Are you confusing bias with DC offset? Be careful if you aren't 100% sure of what you are adjusting. You WILL blow up the output transistors along with other stuff.
Amplifier Distortion, DC-Offset, and You!
- Thread starter EchoWars
- Start date
ernestas0001
New Member
Yes, I think I might be mixing up the things ! Anyways, I haven`t played with them, simply adjusted to correct values according to the manual as they seemed to drift away.
Now, how could I decrease milivolt values on speaker connectors on HK 3490 ?
Now, how could I decrease milivolt values on speaker connectors on HK 3490 ?
Sherwood S-7200. Just purchased for $20. Left channel::0.0mv. Right channel: 42mv. When listening (headphones, haven't hooked it to speakers), right channel is "static-y" and distorted.
Also, inadvertently touched two control knobs at the same time and got a lovely hum in the right channel. Be gentle, as I am a newb
, but I presume this indicates a ground issue? For the hum, at least?
Also, inadvertently touched two control knobs at the same time and got a lovely hum in the right channel. Be gentle, as I am a newb
, but I presume this indicates a ground issue? For the hum, at least?
Beau Geste
Italia
First of all get a manual service .You can find it here : https://elektrotanya.com/sherwood_s-7200_sch.pdf/download.html :After this give look to find the trimmer to set up the DC offset .The left channel seems OK you have to worl to right channel only . Here you can find a lot of advices to proceed...On AK we have the MASTER of Offset...
Measure the DC offset at the speaker terminals with everything disconnected and volume at maximum (select a line input if using an integrated amp).
Volume at minimum, not maximum .
RobinTW
Well-Known Member
I already found answers http://audiokarma.org/forums/index.php?threads/amplifier-distortion-dc-offset-and-you.5634/page-2
EchoWars' excellent explanation!
desertrat748
Super Member
Purchased an refurbished Sansui 661 from local shop. Decent sound but decided to check the offset after warming it up.
Before: R: 22~28 mV
L: 55~58.5 mV
After adj: R: 2.1 ~ 4.8 mV
L: 0.8 ~ 2.6 mV
I still love the sound of this old SS receiver and my mind says it sounds even better now. EDIT: I listened to the Sansui for hours yesterday. Didn't believe it could sound so much better! Unreal now. THANK YOU Echowars!
Checked an old Kenwood KR-5060 that powers up the kitchen turntable over some vintage Sansui speakers (don't laugh, it's just for making coffee and toast in the mornings). This thing sounds really clean and clear, maybe it's because of decent DC offset?
R: 2.2 mV to 4.5mV
L: -1.9 mV to 2.6 mV
Fisher CA-880 amp (has a Darlington pair and can't find where to adjust it). Still sounds really decent though. Clean.
R: 48.2 mV
L: 52.1 mV
Only with the Sansui does the offset mV swing around and fluctuates a lot even when it is really warmed up but it looks like that's okay. This thread is huge and I've only read up to the first 160 pages or so although I jumped to the end to see what's been happening. Thanks Echo for starting and sharing your knowledge!
Before: R: 22~28 mV
L: 55~58.5 mV
After adj: R: 2.1 ~ 4.8 mV
L: 0.8 ~ 2.6 mV
I still love the sound of this old SS receiver and my mind says it sounds even better now. EDIT: I listened to the Sansui for hours yesterday. Didn't believe it could sound so much better! Unreal now. THANK YOU Echowars!
Checked an old Kenwood KR-5060 that powers up the kitchen turntable over some vintage Sansui speakers (don't laugh, it's just for making coffee and toast in the mornings). This thing sounds really clean and clear, maybe it's because of decent DC offset?
R: 2.2 mV to 4.5mV
L: -1.9 mV to 2.6 mV
Fisher CA-880 amp (has a Darlington pair and can't find where to adjust it). Still sounds really decent though. Clean.
R: 48.2 mV
L: 52.1 mV
Only with the Sansui does the offset mV swing around and fluctuates a lot even when it is really warmed up but it looks like that's okay. This thread is huge and I've only read up to the first 160 pages or so although I jumped to the end to see what's been happening. Thanks Echo for starting and sharing your knowledge!
Last edited:
Had to go up a scale - 0.176/0.230 on the little SA-5300
Well, looks like i'm transistor buying. Ain't no trim pots on this baby. Actually, there are two wires you cut when replacing them to "align" the amp - Mine have been cut (before I got it) - Any idea what this is/does? The procedure is in the service manual...
Well, looks like i'm transistor buying. Ain't no trim pots on this baby. Actually, there are two wires you cut when replacing them to "align" the amp - Mine have been cut (before I got it) - Any idea what this is/does? The procedure is in the service manual...
