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Old 1st November 2013, 01:20 PM   #1
iso is offline iso  Finland
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Default Audio Research regulators

I have experimented recently with ARC SP14, Classic 60 and D76A. SP14 and CL60 do perform nicely, but sound quality is slightly congested. Especially in HF. When SP14 is used with D76A, sound is considerably more open, even LF is considerbly less focused and softer. When D76A is used with Conrad Johnson Premier 7B sound quality is quite open.

Circuit topology of most ARC power amps is not doo different up to VT130. Most use crosscouplers and there are some models like D40 and D79B without crosscouplers. Overal feedback ratio is most often close to 20dB. Models like D79A and VT150 use slightly less overal feedback.

If we compare D79A to CL60, better LF controll is most likely due to the triode connected otput stage, better output transformer and more fawourable primary to secondary impedance ratio. If we try to seek reason for more open overal sound, there is on thing that might be reason for this. ARC amplifiers since SP6C and D79 have used feedback regulators for HV PSU:s. Earlier units used simple strings of zeners with cathode followers for screen suplies. Early pre amplifiers replaced cathode followers with solid state devices.

Basic topology of SP3, SP6 and SP8 is quite similar. SP10, 12 and hybrids are quite different. Power suplies after SP6C and SP8 used feedback regulators. HP mentioned in TAS in mid 80īs that ARC house sound did change considerably when SP6C was introduced. D79B and SP8 were also introduced within 1 year from SP6C.

Has anybody thought if the change of regulator topology is the reson for change in ARC house sound. Are earlier zener strings with buffers so much more suitable for audio, if resonable electrolytics are used for bypassing the PSUīs. Op-amps were not too good in the 80īs... but do more recent op-amps improve 80-90īs regulators?

Quite many ARCīs actually used two regulators in series... If we consider that regulator must be faster than signal circuity, then the first regulator must be faster than the second regulator.

Any ideas... can this be the holly grail for good audio?

Best Regards

Kimmo
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Old 1st November 2013, 02:01 PM   #2
SY is offline SY  United States
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I don't understand why a regulator should be "fast." The ideal regulator is infinitely slow.
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Old 1st November 2013, 02:12 PM   #3
TheGimp is offline TheGimp  United States
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Do you mean transient response?
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Old 1st November 2013, 02:39 PM   #4
SY is offline SY  United States
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What's the transient response of an infinitely large, zero ESR/ESL capacitor?
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Old 1st November 2013, 03:55 PM   #5
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Quote:
Originally Posted by iso View Post
Any ideas... can this be the holly grail for good audio?
I doubt anything ARC can be a holy grail for good audio. The regulators are especially toxic, even on the Reference series. You want something that actually sounds good - build a high voltage Salas shunt.
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