AR SP8 mk2 high output volume

@tenoris

Having looked at the schematic supplied by @imhififan I agree that essentially this amplifier is actually a power amplifier supplied with three inputs and a passive volume control.


Since the control is 100K and given the characteristics of the input tube, you can successfully operate the volume control to reduce the level of signal coming from the ARC without degradation.

However if the sources are high level (in other words not phono), I am still having trouble seeing what good the ARC can do for you unless the sources are not physically fairly close to the amplifier. It seems that you are saying that it nevertheless sounds better this way- so I am curious, what improvements are you hearing?

BTW I do not recommend tampering with the feedback resistor- such things can lead to oscillation, and if the schematic is correct there appears to be little or no compensation for a variety of frequency poles present in the amplifier design- by increasing feedback, any one of these poles could cause the amp to be unstable.

Thank you all very much for these valuable contributions.
@atmósfera the one hand it seems good news that the passive attenuator of the A30 does not degrade the signal, but what I do not understand is your question because it seems that the AR is not fulfilling its function as a preamplifier. I gather this because you ask me strangely if I notice any improvement. Is it that the AR is not fulfilling its function like any other preamplifier?
The Puresound as integrated works quite well but when I put the AR I notice a plus in terms of presence and forcefulness of the music

when I put the AR I notice a plus in terms of presence and forcefulness of the music

OK. I asked simply because with a high level signal like a CD player I would not have expected adding additional circuitry would have helped out.

It seems the integrated amp is similar in design, to a power amplifier, connected to a passive unit ( this A30 amp design, is becoming very popular ). What the OP is saying, imo, he does not like passive, as much as the AR's tube line stage, and prefers the extra gain, like many people, that do not like passive. It just so happens, the amp has it's own volume control ( no different than many pro amps having input attenuators ), but still going through a preamp, with gain, or even a passive device, with multiple inputs ( something I am very accustomed to ). Enjoy !, and be well....

This just keeps going around in circles, if you don’t like the sound when it’s used as an integrated, change the source to one you like, instead of coloring it with that premp, and then having your problem of way too much gain.

Just look at the specs of the A30, it’s at FULL POWER already with ONLY 0.5v (500mV) input from a source. Most sources today put out well over 2v!!!

So just use it as is with it’s own passive volume control, and remember Nelson Pass saying to you ("psychological need" to turn it up more) than when the AR pre is in and then sell it.

Nelson Pass,

“We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.”

Cheers George