Help with re-tubing an ARC VT100 MkII

It's now time for me to retube my Audio Research VT100 MkII. It appears that it's no big deal, if I only want to retube the power tubes. However, I think its time to retube the input tubes as well.

Can anyone offer any advise as to:
1) Should I just spend the reported $700-$800 (seems expensive to me) and send it to ARC?
2) Can anyone offer an alternative to No.1 (I don't know anyone here in Memphis, TN that could do it)
3) Any suggestions as to what brands/types of tubes to replace the old ones?

In advance, thank you!

As far as I know ARC is still using EH tubes.
You can change them out yourself, if you know how to
adjust the bias DCmv setting for the power tubes.

Where you buy the tubes is very important, not all dealers spend the time to match them correctly. ARC does a great job but you will pay dearly for it.

I have had good results with Jim McShane.
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


This might be helpful:
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.
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?
Louisl, did you ask him about the input tubes? Is there any bias adjustments?

I have a VT50 and the only adjustments I have to do is the "Output tube Bias Adjustment" for each channel. No big deal.

The owners manual has a section for how to....Have you checked it out?
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
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 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.
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.
I just went through Collins site.... I am sure glad I bought the VT50.

I can not speak for the VT100, but for the VT50 for about the first 10 to 50 hours of tube burn in, for the EH6550 power tubes, I reset the bias trim pots about 6 times , a pain in the butt. I did not notice if Collins mentioned anything about readjusting bias pots after burn-in of the new tubes.

Maybe others who have posted can respond on readjusting bias after burn-in.

You may want to check with ARC. Is ARC pre-burning in the tubes....


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.
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.
>>"Another advantage of getting tubes from upscale is that they run the tubes in for 72 hours before doing any matching."<< [Audphile1]

My Son bought me a new set of EH tubes from "The Tube Store" for my VT50 last Christmas. Obviously they did not pre burn-in the tubes before they tested them.
I will try upscale the next time.
Jea48, Upscale's a little bit more money, but I think it's worth it for what you get from them.