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AR LS 26 and Pass Labs X350.5 Compatible?

Hello to all the audiophiles here on Audiogon. Being new to the high end of audio I was wondering if some of the more knowledgeable experts could give me their opinion on something I've been thinking of.

Recently, I upgraded my venerable Ohm 4s to the 4.5 S3 and I wanted to pair it with an Audio Research LS 26 and a Pass Labs X350.5, both of these choices after reading some of the forum opinions here.

I contacted Pass Labs and a gentlemen named Desmond said there would be no problems with the pairing. However, after reading some opinions on mixing solid state amps with pre amp tubes would they really be compatible or would there be a better alternative? Thanks in advance for any replies!
aurelius
gundam91
506 posts
 
I have the ARC LS-25 Mk I and Pass X350.5. I remember reading somewhere before about the impedance matching issue between these two components, but I could not find the threads again.

I just did some research and this one talked about the impedance matching:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1177894805&read&keyw&zzmatch+impedance

Per the manuals ARC LS-25 Mk I has output impedance of 650 omh (balanced), and the Pass X350.5 input impedance is 20k ohm (balanced). Per the above thread, the ratio should be at least 20x. The imput impedance of the X350.5 is at least 30x of ARC LS-25's output impedance (20k ohm/650 ohm = 33.8), so it should be OK.

FrankC
glai's avatar
glai
446 posts
 
tried ref 3 & 350.5. Very good combo, no problems.
audphile1's avatar
audphile1
5,686 posts
 
Aurelius, best is to try.
Dave(Dpac996) makes an excellent point and provided a good bit of information that should hint you on what to look for and what to ask. Call ARC and ask them all the questions you already have just to put my the mind at ease.
If you are settled on Pass X350.5, then when you buy it, try to get an LS-26 as a loaner to try out at home.
You may love it or the preamp may simply be not your sonic cup of tea. That would be a problem as well. So try before you buy, if you can of course.

As an aside, before I bought my X250.5, I called Pass Labs and also spoke with Desmond and asked him if my ARC LS-25MkI would be a good match with X250.5 and I provided all the specs to him. He said it would be no problems and he knows of many ARC tube pre/Pass amp combos.
I took his word for it and 15 months later I am still using and enjoying the very same combo and am very happy with the way my system sounds.

But do your research and make all necessary phone calls to confirm things with proper authorities(ARC and Pass Labs) to be more or less certain there will be no flukes.
audiofeil
4,011 posts
 
I think there's sufficient end user confirmation and information from the manufacturer to resolve the OP's question and ignore the guesstimators.

To correct an earlier post, all Pass Labs X.5 series amps have a balanced input rated at 22K not 20K.

The XA.5 series' balanced input is a bit higher at 30K.
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