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Old 26th December 2017, 11:42 AM   #1411
BYRTT is offline BYRTT  Denmark
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Right its looks be pure DC supply portion part and PCB also include reasonable high value capacitive buffer, but think the way power pull will be from DC supply is AC switching dictated as input audio signal demands power from DC supply.

Then again complete unit is so small so probably no problems at all for this build making it a good stiff low impedance supply

Last edited by BYRTT; 26th December 2017 at 11:45 AM.
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Old 27th December 2017, 07:40 PM   #1412
diyricky is offline diyricky  United Kingdom
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Hi,

Just trying to find my way around the design and this large thread.

On the opening post there is this line -

Quote:
Edit (Dec 22, 2017) - here is the latest BOM that I use for low impedance cans with a smooth sound signature.
If I click on it, it just opened a blank page ?
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Old 27th December 2017, 08:28 PM   #1413
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by diyricky View Post
Hi,

Just trying to find my way around the design and this large thread.

On the opening post there is this line -



If I click on it, it just opened a blank page ?
Sorry about that bad link.

Should be this:

xrk971 Pocket Class A Headamp GB

Let me fix index. Thanks.
X
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Old 28th December 2017, 07:46 PM   #1414
freebee is online now freebee  Netherlands
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Probably not a good idea, but would it be possible to substitute R5 and RL 270 Ohm with either 200 or 330 Ohm? For some reason I'd like to use the following 'audio' resistors :

Mouser No: 754-RS2012P-331-DT53
Mfr. No: RS2012P-331-D-T5-3
Mfr.: Susumu

Otherwise I'll just use 270 Ohm from a different series.
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Old 28th December 2017, 10:19 PM   #1415
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by freebee View Post
Probably not a good idea, but would it be possible to substitute R5 and RL 270 Ohm with either 200 or 330 Ohm? For some reason I'd like to use the following 'audio' resistors :

Mouser No: 754-RS2012P-331-DT53
Mfr. No: RS2012P-331-D-T5-3
Mfr.: Susumu

Otherwise I'll just use 270 Ohm from a different series.
Make R5=200ohm and RL=330ohm and it should work fine. Nice performance actually. This is pushing 1.2vpp into 330ohms with 58mA bias current from 16.4v supply.

Quote:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 9.126e-01 1.000e+00 -179.97° 0.00°
2 2.000e+03 2.724e-04 2.985e-04 90.14° 270.10°
3 3.000e+03 5.728e-05 6.276e-05 -179.89° 0.08°
4 4.000e+03 1.017e-06 1.114e-06 -102.06° 77.90°
5 5.000e+03 5.473e-08 5.997e-08 179.87° 359.84°
6 6.000e+03 1.409e-07 1.544e-07 179.51° 359.48°
7 7.000e+03 1.214e-07 1.330e-07 179.98° 359.95°
8 8.000e+03 1.062e-07 1.164e-07 179.98° 359.95°
9 9.000e+03 9.469e-08 1.038e-07 179.99° 359.95°
Total Harmonic Distortion: 0.030507%(0.030480%)
Click the image to open in full size.
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File Type: jpg Pocket-Class-A-R5-200ohms-RL-330ohms.jpg (29.6 KB, 223 views)
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Last edited by xrk971; 28th December 2017 at 10:21 PM.
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Old 29th December 2017, 01:10 PM   #1416
freebee is online now freebee  Netherlands
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Great! Thanks a million! Almost ready to order the parts. Will let you know how it turned out. Any reason for using Nichicon KA 2200uf 16v instead of Silmic (apart from size)?
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Old 29th December 2017, 02:08 PM   #1417
xrk971 is offline xrk971  United States
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According to StellearElephant, who did listening tests (all subjective), if I can paraphrase him, KA sounds more detailed and has good bass and balanced . Silmic II is smoother and less forward and softer details. It’s all a matter of taste. He also found that adding film bypass did not change much.
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Old 30th December 2017, 07:05 PM   #1418
freebee is online now freebee  Netherlands
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I've been trying to find a 6mm d-shaft max. 12mm knob, however they seem to be difficult to come by. Any idea as where to get one?

Also is it ok to use 10K or 15K for RLED (instead of 12K)?
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Old 30th December 2017, 08:03 PM   #1419
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by freebee View Post
I've been trying to find a 6mm d-shaft max. 12mm knob, however they seem to be difficult to come by. Any idea as where to get one?

Also is it ok to use 10K or 15K for RLED (instead of 12K)?
Work fine aluminum alloy knob 15MM * 16.5MM 15MM * 17MM silver half shaft hole D hole potentiometer-in Switch Caps from Home Improvement on Aliexpress.com | Alibaba Group
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Old 30th December 2017, 08:10 PM   #1420
diyricky is offline diyricky  United Kingdom
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Quote:
Originally Posted by freebee View Post

Also is it ok to use 10K or 15K for RLED (instead of 12K)?
Always go for the larger 15k resistance which means the led will be dimmer.

Generally you find such indicator leds annoying if they are too bright

Cannot be more precise since we do not know the exact parameters of the led you purchase, they all vary slightly.
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