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"WHAMMY" Pass DIY headphone amp guide
"WHAMMY" Pass DIY headphone amp guide
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Old 13th June 2018, 08:55 AM   #311
schultzsch is online now schultzsch  Europe
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Hello guys,

I am following the thread for a while but didn’t noticed anyone asking the following question.
I use a sony vfet part 2 frontend(balanced) as a preamp that I like very much.
I would like to direct couple the output stage of WHAMMY to the output of the preamp without including the buffer in the global feedback loop of the preamp. Soundwise is it better to include the buffer in the global feedback loop?
I will use coupling caps after the buffer if needed.
The entire setup won’t be used to drive headphones and only in front of my aleph j monoblocks.

For setting the dc offset after the buffer I was thinking to add a pot like in the m2 amp

Any ideas if something like this could work?
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Old 13th June 2018, 03:38 PM   #312
seanwu is offline seanwu  Taiwan
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I have done my WHAMMY with LM833 opamp, FQP FETs, 60ma bias, 20KA pots.
The sound quality is awesome. Thanks Wayne.
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Old 13th June 2018, 06:51 PM   #313
wayne is offline wayne  United States
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"WHAMMY" Pass DIY headphone amp guide
Nice routing on the wires and the chassis. White board solder mask?
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Old 13th June 2018, 08:19 PM   #314
kpsthakur is offline kpsthakur  India
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I may have messed something up, while changing the voltage regulators... the 7918 side gives -19.3V and the LED is lit, the +ve side has got some issues...the output is -7.65V post regulation...this is not right...I have changed the regulators twice (7818's), but the issue remains the same...it could be the diodes or if I have fried the LED or something else...not made any other changes to the circuit...any suggestions
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Old 13th June 2018, 09:00 PM   #315
chip_mk is offline chip_mk  Macedonia
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What is the voltage on other pins of 7818?
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Old 13th June 2018, 10:23 PM   #316
kpsthakur is offline kpsthakur  India
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Pin 1 +36.6V
Pin 2 -6.75V
Pin3 -7.65V
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Old 13th June 2018, 11:01 PM   #317
wayne is offline wayne  United States
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"WHAMMY" Pass DIY headphone amp guide
- Voltage on pin three is a big clue. Something in the circuit is putting a - voltage on the output of the regulator.
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Old 14th June 2018, 02:58 AM   #318
seanwu is offline seanwu  Taiwan
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Quote:
Originally Posted by wayne View Post
Nice routing on the wires and the chassis. White board solder mask?
Yes
I ordered 10 boards for around USD$100 here in Taiwan.
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Old 14th June 2018, 03:56 AM   #319
seanwu is offline seanwu  Taiwan
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Quote:
Originally Posted by kpsthakur View Post
Click the image to open in full size.
Your amp looks delicious.

Last edited by seanwu; 14th June 2018 at 03:59 AM.
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Old 14th June 2018, 06:55 AM   #320
kpsthakur is offline kpsthakur  India
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Default Resolved

Quote:
Originally Posted by wayne View Post
- Voltage on pin three is a big clue. Something in the circuit is putting a - voltage on the output of the regulator.
Busted LED...replaced (getting soldering off took almost 2 hours), all is good now....board back in the box now & singing.

Thanks Wayne, great solid amp...no reduction in performance between moving from low ohm to very high ohm headphones...in fact it becomes way better...the extra volts on the PSU provides enough room I presume.

Although I am using shielded cables and twisted to ensure no crosstalk or interference, I feel a very very faint hiss when nothing's playing. Also a power up/power down thump has arrived...none of this bothers me much but would definitely like to troubleshoot. I am grounding the input jacks via 0.01uF cap
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