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GB for DC coupled B1 buffer with shunt PSUs

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#1,883
Salas said:
-Pads for 5,10, and 15 mm WIMA
-Put the connector at Vout
DONE
😀
Click to expand...


Hi please ask CRT to put rectifiers at the side of the board as AC carrying wires will need to be long now and it is not esthetically pleasing. Not all transformers have such long wires. It will be better to avoid AC carrying wires near DC circuits too. Small effort with the 4 caps that are in the design now.

Also a request for moving the mute relay out of the signal path. The output can be shorted to ground "after" the 220 Ohm output resistors. It won't kill the JFETs AFAIK. If there would be any risk with 220 Ohm then 330 or 470 Ohm can be used. Or a resistor can be in series to ground for a kind of muting that is not totally 100 % silent which won't be a problem if one wants optimum sound quality while the device is used. For example 100 Ohm. For a high end version a relay in the signal path can't be accepted. When the output is shorted I would also recommend a much smaller relay for better routing of the tracks as that is more important and the relay does not need to be ultra high quality in that case too.

When the muting circuit will be placed somewhat lower the input connector can be moved to the right in the middle which will be more practical when wiring the thing. The more distance from the output the better.


Salas, I see that the 0.22 uF over the 5 LED string seems a better choice than electrolytic caps. What about 4.7 uF MKS 2 caps ? Or is the value of less importance ?
 
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#1,884
We have analyzed in the building thread that we have to up the buffer resistors to 1k surely not to lose audio Jfets when muting to ground. That impedes the subjective dynamics noticeably in my experience. The relay contact in signal path is preferable than upping the buffer resistors IMO.

Value is of less importance than quality for the Vref cap. Tests with larger have been done, the Wima 0.22uF was Fran's best, there are many to have. Whatever good film you got and fits size, works.

Don't know if CRT had way to turn things further handier, will link it to him.


Regards.
 
#1,885
OK, if the JFETS need 1KOhm that would not be optimal. I have always used the 220 Ohm and did not change values. What about ultra miniature relays with both switches in parallel ? So 2 relays, one for the left and one for the right channel. I have relays in stock ( for my own purposes ) that are 8 mm long and 5 mm wide with double switches and gold plated silver contacts. Routing would benefit too. They only take 15 mA which is roughly the same as a LED ! I also thought about muting the output to ground with one of the relay contacts while the other contacts switch on the signal to the RCA connector. A "switch over" situation that grounds the input of the power amp while the buffer is stabilizing...


The purpose of the cap is to filter out possible noise right ? So would you recommend to take out Pana FC 120 uf electrolytic caps and use small value MKT instead ?

And maybe the 4 caps for filtering need a resistor in between ?
 
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#1,886
#1,892
Salas said:
We have analyzed in the building thread that we have to up the buffer resistors to 1k surely not to lose audio Jfets when muting to ground. That impedes the subjective dynamics noticeably in my experience. The relay contact in signal path is preferable than upping the buffer resistors IMO.

Value is of less importance than quality for the Vref cap. Tests with larger have been done, the Wima 0.22uF was Fran's best, there are many to have. Whatever good film you got and fits size, works.

Don't know if CRT had way to turn things further handier, will link it to him.


Regards.
Click to expand...

If anything is planned - better to move the rectifier diodes from the inside to end - as I find this board is a great PSU regulator board as well - great stability/performance compared anything else - good rig to mod for whatever voltage you need- Even adding a fuse block ( if possible to protect the regulator of any short will be nice. It can be planned now before a group buy is planned due to great success of this GB
my 2 cents
thanks guys for making this and working on improving
kannan
 
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