Besides not being a technically inclined audiophile, I have not read every post, sorry for asking.
Those details should be in your amps' manual as well, if I remember correctly.
Besides not being a technically inclined audiophile, I have not read every post, sorry for asking.
The Nagra preamps (Jazz and PL-L) are only coupled by a transformer if the unit was ordered with them as they are optional. The output impedance for the single ended outputs is actually lower than the XLR transformer balanced outputs. I have a PL-L and the single ended outputs were measured by stereophile. "The unbalanced output impedance was 36 ohms across most of the audioband, this increasing slightly to 125 ohms at 20Hz. The balanced figures, from the optional transformer-coupled XLR output, were 63 ohms at 1kHz, 66 ohms at 20kHz, and 158 ohms at 20kHz." They should work fine especially with the MIT interconnects.
It's not a matter of blowing up equipment, it's about optimal operation. And you would need a high impedance version of the cables for the sources. WRT the amps the impedances may be compatible but also keep in mind they need 100-200mA of current to be driven properly. This has been discussed numerous times before.
They are mostly current-driven amplifiers. This is why their preamps put out 1 to 2A (peaks)
Preamp input impedance is totally irrelevant to the discussion about driving an amplifier; you are mixing in another interface, that of the source to the preamp, which is entirely different and independent.
They claim 10K ohms input impedance, so not much else to say. I am sure the voltages that their preamps swing also help (80-100V peak with the 30SV).
Tube and most solid-state preamplifiers cannot drive the DMA-400 input circuit properly. CD players and digital processors also should never be used to drive the DMA-400. Only high-performance solid-state preamplifiers with high output current capability (minimum 180mA continuous) will be compatible with the low input impedance and very high speed operation of the DMA-400 amplifier. Failure to use a high-current preamplifier such as those from Spectral may result in serious damage to the DMA-400 output section.
Not sure where the disconnect is... You keep talking RMS and I keep talking peak - the amp might be drawing tens of mA peak at 100V peak output from the preamp, if not more. Do the amps sound loud, even maxed out, at 1.5V RMS? Sure, I measure around 0.9V at 1kHz from the Berkeley if I recall correctly, and with unity gain in the preamp, it's pretty loud. But that's not the point. For example, we have posted in the past that the Berkeley just can't drive the amps correctly during complex dynamic swings, and it's easy to prove - see also this post http://www.whatsbestforum.com/showt...ates-Believers&p=219121&viewfull=1#post219121. Feel free to call them up and have them correct their manuals, if you feel like they are in error; but the whole issue is about optimal *performance* and amplifier stability.
And for what it's worth, here's the language from the DMA-400RS manual:
(...)
So basically, when I said 100-200mA earlier, it was based on this latest figure (180mA) and previous ones in older amps (100mA). So take it as you may. Finally, as marty pointed out, I believe the aforementioned language has changed again since then (in the 300RS, I think), to again REQUIRE a Spectral preamp, and be set up by dealer so he can attest to the system approach for warranty coverage.
What you are alluding to is that by simply removing the Spectral preamp from the picture, there is no issue properly driving their amps, contrary to the manual's language. People can draw their own conclusions, and I may be the only one who doesn't understand what you are talking about, but it shouldn't really matter at this point. And yes, 600ohms is even lower impedance, and I have seen even lower than that (Krell, DartZeel - 50ohms), but I also think this is just irrelevant to this discussion.
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