Help with re-tubing an ARC VT100 MkII

Jea48, Upscale's a little bit more money, but I think it's worth it for what you get from them.

Another advantage of getting tubes from upscale is that they run the tubes in for 72 hours before doing any matching. At least they do that when you get their platinum grade. So I think you can expect the tubes to be stabilized by the time you receive them. I don't know if Research runs the tubes in before doing adjustments, but I would think that they do. At least this would be logical to do on their part. ARC should tell you though. Good luck.

Louis:

The biasing of the input tubes is very tedious and requires several iterations to obtain the optimal settings. It is easier if you have two digital voltmeters and several clip-on cables for the test points. You must bias the input tubes first.

For the output tubes use a rough setting prior to burn-in. There will be some drift of the bias as the tubes burn-in. You need to repeat the final bias after the tubes are sufficiently burned in.

Jea48...yes there are bias adjustments for the input tubes as well as the output tubes.

Gmorris and Rlips...thanks for the input. I have the Collins site and have printed it. The biasing of the input tubes however, looks a little difficult. Any further thoughts?

Audphil1, thanks also, I'll give Kevin a call.

Jea48

I retubed my VT100 MKII using the instructions above from Collins. A matched octet(8) from Upscale audio will cost about $240. A set of 8 low noise input tubes 6H23 (6922) will cost about $200. Total $420 plus shipping. You may want to speak to kevin Deal at Upscale. You must use input tubes with close tolerances.

that's a lot of money they charge, these ARC guys. I am considering this amp myself and curious what the outcome of this will be as far as what you can do yourslef vs what has to be done by ARC. As far as buying tubes for my ARC LS-15 pre, I had great experience with www.upscaleaudio.com
Kevin really knows his stuff and their tube matching is very reputable. So far the tubes I got from Kevin made my pre-amp sing and I tried a lot of tubes from lots of different stores. You may actually save some money with UpscaleAudio vs. ARC. Just a thought.

I just spoke with Leonard at ARC. Here's the breakdown on charges...

$150 a match pr. * 4 = $600
$30 a piece for the inputs tubes * 8 = $240
Roughly $80 for labor (one hour) = $80
Subtotal = $920
Shipping (round trip) roughly $100
Total cost for ARC to retube =$1,020

Anyone think this is a bit on the high side?

I would let the ARC do it if you are going to replace the input tubes as well. Output tubes are easy to replace and bias, but those input tube biasing is not easy.
If you are going to buy all those (perfectly) matched tubes, it will cost $400 anyway. If you send it to ARC, they will not only do it correctly but also check all the other specs and do the necessary maintenance.

Hi,

This might be helpful:

http://mycollins.net/audio/artube1.html

I personally do not think you need to have the unit sent back to ARC. I had a VT-100MKII for a while, and I purchased new tubes from ARC and retubed it myself, easily.
Biasing the power tubes is easy. I do not know how to bias the input tubes, but I think it might be unnecessary.
Ask around- there was a website with information about input tube biasing once, I believe...
Good luck

Will