Pearl Two

6 ,

I went on you tube to get the set up advice . The cartridge is a Pro S Ortofon.

The counter weight just wont adjust . Set as advised , float the arm and Zero the weight , then add weight ,but nothing happens . I had to set it by ear .

Keeping the same arm for the moment . There are other upgrades I'd like to do first : PSU , cartridge , oil damping .

thanks .
 
Get one of those precision scales from Dealextreme. They cost next to nothing and are way more accurate in setting tracking weight than just believing what the indicator on the tonearm says.

Anyway, congratulations on your build, I too would like to see some pictures and hear more detailed experiences.
 
6 ,

I went on you tube to get the set up advice . The cartridge is a Pro S Ortofon.

The counter weight just wont adjust . Set as advised , float the arm and Zero the weight , then add weight ,but nothing happens . I had to set it by ear .

Keeping the same arm for the moment . There are other upgrades I'd like to do first : PSU , cartridge , oil damping .

thanks .

Once the weight indicator ring is zero and the arm is floating, turn the counterweight (not the indicator ring) so that it screws in and moves closer to the tonearm pivot. The closer the weight to the pivot, the more weight on the cartridge.
 

6L6

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kop89 - look at the original Pearl 2 article on PassDIY - there is a partial BOM with some part numbers, and you can take a look at the suggested parts to see what dimensions you need. It's a great way to find out that kind of stuff, and some pieces and parts might be NLA or obsolete (probably not for the Pearl 2, it's a recent article) you can get the basic idea of what is needed by cross-referencing the datasheets from the BOM parts with similar parts.
 
kop89 - look at the original Pearl 2 article on PassDIY - there is a partial BOM with some part numbers, and you can take a look at the suggested parts to see what dimensions you need. It's a great way to find out that kind of stuff, and some pieces and parts might be NLA or obsolete (probably not for the Pearl 2, it's a recent article) you can get the basic idea of what is needed by cross-referencing the datasheets from the BOM parts with similar parts.

Here's my BOM updated as of a year ago. Hope this is useful.

http://dl.dropbox.com/u/370002/Pearl-2%20BOM.xls
 
Quick eyeball from the experts. I took Salas suggestion to increase the resistance of R21-R24 to increase the voltage around Q3. My differed quite a bit from Wayne's. A few of you said this was probably due to different values for ldss on the FETs I had vs what Wayne had.

I swapped in 20R resistors for the R21-R24 and measured - see attached. Original values for 10R in in parentheses. Voltages are pretty close, still a little under.

Close enough? How important is to be spot on with these?

Also, my voltage across R6 is higher, at 1.8 vs 1.5. Is this acceptable, close enough?

It sounds really good on the bench with my cheap test system - no issues. As I put a fair bit of expense and time into this project, I would like to tune it to its full potential, within reason.
 
Here is the photo of my measurements.
 

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diyAudio Chief Moderator
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Quick eyeball from the experts. I took Salas suggestion to increase the resistance of R21-R24 to increase the voltage around Q3. My differed quite a bit from Wayne's. A few of you said this was probably due to different values for ldss on the FETs I had vs what Wayne had.

I swapped in 20R resistors for the R21-R24 and measured - see attached. Original values for 10R in in parentheses. Voltages are pretty close, still a little under.

Close enough? How important is to be spot on with these?

Also, my voltage across R6 is higher, at 1.8 vs 1.5. Is this acceptable, close enough?

It sounds really good on the bench with my cheap test system - no issues. As I put a fair bit of expense and time into this project, I would like to tune it to its full potential, within reason.

It looks much better for voltage bias now. ~23mA total draw by the JFETs when the original annotation suggests 20mA (VR9/R9). Also 0.7V Vbe for Q3 looks normal at the current it passes. How is the current sharing between JFETS? I.e. is the mV drop across each 20R fairly close? Should be about 115mV? 1.8V across R6 means 1.2mA VS 1mA which is easily done if the LED is happier for forward voltage drop than in the prototype. No big deal.
 

6L6

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Salas has the proper analysis... It looks great.

The 1.8v across the resistor could be trimmed with a different LED, but honestly, don't bother.

Set it up on your main system and play a bunch or records. If it sounds good, play a bunch more. After 30-40 discs open it up and re-measure, just to see if it's stable. If it is (which it will be in all probability) then you now have permission to buy a new cartridge or start a new project. :) :) :) :) :)
 
diyAudio Chief Moderator
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As for the spot on importance question, look at this Toshiba chart. Its the transconductance VS drain current. As you see 5 to 5.6 is practically the same just above the 30 millisiemens mark. So your input stage gain is very close to the original (23mA/4JFETS=5.75mA each on average VS 5mA in original). The larger resistors promote better sharing also. Wayne knew that there is an optimal region at about 5-6mA for the type no matter if adding a bit of nVsqrtHz from the net Rs resistance (Value/4). Its a thermal trade off for each one's dissipation at IDSS and noise most probably. 8.5V or 9.4V VDS at about 0.1V VGS look linear alike. Gate leakage current should be very close too. In a nutshell you should be sorted as you are.
 

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Salas has the proper analysis... It looks great.

The 1.8v across the resistor could be trimmed with a different LED, but honestly, don't bother.

Set it up on your main system and play a bunch or records. If it sounds good, play a bunch more. After 30-40 discs open it up and re-measure, just to see if it's stable. If it is (which it will be in all probability) then you now have permission to buy a new cartridge or start a new project. :) :) :) :) :)

Thanks. My audio budget in Quicken has been red flagged by the wife. :eek: May have to cool it for a bit. I do need to get a chassis as I have most of the parts for a B1. Buying the chassis is the hardest part on the wallet.
 
As for the spot on importance question, look at this Toshiba chart. Its the transconductance VS drain current. As you see 5 to 5.6 is practically the same just above the 30 millisiemens mark. So your input stage gain is very close to the original (23mA/4JFETS=5.75mA each on average VS 5mA in original). The larger resistors promote better sharing also. Wayne knew that there is an optimal region at about 5-6mA for the type no matter if adding a bit of nVsqrtHz from the net Rs resistance (Value/4). Its a thermal trade off for each one's dissipation at IDSS and noise most probably. 8.5V or 9.4V VDS at about 0.1V VGS look linear alike. Gate leakage current should be very close too. In a nutshell you should be sorted as you are.

I appreciate the explanation. I get the gist of what you are saying, but I still have fair bit to learn. Thanks for reviewing with me.
 
go to Ikea and buy wooden drawer

then wax it and voila!

if screening is needed - use either copper or Al foil laid on inside walls

if good for Stratocaster , it's good for phono gadget
I have the Parmetal cases for the Pearl 2. I may need to be resourceful for the B1.

My F5 is sitting on the floor in the Living Room. Very low WAF. My wife made me custom order a cherry end table to put it on. Also got the quote from the landscaper yesterday to replace a retaining wall.:eek: