[cpw]

OK so I got my new AR power amp (VS55) in the mail today and I'm trying to figure out how to set the bias adjustment without causing peril to my amp, home, family and pets.
I have lots of questions:
1) Does a load have to be connected to set bias?
2) Does amp have to be warmed up to set bias?
3) Instructions say to use included plastic tool for bias adjustment (none in box). Metal screwdriver ok or not?
4) I have no idea which lugs on my multimeter to use nor where to set the dial. I need to set the bias for 65mVDC. Here's what my meter looks like:

Here are the lugs:

Can someone tell me how to work this thing?
Thanks.
My family's safety is in your hands.
CPW

 

[kramer5150]

I always thought you need an oscilloscope and signal generator too... to set it???

Youre wise to play it safe. I retubed with EL34s and I had a nuclear holocaust. My new tubes glowed white like a lightbulb

I immediately powered down and replaced them with GT grade6 tubes. Problem solved.

Garrett

 

[Swampwalker]

1) Does a load have to be connected to set bias?
I would do it that way.
2) Does amp have to be warmed up to set bias?
Bias will change as amp warms up.
3) Instructions say to use included plastic tool for bias adjustment (none in box). Metal screwdriver ok or not?
If the screw is exposed, should be fine. If you have to poke around blind in the innards, I would use a plastic screwdriver.
4) I have no idea which lugs on my multimeter to use nor where to set the dial. I need to set the bias for 65mVDC. Here's what my meter looks like:
don't you have an instruction manual for it? You want to set it up to measure DC voltage. Just guessing, I would say to set the pointer to the 200 in the white range to left of center (11:00 position). Black lead would go to center (COmm), hot lead not sure; you could try either way and see if the reading you get makes sense.

 

[cpw]

Thanks for the help guys.
Here were the answers from Audio Research (if anyone cares):
1. No load required with this amp. Stable regardless of load.
2. Yes, it should be warm.
3. Plastic prefered as you are going in through a hole in the chassis and could possibly contact something on PC & cause damage.
4. Lugs were center and right, dial set at 9 o'clock (200m). Reading shows 65.0 instead of .065 at this setting.
Piece of cake once I wasn't afraid of blowin' somthing up.
Sounds great. (another thread)
Thx,
CPW

 

[sacd lover]

Congratulations on the amp. I used to drool over the past versions of your amp whenever I visited Progressive Audio. I loved this amp with the response 2 speakers.

 

[cpw]

Thanks. Haven't had much time yet for critical listening but initial audition is pretty much what I'd hoped for. Very nice mids and incredible dynamics. Bass seems abit on the round side but I may just need to redial my powered sub to match up with this amp a bit better.
I'll start a thread on the amp once I actually have something to say based on more than a few minutes of listening just in case anyone else is looking at one of these.
The construction of the chassis is a bit on the budget side but the board looks very clean and the one I got is extremely clean though it was used.
Overall quite happy so far. This was supposed to be the final addition to my office rig but now a DAC and one more HP amp looks likely!
CPW

 

[sacd lover]

Quote:

Originally Posted by cpw Thanks. Haven't had much time yet for critical listening but initial audition is pretty much what I'd hoped for. Very nice mids and incredible dynamics. Bass seems abit on the round side but I may just need to redial my powered sub to match up with this amp a bit better. I'll start a thread on the amp once I actually have something to say based on more than a few minutes of listening just in case anyone else is looking at one of these. The construction of the chassis is a bit on the budget side but the board looks very clean and the one I got is extremely clean though it was used. Overall quite happy so far. This was supposed to be the final addition to my office rig but now a DAC and one more HP amp looks likely! CPW

The response 2's were two way monitors. The rounded bass works really well with bass resticted two ways like that speaker; for my tastes anyway. But the upper mids expecially were so much more realistic with that amp. A nice efficient two way is my design of choice and the AR took full advantage of that designs strenghts. What are you using for speakers?

 

[cpw]

Quote:

Originally Posted by sacd lover The response 2's were two way monitors. The rounded bass works really well with bass resticted two ways like that speaker; for my tastes anyway. But the upper mids expecially were so much more realistic with that amp. A nice efficient two way is my design of choice and the AR took full advantage of that designs strenghts. What are you using for speakers?

Von schweikert VR1 (also a 2 way design) w/ a Von Schweikert VRS-1 Sub.
The bass is only "rounded" relative to my solid state amp and, as I said, it's way too early to tell definitively. I may just turn down the sub a hair and make it perfect.
CPW

 

[sacd lover]

Quote:

Originally Posted by cpw Von schweikert VR1 (also a 2 way design) w/ a Von Schweikert VRS-1 Sub. The bass is only "rounded" relative to my solid state amp and, as I said, it's way too early to tell definitively. I may just turn down the sub a hair and make it perfect. CPW

Good choice! I am partial to the JMLabs myself.