Wonderful!! Congratulations on such a fine construction.
It appears to be a very well done project. I like the common regulators.
It appears to be a very well done project. I like the common regulators.
Some measurements. Comparison of the Pearl Two "front end" with supplied JFETs on the stock boards vis a vis OPA2604 run at the top of the permissible voltages. Gain is identical for each, and each preamplifier is loaded resistively with 6k8:
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That's why the Pearl is best with a MC cartridge. With a 5mV MM cartridge @1kHz you get 100mV production at 20kHz x 35dB gain = a lot of distortion. With a 500uV MC cartridge you're OK.
(I'm getting 32dB gain in the first stage btw)
(I'm getting 32dB gain in the first stage btw)
Thank you Lajozs.
Here are three fotos of my drawings for the boards, maybee they can be to some help. They are seen from the component side. When I do my circuitboards I make a copy of my drawing and tape it on the component side of the of the board. I drill through and after som work whith the sharp cupperedges round the hole whith a handheld drill, some cleaning and a few gentle whipes whith steel wool I handpaint the cuppertrases whith a special pen. Then I ets the boards and they are ready for soldering!
By the way I also have bult some other Passamps. 20W from the -70's, ZEN mk2, B1 and F5 turbo.
Here are three fotos of my drawings for the boards, maybee they can be to some help. They are seen from the component side. When I do my circuitboards I make a copy of my drawing and tape it on the component side of the of the board. I drill through and after som work whith the sharp cupperedges round the hole whith a handheld drill, some cleaning and a few gentle whipes whith steel wool I handpaint the cuppertrases whith a special pen. Then I ets the boards and they are ready for soldering!
By the way I also have bult some other Passamps. 20W from the -70's, ZEN mk2, B1 and F5 turbo.
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@Abrandt:
Thanks for the attachements!
Nice stereo job on such a little piece of PCB (your figures attested by the number of squares 🙂). Unfortunately, my special pen (used last time in '90s) has dried up long ago. My last circuits were made with an engraving handtool: not very comfortable, ugly a bit - but efficient...
Thanks for the attachements!
Nice stereo job on such a little piece of PCB (your figures attested by the number of squares 🙂). Unfortunately, my special pen (used last time in '90s) has dried up long ago. My last circuits were made with an engraving handtool: not very comfortable, ugly a bit - but efficient...
Hi Boys,
Has anyone tried integrating a pair of Cinimag step up transformers in a pearl two case to have a "built in MM/MC option?- if so how was it, I am thinking of doing this.
cheers
Johnny
Has anyone tried integrating a pair of Cinimag step up transformers in a pearl two case to have a "built in MM/MC option?- if so how was it, I am thinking of doing this.
cheers
Johnny
Abrandt - Thank you for showing your layout notes... it seems that you made very nice PCB... I have always liked smooth lines and turns instead of 90deg angles as CAD programs make.
Johnnycr100 - There's no reason why it won't work, give it a try. 🙂 CineMag makes very nice transformers.
Johnnycr100 - There's no reason why it won't work, give it a try. 🙂 CineMag makes very nice transformers.
Thank you Wayne and Nelson, for your never ending support of us DIYers! Even without being able to build all of your designs, I had so many great nights reading and discussing these designs I lost count! Luckily BoSoZ kept me company all this time 😀.
Now that Toshiba has ended the production of the 2SK370/2SK170 families of JFETs, they are getting rather rare. On a Dutch forum we try to build at least 10 Pearl two's but locating a supplier who can deliver like 150+ devices is a little difficult. 150+ to be able to match and have some spare seems allmost undoable. Without reading all the pages on this brilliant site so far, is there a good replacement for these JFETs?
Now that Toshiba has ended the production of the 2SK370/2SK170 families of JFETs, they are getting rather rare. On a Dutch forum we try to build at least 10 Pearl two's but locating a supplier who can deliver like 150+ devices is a little difficult. 150+ to be able to match and have some spare seems allmost undoable. Without reading all the pages on this brilliant site so far, is there a good replacement for these JFETs?
Aliexpress is full with 2SK170...
Are they chinese fake or can be considered? Any experience?
Are they chinese fake or can be considered? Any experience?
no way to guess.
get them to give you a samples to test.
otherwise, go with a safe bet of purchasing LS devices or buy 2SK170 only from a "KNOWN RELIABLE SOURCE".
mlloyd1
get them to give you a samples to test.
otherwise, go with a safe bet of purchasing LS devices or buy 2SK170 only from a "KNOWN RELIABLE SOURCE".
mlloyd1
Power supply is completed and working! 31.5V on one side and -31.6V on the other. I'm going to use DMX/XLR cable as my umbilical and waiting for my 10mm faceplate back from the machine shop to mount the Neutrik XLR connector.
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Trial Run!
First impression - where was that bass before?
Second impression - dead quiet even with no chassis spaghetti wiring!
Third impression - my tube phono pre sure added coloration
Fourth impression - more detail
I think I'll keep it! 😀
I also had to do a little creative component placement as my NOS ERO caps that I used in the RIAA filter were a touch bigger than the WIMA.
First impression - where was that bass before?
Second impression - dead quiet even with no chassis spaghetti wiring!
Third impression - my tube phono pre sure added coloration
Fourth impression - more detail
I think I'll keep it! 😀
I also had to do a little creative component placement as my NOS ERO caps that I used in the RIAA filter were a touch bigger than the WIMA.
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Nice... Isn't it? 🙂 🙂 🙂
Box it up and call it done!
... And I see you buy the best interconnects in the world also. Well done.
Box it up and call it done!
... And I see you buy the best interconnects in the world also. Well done.
Use Spencer @ FETAudio ... reasonable prices, matched devices and fast shipping. Oh, and NO FAKES!
FWIW, I had some reservations about this preamp being enough gain for my DL-103R. I am running it in stock configuration (50dB) and I have PLENTY of gain with no need for a SUT!
Just thought I'd share for those concerned running low output MC's.
Just thought I'd share for those concerned running low output MC's.