Experience using Spectral without MIT or preamp

Flex: Spectral avoids putting an inductor in the output stage as this reduces rise times and power bandwidth. The end result is that the amp can go into oscillation and destroy itself IF it sees a load that will allow this to happen. By using the appropriate parts to build a zobel, the amp sees a load that it can deal with at high frequencies WITHOUT affecting in-band performance in the least. You get the benefits of the "non-inductor speed & bandwidth" with the stability of a networked cable without the in-band effects that the networks produce. By altering the values of the components used to build the zobel, you can change the hinge frequency as to where it comes into effect.

As to the stability of their amps, i work with RF devices that put out 100's of watts PER DEVICE. Sometimes, these are operating into loads that are phenomenally out of tune in terms of the load impedances that they see and this situation remains consistent over prolonged periods of time. These devices will typically hold their own under horrible conditions.

Now if you take into account that some of these devices are rated for under 100 watts apiece by the manufacturer and we are running them well above that level at extended duty cycles at 25% - 50% above specified operating voltages and less than optimum loads on them and they don't blow up, i would think that Spectral ( or anybody else ) should be able to build a device that can hold up under normal and even somewhat specialized conditions ( Zobel's installed for protection ) without much of a challenge. If they can't do this, they are either technologically challenged or their parts matching is not what it should be. Then again, i've always thought that if the average audio engineer was designing RF circuitry, we'd still be using tin cans and strings for communications. Sean
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Spectral requires the use of MIT cables on both input and output of most of their amps. On the input side because of the zobel filter requirement, and on the output side because, by design, an inductor termination is provided by the networked speaker cable rather than in the amp. There was a time when Transparent cables were acceptable alternates but I don't know if this is still true.

Spectral preamps are required with most amps because the amps need adequate high current drive to function best, and because of impedance matching between the pre and amp. This is supposedly a warranty issue, so it may be worth checking whether the use of the CDP drive voids the warranty. Several of the older amps and the dma 150-S don't need MIT or Spectral pre's.

One other comment: Spectal is designed as a system, with every attempt to optimize linearity, low noise, and sound quality. I wouldn't heed the comments by those unfamiliar with Spectral, since general comments about zip cord and zobel networks can be well-intended but wrong (and will void your warranty if used).

I'm using Wadia 6 CDP directly connected to DMA 150 power amp with MIT MI350 interconnect cables, which is not the correct one that Spectral recommended. But I'm using Spectral recommended MH770 speaker cables between DMA 150 and Spandor 3/5A Speakers.

With small and big volumes, sound's very clear and wonderful. And can't find any troubles in my system.

I'm going to add Spectral pre amp to my system because system with pre amp can give me better Spectral sound.

For best results, use something other than zip cord as a speaker cable, install a Zobel network ( resistor & capacitor ) at the speaker terminals and don't worry about it. Sean
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"the president of Spectral is good friends with the president of MIT, so maybe that explains it" Only partly.
Experiment, if you must, with care & VERY low volume.
The Spectral is a wide-bandwidth design and will thereby accept input signals in the MHz region. Spurious signals entering the system in the very high hi's could send the amp into oscillation.
That PARTICULAR mit cable allegedly rejects such signals, so is recommended. It cuold have been another cable producer, maybe that's where the friendship comes in...

For the record, I've tried Spectral amps w/out a pre and with another pre (through cdp). While I detected no problems -- visible (i.e. drive units excursions) or audible -- I was in a relatively "clean" zone... the system picked up noise from a cell phone though, so nothing is "invulnerable". And I was playing at "whisper" volumes just to be safe!