Thanks for the tip AVWERK. Finding a great transformer i can feel confident in is a challenge. I'll look into it. Ive heard ofnthem, but mostly passed them by at first notice as they seem obscure. Thats not a bad thing necessarily. I want to get the best out of the pearl i can first time through.
Any advise is great
Any advise is great
Go slow, ask LOTS of questions. The only dumb question is the one not asked.
The general order of operations -
Build and test the PSU first.
Build the regulator portion of the RIAA, test.
Build the rest. Tweak and adjust.
Enjoy!
For me, the tricky part were some of the options in the BOM. When to use a jumper, when to use a component, when to keep it open, etc. .
C15 - Leave out ( I put a jumper in by mistake)
R15 - Jumper
C22 - Leave Out, no jumper
R20 - Leave out, no jumper
C7 - Can cause issues. Wayne after the Pearl 2 article was published recommends leaving out.
Of course, double checking your component values before soldering - using the correct part. I got on a roll with all those 10R resistors and used them at R8 and R10 by mistake - they should be 10k! Also, good soldering, especially on the ground plane side of the caps, takes a little more to flow the solder well.
I learned a lot doing the Pearl 2.It took a lot longer than I planned - a couple months. Patience - number 1 skill.
C15 - Leave out ( I put a jumper in by mistake)
R15 - Jumper
C22 - Leave Out, no jumper
R20 - Leave out, no jumper
C7 - Can cause issues. Wayne after the Pearl 2 article was published recommends leaving out.
Of course, double checking your component values before soldering - using the correct part. I got on a roll with all those 10R resistors and used them at R8 and R10 by mistake - they should be 10k! Also, good soldering, especially on the ground plane side of the caps, takes a little more to flow the solder well.
I learned a lot doing the Pearl 2.It took a lot longer than I planned - a couple months. Patience - number 1 skill.
You guys are great. Im glad i found this forum!
Regarding R19, 47.5k .. Im assuming thats the default value / resistor slot for the cartidge loading.
Then theres R20, which is left open and exist as an optional slot for alternative cart loading..
Quesion: say i wish to try loading my cartridge with a higher resistance cart to brighten it up. loading R20 with a given cartridge load-value resistor to achieve a target of 100k loading (higher than 47) vs loading to achieve a target of 35kohm (lower than 47) would be accomplihed best how?
It looks like a paralell (not series)organization so adding resistors to r20 would drop the cart loading (due to the inverse mathematics af resistance in paralell - if i recall correcty)..
What would you recommend to allow easy cart load swapping within the full range of say 13k to 150k? I was thinking of replacing R19 47.5k with a couple of gold plated TO pin sockets based on the assumption thAt if i wish to go above 47.5k i will need to be able to remove it. Which leads me to ask why r20 was put in at all and why r20 is the "user selectable loading slot". My understanding is limited so any thoughts regarding the setting of cart loading would be great.
Regarding R19, 47.5k .. Im assuming thats the default value / resistor slot for the cartidge loading.
Then theres R20, which is left open and exist as an optional slot for alternative cart loading..
Quesion: say i wish to try loading my cartridge with a higher resistance cart to brighten it up. loading R20 with a given cartridge load-value resistor to achieve a target of 100k loading (higher than 47) vs loading to achieve a target of 35kohm (lower than 47) would be accomplihed best how?
It looks like a paralell (not series)organization so adding resistors to r20 would drop the cart loading (due to the inverse mathematics af resistance in paralell - if i recall correcty)..
What would you recommend to allow easy cart load swapping within the full range of say 13k to 150k? I was thinking of replacing R19 47.5k with a couple of gold plated TO pin sockets based on the assumption thAt if i wish to go above 47.5k i will need to be able to remove it. Which leads me to ask why r20 was put in at all and why r20 is the "user selectable loading slot". My understanding is limited so any thoughts regarding the setting of cart loading would be great.
Continuing to learn about transformers.
Anyone know a source for a good 2x22 r-core ... Or is it not worth the trouble? Strange they are so rare. Ill be waiting for a transformer regardless i think (as plintron and antek are favorites at the moment) and im willing to be reasonably patient to ensure i get a good one. Antek has stock coming on torroids, and plintron may make one for me though they are pricey and would have to be worth the cost. The use of EI cores would likely be okay if a good one was found as it is encased in a separate enclosure, but finding one quiet enough amidst the multitude of cheap and questionable cores would be daunting and a little random chance.
There're Chinese r-cores on eBay but I'm hesitant as they look unbranded - not just because they are chinese. Found some in france but the web info is critically limited and they are likely all 230-240v primaries.
