Audio Research VT100 power tubes

[wabun]

Any issue if only use one pair of matched 6550 instead of 4 tubes per side ? I do not need that 100W, wil this work ? Or sound better since less concern on matching

 

[Mark Tillotson]

Apart from the need to use a different OPT you mean?

 

[DF96]

You could avoid the need for a different OPT by using a different speaker - one with nominal impedance around 20-30 ohms?

 

[Zung]

... or connect your 8 ohms speaker to the 4 ohms tap. ARC amps usually have a pretty broad power vs impedance curve, i.e. not too fussy regarding load.
This is also a common trick used by guitar players.

 

[rayma]

... or connect your 8 ohms speaker to the 4 ohms tap. ARC amps usually have
a pretty broad power vs impedance curve, i.e. not too fussy regarding load.

That should work reasonably well in this case.

 

[OldHector]

Extrapolating from the replies to the question, could one take an OPT with 16, 8 and 4 ohm taps, and reign an amp for 4 and 8 ohm speakers, with optional paralleled output valves? Using the 16 or 8 ohm tap depending on parallel or single valves respectively?
oPT primary Impedance would need to be a compromise in one configuration.
Could it be like those american V8s that could use 4 cylinders for economy?

 

[Zung]

The analogy is good, but you have to be aware it's a compromise between power, distortion, and bandwidth.

 

[Zung]

Attached are some measurements I did on my Leak ST60 long ago. The 2nd chart is normalized; you can see the ARC in red is more load-tolerant than the Leak.
I know, the X axis shouldn't be log, but that was the only chart paper I had at that time.

 

[huggygood]

@ Wabun
sell your VT100 and buy a less powerful amp that suits you, this is not what is missing on the second hand market.