that well without spending few grands in trying different gears.
Here's what I got with my 6.9Ohms output resistor = 83mA bias:
Load (Ω) ; Max Voltage before clipping (Vrms) ; Power (W) :
300Ω - 9.8Vrms - 0.320W
68Ω - 8.75Vrms - 1.126W
43.7Ω - 6.4Vrms - 0.937W
18.5Ω - 3.05Vrms - 0.503W
100mA output Bias is very high, I'd say that you will need the 22V transformer if you want to run the "LED reference" PSU option.
Since I saw very little PSU sag before the regulator while measuring max power, I'd assume that you should be fine running the 15V transfo with naked regulator and 100mA bias.
I actually have some plans to listen again to lower output Bias, since I've noticed the Whammy sounds a bit better when running very cool (top cover removed) - at least with my IRF610PBF /IRF9610PBF output transistors.
Also I fully agree, it's very subjective in the end and it's rare to be able to tailor your system that well without spending few grands in trying different gears.
Here's what I got with my 6.9Ohms output resistor = 83mA bias:
Load (Ω) ; Max Voltage before clipping (Vrms) ; Power (W) :
300Ω - 9.8Vrms - 0.320W
68Ω - 8.75Vrms - 1.126W
43.7Ω - 6.4Vrms - 0.937W
18.5Ω - 3.05Vrms - 0.503W
100mA output Bias is very high, I'd say that you will need the 22V transformer if you want to run the "LED reference" PSU option.
Since I saw very little PSU sag before the regulator while measuring max power, I'd assume that you should be fine running the 15V transfo with naked regulator and 100mA bias.
I actually have some plans to listen again to lower output Bias, since I've noticed the Whammy sounds a bit better when running very cool (top cover removed) - at least with my IRF610PBF /IRF9610PBF output transistors.
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Hello,
I’ve made a small mistake today. I’ve put in the opa2604 the wrong way and left it on for about 30 secs. No smoke but there was a funny smell. Unfortunately there are no parts which look suspicious to me. Have you any idea which patt(s) might have caused the smell?
I’ve turned the Opamp and tried again. It was playing nicely.
I have 15V transformers and the psu with led.
Many thanks, tom
I’ve made a small mistake today. I’ve put in the opa2604 the wrong way and left it on for about 30 secs. No smoke but there was a funny smell. Unfortunately there are no parts which look suspicious to me. Have you any idea which patt(s) might have caused the smell?
I’ve turned the Opamp and tried again. It was playing nicely.
I have 15V transformers and the psu with led.
Many thanks, tom
