2. amps-preamps
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Audio Research amps - balanced & non

Ideas/suggestions anyone?
I have an original ARC SP-10 pre-amp (perfect, re-tubing once in a blue moon but totally reliable after ~25 yrs so reluctant to replace) but I would like to replace my original D-115 amp with VTM 200's (i.e. balanced) or get a VT-130SE (also balanced) to bi-amp alongside the D-115 to drive the bass end, assuming that's even possible.

Question - can balanced power amps work with a 'pre-balanced' pre-amp like the SP-10, or even work in a bi-amp arrangement as the only balanced component? I suspect not but would like some user comments.
Thanks!!
westchr
eldartford
4,262 posts
 
There is a way to create a quasi-balanced output from a single-ended source. Ashly (pro sound equipment) uses it, and it works.

From the single-ended signal ground connect a resistor equal to the output impedance of the signal to the (-) wire of a balanced interconnect. Since the (-) impedance matches the signal (+) impedance both wires will pick up the same noise, and this will be canceled in the balanced input circuitry of the power amp.
Post removed 
jafox
1,459 posts
 
By adding all this junk to the signal path, you significantly defeat the major strengths of the SP-10 and the VT-130.....and this is portrayal of space. These both were at the top of their class in this key area. Keep things simple and you will be rewarded by what these products can do.
dgarretson
2,599 posts
 
"The VT-130SE does not have a phase splitter and requires a true balanced input to operate correctly."

It will operate "correctly" but not "optimally" in conjunction with a single-ended source. With an SE source and an RCA/XLR adaptor, one phase of balanced circuitry floats unused.

BTW, VT130 is a much better amp with Infinicap or similar upgraded coupling caps.
martykl
3,578 posts
 
Dgarretson,

With a single ended input through an XLR adaptor the VT -130 SE will produce less than half the power output that it will produce with a true balanced input signal and that only with THD nearly an order of magnitude higher. I'm unsure of the precise reason for this result, but that was the position of the tech dept. at ARC when I posed this question to them some years back. I feel okay about describing such operation as "incorrect" rather than "sub-optimal", but I'm you're certainly entitled to feel differently about that.

Marty

Marty
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