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"WHAMMY" Pass DIY headphone amp guide
"WHAMMY" Pass DIY headphone amp guide
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Old 25th March 2020, 12:14 AM   #2211
YouAgain is offline YouAgain  United States
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The chassis really isn't that important in the big picture but it should be floating from your signal grounds at the signal inputs and outputs. That means your RCA inputs are isolated from the chassis with plastic washers or bushings and your headphone jack's common between right and left should not have any connection at the chassis. That means that a bunch of the popular 1/4" tip-ring-sleeve jacks will not work for this. If you have a chassis (I'm still holding out for a good one with mine mounted out in the open on plywood) you should bond the power cord's ground directly to the chassis. Wisdom holds that your reference ground point on the Whammy (or any other kind of audio device you build) should have low impedance at high frequencies (like a 0.01 uF capacitor direct connected) and higher impedance at low frequencies like a CL 60 or similar or a 10 Ohm resistor also direct connected. There are several examples of circuits that also use diodes back to back in parallel with these.
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Old 25th March 2020, 12:52 AM   #2212
sp33ls is offline sp33ls
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YouAgain, do you have a capacitor between your AC ground and input ground atm? I'm also waiting on a chassis but I soldered a cap between these and felt like it's caused more issues than solved. And that might explain why if the cap is only there for RF purposes to prevent ground loop noises to the chassis ground. Do I have that right?
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Old 25th March 2020, 02:05 AM   #2213
YouAgain is offline YouAgain  United States
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Quote:
Originally Posted by sp33ls View Post
YouAgain, do you have a capacitor between your AC ground and input ground atm? I'm also waiting on a chassis but I soldered a cap between these and felt like it's caused more issues than solved. And that might explain why if the cap is only there for RF purposes to prevent ground loop noises to the chassis ground. Do I have that right?
No, my AC feed is devoid of a ground conductor at this point. My input and output connectors are at the ends of cables going to the Whammy. The only important connection to ground is the potentiometer shaft connecting to board ground by a single wire. It is silent like this.

If you don't have a metal chassis there is really no reason to connect the AC ground to the circuit. The whole idea of that is to prevent you from getting a shock if there is some kind of short from AC mains to metal chassis. If there is nothing metal to fault to there is no need to protect yourself.

Of course when we put it into a chassis we will play by those rules and the added complexity of the ground path.
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Old 25th March 2020, 03:19 AM   #2214
sp33ls is offline sp33ls
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Originally Posted by YouAgain View Post
No, my AC feed is devoid of a ground conductor at this point. My input and output connectors are at the ends of cables going to the Whammy. The only important connection to ground is the potentiometer shaft connecting to board ground by a single wire. It is silent like this.
I just gave this a shot and it's now dead quiet, even with the OPA1612.

About that chassis tho...
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Old 25th March 2020, 04:00 PM   #2215
YouAgain is offline YouAgain  United States
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I just gave this a shot and it's now dead quiet, even with the OPA1612.

About that chassis tho...

Great that it worked for you. And my amp wasn't built to look at! Not yet at least.
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Old Yesterday, 01:19 AM   #2216
Gaz2613 is offline Gaz2613  United Kingdom
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Hey guys. I have been getting handy with KiCad just lately and made a few power supply PCB designs based on the one on the Whammy and I also made a PCB of the circuit 6L6 posted which provides a rectifier to drive an LED for power on indicator.

I got some boards made of the single rail positive power supply and the LED rectifier and I am just awaiting the components from Mouser so I can build some for testing.

I made an alteration to the schematic 6L6 posted on the rectifier and made the addition of a 10K trim pot so you can adjust the brightness of the power LED on the fly.

These designs aren't just useful for the Whammy but can be useful for many other future projects.

I also did two types of the dual rail PCB. One with a positive and negative supply which is pictured and the other which is dual positive which is useful for building standalone linear power supply boxes.

Let me know what you guys think.
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Old Yesterday, 01:26 AM   #2217
6L6 is offline 6L6  United States
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"WHAMMY" Pass DIY headphone amp guide
Absolutely fantastic!! Well done!!
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Old Yesterday, 01:43 AM   #2218
Gaz2613 is offline Gaz2613  United Kingdom
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Absolutely fantastic!! Well done!!
Those rectifier boards are tiny! Can easily hide them in heat shrink tubing or mount on the inside of the front panel with some double sided foam pads.
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Old Yesterday, 12:46 PM   #2219
pfarrell is offline pfarrell  United States
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Love it! Yes. Are you planning on a group buy run? Waynes own BA18 Pre would enjoy the PSU.
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Old Yesterday, 12:54 PM   #2220
aradan is offline aradan  Singapore
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Great boards, I am definetely in for the led board
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