Spectral DMA 150 Upgrade

ack

VIP/Donor & WBF Founding Member
May 6, 2010
5,633
238
63
Boston, MA
#21
Hi ack
Thank you.

Dear ack
One question, this model is the XLR input, pin 3 is +, and pin 2 is -.
The recent models of Spectral is same a conection? By rule, pin 2 is the positive and the negative pin 3, pin 1 is always the ground.
If this is a European model, which it appears to be, I am not surprised that pins 2 and 3 are reversed - I don't know how recent models are wired, but the manuals make it clear, and certainly the US versions are the opposite. Could it also be that whoever owned this before went ahead ahead and swapped the pins? Phase orientation is something I always test for, and for example, I discovered years ago that on my VPI's junction box, those pins are also reversed - the astute observer will then notice in my avatar that the red and green wires are swapped on my cartridge!

BTW, I laughed so hard at your washing of the heat sinks. There are obvious signs of corrosion in the fuses, so it looks like this amp was not really cared for. And before I forget, do bypass those silly fuses.
 
Last edited:

Jon Q

VIP/Donor
Jun 16, 2019
19
1
3
47
#22
If this is a European model, which it appears to be, I am not surprised that pins 2 and 3 are reversed - I don't know how recent models are wired, but the manuals make it clear, and certainly the US versions are the opposite. Could it also be that whoever owned this before went ahead ahead and swapped the pins? Phase orientation is something I always test for, and for example, I discovered years ago that on my VPI's junction box, those pins are also reversed - the astute observer will then notice in my avatar that the red and green wires are swapped on my cartridge!

BTW, I laughed so hard at your washing of the heat sinks. There are obvious signs of corrosion in the fuses, so it looks like this amp was not really cared for. And before I forget, do bypass those silly fuses.

Dear ack
Thanks for your reply.
I already keep in mind, that I would make the connection by default. 2 positive, 3 negative, and 1 gnd.

Yes, the fuses, RCA, XLR connectors, and Binding Posts, in the end I'll make a careful choice.
The connection to the speaker terminals is also updated. At this moment I have the two brands that Spectral uses, the original (Ca ... e) color gray cable, I think it is the same that is used in the Spectral DMA 500 and also have the other black color of the mogami, this is used on the DMA 300.

http://www.spectralaudio.com/DMA300/300_1 Large.gif

The choice is hard, I like both, but I can only apply one of the manufacturers

Now it's the electronics upgrade (voltage amplifier) ... I drew the whole schematic diagram of the DMA150, and there are a few little/very small things that don't go with my concept.

Other things are happening ...

cheers


ps: there may be some errors in writing... my english is no big deal
 

ack

VIP/Donor & WBF Founding Member
May 6, 2010
5,633
238
63
Boston, MA
#23
The choice of wiring will affect the overall circuit capacitance and inductance, and in lieu of the typical stabilizing output inductors, be careful and keep in mind they don't make those wiring decisions lightly, which again, are always in the context of the entire circuit. Same goes for the speaker cable binding posts; but given the chance, do consider the newer Mundorf that so many are using, including their later models.
 
Last edited:

Jon Q

VIP/Donor
Jun 16, 2019
19
1
3
47
#24
Yes that's true, the two wiring choices I have under test are the same models the brand uses. About, binding posts, I have two options, Cardas and curiously... Mundorf, in Europe is very easy find Mundorf than Cardas
Both models have no gold, rhodium or silver plating, only copper.

I think from photography, the terminals are the same as the one I have under test from mundorf, TPCU670C but I don't know if it's gold plated or only copper.

http://www.spectralaudio.com/DMA300/300_2 Large.gif
 

ack

VIP/Donor & WBF Founding Member
May 6, 2010
5,633
238
63
Boston, MA
#25
Yes, these are the Mundorf posts, all copper; been using them in my custom speakers as well.
 

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