Thanks for the drawing ahaja!
A pic of the boards is in post 19 here.
http://www.diyaudio.com/forums/audio-sector/151938-phono-stage-2.html#post1935063
The dual hole marked SG is signal ground on the phono board. This is connected to power supply common between C4 and C5. This is also where the TT ground is connected.
Here, signal ground SG = power PG = TT gnd.
The input is directly above it. Cap C1 is connected *behind* signal input. I am going to connect the RC network between the two holes marked SG and IN.
A pic of the boards is in post 19 here.
http://www.diyaudio.com/forums/audio-sector/151938-phono-stage-2.html#post1935063
The dual hole marked SG is signal ground on the phono board. This is connected to power supply common between C4 and C5. This is also where the TT ground is connected.
Here, signal ground SG = power PG = TT gnd.
The input is directly above it. Cap C1 is connected *behind* signal input. I am going to connect the RC network between the two holes marked SG and IN.
ok.
I only have a mica 470pf. Hopefully that will solve the problem, and I can get some good ones later...
I only have a mica 470pf. Hopefully that will solve the problem, and I can get some good ones later...
RC network in place.
No significant change with the OPA627 - I did not break it....
Need parts for bypassing the LME49990 at the adaptor level. This is the next step.
Will keep you posted.
No significant change with the OPA627 - I did not break it....
Need parts for bypassing the LME49990 at the adaptor level. This is the next step.
Will keep you posted.
yeah well in the headphone amps and low power poweramp designs by opc he gets essentially perfect results (-160db with all spurs under -148db) heres comprehensive measures of the headphone amps (only the SE-SE and BAL-SE are using the lme as front end) no rail to rail bypasses, just main slightly 'remote' 330uf polymer caps, 10uf X7R ceramics on the buffers rails and 1uf on the 49990 rails, both directly on or very close to the pins and shunting to the solid ground plane. with good PCB layout and careful wire/connection routing, there is no need for so much parallel capacitance.
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Hi,
If you see closely my DIY CNC phonostage,you will find 4 (yello colour) .1uf 50V multilayer Ceramic caps very close to Opamp socket pins.They are there to stop oscillation from Opamps.
Regards,
Sachin
If you see closely my DIY CNC phonostage,you will find 4 (yello colour) .1uf 50V multilayer Ceramic caps very close to Opamp socket pins.They are there to stop oscillation from Opamps.
Regards,
Sachin
use a solid piece of copper foil and make it your ground plane, or you can buy soic adapters that already have bypass cap positions
Could you tell me please, where can I find those soic adapters?
The goal here is to replace a socketted opa627 with the LME49990.
I got my LME49990s pre-mounted from proto-advantage.com. They are Canadian, and ordered the opamps for me, thus extreme shipping costs.
The goal here is to replace a socketted opa627 with the LME49990.
I got my LME49990s pre-mounted from proto-advantage.com. They are Canadian, and ordered the opamps for me, thus extreme shipping costs.
Hi,
Cheapest I have found here 2* Dual SOIC to DIP-8 Convert PCB Adapter SMD OPA627 | eBay
BTW PM me if you want to try CNC MM Phonostage ,(see my signature)This is the best Phonostage I have ever heard and can be built under $50.
Regards,
Sachin
Thanks for the link!
I had a close look at the adapter board I have, and it might not be possible to add the required circuit. The pins are *surface mount*. Every second pin bends the other way. Heating this is just asking for trouble. The only place to put this is on the socket pins on the underside of the board...
I had a close look at the adapter board I have, and it might not be possible to add the required circuit. The pins are *surface mount*. Every second pin bends the other way. Heating this is just asking for trouble. The only place to put this is on the socket pins on the underside of the board...
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