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Old 8th July 2009, 10:10 PM   #1
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Default DIY option for spectral amps?

Does anyone have any ideas into a DIY option for cables/zobel to use with spectral equipment. I'm looking more for network recommendations than cable. I've purchased some older gear (DMC-10 and DMA-50), and don't feel like dropping the silly cash required for the MIT cables. Of course their marketing has scared me just enough that I would rather not have the amp oscillate into oblivion either
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Old 8th July 2009, 10:31 PM   #2
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I don't think they are known for oscillation... but read this:

http://uk.geocities.com/cyrilb2@btin...m/cable_3.html

will probably give you peace of mind...

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Old 9th July 2009, 12:38 AM   #3
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Thanks for the link! I'll read up and see what he has to say. It's just a bit irksome that they are "insistent" on using MIT cables with their equipment. Especially on older products, the last thing you want to do is cause some harm. Other than that, I think they are some of the best sounding amps out there and I need a "non diy" system as well so the tunes are always flowing
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Old 9th July 2009, 01:11 PM   #4
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I doubt that you have to use MIT...

Many people have Spectral and use other cables.
Regardless the article solves the underlying problem - if there is one.

DIY amps, fwiw, can be just as reliable as a Spectral - depends on the amp and the user no matter what design it is.

Fwiw the designer of the Spectral amps participates here...

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Old 9th July 2009, 08:48 PM   #5
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Yeah, I read that paper...very interesting! I had no idea that reflections based on quarter wave theory were to blame. It also made me wonder what is going on with the higher end MIT boxes that tout having 28 poles. It seems as if there wouldn't be much (if any) of a benefit over a standard network like the author describes in the paper.

I didn't understand any of the modeling specifics he was talking about, but surprisingly got the rest of it. I now have 100% confidence in using some standard cables with the addition of a C/R network at the speaker end of things.

Of course it also now makes sense that Spectral amps could be more prone to serious issues (if RF reflections were taking place) since the amps operate so linearly into the Mhz range.

I cracked open the DMA-50 last night because I thought spectral didn't utilize any type of network on their outputs (and relied solely on the MIT cables). Much to my surprise there was a network across the outputs. That is good to know as it seems from the paper that having one inside the amp and one at the speaker terminals was more efficient than just having the network at the speaker terminals.

As for DIY solid state...i'm completely ignorant. I built one of the xen variations, but as a rule, solid state eludes me. I'm just a good craftsman, not an engineer Most of my DIY amp building has been tube amps as they are simpler as a rule and I "get" them. I'm not against building another solid state amp, but again...the point behind buying this gear was to have a "tweak free" setup so I always have something running.

Finally, I didn't realize that the designer of the Spectral gear was active here. Is it Keith Johnson you're referring to? I'm not super familiar with their design team, but had read that he was on board.

Thanks again for the link!

**digression**

One thing that also draws me to Spectral products (other than sounding amazing) is the firm grounding in science as opposed to voodoo. I got sucked into the whole realm of psycho-acoustics, and it took me years to drag myself out. From now on, I'd like to concentrate more on the measurable than the hyperbole. Audio engineering (as any engineering) is an art for sure. But it's the creative thought of the design itself that I feel lends toward better designs, better sound, etc. Not which brand of capacitor you are using (not counting measurable properties of said capacitor).
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Old 9th July 2009, 09:48 PM   #6
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Default Spectral Cables

I acquired as set of old MIT cables and opened up the transmission boxes because something was rattling around in there. The network had come off and was flying around.

It was an RC to ground (zobel) but I forget the values. I may have pictures somewhere if it will help. I recall it was one of those old transparent caps. Anyway, sorry I cannot help more.
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Old 10th July 2009, 12:48 AM   #7
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Thanks a lot for the offer, but it's not necessary at this point. The paper bear posted a link to put my mind at ease on that front. And spectral actually has specific cables that MIT manufactures for them, so I bet the networks are different inside.

I've seen photos online somewhere of the inside of an MIT cable. Were those your pictures?
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Old 10th July 2009, 07:50 PM   #8
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Quote:
Originally posted by enochRoot
***
I've seen photos online somewhere of the inside of an MIT cable. Were those your pictures?

No problem. I did see these pics recently and wondered if I had posted or not. So the answer is "I forget!"
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Old 11th July 2009, 01:02 AM   #9
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Hi Enochroot,

No Kieth Johnson afaik is not here...

I think that because of the wider bandwidth of the Spectral the signals that might bother most amplifiers will not, but signal of higher frequency might... guessing here.

lgreen, post 'em up here, would like to see the innards...

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Old 11th July 2009, 08:26 AM   #10
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http://www.epidauro.org/phpBB3/viewt...hp?f=44&t=5089


The ones i had were a lot simpler.
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