[lanchile]

Hello guys! The other day I had a curiosity about the offset of my amp.... and I took my digital meter and read the offset in my Bryston B60-R. I was really surprise that it read a steady 3.4 millivolts on the right channel and 3.7 millivolts on the left channel (very good). The reading was really steady. I heard some of Bryston amps have a 1 millivolt offset. Just to see and compare one from another...let's see how much is the "difference" in dc offset from one to another in Bryston amps and integrated too.
 just put the Model and the DC offset of each channel.in my case I would do like this:
 
Bryston B60-R  (L) 3.7 millivolts (R) 3.4 millivolts

 PS: you do not need to open your amp for this and you should let it play for at least 1/2 hour before reading DC offset.
 

[vegasdave]

Do you mean the DC offset was too high?

[lanchile]

Nope! the DC offset is very low and steady ( Very good) The way I like it lol .

[vegasdave]

Well, that's cool...I got worried there for a minute, haha.

[Levi]

My 7B states...

(L) 4.4 millivolts (R) 7.7 millivolts

James, should I send mine for service?   

[vegasdave]

haha. Yeah, the right channel is off a bit!

[Levi]

First, let us set the standard. 

This is how I measured mine:
1. Speakers disconnected
2. Input set to an unused position
3. Volume control at minimum.
4. Balance in center
5. Tone controls either defeated or set to mid position
6. Set your meter to read DC, and set to a low scale (300mV scale is common) Connect directly to the Pos and Neg of the speaker terminals
7. Give the amp 10 minutes to settle then take measurements.

Here are the corrected measurements...

(L - 7B) 006.3  Millivolts DC (R - 7B) 0010.6 millivolts DC

[Levi]

http://audiokarma.org/forums/showthread.php?t=5634

Time for one of those long, boring semi-technical posts that no one here reads...
...

If you read:

0 - 15mV: Damn good!! If you read '0V', you may have a capacitor output, or your meter is set wrong

16mV - 50mV: An acceptable value, especially at the lower end of this range. 2nd harmonic distortion is probably twice to four times what manufacturer's spec calls for at higher frequencies. Probably not audible, as the distortion is mostly in the upper octaves. At the upper end of this range I begin to raise an eyebrow. :saywhat:

50 - 85mV: Something is certainly amiss, and while this is not enough to put your speakers or equipment in jeopardy, the amp is running nowhere near where it should. I'd venture to guess that most of the DC-coupled amps that are in use by forum members here fall into this range.

100mV to ?: A high enough voltage will cause the DC protection to kick in. This happens at a level determined by the designer, but is usually equivalent to about a diode drop (600mV)or so. Needless to say, if you are listening to an amp with 100mV or more of DC offset, you have no idea what the amp really is supposed to sound like. Indeed, some amps without a differential input are actually designed to have a bit of DC at the outputs, but this is triple-rare, and I don't think anyone here owns one. (in my book it's piss-poor design, but if you can sell it WTH..)

Soooooo...go grab a meter and tell me what you find...

http://audiokarma.org/forums/showthread.php?t=5634 

[vegasdave]

Thanks for the info! Great specs on the BRYSTON. I had no doubts!

[Levi]

You are welcome.  The thread above has lots of good information.

[Napalm]

Can we start a "my offset is bigger than yours" contest?

On second thought this would be one I wouldn't want to win 

[lanchile]

Can we start a "my offset is bigger than yours" contest?

On second thought this would be one I wouldn't want to win 

hahahaha yeah I agree too! I do not want to see my amp wining this contest. 
But I think it is a good idea to check your loved amp to see if it is healthy.
as Levi posted above, it is easy to check the dc offset in your amp, but I would leave the amp to "warm up" a little more, I would say 1/2 hour normal listening then do the test.

[lanchile]

My 7B states...

(L) 4.4 millivolts (R) 7.7 millivolts

James, should I send mine for service?   

Nice amp you got there Levi! and the offset is very good.

[Levi]

Thanks. They sounded sweet too!

[BrysTony]

My 7BSST2s have to be pulled out of the rack to be measured and I am too lazy to do that right now.  However, I have a McIntosh Integrated that I am not using so I measured it at:  R -7.7mV and L -8.1mV.  What do the negative voltages mean?  Maybe the autoformers have something to do with it?

Tony

[loopyground]

Followed instructions to the letter I got the following results:

Left 7B SST2 4.2 miilivolts  Right 7B SST2 5.6 millivolts

Now I can sleep at night as I am in the right range.....phew!!

The last time measured DC offset was after I had upgraded a Quad 405-2 amp and the instructions told me to put on safety glasses before powering up.  I guess the writer did not trust my soldering prowess and frankly neither did I as I had to solder an 8-pin Burr Brown op amp to the PCB which was really tough.  The early instuctions said that if I installed the big blue capacitors incorrectly they would explode!!!  Everything worked out luckily with the offset within the stated range.


   

[loopyground]

My 7BSST2s have to be pulled out of the rack to be measured and I am too lazy to do that right now.  However, I have a McIntosh Integrated that I am not using so I measured it at:  R -7.7mV and L -8.1mV.  What do the negative voltages mean?  Maybe the autoformers have something to do with it?

Tony

Are you in the southern hemisphere?

[lanchile]

I would consider a very good dc offset under 10 millivolts over that.......mmm not so in my test or tolerance!