Amplifier Distortion, DC-Offset, and You!

A very warmed-up 1989 Pioneer VSX-4500S receiver.
Set my Radio Shack multi-tester to 2V -- the lowest DCV setting I have.
L: .067
R: .072
I'm no math major, but would I move the decimal point by three places to get 67mV and 72mV, respectively? Or move it two places to get 6.7 and 7.2? Thanks for any guidance.
 
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Thanks, redk9258. So, just to confirm: I take my readings with my DMM set to my lowest available DCV setting of 2V. Then I take any readings I get and move the decimal point three places to the right to get my "mV" settings. So, in my post (two posts earlier) my Pioneer's left channel read .067, which means my DC offset for that channel is actually 67mV -- not great. (.067 DC volts = 67 millivolts.) And the right channel measured .072 DC volts, or 72mV, not great again. With these settings, "Something is amiss" according to EchoWars who started this iconic thread.

BTW, some posters simply list/leave their actual readings as DC volts (which would be 0.67 and .072 in my case).

Sorry for the silly, basic math questions. But EchoWars recommended that we set our meters "...to a low scale (300mV scale is common)." My DMM doesn't have a scale that low, so I wanted to make sure my math was in line. Thanks, again.
 
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FWIW All my 8 Crown DC 300/D150 & Phase Linear 400/700 amps that I own, have much less than 3 mV DC offset after full warm up/stabilize per channel.

Sometimes 10 turn replacement/upgrade pots can help dialing in the lowest offset/bias, as original 270 degree rotation OEM controls are usually too course and can be too touchy to dial in unless your a safe cracker with Zen breathing discipline..

But DC coupled amps must be functioning proper first and stabilized..
Did same with the bias pots as well..

Speakers tend to sound best when not "DC biased" IMHO/E !! No grit.

Often the specs indicate +/- 10mV offset, I say much lower is better..

But that`s just me and my OCD..

Enjoy the music as it best fits your ears and tastes.

Kind regards, OKB
 
Quad 405-2, in fact a Quad 405 bought new by me in 1976 and upgraded using Quad conversion kit around 1987.

Right 0.7 mV

Left 0.6 mV

I'm quite impressed.
 
B&K ST-140 #1 = Left .009 Right .047
B&K ST-140 #2 = Left .010 Right .040
Both of these have been refurbished within the last year. Interesting that they're so similar L to R.

APT Corporation Power Amp One #1 = Left .009 Right .020
APT Corporation Power Amp One #2 = Left .002 Right .007
Neither of these have been refurbished, and they sound almost as nice as the ST-140 (although the ST-140 has the better bottom end).
 
Onkyo TX-26 receiver. Left is .001. Right is .007.
Sony STR-D665 AV receiver. Left is .000. Right is .002.
Onkyo A-8170 amp. Left is mostly .002, but once varied from -.005 to +.006. Right is .002.

Question: Am I (finally) getting lucky with finding older/vintage equipment that has respectable DC offset measurements? Or am I using the wrong DMM/process? In every case above: Volume is minimum. Bass/treble/balance are all centered. CD input selected -- but no CD player or other equipment connected. No speakers connected. Vintage Radio Shack DMM set to 2VDC (my lowest available DC setting). Red positive; black negative. When I disconnect the DMM its reading goes to zero.

I'm sort of shocked by the good readings on all three. Lucky? Should I buy a lottery ticket? Any thoughts would be welcomed and appreciated. TIA.
 
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Harman Kardon 930
Right = 113mv
Left = 57mv

The readings are high, and the right speaker fuse just blew out. What should I do next? A complete recap first? Or is there something else I should try?
Thanks a lot!
 
I've been struggling with this for way to long. My Anthem MRX300 powers up with Front Left DC offset of about 100mV which causes it to power down into protection mode a second or so later. Gut told me it should be a problem with the driver, so I proceeded to trace the schematic. The latter takes many hours...So far I've checked every transistor (OK) and replaced all electrolytics. The only thing I've found that's remotely suspicious is the differential pair gains are not precisely the same (i.e. Q4001/Gain 431 versus Q4002/Gain 505). My initial thoughts were that the swamping resistors would have negated small differences in gain. Regardless, I have swapped Q4001 with Q4024 (Gain 499) but have not powered it up yet. It sure would be nice if I had the Power Amp schematic...Any ideas?
 
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Geez. .

Sansui G-6000

R: - 250mv
L: - 90mv

Have to do something about this lol, no wonder it goes into protection mode for nothing. ..
 
It don't help with capacitor distortion, maybe in a instrument amplifier even then a lot of it's not that good, thanks to when mettalized stuff came around and china making like some of the awfulest sounding ones.
 
Harman kardon hk 460i
Left channel- 65mv
Right -110mv
No wonder why it sounded so muddy! Probably should’ve checked before using it. Thankfully, this amp has an offset adjustment, so it shouldn’t be too bad.
 
Lol, forgot about the decimal point and that I had turned down the treble. :confused:
Harman kardon hk 460i after idling for an hour
Left- 19.2
Right- 17.6
 
Rotel RB-980BX power amp. Manufactured in 1994. Left channel measures 13.7mV, right channel measures 13.6mV.
 
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