Spectral amp and VTL preamp

@Katfnc

Thanks for the nice response.

Thinking about it a little further, though, I’m not completely certain as to the correct interpretation of Spectral’s reference to a "0.5 volt range" of the "DC protection servo." And a good deal of further research I did failed to shed any light on its intended meaning.

One interpretation, which was the basis of my previous response, is that the design incorporates a protection mechanism that will limit any DC that may appear at the output of the amplifier to a maximum of 0.5 volts. That would be fine.

Another possible interpretation, though, is that the "protection" will only be effective for DC voltages at the amp’s output that would be no greater than 0.5 volts in the absence of the so-called protection. Under that interpretation the "protection" would essentially amount to a performance enhancer, as I see it, as opposed to providing effective protection against secondary damage that might result from major failures.

It might be worth contacting Spectral and asking them to clarify exactly what that spec means.

BTW, that same spec and wording appears in the description of many of their amplifiers, not just your DMA-260.

Best regards,
-- Al

Thanks Al, as always, and good luck katfnc.

@almarg Thanks for your further clarification. Does Spectral has an email address? I live in Italy and I’d prefer to contact them by email ‘cause it’s much more easy for me to write than to have an intercontinental phone call... also because I’m sure that they could better understand me (and I could better understand them!)
:-)) 

@almarg Another thing Al... I think that the crux of the matter is: has the Spectral DMC-30SS Series 2 some kind of protection that the VTL hasn’t? This because the power amp would be the same (DMA-260) and my doubt is if the use of the VTL could increase the risks of malfunction... So if with the VTL the risks are the same (or even less for some reason), keep the Spectral preamp won’t give me a safier situation...

Katfnc, you make a very good point in your post just above. And in looking further at the descriptions of the two preamps it appears to me that you would be at least as safe with the VTL as you are with the Spectral, regardless of how effective or ineffective the DC protection mechanism in the amplifier may be.

The VTL design includes coupling capacitors at its outputs, even though its output stage is apparently solid state, as well as coupling capacitors in its internal signal path for the tube stages. Those will block any DC that may originate in the preamp or the CD player (or in any other source component).

In addition to providing protection against DC, the Spectral preamp is described as providing protection against oscillation. But I would feel certain that the VTL requires no such protection, due to its much lower and more conventional bandwidth, and the fact that it uses zero global feedback and very minimal (less than 2 db) local feedback. The Spectral’s description does mention the use of feedback (although not quantitatively), and of course as is typical of Spectral designs it has ultra-wide bandwidth. So the reason it provides protection against the possibility of oscillation is that it needs it.

Regarding Spectral’s email address, it’s strange that their website provides neither that or a means of contacting them directly via the site. But I found elsewhere that their email address is, or at least has been, spectral@prodigy.net.

Best regards,
-- Al