Spectral DMA 100 Help needed

Demian:

Thanks for sharing this.

I'm curious - I didn't think those old Supertex VN1306 were Depletion Mode MOSFETs. Assuming they really are not, how does the front-end diff amp in the "DMA-50 driver revised" bias up properly? I would have expected some high IDSS JFET like a pair of J111 as cascodes instead for this kind of cascode configuration ...

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Thanks for the comments,yes the DMA 100 is amazing ……1 audio,if you could divulge a bit on the Crosby mods,can I do better?
Also,any way to find the front logo light array,it’s getting dimmer by the day…..Dave
 

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You have the full Crosby mod. There are possibly other areas to tweak but not many and not much ROI for huge effort.
The Crosby mod started with the active regulator for the input/driver circuit. I believe there was also a seperate always on supply for the regulator. (There is in the DMA 50 mod) Then additional caps and component tweaks on the modules. Since it used very premium parts initially there is not a lot to upgrade.
The backlight is an electrolumincent panel. An LED backlight for a display would be the best modern option. This may be a "direct fit" option: https://www.adafruit.com/product/625
 
Hi,working on building up the spectral DMA power supply,do you have a figure for the max voltage to the output section….
Currently running 48 vdc +/- …I have a pair of 1000va 25volt transformers,want to use them since it’s no money out,can the output section handle the increase….25 volt in series,50 volt,so,would be 68.7….you had referenced to 50 vdc for full output,48 vdc works fine though,but present supply is a single 500va transformer feeding both boards……