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"WHAMMY" Pass DIY headphone amp guide
"WHAMMY" Pass DIY headphone amp guide
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Old 4th August 2019, 05:22 PM   #1521
KenI is offline KenI  Canada
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"WHAMMY" Pass DIY headphone amp guide
Dan/Mark


Thank you for your replies.I have the datasheets open for all three and it's just a bewildering amount of information...


It will be the OPA1612AIDR I add to my cart.


Thanks again.


Ken
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Old 4th August 2019, 09:25 PM   #1522
adam1016 is offline adam1016  United States
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Interested in possibly using my whammy as a preamp, was wondering a couple of things:

Do I need to switch the ground as well as the signal lines? I assume so, to keep noise from downstream components coming back into the signal path. What switch should I use for this? Are there any other considerations I need to take into account before using this project as a preamp?
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Old 4th August 2019, 10:09 PM   #1523
6L6 is offline 6L6  United States
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"WHAMMY" Pass DIY headphone amp guide
No.
Nope, but it doesn't hurt.
One with enough contacts for the number of sources you have, in stereo.
It works beautifully as a preamp. You may want to have a switching headphone jack so the RCAs are muted when the headphone jack is in use.
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Old 8th August 2019, 03:32 AM   #1524
slowpogo is offline slowpogo  United States
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Hello...I just finished building my Whammy and it was working and sounding great, and was super fun to build. The last step I had was to try and add a front panel LED.

However while trying to test my LED, I accidentally shorted the anode of D4 to the cathode of C28. The connection was very brief but there was a whiff of smoke from what looked like U2 7915 (or at least that area). The D6 LED sputtered and turned off. My voltage test between R13 and R14 had been -16.9, now it's -32.

*sigh* what have I done? Do I just need to replace U2? rebuild the PSU? Please help! I think the worst feeling in DIY is to have a finished, beautiful project, then f*** it up for no good reason.

oh, and while it's less important at the moment, can someone give some specific instructions for adding a front panel LED? with the actual pads to use, etc? I've searched the thread but all I can find is a circuit diagram and "run it off the secondary." I've built a ton of stuff but my actual electronics knowledge is (obviously) not up to the task.
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Old 8th August 2019, 05:02 AM   #1525
avdesignguru is offline avdesignguru  United States
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Quote:
Originally Posted by slowpogo View Post
oh, and while it's less important at the moment, can someone give some specific instructions for adding a front panel LED? with the actual pads to use, etc? I've searched the thread but all I can find is a circuit diagram and "run it off the secondary." I've built a ton of stuff but my actual electronics knowledge is (obviously) not up to the task.
Note: the following is based on using LED referencing of the regulators, where you do not stuff or solder resistors R9 and R10 on the PCB.

Solder one end of your LED dropping resistor into the +15 end of the unused position for component R10 (the end towards the front of the PCB). Air wire the free end of the resistor to the anode of the "Power On" LED.

Connect the cathode of the "Power On" LED to the unused grounded side of the component position for component R9 (again, the end towards the front of the PCB).
Attached Images
File Type: jpg LED cropped.jpg (262.3 KB, 308 views)
File Type: jpg LED Schematic.jpg (595.2 KB, 267 views)
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Old 8th August 2019, 05:37 AM   #1526
AudioSan is offline AudioSan  Norway
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I did it the easy way. I connected the LED positive to det leg of the CRC resistor on the positive rail, with a 10K resistor in series with the LED. And the LED negative to a unused GND spot.

Last edited by AudioSan; 8th August 2019 at 05:39 AM.
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Old 8th August 2019, 03:26 PM   #1527
slowpogo is offline slowpogo  United States
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Quote:
Originally Posted by avdesignguru View Post
Note: the following is based on using LED referencing of the regulators, where you do not stuff or solder resistors R9 and R10 on the PCB.

Solder one end of your LED dropping resistor into the +15 end of the unused position for component R10 (the end towards the front of the PCB). Air wire the free end of the resistor to the anode of the "Power On" LED.

