Mpp - Page 749

Joachim Gerhard · 5th October 2012, 10:53 AM

Alfred, i have read your instructions. I like it a lot.
I will read the offset part again and may do some additions i talked about.
Also on the matching of the input devices.

MiiB · 11:01 AM

The buffer off set can be adjusted with the resistor. with the SK170 and 5 ohm it is app 60-70 mV.. with 11 ohms it practically Nill... (8,5 mA through the Jfet)

RCruz · 5th October 2012, 07:37 PM

Quote:

Originally Posted by MiiB

The buffer off set can be adjusted with the resistor. with the SK170 and 5 ohm it is app 60-70 mV.. with 11 ohms it practically Nill... (8,5 mA through the Jfet)

Thank you Miib... precious info

Algar_emi · 09:40 PM

Hi. Since the official R3 PCB was no longer available, I did my own

I also did a pcb for the pre-reg according to the included schematic. I should have them built by the end of the day.
The latest version of the parts list match these PCB.

Algar_emi · 5th October 2012, 09:45 PM

Question about the BC327/337 HFE matching. Is it necessary to match all the transistor one one channel pcb, or just the Gain Cell ones (Q2,25,26,29 and Q1,30,31,32). And finally, I guest it is necessary to match both channel together as well to get the same gain?

Thanks.

Stefanoo · 5th October 2012, 09:55 PM

yep the input devices.
also it would be good to match the current mirror (not the one on the servo) for best performance.

Bksabath · 5th October 2012, 10:09 PM

Quote:

Originally Posted by Algar_emi

Question about the BC327/337 HFE matching. Is it necessary to match all the transistor one one channel pcb, or just the Gain Cell ones (Q2,25,26,29 and Q1,30,31,32). And finally, I guest it is necessary to match both channel together as well to get the same gain?

Thanks.

Hesener Put this mach beter way in the guide.
Paradise Builders

Se post 13

Match 10% or better pick closest matched and fit in groups as in circuit
Imput Current mirrors and soon

Joachim Gerhard · 5th October 2012, 10:17 PM

Cool, we have a PCB for the prereg.

Algar_emi · 5th October 2012, 10:23 PM

Here the completed PCB. Do we need a GB for the Pre-Reg PCB

Joachim Gerhard · 5th October 2012, 11:40 PM

Well, i was designing a prereg too that could lead to a group buy. That is obsolete now.
I would like to try your PCB and add chokes and output caps eventually.

5th October 2012, 10:55 AM	#7482
MiiB diyAudio Member Join Date: May 2005 Location: Denmark	The buffer off set can be adjusted with the resistor. with the SK170 and 5 ohm it is app 60-70 mV.. with 11 ohms it practically Nill... (8,5 mA through the Jfet) __________________ http://www.linkedin.com/pub/michael-...esen/a/a55/544 http://www.raidho.dk/ Last edited by MiiB; 5th October 2012 at 11:01 AM.

5th October 2012, 09:55 PM	#7486
Stefanoo diyAudio Member Join Date: Apr 2006 Location: italia - ora USA -WI	yep the input devices. also it would be good to match the current mirror (not the one on the servo) for best performance. __________________ Stefano

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5th October 2012, 10:53 AM	#7481
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Alfred, i have read your instructions. I like it a lot. I will read the offset part again and may do some additions i talked about. Also on the matching of the input devices.

5th October 2012, 09:45 PM	#7485
Algar_emi diyAudio Member Join Date: Oct 2002 Location: Canada, Qc	Question about the BC327/337 HFE matching. Is it necessary to match all the transistor one one channel pcb, or just the Gain Cell ones (Q2,25,26,29 and Q1,30,31,32). And finally, I guest it is necessary to match both channel together as well to get the same gain? Thanks.

5th October 2012, 10:17 PM	#7488
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Cool, we have a PCB for the prereg.

5th October 2012, 11:40 PM	#7490
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Well, i was designing a prereg too that could lead to a group buy. That is obsolete now. I would like to try your PCB and add chokes and output caps eventually.