Salas hotrodded blue DCB1 build - Page 218

wushuliu · 01:45 AM

Quote:

Originally Posted by Salas

Let us know, I hope the sinking is enough for 1A yes? 1A means 20W dissipation per rail constantly for DCB1 usual voltages across the power semis.

Ended up replacing all fets with new and spares - 240s and 9140s. This time with lots of arctic silver on fets/pads/chassis contact. Now I have a tight -10.2 and 10v. With 1.5R instead of 1R I am pulling 866mA and 1A

. But I have a PC fan on the enclosure (Antek 12in*12*2) so we'll see how it goes. An infrared thermometer is on the way so I can properly gauge temps. Not sure what happened before, must have shorted something?

Salas · 25th August 2012, 02:13 AM

Probably no good thermal transfer because you caught a couple of loose screws, when you pushed the amperage, boom. Can you feel a difference in your system from 600mA to circa 1A?

wushuliu · 25th August 2012, 08:34 AM

1A is more refined with increased three dimensional qualities. Not huge but noticeable. I also swapped out Muse KW 100ufs for Silmic IIs and the 470r metals for carbon comp. Not sure which is responsible but delivery is smoother - there was a slight etchiness before, not bad per se but board sounds different now.

Heat dissipation is MUCH better; the chassis is barely warm by the fets at shutdown.

Salas · 25th August 2012, 09:01 AM

Some tightening and a good thermal compound can do wonders.

wushuliu · 1st September 2012, 07:09 AM

Out of curiosity: what is the lowest value that can be used for output impedance resistors?

Salas · 1st September 2012, 08:37 AM

Takes to know it does not oscillate in a certain setup by scoping the output down to a minimal value. Maybe 100 Ohm or less depending on interconnects used.

wushuliu · 1st September 2012, 08:50 AM

Ok, I've been using 100R with dcb1 more or less directly to the amp with only a few inches of wire. I am curious because with this current build and the previous I have found the lower I go the more dynamic, open, and transparent the sound (previous amp had 7kinput imp, current amp 16k)...

AndrewT · 1st September 2012, 10:49 AM

A lower value of gate stopper allows the FET to operate faster. The filter created by the gate stopper and the internal capacitance of the FET moves to a higher frequency.

You can go as low as you like with the gate stopper value. The limit will be when instability sets in.
You will need to test the circuit thoroughly with all manner of interference and fast changing demands to ensure that stability is good. The lower the gate stopper value the more thorough your testing regime must be.

Or just play safe and use the recommended value or half the recommended value if you like to take chances.

But listening and hearing extra detail may be the sign/symptom that the PSU has already reached the instability operating area and the non smooth output is affecting the amplifier and giving the "sound effect" of extra detail.
you really need to test the PSU properly if you reduce the gate stopper value.

wushuliu · 1st September 2012, 10:31 PM

Ok, thanks Andrew. I'll play it safe and keep things as they are.

boywonder · 2nd September 2012, 01:27 AM

Quote:

Originally Posted by AndrewT

you really need to test the PSU properly if you reduce the gate stopper value.

Can you share some details of how to do this? (The PSU testing part, I know how to change the gate stopper

)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
dcb1 buffer with shunt reg.	merlin2069er	Swap Meet	0	3rd August 2010 05:25 PM
F2 and DCB1 parts selection - please advice!	DQ	Pass Labs	6	25th November 2009 03:20 PM
Y B Blue - how blue LED improves the CD playback	Peter Daniel	Digital Source	176	25th September 2003 07:40 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

25th August 2012, 02:13 AM	#2172
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Probably no good thermal transfer because you caught a couple of loose screws, when you pushed the amperage, boom. Can you feel a difference in your system from 600mA to circa 1A?

25th August 2012, 08:34 AM	#2173
wushuliu diyAudio Member Join Date: May 2008 Location: Los Angeles	1A is more refined with increased three dimensional qualities. Not huge but noticeable. I also swapped out Muse KW 100ufs for Silmic IIs and the 470r metals for carbon comp. Not sure which is responsible but delivery is smoother - there was a slight etchiness before, not bad per se but board sounds different now. Heat dissipation is MUCH better; the chassis is barely warm by the fets at shutdown.

25th August 2012, 09:01 AM	#2174
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Some tightening and a good thermal compound can do wonders.

1st September 2012, 07:09 AM	#2175
wushuliu diyAudio Member Join Date: May 2008 Location: Los Angeles	Out of curiosity: what is the lowest value that can be used for output impedance resistors?

1st September 2012, 08:37 AM	#2176
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Takes to know it does not oscillate in a certain setup by scoping the output down to a minimal value. Maybe 100 Ohm or less depending on interconnects used.

1st September 2012, 08:50 AM	#2177
wushuliu diyAudio Member Join Date: May 2008 Location: Los Angeles	Ok, I've been using 100R with dcb1 more or less directly to the amp with only a few inches of wire. I am curious because with this current build and the previous I have found the lower I go the more dynamic, open, and transparent the sound (previous amp had 7kinput imp, current amp 16k)...

1st September 2012, 10:49 AM	#2178
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	A lower value of gate stopper allows the FET to operate faster. The filter created by the gate stopper and the internal capacitance of the FET moves to a higher frequency. You can go as low as you like with the gate stopper value. The limit will be when instability sets in. You will need to test the circuit thoroughly with all manner of interference and fast changing demands to ensure that stability is good. The lower the gate stopper value the more thorough your testing regime must be. Or just play safe and use the recommended value or half the recommended value if you like to take chances. But listening and hearing extra detail may be the sign/symptom that the PSU has already reached the instability operating area and the non smooth output is affecting the amplifier and giving the "sound effect" of extra detail. you really need to test the PSU properly if you reduce the gate stopper value.

1st September 2012, 10:31 PM	#2179
wushuliu diyAudio Member Join Date: May 2008 Location: Los Angeles	Ok, thanks Andrew. I'll play it safe and keep things as they are.