2. amps-preamps
  3. 1243215247

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

Showing 5 responses by eldartford

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.
eldartford
4,262 posts
 
The quasi-balanced interface that I suggested (using a resistor to ground for the (-) wire) gets you the noise pickup reduction benefit of balanced lines. It is appropriate for equipment which is single ended internally, and useful (instead of an RCA/XLR adapter) if the power amp has only balanced input.

If the power amp has internally balanced circuitry, and performs poorly single ended, (as appears in this case) the transformer suggested by Bob_reynolds is the way to go. To describe such a transformer as "junk" reflects ignorance.
eldartford
4,262 posts
 
The Jensen transformers are excellent, and priced accordingly.
eldartford
4,262 posts
 
Hifigeek1... A step-up transformer, such as used with MC cartridges, is a lot different from a 1:1 transformer used for stage-to-stage coupling, which is what we are talking about here. A little circuit with an IC is a lot simpler and cheaper that a Jensen transformer, and no doubt was a good decision by AR. The one big advantage of the transformer is that it is passive...no power supply needed.
eldartford
4,262 posts
 
Hifigeek1...Before suggesting that Jensen signal transformers exhibit frequency roll off you really ought to check the specs. I know that high power audio output transformers exhibit roll off (usually corrected by ultralinear feedback) but these low level transformers are a different kettle of fish.

If you comment further, please report the specs you find.
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