Salas hotrodded blue DCB1 build - Page 184

KatieandDad · 04:04 PM

Quote:

Originally Posted by Nick77

I finally decided to install a couple of 4.5R mills resistors i had on hand, which replaced the Mills 10R. Resolution was a very nice bump, well worth the effort. Barely ran warm before but running about 100 degress on the sinks (37.7 celsius).

Cant find acceptable temp ranges, thanks. Using large L bars bolted to chassi

Is 100 degrees an acceptable temp?

I went from 10R to 3R0 and the sinks got too hot for my liking, They were stable at about 55 Degrees C.

I might just try 4R7 as you have - allbeit 4R5 in your case.

Salas · 10th April 2012, 04:02 PM

Nick, maybe a picture as sinked?

Nick77 · 10th April 2012, 06:22 PM

Had some larger sinks on hand but ran out of chassis space.

KatieandDad · 06:34 PM

I still cant see why mine were getting so warm at 3R0.

Maybe I was just being too cautious. After about 30 mins with the lid off my sinks were at 55 Degrees C or so. I felt, that, with the lid on, things would just get too warm and things would start to fail.

Maybe that's me being too cautious. Maybe 3R0 was too far. I am tempted to try 4R7 though - I've already ordered them.

I seem to recall that the heatsinks were about 3.6 Deg C/W. I've used one per side so there are two IRFPs on each sink.

At 10R0 they run at about 30-35 Degrees C.

Siberia · 11th April 2012, 06:20 AM

Quote:

Originally Posted by Salas

Run a wire from 0 PSU on DCB1 to its chassis.

Worked like a charm. Ευχαριστώ!

Salas · 11th April 2012, 01:49 PM

Parakalw! (=You are welcome).

schubert · 12th April 2012, 08:14 PM

I'm planning a 6-channel DCB1 along these lines:

with Hypnotize boards in place of the DACT modules.

DACT recommends 10K pots for the master and individual channel controls, while Mr. Pass recommends a nominal 25K. I've a mind to use 20K as a compromise (PEC carbon for each channel and Goldpoint for the master), though I don't know how having two pots in a row affects the total input impedance. Can anyone enlighten me as to how the attenuator impedance affects the sound? Any recommendations?

Salas · 12th April 2012, 11:27 PM

Use 10K pots so not to exceed 20K in series. Those Jfets have enough input capacitance to start losing noticeable bandwidth after that driving impedance level.

schubert · 13th April 2012, 02:54 AM

OK thanks Salas

AndrewT · 13th April 2012, 09:28 AM

A pair of series connected pots to control volume !!!!!

Have you considered each pot as a receiver and then again as a transmitter?

The Source sees the pot1 and the cable in between.
Pot1 sees the source and the cable in between.

Pot2 sees pot1 and the cable in between.
Pot1 sees pot2 and the cable in between.

Pot2 sees the DCB1 and the cable in between.
The DCB1 sees pot2 and the cable in between.

You have six IN/OUT systems from Source to DCB1.

You must satisfy good practice in transferring signal through all six systems.

What you are proposing has not been thought through thoroughly.

10th April 2012, 06:32 PM	#1834
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	I still cant see why mine were getting so warm at 3R0. Maybe I was just being too cautious. After about 30 mins with the lid off my sinks were at 55 Degrees C or so. I felt, that, with the lid on, things would just get too warm and things would start to fail. Maybe that's me being too cautious. Maybe 3R0 was too far. I am tempted to try 4R7 though - I've already ordered them. I seem to recall that the heatsinks were about 3.6 Deg C/W. I've used one per side so there are two IRFPs on each sink. At 10R0 they run at about 30-35 Degrees C. Last edited by KatieandDad; 10th April 2012 at 06:34 PM.

12th April 2012, 08:14 PM	#1837
schubert diyAudio Member Join Date: Sep 2008 Location: Pennsylvania, USA	Attenuator question I'm planning a 6-channel DCB1 along these lines: with Hypnotize boards in place of the DACT modules. DACT recommends 10K pots for the master and individual channel controls, while Mr. Pass recommends a nominal 25K. I've a mind to use 20K as a compromise (PEC carbon for each channel and Goldpoint for the master), though I don't know how having two pots in a row affects the total input impedance. Can anyone enlighten me as to how the attenuator impedance affects the sound? Any recommendations?

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10th April 2012, 04:02 PM	#1832
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Nick, maybe a picture as sinked?

10th April 2012, 06:22 PM	#1833
Nick77 diyAudio Member Join Date: Dec 2009 Location: Austin Tx	Had some larger sinks on hand but ran out of chassis space.

11th April 2012, 01:49 PM	#1836
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Parakalw! (=You are welcome).

12th April 2012, 11:27 PM	#1838
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Use 10K pots so not to exceed 20K in series. Those Jfets have enough input capacitance to start losing noticeable bandwidth after that driving impedance level.

13th April 2012, 02:54 AM	#1839
schubert diyAudio Member Join Date: Sep 2008 Location: Pennsylvania, USA	OK thanks Salas

13th April 2012, 09:28 AM	#1840
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	A pair of series connected pots to control volume !!!!! Have you considered each pot as a receiver and then again as a transmitter? The Source sees the pot1 and the cable in between. Pot1 sees the source and the cable in between. Pot2 sees pot1 and the cable in between. Pot1 sees pot2 and the cable in between. Pot2 sees the DCB1 and the cable in between. The DCB1 sees pot2 and the cable in between. You have six IN/OUT systems from Source to DCB1. You must satisfy good practice in transferring signal through all six systems. What you are proposing has not been thought through thoroughly.