Salas DCG3 preamp (line & headphone)

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
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337alant said:
Progress so far all boards built up but no wiring yet
Just going to be using a 4 input selector for now that I already had built up
PS not sure about the transformer as they are only 25VA each, ? are they adequate ?

Alan
Click to expand...

Those 25VA Talema are potted but they should be efficient enough also. You will judge from their cases temperature under load. The preamp is heavily biased Class A and it will massage them fast enough to a plateau. Up to 40C with the lid closed should be nice, and if reaching 40-50C hot enough but not alarming yet. You may still stick sinks on them if they will go too hot for your liking. Your box is tall enough. There are thermal adhesives for such jobs I believe.

By the way your arrangement looks very orderly and the box very sturdy, roomy, and modernly nice.
 
337alant

337alant

Member
Joined 2008
337alant

337alant

Member
Joined 2008
Salas said:
Those 25VA Talema are potted but they should be efficient enough also. You will judge from their cases temperature under load. The preamp is heavily biased Class A and it will massage them fast enough to a plateau. Up to 40C with the lid closed should be nice, and if reaching 40-50C hot enough but not alarming yet. You may still stick sinks on them if they will go too hot for your liking. Your box is tall enough. There are thermal adhesives for such jobs I believe.

By the way your arrangement looks very orderly and the box very sturdy, roomy, and modernly nice.
Click to expand...

Salas

Thanks I am just waiting for a few bits then I will fire it up for testing :)eek:)
and will measure the temp on the trannys, if necessary they can be replaced

Alan
 
S

stew1234

Member
Joined 2010
Salas said:
Simplest method is NA2MPMF | Neutrik

For switching at balanced realm there are relay boards configured for that. For same number of relays half the number of inputs.

Without SE to BAL transformer (or special chip) most obvious difference is balanced sources remaining twice stronger than alike SE sources.
Click to expand...

For balanced input selection, is there any reason you couldn't wire up two I-Select boards using a 2 pole selector switch (half wired to PCB 1 and half to PCB 2) and a 4 gage potentiometer?
 
337alant

337alant

Member
Joined 2008
I have tested my DCG3 today and fortunately it didnt blow up :rolleyes::D

Right channel
Bias - 133.4ma (10R)
Voltage rails 17.05/ 17.06
DC Offset 0.3mv
PS Heat sink temp 34C
Output Transistors 28 - 34C
Transformers lid off 24C

Left channel
Bias - 132.4 ma (10R)
Voltage rails 17.17 / 17.07
DC Offset -0.5mv
PS heat sinks 38C
Output transistors 28 - 36C
Transformer lid off 24C

DC Offset by Alan Towell, on Flickr

Alan
 
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donhughes111

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Joined 2019
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Salas

Salas

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Joined 2002
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Maybe from PSU zero to a standoff's screw of its PCB. Not to be drilling for test moves. Or XLR pin1 to its chassis screw. Or nowhere, only the pot's metal neck contacting the mains earthed chassis. Best is to use FFT and find lowest harmonic noise grounding for any build's specific config. Also testing for when interconnected to other gear.
 
337alant

337alant

Member
Joined 2008
Salas said:
Maybe from PSU zero to a standoff's screw of its PCB. Not to be drilling for test moves. Or XLR pin1 to its chassis screw. Or nowhere, only the pot's metal neck contacting the mains earthed chassis. Best is to use FFT and find lowest harmonic noise grounding for any build's specific config. Also testing for when interconnected to other gear.
Click to expand...

Had a look at it with the scope this morning and it was quietest when connected to a power supply ground at the connector to the DCG3

Alan
 
337alant

337alant

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Joined 2008
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