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Spectral amp and VTL preamp

Hi guys, after some days spent with the Soulution 721, the Spectral DMC30SS Series 2 has returned to my system. The CD player is a Soulution 540, the power amp is a Spectral DMA260 (MIT Magnum MA speaker cables and Cardas Golden Reference interconnects). I’ve also tried a VTL 7.5 Series III and it was the sound I liked the most between these three preamps. Each of them has its strengths but I think that the VTL has a little more musical elegance. The (maybe silly) question is: are there some risks in using the VTL with the DMA260? I read dozens of times that Spectral power amps shouldn’t be used with other than Spectral preamps but I also read dozens of times that someone had very good results using a Spectral power amp with a non-Spectral preamp. Apart from the output impedance of the VTL (25 Ohms, max 150 Ohm at 10Hz) and the input impedance of the Spectral (10 KOhms), are there other things that should be considered? I don’t want to take any chances. Is there something else to consider? Some risks about potential DC-offset? Spectral amps should be DC coupled... and the VTL? I think that both of them should have some kind of protection against DC but I don’t know too much about this topic so I’m asking to you...
Thanks a lot in advance.
katfnc
roxy54's avatar
roxy54
7,994 posts
 
Where are you Al? Are there electrical compatibility issues?
almarg's avatar
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almarg
9,670 posts
 
I’m here, John (Roxy54), thanks :-)

Katfnc, after looking at the specs and descriptions of your Spectral amp and the Spectral and VTL preamps I don’t see any technical issues that would arise with the VTL preamp/Spectral amp combination.

Regarding DC offset, I see that the amp incorporates a "DC protection servo" having a "0.5 volt range." Assuming (as I do) that the 0.5 volt figure pertains to the output of the amp, that seems to me to be adequate protection against DC that may originate anywhere in the system.

The gain of both preamps, assuming you are using balanced interconnections at their inputs and outputs, is somewhat higher than I would generally prefer to see when a digital source is being used. Those numbers being 19.2 db for the VTL and an option of either 15 or 21 db for the Spectral. But if that were an issue in your application (which depends on speaker efficiency among other factors) you would already have found that you have to use volume control settings that are undesirably low.

Regarding impedance compatibility, I don’t see any problems.

Good luck. Regards,
-- Al

katfnc OP
14 posts
 
Al, thanks for your full and comprehensive answer! This is exactly what I was hoping for ‘cause I like a lot how the VTL sounds with the Spectral. 
Thanks also to John (roxy54) for inviting Al to answer my questions! :-))
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almarg
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@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
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roxy54
7,994 posts
 
Thanks Al, as always, and good luck katfnc.
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