DIY Phonostage

[hypertone]

I started building my phonostage yesterday. It is based on the VSPS schematic, but I used an additional gain stage as my amp only has passive volume control. I estimate this thing is giving around 58dB of gain. I tried it with the OPA2134 and OPA2228 opamps. The 2228 has more prescence and definition. It's not ready to plug into the main rig yet, but it sounds pretty damn good on my Wharfedales. It is lightyears ahead of the Realistic reciever I was using in terms of clarity, definition; theres no comparison. :)

Here is the cobbled together, electrocution hazard mess. The next mission is to find an enclosure.

[GV#27]

Cool

The next mission is to find an enclosure.

I like using these.http://www.hammondmfg.com/1455ptbla.htm

[Face]

Very cool! I'd love to build something like that and have it work too. :D

[mhardy6647]

Two other options for the slightly less adventurous:
http://www.hagtech.com/bugle.html
http://www.bottlehead.com/et/adobesp.../seduction.htm

[billbillw]

I'm currently working on the PassLabs DIY Pearl phono stage. This is probably a slightly more adventurous option, and its getting hard to find the boards, the quad matched JFETs, or the dual monolithic FET (2SK389BL) for this project. I had to get mine from a German member at the DIYaudio forum who organized a group buy last year. Luckily he still had a few parts left.
http://www.passdiy.com/projects/pearlono1.htm

All the board soldering is done. I'm just waiting for a small box for the power supply to come back in stock at P.E. to finish the job. When done, the PS will have a separate dual channel power supply with a twin output toroid, discrete rectification, and 2x 10000uf caps + Mundorf M-caps for bypass. The Phono stage itself is just like what you see at the PassDIY website. Its a dual mono, fully discrete with about 59db through a two gain stage configuration. I'll snap some photos when it starts coming together.

[GV#27]

its getting hard to find .. the dual monolithic FET (2SK389BL) for this project. I had to get mine from a German member at the DIYaudio forum who organized a group buy last year. Luckily he still had a few parts left.

I am currently using a pre amp based on a circuit in Pass's Diy Op-amp articles that use those Toshiba dual jfets.Had I known they would become so scarce I would have stocked up.As it is I only have two spares.(if you are in need of one let me know)

I bet the Pearl like all of NP's designs will sound very good and that is an insane PS for a phono pre.I have built three Pass pre amps (my current one and two Bride of Zens) and an original ZEN amp.While they are simple designs circuit wise they are sonically excellent.

[billbillw]

I am currently using a pre amp based on a circuit in Pass's Diy Op-amp articles that use those Toshiba dual jfets.Had I known they would become so scarce I would have stocked up.As it is I only have two spares.(if you are in need of one let me know)

I bet the Pearl like all of NP's designs will sound very good and that is an insane PS for a phono pre.I have built three Pass pre amps (my current one and two Bride of Zens) and an original ZEN amp.While they are simple designs circuit wise they are sonically excellent.

Yeah, I'm slightly worried about one of those Toshiba Jfets going bad at some point in the future. There was just a group buy for them at DIYaudio, but they were not the BL version that the Pearl uses.

I'm really looking forward to hearing this project, but it will probably be December before I can actually get things wrapped up enough to test/listen.

[billbillw]

Dredging up an old thread here.

OK, almost 2 1/2 years later, I've got an update on my progress on my PassDIY Pearl Phono Stage.

Its embarrassing, but I never finished this. I was working feverishly on this project back in Fall 2007, then around that Thanksgiving, my wife and I found out we were expecting our 2nd child. Priorities suddenly shifted and the Pearl was boxed up in an uncompleted state. I had the Pearl boards fully stuffed and soldered, I had the power supply boards stuffed and soldered, I had all the parts on hand, a nice steel enclosure for the phono stage, a cheapie aluminum case for the power supply, a toroid for the PS, all the connectors, etc.

The only thing I really needed to do was cut holes in the cases (for IEC, fuse, power connections, RCA in/outs), mount the boards, create an umbilical cord, and wire everything up, and of course, test/troubleshoot, etc.

For more than 2 years, I just couldn't seem to find time to devote to finishing this project. It wasn't really a priority since I dismantled my dedicated 2-ch system, but it drove me slightly nuts every time I saw the box of parts sitting out in my garage.

So, last Friday, I finally said enough is enough. I'm finishing this sucker! A few hours Friday making holes in the PS case, getting the power supply mounted/wired, and making the umbilical cord. A few hours Sunday making holes in the steel case and mounting the in/outs etc. A few hours last night finalizing the wiring and testing. First results not good. I have hum and grounding issues. More work scheduled for tonight and hopefully I can get some photos (and hopefully some good sounds out of the phono stage).

[ViperZ]

1). Where are the pictures???

2). Phono stages or first preamp stages are the hardest things to wire / put together properly, because they are so sensitive to noise. Good luck!

[billbillw]

1). Where are the pictures???

Hopefully tonight.

[billbillw]

SUCCESS! Problems I was having with the Pearl last night were due to a missing ground link on the board. The instructions were vague at best, but I just had to wire a jumper between the - lead on one of the big E-caps and solder it to a ground point which connects the bottom foils to the top ground plane.

I hooked here up in an un-burned in state and only had time to listen to two albums. It was pure joy though. Incredible dynamics and a very low noise floor. The sound is very smooth without a hint of grain to it. If I didn't know better, I would say it sounds more like a tube stage than a solid state stage. Nothing like the op-amp based stages I've heard.

Snapped a few photos, but the lighting is bad tonight. I'll get some better ones tomorrow.

I'm just very happy to finally have this project finished.

[ben62670]

Congrats Bro. Can't wait to hear it:)

[billbillw]

OK, Finally wrapped up the Pearl project. Went back and added a ground wire through my umbilical cord. It didn't make any difference in sound, but for safety. This thing is even quieter once I installed it in the steel case and buttoned up everything. Its barely noisier than my empty tape input! A good 10+dB quieter than the built in phono stage on my NAD 3140, which is pretty respectable by itself. I'm pretty happy with the way things are right now. I may go back and re-do the input/outputs. I used some teflon/silver coax cable that my brother gave me a while back (something he got on surplus). It has extremely low capacitance and good sound, but its just very hard to work with. The silver center conductors are very fine and there are probably only 10 strands, so I don't think it will be that durable. I also noticed after the fact that I have my channels kinda reversed with respect to most equipment. I did R/L while facing the back of the box. If I re-do it, I will do it the conventional way of facing the front of the box and just use some normal copper hookup wire.


Anyway, here are some photos.
Power supply:





The guts of the Pearl:








Finished product (forgot to show the umbilical, which was a pain to make!)




Kinda ironic, but I just finished this up as PassDIY announced that they have developed the Pearl 2 and will have build kits available soon. Oh well.

The other bummer is that when I bought the build kit from the guy in Germany, the Euro was really strong against the dollar (thanks to Bush). So, that meant that I had to spend about 50% more than I would have if I had bought the kit a year earlier or probably even a year later.

In case you were wondering, those large caps on the Pearl boards are 10000uF each. The smaller ones are 3300uF each. Combined with the power supply, that's over 100,000uF for the whole phono stage. Talk about over kill on something that only draws about 50mA per channel!

[ViperZ]

Very nice build! Love seeing the photos!

[heiney9]

Nice work on what should be a stellar phono pre

H9