"WHAMMY" Pass DIY headphone amp guide

[ahess]

Yeah, my headphones are 250 ohms, so that's 0.000002. You don't think I can hear that???

Point taken.

 

[AllanMarcus]

Well, another WHAMMY has become a WHAMMM. It took most of the day, but I'm happy with the results. It's dead silent even at full volume (oh, wait, it was off...that's better. No, still silent). The biggest change to the music is that the bass is much, much more defined. Before there was often a bass-cloud that bled into everything. Now the bass is tighter, and you get more of a sense of an instrument playing it. I think there is also more dynamics overall, but I need time to listen more.

An externally hosted image should be here but it was not working when we last tested it.

Thanks, Wayne, and everyone here who chipped in with ideas.

Gotta go listen to music...

Congratulations!

What are you comparing it to?

 

[ahess]

I was using the headphone out for the Sony TA-4650 amp, which I think is pretty terrific. But evidently the headphone has different requirements. If I bring down the output gain (am I saying that right?) then I can keep my digital volume at 100, which should bump up the resolution even more.

Woo hoo!!

 

[6L6]

Yes. Altering the volume in digital removes bits, so if you can keep it all the way up your resolution should be full as you surmise.

 

[ahess]

Can you recommend a quality DIY attenuator solution--one that would go after the preamp?

 

[6L6]

Absolutely! An Alps RK27 with a value of between 25K and 100K, before the Whammy would be an ideal solution to make the signal from your digital source/preamp the proper level before the whammy amplifies it to the output level you want for listening.

 

[AllanMarcus]

Can you recommend a quality DIY attenuator solution--one that would go after the preamp?

Maybe this with the rk27
ALPS RK27 RK16 Volume Control Potentiometer Passive Preamp For Power Amplifier | eBay

 

[6L6]

Even better than that, there’s a place on the PCB to attach one...

 

[AllanMarcus]

So that’s what those 6 holes are for!

 

[fireangel]

Hello guys,

Yesterday I finished my whammy. I tried it: there was a constant hum. All the ground connection where done, cap in the input, ground to the case etc.. So I tried to connect the body of the potentiometer to the case ground: no differences. I tried to connect the back screw of the rk27 pot to the ground of r9 (not used) : now there is deadly black background, no noise, no hum, and it sounds perfect. Is is it ok?

Thanks a lot

Tony

 

[ahess]

Even better than that, there’s a place on the PCB to attach one...

Yeah, but that doesn't do what I need. I have:

rPi --> Transporter (digital volume) --> Whammy --> me
or --> amp --> speakers -->

I want the dig. volume at 100%, then set the volume for either Whammy or speakers.

I'm looking at the Nelson Pass B1 buffer/preamp. Is that a meaningful upgrade from a simple pot? Or is there a better option?

 

[silasmellor]

Are you saying you want the pot after the amp? Placing a passive attenuator before the whammy is the same as putting an RK27 on the board (except more wire in the former case).


Fireangel: Yes, congrats )

 

[ahess]

No, I want it after the Transporter and before the Whammy or amp.

 

[silasmellor]

In that case take 6L6's advice and put an RK27 on the board. The end result is the same. The input from the RCAs go directly to the volume pot before the amp.

 

[ahess]

Interesting! I wish I hadn't put my jack in that spot--maybe the pot will line up with the hole I made for the jack.

So then I wire the output of the pot to also go to the RCA jacks in the back that feed the amp? So the signal go in, to the pot, then either to the amp or the Whammy circuit?

That's just crazy enough to work!

 

[silasmellor]

Look at the schematic, this is what the happens if you put the put on the board (though with the 2.2k resistors in between, which may or may not be necessary). You can also connect your rca's to the input on the board and run wires to the Alps pot from their respective through holes on the board.


If you use the alps pot off-board i can recommend an adaptor pcb to make connecting the wires a bit easier. Soldering wires to the those through hole tabs is not a lot of fun.

 

[6L6]

Are you going to listen to headphones and speakers at the same time?

You seem to be wanting to add an extra step somewhere in the middle that’s confusing me since I’m not sure exactly what you are thinking...

 

[ahess]

I can see using just the headphones or just the speakers. It didn't occur to me that the pot in the Whammy could be wired for the Whammy or back to the RCA output that goes to the amp. I think that's the way to go.

FYI, I didn't include the pot because I was just going to use the volume for the Transporter. Then I learned that it's digital volume control that degrades the sound. <sigh>

 

[6L6]

It makes more sense to use a switching headphone jack and wire the output RCAs downstream of the jack.

If the headphones are not connected, then the jack's switches are closed, and the output RCAs have the signal. If headphones are connected, the signal goes to the headphones.

Neutrik NMJ6HC-S 1/4" Stereo Phone Jack Switched

 

[ahess]

Interesting. This way, my amp will get the signal after it's gone through the preamp and the whammy headphone amp circuit. is that better than sending the signal directly to the amp from the preamp and leaving out the whammy circuit? I was imagining sending the signal directly from the pot to the RCA outputs leading to the amp. If that way works, can I just solder wires from the pot to the outputs, or should I have a switch that sends the signal to either the headphone amp or the regular amp?