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Old 16th July 2012, 04:32 AM   #371
sonidos is offline sonidos  United States
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I'll have matching results this week on the jfets I purchased. I'm still putting together the order with Mouser and have mostly picked On Semi for this build.

Someone bought up all of what they had on stock for one of the OnSemi transistors, but they refilled inventory asap with several thousands. I think it was the 2N5088G.
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Old 16th July 2012, 05:49 AM   #372
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Default about having ground plane

Quote:
Originally Posted by RNMarsh View Post
No. Thats fine. can also put a bypass cap across the 10 ohms so the ground is low at Hf and only affective at 'hum' frequencies.
Also can try using shunt caps, as shown on pcb, withOUT lowest esr for damping, if needed.
I have been researching a lot about ground loops and come across digital and analog plain ground in a single pcb.one way to accomplish it is having a two ground returns for analog and digital. but this two ground plane should meet at one point in pcb and having one return gnd..having two returns for this two ground going to star gnd,,,,pcb will act like a dipole antenna and will attract more noise.

I am not an engineer but this confuse me...and needs a lot of understanding.

regards,
joel

p.s.

I have been studying your layout and want to know if you intended to separate the power gnd and signal making sure that it does not cross each other boundary.

Last edited by drowranger; 16th July 2012 at 06:03 AM.
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Old 16th July 2012, 07:00 PM   #373
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by drowranger View Post
p.s.

I have been studying your layout and want to know if you intended to separate the power gnd and signal making sure that it does not cross each other boundary.
Yes.
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Old 16th July 2012, 08:50 PM   #374
sonidos is offline sonidos  United States
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Quote:
Originally Posted by drowranger View Post
I have been studying your layout and want to know if you intended to separate the power gnd and signal making sure that it does not cross each other boundary.

See his post at Marsh headphone amp from Linear Audio

This explains his approach quite well.
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Old 17th July 2012, 12:37 AM   #375
Unomas is offline Unomas  Spain
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Originally Posted by RNMarsh View Post
Good that the Vbe match as compliments. Isnt so important that the Hfe match as the configuration and the fact they are used as followers reduces the matter. use them. Match the fets and the to92 devices for Hfe and Vbe... did those test ok for you?
Well I just finish testing the rest of semiconductors. This time I have been luckier. I could find good complements for both the 2n5087/5088 (equal Vbe and almost equal Hfe in the range 395 to 420) and JFET 2n5457/5460 (tested using the method you described in Linear Audio article gave me a range of 0.8 to 0.9 in a good bunch of pieces). So, according to your suggestion I could try with the MJE's available, despite not being a perfect match.

Anyway, I will receive the new MJE's from On Semi this week so I hope I may find better complements.

Javier
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Old 17th July 2012, 05:33 AM   #376
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Default about grounding..

check this...

http://www.hottconsultants.com/pdf_f...ixedsignal.pdf

regards,
joel
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Old 17th July 2012, 05:57 AM   #377
jcx is offline jcx  United States
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once again you need to know the frequency dependence - his digital current concentration plot only applies for MHz signal components

the partial mutual inductance Fast Henry sim I posted shows that you're only ~ 1/2 way there by 20 kHz

most Power Supply gnd contamination effects happen at low multiples of the line frequency - your only hope of controlling these currents is by physically restricting the path - discrete pwr/return trace routing - not planes

most audio current effects are also too low for the single plane concept to work

hierarchical gnds, star on star, “clean’, “dirty” paths established by explicit wires, trace geometry, ordering are the audio frequency tools you need

Ott shows how to get these low frequency effects right too - just not emphasized in that link
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Old 17th July 2012, 06:38 AM   #378
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jcx View Post
once again you need to know the frequency dependence - his digital current concentration plot only applies for MHz signal components

the partial mutual inductance Fast Henry sim I posted shows that you're only ~ 1/2 way there by 20 kHz

most Power Supply gnd contamination effects happen at low multiples of the line frequency - your only hope of controlling these currents is by physically restricting the path - discrete pwr/return trace routing - not planes

most audio current effects are also too low for the single plane concept to work

hierarchical gnds, star on star, “clean’, “dirty” paths established by explicit wires, trace geometry, ordering are the audio frequency tools you need

Ott shows how to get these low frequency effects right too - just not emphasized in that link
Dont rule out shielding for use of planes opposite the pcb wires and for low Z at Mhz for stability. -RNM
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Old 17th July 2012, 06:51 AM   #379
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Default this bothers me....

Is it ok not to use bridge on those two ground planes?how about the high resistance it would create plus running wires to star gnd.?are these ideas applicable only for mixed analog and digital signal?how about gnd loops are these cause by high resistance?

as what you have said gnd planes are for shield and would be very difficult to separate diff gnd, returns if I use it.



regards,
joel
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Old 17th July 2012, 06:38 PM   #380
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by drowranger View Post
Is it ok not to use bridge on those two ground planes?how about the high resistance it would create plus running wires to star gnd.?are these ideas applicable only for mixed analog and digital signal?how about gnd loops are these cause by high resistance?

as what you have said gnd planes are for shield and would be very difficult to separate diff gnd, returns if I use it.


regards,
joel
For perfectionist way -- I always advocate having the power supply reg right at the amp circuit. .. shortest distance from circuit and ditto for the grounds.
Integrate the pwr supply onto the amp pcb is best way. Or, second best, locate the pwr supply pcb right close to the amp pcb.

Last edited by RNMarsh; 17th July 2012 at 06:41 PM.
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