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"WHAMMY" Pass DIY headphone amp guide
"WHAMMY" Pass DIY headphone amp guide
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Old 8th August 2019, 05:56 PM   #1531
slowpogo is offline slowpogo  United States
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Quote:
Originally Posted by avdesignguru View Post
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
Thanks, I've been meaning to get one of those testers anyway since I build a lot of guitar pedals, which often work best with transistors of certain hFe and leakage, etc.

The U2 regulator is only 56 cents, so I'll order one just in case along with new LEDs. Just so I'm clear, if U2 is outputting the full raw supply voltage, does that endanger any other components, or no?
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Old 8th August 2019, 06:04 PM   #1532
avdesignguru is offline avdesignguru  United States
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Quote:
Originally Posted by Mark Johnson View Post
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.

_
Great suggestion, Mark. I've got a few builds I may go back and change to this scheme. I too am bothered by the long bleed down.

Also If you look at the photo in my post 1525 you will see the diode glued into a small metal plate (I sometimes use hardwood). This is double side taped over a 1/16" hole inside the front panel. This allows me to use a 5mm diode and create a 1.5mm "stealth" indicator on the front panel.
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Old 8th August 2019, 06:17 PM   #1533
avdesignguru is offline avdesignguru  United States
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Quote:
Originally Posted by slowpogo View Post
Thanks, I've been meaning to get one of those testers anyway since I build a lot of guitar pedals, which often work best with transistors of certain hFe and leakage, etc.

The U2 regulator is only 56 cents, so I'll order one just in case along with new LEDs. Just so I'm clear, if U2 is outputting the full raw supply voltage, does that endanger any other components, or no?
Theoretically, if you have exceeded rated voltages, yes. In practicality, if you did not apply a headphone load to the circuit and drive a signal through it, probably no damage was done. Maybe the opamp if it was installed. The optocouplers and mosfets are pretty tough.
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Old 8th August 2019, 06:32 PM   #1534
slowpogo is offline slowpogo  United States
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Quote:
Originally Posted by avdesignguru View Post
Theoretically, if you have exceeded rated voltages, yes. In practicality, if you did not apply a headphone load to the circuit and drive a signal through it, probably no damage was done. Maybe the opamp if it was installed. The optocouplers and mosfets are pretty tough.
There was no source connected but the headphones may have been plugged in, I don't recall honestly. The opamp was installed but it wasn't my favorite and I've got others. Hopefully the damage is limited to the LED or U2.
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Old 8th August 2019, 09:49 PM   #1535
wayne is offline wayne  United States
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"WHAMMY" Pass DIY headphone amp guide
Probably just the regulator and led were damaged. Opamp may or may not have survived but hopefully you have a socket.
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Old 10th August 2019, 04:49 PM   #1536
slowpogo is offline slowpogo  United States
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Sometimes you gotta overnight parts from Mouser, and this was one such occasion. I replaced the regulator and LED in my Whammy, and voila, everything's working including the opamp. I also utilized Mark Johnson's front panel LED suggestion directly from the secondary (using a 1N4148) and it works like a charm. All is good, thanks Wayne for the amp, and everyone for their prompt assistance!
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Old 10th August 2019, 05:19 PM   #1537
avdesignguru is offline avdesignguru  United States
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Just received and installed an OPA2134. Had been listening to an LM833. Definitely my new favorite. Hard to imagine it getting any better. Thank you, Wayne, for this excellent HPA design.
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Old 11th August 2019, 03:30 AM   #1538
wayne is offline wayne  United States
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"WHAMMY" Pass DIY headphone amp guide
Its good to see successful builds on this project. Thanks to all the people helping each other especially 6L6 for encouraging these things and documenting them.

And thanks for the pink jazz album from Poland I lost your contact info.
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Old 13th August 2019, 01:22 AM   #1539
Gaz2613 is offline Gaz2613  United Kingdom
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Okay guys I have spent quite a bit of time and money on obtaining OP Amps for testing and here are by findings:

Dual Op Amps (8P-DIP):

AD823ANZ:
Operating Voltage: 36v MAX
Slew Rate: 22v/s
DC Offset: L 0.5mV / R -0.2mV
FET: Yes
Notes: Vocals very good but some mids and treble sounds a little raspy.

LM833-N:
Operating Voltage: 36v MAX
Slew Rate: 7v/s
DC Offset: L -0.1mV / R 3.4mV
FET: No
Notes: Very good all round OP Amp with clear vocals, good soundstage and natural bass.

LM833P:
Operating Voltage: 36v MAX
Slew Rate: 7v/s
DC Offset: L 22.9mV / R 26.2mV
FET: No
Notes: Very good OP Amp with clear vocals and good soundstage. Improved version of the LM833-N although DC offset is considerably higher.

RC4580 (Texas Instruments):
Operating Voltage: 18v MAX
Slew Rate: 5v/s
DC Offset: L 14.2mV / R 14.1mV
FET: No
Notes: Good general OP Amp with tiny noticable distortion amounts with certain types of music, sounds best with dance music.

OPA2134PA SoundPlus:
Operating Voltage: 18v MAX
Slew Rate: 20v/s
DC Offset: L 0.6mV / R 0.4mV
FET: Yes
Notes: Very clear with good soundstage and vocals very pronounced. Very nice OP Amp.

OPA2228PA
Operating Voltage: 18v MAX
Slew Rate: 2.3v/s
DC Offset: L -0.2mV / R -0.1mV
FET: No
Notes: Very good, clear up front vocals, very good mid and treble, wide soundstage, overall I like this OP Amp.

OPA2107AP
Operating Voltage: 18v MAX
Slew Rate: 18v/s
DC Offset: L -0.2mV / R -0.3mV
FET: Yes
Notes: Very clear and concise right through all the ranges. Vocals very prominent and wide soundstage. I really like this one.

LME49720NA
Operating Voltage: 17v MAX
Slew Rate: 20v/s
DC Offset: L 0.8mV R 1.6mV
FET: No
Notes: Nice all round OP Amp with good soundstage. Very clear but mellow sounding.

AD746JNZ
Operating Voltage: 18v MAX
Slew Rate: 75v/s
DC Offset: L -0.3mV / R -0.2mV
FET: Yes
Notes: Very nice sounding with wide soundstage, clear mids and treble with punchy bass. I really like this one.

LM4562NA:
Operating Voltage: 17v MAX
Slew Rate: 20mv/s
DC Offset: L -0.4mV / R -1.1mV
FET: No
Notes: Very good all round OP Amp with clear vocals and good soundstage.

NJM4556AD:
Operating Voltage: 18v MAX
Slew Rate: 3v/s
DC Offset: L 5.8mV / R 5.4mV
FET: No
Notes: Nice OP Amp with clear vocals, wide soundstage and balanced bass. Mids and trebles seem a little softer compared with other OP Amps.

Burson V6 Vivid Dual:
Operating Voltage: 33v MAX
Slew Rate: 45v/s
DC Offset: L -2.0mV / R -1.5mV
FET: Yes (Fully Discrete)
Notes: Premium OP Amp obviously by far the best I've tried so far. Deep and wide reaching soundstage and up front clear vocals. My number one choice.

Next time I will be testing the following SOIC OP Amps on 8P-DIP adapters:

OPA1622, OPA1662, OPA2210, OPA2189 and OPA1692

Hope some of you find this helpful.
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Old 13th August 2019, 10:39 AM   #1540
Gaz2613 is offline Gaz2613  United Kingdom
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Forgot to mention I tested these OP Amps with HiFiMan HE400i headphones and a Topping D50 DAC. I used FLAC audio 96Khz 24 bit. Evanescence Synthesis album.
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