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Old 30th September 2013, 07:16 PM   #3431
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Quote:
Originally Posted by Vigo View Post
...The gain button, what does it do?
The gain switch gives 2 options-

High-gain for high impedance/low sensitivity cans/ weak input sources like mp3 player/ipod e.t.c.

Low gain(recommended) for low impedance/high sensitivity cans/ strong input sources like ODAC/CD player line out

further reading NwAvGuy: O2 Details
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Old 1st October 2013, 02:00 AM   #3432
agdr is offline agdr  United States
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Quote:
Originally Posted by sonichedgehog36 View Post
I am looking into alternatives to Q1 and Q2 since I may or may not be able to get the samples from Fairchild.
I wouldn't have any suggestions there, but those mosfets are around $0.80 at Mouser. Hard to beat that.
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Old 1st October 2013, 03:35 AM   #3433
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I wouldn't have any suggestions there, but those mosfets are around $0.80 at Mouser. Hard to beat that.
OK. Thank you! The ever so slightly pricey part about the shipping, not the product itself, is what bothers me.
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Old 1st October 2013, 11:15 AM   #3434
Vigo is offline Vigo  Sweden
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Quote:
Quote:
Originally Posted by Vigo View Post
...The gain button, what does it do?
The gain switch gives 2 options-

High-gain for high impedance/low sensitivity cans/ weak input sources like mp3 player/ipod e.t.c.

Low gain(recommended) for low impedance/high sensitivity cans/ strong input sources like ODAC/CD player line out

further reading NwAvGuy: O2 Details
Thank you availlyrics, good explanation
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Old 1st October 2013, 12:51 PM   #3435
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Quote:
Originally Posted by sonichedgehog36 View Post
OK. Thank you! The ever so slightly pricey part about the shipping, not the product itself, is what bothers me.
Try living in europe, anything you buy costs at least 20 to ship, or if you spend over 60 you get free shipping... so before you know it you have bought 40 worth of crap you didnt need just to get that one part you did. Damn you mouser
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Old 3rd October 2013, 03:44 AM   #3436
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I am a first class cheapskate--or would that be third class, saddled camel through the Arabian desert, canoe braving the ocean waters, all in the name of that last cent, no better than Scoorge McDuck, cheapskate?

I am going to order from Digikey using the free shipping via check or money order trick. Since it's been a while, it took me some time to remember that Digikey had that special clause in place (see #6 http://dkc1.digikey.com/us/en/mkt/Terms.html ). Just pay about half a buck for postage, enclose your check or money order and--presto!--free shipping.

UPDATE: After further explanation to the Fairchild representative, I now have the parts on delivery, five each of the stock MOSFETs. No Digikey for now. Luckily, I did not strike the ink to the check yet!

Last edited by sonichedgehog36; 3rd October 2013 at 04:01 AM.
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Old 8th October 2013, 06:18 AM   #3437
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I got the parts and put them in with plenty of TLC, as well as proper grounding and heat protection. Something is clearly still wrong--I am getting 17.5 volts DC across the outer battery terminals. Could the other TO-220 chips be the culprit?
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Old 8th October 2013, 01:25 PM   #3438
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Maybe thats right, 9v x2 = 18v. Have you tested these points,

Click the image to open in full size.

Click the image to open in full size.

Last edited by mcandmar; 8th October 2013 at 01:30 PM.
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Old 8th October 2013, 01:29 PM   #3439
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Take voltage measurements along the power supply path - AC input first, then ground referenced DC across the filter caps, regulator inputs, each side of D1 & D5. This can be done with the unit off and verifies the power supply operation.
If that checks out OK, the unit can be switched on and the DC distribution to the rest of the circuit can be checked.
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Old 8th October 2013, 09:21 PM   #3440
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Originally Posted by mcandmar View Post
Maybe thats right, 9v x2 = 18v. Have you tested these points,

Click the image to open in full size.

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Thank you everyone so far! Using this as a blueprint, and measuring as specified, ground (BT1-) to each point, but without U2 installed and the device "off":

BT1+: 17.32 V
BT2-: -0.01V

D3 (left/right): 18.06 V/ 0 V
D4 (bottom): -18.13 V
U4 (P4/P8): .67/.16
U2 (all pins): 0.01-0.02 V

D5 (top/bottom): Starts around 3.5 V, lowering/
D1 (top/bottom): 17.34 V/17.34 V

For reference, I am using all the recommended parts as listed in the BOM. Previous to voltage testing, all resistor values had been tested and verified.

Last edited by sonichedgehog36; 8th October 2013 at 09:30 PM.
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