The Phonoclone and VSPS PCB Help Desk - Page 136

TB · 15th March 2010, 12:20 AM

Hello,
I have been working on two projects: VSPS and opamp-based headphone amplifier. For VSPS everything is clear thanks for this post and RJM website, but when I started to search the forum for more information about noise and proper grounding I have found this thread: http://www.diyaudio.com/forums/chip-...grounding.html
The thread also refers to Rod Elliott website article: Earthing (Grounding) Your Hi-Fi - Tricks and Techniques.
My question is about one detail which cought my attention: the way how ground connection is made in ESP schematic and not used in RJM PSU connection (please disregard ground loop braker shown in ESP site. My question is not about it).
Let's talk about VSPS PSU: RJM Audio - Construction Guide
In the first drawing of the PSU, the earth connection from the IEC socket goes directly to the case (there is also a note to connect transformer's shield if exists). So, this is the same for both threads. Now, what is different is secondary side of the transformer. In RJM site the green common wire, COM, goes directly with V+ and V- out to the amp case. There, I guess, all signal grounds are connected together, and with added COM connection are connected to the amp's case.
The detail, which is different from VSPS PSU is connection of common wire, COM, on the secondary side of the transformer to the case in ESP PSU.
Sorry, if that question was already asked, but the thread grow up to really big one and I was not able to find an answer. Are both approaches correct in reference to different project than VSPS? As I have mentioned at the beginning I want to build headphone amplifier based on OPA134 chips with external PSU. Like VSPS, I want to put voltage regulators by each chip. Since I am a beginner I am not sure which option to use and not to have problems with hum.
My worry is also about safety. If PSU and amp's cases are not linked together, like in VSPS, will fuse be triggered if something happens in amplifier case?
Thank you for the help !!!!!

rjm · 15th March 2010, 07:06 AM

The grounding scheme of the VSPS etc. will work equally well for a headphone amplifier. Try it and see. There is no risk of electrical shock as the output voltages are isolated and low.

High voltages, the story changes. I'd use a loop breaker as described by ESP for all but the amplifier, which can be earthed directly.

TB · 16th March 2010, 02:12 AM

Hello,
Thanks for the replay.

barossi · 16th March 2010, 11:10 AM

Hi,
could you please tell me, what is the input AC voltage for the VSPS 300 board?

KR Barossi

rjm · 16th March 2010, 11:50 AM

All the boards have V++ V-- and COM pads that take the rectified output from 12 VAC secondaries.

barossi · 12:31 PM

Hi,
Thanks!

KR Barossi

presbel · 18th March 2010, 07:30 AM

Hi,
I am planning to buy the phonoclone 3 board but I would like first to inquire if I can use OPA 627 instead of OPA27.

Rey

rjm · 18th March 2010, 10:02 AM

The 627 is the JFET input version of the 27. It should work without any difficulty though I haven't tried it.

I can tell you that the Phonoclone output noise floor will be 5 dB higher, however.

tkwou · 18th March 2010, 06:16 PM

Would the LME49713 current feedback opamp work in the first stage?

presbel · 19th March 2010, 04:08 AM

Hi,
Thanks.

Rey

15th March 2010, 12:20 AM	#1351
TB diyAudio Member Join Date: Jun 2004 Location: Northern VA	External PSU and amp case connection Hello, I have been working on two projects: VSPS and opamp-based headphone amplifier. For VSPS everything is clear thanks for this post and RJM website, but when I started to search the forum for more information about noise and proper grounding I have found this thread: http://www.diyaudio.com/forums/chip-...grounding.html The thread also refers to Rod Elliott website article: Earthing (Grounding) Your Hi-Fi - Tricks and Techniques. My question is about one detail which cought my attention: the way how ground connection is made in ESP schematic and not used in RJM PSU connection (please disregard ground loop braker shown in ESP site. My question is not about it). Let's talk about VSPS PSU: RJM Audio - Construction Guide In the first drawing of the PSU, the earth connection from the IEC socket goes directly to the case (there is also a note to connect transformer's shield if exists). So, this is the same for both threads. Now, what is different is secondary side of the transformer. In RJM site the green common wire, COM, goes directly with V+ and V- out to the amp case. There, I guess, all signal grounds are connected together, and with added COM connection are connected to the amp's case. The detail, which is different from VSPS PSU is connection of common wire, COM, on the secondary side of the transformer to the case in ESP PSU. Sorry, if that question was already asked, but the thread grow up to really big one and I was not able to find an answer. Are both approaches correct in reference to different project than VSPS? As I have mentioned at the beginning I want to build headphone amplifier based on OPA134 chips with external PSU. Like VSPS, I want to put voltage regulators by each chip. Since I am a beginner I am not sure which option to use and not to have problems with hum. My worry is also about safety. If PSU and amp's cases are not linked together, like in VSPS, will fuse be triggered if something happens in amplifier case? Thank you for the help !!!!!

15th March 2010, 07:06 AM	#1352
rjm Richard Murdey diyAudio Member Join Date: May 2004 Location: Kyoto Blog Entries: 32	The grounding scheme of the VSPS etc. will work equally well for a headphone amplifier. Try it and see. There is no risk of electrical shock as the output voltages are isolated and low. High voltages, the story changes. I'd use a loop breaker as described by ESP for all but the amplifier, which can be earthed directly. __________________ RJM Audio (phonoclone.com)

16th March 2010, 11:50 AM	#1355
rjm Richard Murdey diyAudio Member Join Date: May 2004 Location: Kyoto Blog Entries: 32	All the boards have V++ V-- and COM pads that take the rectified output from 12 VAC secondaries. __________________ RJM Audio (phonoclone.com)

16th March 2010, 12:16 PM	#1356
barossi diyAudio Member Join Date: Oct 2003 Location: near hamburg	Hi, Thanks! KR Barossi Last edited by barossi; 16th March 2010 at 12:31 PM.

18th March 2010, 10:02 AM	#1358
rjm Richard Murdey diyAudio Member Join Date: May 2004 Location: Kyoto Blog Entries: 32	The 627 is the JFET input version of the 27. It should work without any difficulty though I haven't tried it. I can tell you that the Phonoclone output noise floor will be 5 dB higher, however. __________________ RJM Audio (phonoclone.com)


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16th March 2010, 02:12 AM	#1353
TB diyAudio Member Join Date: Jun 2004 Location: Northern VA	Hello, Thanks for the replay.

16th March 2010, 11:10 AM	#1354
barossi diyAudio Member Join Date: Oct 2003 Location: near hamburg	Hi, could you please tell me, what is the input AC voltage for the VSPS 300 board? KR Barossi

18th March 2010, 07:30 AM	#1357
presbel diyAudio Member Join Date: Sep 2006	Hi, I am planning to buy the phonoclone 3 board but I would like first to inquire if I can use OPA 627 instead of OPA27. Rey

18th March 2010, 06:16 PM	#1359
tkwou diyAudio Member Join Date: Feb 2006 Location: Vancouver	Would the LME49713 current feedback opamp work in the first stage?

19th March 2010, 04:08 AM	#1360
presbel diyAudio Member Join Date: Sep 2006	Hi, Thanks. Rey

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