PCB for Joachim Gerhard's Filter
Hello All -
I got interested in this thread and made a PCB for the filter circuit by Joachim Gerhard. It uses MELF resistors and 805 Capacitors. I will be etching the pcb this weekend and try it out.
Thought would publish the PCB so that interested DIYers can make one for themself. The pdf file has the 100% scaled image for PCB and the image has the silk screen on it. Its on the top layer so make sure you do a mirror print when transferring to pcb.
Cheers,
free2dev
Hello All -
I got interested in this thread and made a PCB for the filter circuit by Joachim Gerhard. It uses MELF resistors and 805 Capacitors. I will be etching the pcb this weekend and try it out.
Thought would publish the PCB so that interested DIYers can make one for themself. The pdf file has the 100% scaled image for PCB and the image has the silk screen on it. Its on the top layer so make sure you do a mirror print when transferring to pcb.
Cheers,
free2dev
Attachments
For proper DC tracking, you need to thermally couple the JFETs, so they want to be placed closed to each other and also thermal glued to a common heat sink.
Our prototype PCB is being factory manufactured right now, but the Fastron inductors might take longer from Mouser.
Will keep you posted once we have them.
Patrick
Our prototype PCB is being factory manufactured right now, but the Fastron inductors might take longer from Mouser.
Will keep you posted once we have them.
Patrick
Thanks Patrick for the suggestion. I will try to move the JFETs closer and when I build I will stick a heat sink on top of them.
free2dev
free2dev
I found another design that uses coils in the anti aliasing filter. This is third order.file:///Users/admin/Documents/Ray's%20Audio%20Page.webarchive
Maybe this works better :file:///Users/admin/Documents/Ray's%20Audio%20Page.webarchive
go to CD discrete output stage.
go to CD discrete output stage.
Here's the datasheet for the 10mH coils he's using : http://www.farnell.com/datasheets/50809.pdf
What it doesn't tell us is the SRF - I'd expect 10mH to have a very low figure... The plots he shows look to be a from a simulation rather than measured.
What it doesn't tell us is the SRF - I'd expect 10mH to have a very low figure... The plots he shows look to be a from a simulation rather than measured.
I have difficulty to find that link again myself but i will try again.
This Panasonic coils are even recommended for Audio, good.
This Panasonic coils are even recommended for Audio, good.
Discrete uitgangstrap
http://www.raylectronics.nl/pdfs/CD_outputstage_PCB.pdf
is this what you are looking for ?
I can read Dutch ;-)
JBdV
http://www.raylectronics.nl/pdfs/CD_outputstage_PCB.pdf
is this what you are looking for ?
I can read Dutch ;-)
JBdV
Good, we have the link now. In fact my filter can be redesigned for 3rd order too if so desired without much effort.
I built Joachim Gerhard buffer / filter over the weekend and listened to it for few hours on Sunday. Sounds good and I like it. Will play around with it for some more time. I used the Fastron Inductor from mouser.com.
Thanks!
free2dev
Thanks!
free2dev
Thanks, that is good new, so the Fastron works. What happens if you jumper it ?
I made some simulation on a 3rd order filter but i can not make it phase linear without drop in the treble with the default 4,7nF cap. I like the second order better anyway. I really listened careful so that it does not take too much sparkle and air away.
I made some simulation on a 3rd order filter but i can not make it phase linear without drop in the treble with the default 4,7nF cap. I like the second order better anyway. I really listened careful so that it does not take too much sparkle and air away.
Hi Joachim, I haven't tried it. I will jumper it when I get home and see how it sounds.
-free2dev
-free2dev
We are still waiting for delivery from Mouser. 🙁
Joachim, no problem changing the 4.7n cap if necessary.
Patrick
Joachim, no problem changing the 4.7n cap if necessary.
Patrick
I made some simulations and the price of the 3rd oder filter is more latency or an undershot of the impulse response so i stick with the second order filter. What could be tried is to lover the "ballast" resistor before the buffer and then we could use a lower inductance coil with potentially higher self resonance but then we load the DA converter more and that gives more distortion. I really do not want to go under 10kOhm or the buffer makes not much sense. I think my solution is as good as it gets, all considered.
Wow, that was fast. Looks very good. I will listen to it carefully.
I just made some improvements to my system that have to do with more precise and transparent volume control plus new speaker placement, so i am in a better position now.
I just made some improvements to my system that have to do with more precise and transparent volume control plus new speaker placement, so i am in a better position now.
I was requested by PM to give an update for the Joachim gerhard buffer.
We have the PCBs as you can see. We matched the BF862's.
But before we could match the J111, the team member involved has a family emergency.
That has taken him out of hobbies for the past 2.5 weeks.
As you would all appreciate, work and family come first for us.
I cannot give you a date as to when that situation would be relieved, such is its nature.
So I can only ask for your patience in the meantime.
Patrick
We have the PCBs as you can see. We matched the BF862's.
But before we could match the J111, the team member involved has a family emergency.
That has taken him out of hobbies for the past 2.5 weeks.
As you would all appreciate, work and family come first for us.
I cannot give you a date as to when that situation would be relieved, such is its nature.
So I can only ask for your patience in the meantime.
Patrick
- Status
- Not open for further replies.