Connect the cathode of the "Power On" LED to the unused grounded side of the component position for component R9 (again, the end towards the front of the PCB).
Thank you, exactly what I was looking for.
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Old 8th August 2019, 03:31 PM   #1528
slowpogo is offline slowpogo  United States
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Quote:
Originally Posted by slowpogo View Post
Hello...I just finished building my Whammy and it was working and sounding great, and was super fun to build. The last step I had was to try and add a front panel LED.

However while trying to test my LED, I accidentally shorted the anode of D4 to the cathode of C28. The connection was very brief but there was a whiff of smoke from what looked like U2 7915 (or at least that area). The D6 LED sputtered and turned off. My voltage test between R13 and R14 had been -16.9, now it's -32.

*sigh* what have I done? Do I just need to replace U2? rebuild the PSU? Please help! I think the worst feeling in DIY is to have a finished, beautiful project, then f*** it up for no good reason.
Trying to puzzle this out a little further, based on my limited knowledge. I apparently fried the regulator of the negative rail. Does that mean components downstream were potentially exposed to more power than they are rated for, potentially frying them as well? Or does the LED act as a sacrificial diode, so when it got overloaded and died, power did not pass beyond the PSU?

I'm planning an order from Mouser for another regulator and hoping to get that out ASAP...I'm hoping I didn't fry any MOSFETs or anything else too..

Last edited by slowpogo; 8th August 2019 at 03:33 PM.
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Old 8th August 2019, 04:31 PM   #1529
avdesignguru is offline avdesignguru  United States
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Quote:
Originally Posted by slowpogo View Post
Trying to puzzle this out a little further, based on my limited knowledge. I apparently fried the regulator of the negative rail. Does that mean components downstream were potentially exposed to more power than they are rated for, potentially frying them as well? Or does the LED act as a sacrificial diode, so when it got overloaded and died, power did not pass beyond the PSU?

I'm planning an order from Mouser for another regulator and hoping to get that out ASAP...I'm hoping I didn't fry any MOSFETs or anything else too..
If D6 is dead (open circuit), or installed backwards, there will be no regulation reference and the output of U2 will go to the full raw supply voltage. It's pretty hard to kill U2. My guess is D6 is fried.

BTW, a good investment for testing transistors and diodes is a mega 328 tester. It will also show a schematic of a functioning device with marked pinouts on screen. It's inexpensive, and available with or without a plastic enclosure.

Aideepen Mega328 LCR-T4 Transistor Tester Diode Triode Capacitance LCR ESR Meter Module MOS PNP/NPN M328 (Battery Buckle): Amazon.com: Industrial & Scientific

LCR-T4 Mega328 Transistor Tester Diode Triode Capacitance ESR Meter W/ Shell US 6630597742690 | eBay
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Builds: F6, B1, B1-Korg, LXmini ACN, MoFo, T2 HPA, NuTube Buffer, NuHybrid HPA, NuClassD Amp, Aikido Preamp, Whammy HPA; M2x Amp

Last edited by avdesignguru; 8th August 2019 at 04:50 PM.
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Old 8th August 2019, 04:47 PM   #1530
Mark Johnson is offline Mark Johnson  United States
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"WHAMMY" Pass DIY headphone amp guide
In one of my recent builds I decided I wanted a power indicator LED that stopped glowing the very instant I turned off the power switch. The DC supply rails don't bleed down to zero for many seconds, so I couldn't connect my "pilot light" there; it would remain ON for a long time after the power was switched OFF.

I connected it to the transformer secondary (AC voltage) because that DOES instantly drop to zero when the mains power is switched off. A series diode was installed to prevent the LED from entering reverse breakdown. The diode means I'm applying half wave rectified pulses to the LED, and relying upon persistence of vision to give the perception that this 60 Hertz flickering LED, appears to emit a continuous unchanging beam of light.

The rectifier diode is a 1N3595 because I've got a drawer full of them; they are small and have very low reverse leakage current, so the LED is very well protected. Probably a 1N4148 would have worked well enough. The LED is a wide viewing angle (112 deg) blue diode whose brightness rating is pretty high: 5000 mcd. So I'm running it at about 1 milliamp of RMS current.

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