Anyone know a source for a good 2x22 r-core ... Or is it not worth the trouble? Strange they are so rare. Ill be waiting for a transformer regardless i think (as plintron and antek are favorites at the moment) and im willing to be reasonably patient to ensure i get a good one. Antek has stock coming on torroids, and plintron may make one for me though they are pricey and would have to be worth the cost. The use of EI cores would likely be okay if a good one was found as it is encased in a separate enclosure, but finding one quiet enough amidst the multitude of cheap and questionable cores would be daunting and a little random chance.
There're Chinese r-cores on eBay but I'm hesitant as they look unbranded - not just because they are chinese. Found some in france but the web info is critically limited and they are likely all 230-240v primaries.
Okay, I must be mentally deficient - which way round do the ZTX450s go? They confused me by putting the writing on the small side. These are the Diodes Inc. parts. The pinout on Digikey's site looks opposite to the photos of 6L6's boards. Thanks for any help.
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Anyone ever house each channel of the Pearl in small separate enclosures? advantages? drawbacks?
Thanks AV werk. I ordered a 24volt model. Fingers crossed its not over voltage like yours was. If it is should I add regulator chips (redundant) to ensure stable exiting voltage, or use series resistors? Is there another way to shed voltage that might be useful? like a light or screen on something? LEDs?
Thanks AV werk. I ordered a 24volt model. Fingers crossed its not over voltage like yours was. If it is should I add regulator chips (redundant) to ensure stable exiting voltage, or use series resistors? Is there another way to shed voltage that might be useful? like a light or screen on something? LEDs?
Yes, there was at least one 3-chassis build. It looked very nice.
Let me repeat myself - It's not necessary, the external PSU is a CR filter with lots of capacitance, and the Pearl 2 PCB has an additional CR filter and regulator for each rail. What you are asking about is already designed into the project!
Also I will add that the original specified 7824/7924 can take in input voltage of 40v. So unless your transformer is wildly out of spec, there is nothing to worry about.
Cool. Didn't mean to make you repeat yourself 6L6. Thanks. My concern relates to the scenario you found yourself in, which I too may have to address. As you pointed out for us, The psu output needs to be 29-40v, though I don't want to input at max voltage, and would prefer to see around 30-35 to give some breathing room for variable power conditions.
I recall that you needed to add resistors between your caps in your build to get the PSU down a few volts because you used that nice plintron 30V. I just ordered a 24v P-Core from Hong Kong and Im hoping its not out of spec as AVWERK found with a similar P-core. If mine turns out to be, i was wanting to be prepared to handle the situation as well as you have. I dont have excess parts to play with and am preparing to place an order for a few tidbits and might throw in a few basic components now to cut down on shipping.
As you found you went over voltage with your 30V transformer, I too could if my 25v is as 'out of spec' as others have been noted to be. .. at 25v Im looking at max 35, but if it's out by 4 volts like others have been, ill need to be careful.
Its nice that the reg is on the board and in the design. Ive seen some discuss by-passing it and putting the reg in the power supply itself though im not contemplating it at this time, however would if my final voltage is too high. or if a sonic benefit might be had.
Is there an higher performance alternative to 7824/924 that might be okay to say 45V? this would be another idea.
just fishin'
.. re the PSU. any other foreseeable DC quality improvements to be made? ive picked out some 11.5ns Schottky diodes with soft switching already hoping to keep switching noise as low as possible
I recall that you needed to add resistors between your caps in your build to get the PSU down a few volts because you used that nice plintron 30V. I just ordered a 24v P-Core from Hong Kong and Im hoping its not out of spec as AVWERK found with a similar P-core. If mine turns out to be, i was wanting to be prepared to handle the situation as well as you have. I dont have excess parts to play with and am preparing to place an order for a few tidbits and might throw in a few basic components now to cut down on shipping.
As you found you went over voltage with your 30V transformer, I too could if my 25v is as 'out of spec' as others have been noted to be. .. at 25v Im looking at max 35, but if it's out by 4 volts like others have been, ill need to be careful.
Its nice that the reg is on the board and in the design. Ive seen some discuss by-passing it and putting the reg in the power supply itself though im not contemplating it at this time, however would if my final voltage is too high. or if a sonic benefit might be had.
Is there an higher performance alternative to 7824/924 that might be okay to say 45V? this would be another idea.
just fishin'
.. re the PSU. any other foreseeable DC quality improvements to be made? ive picked out some 11.5ns Schottky diodes with soft switching already hoping to keep switching noise as low as possible
What jfets did you use. Pass wants alot for theirs... Having issues orderng the boards... Te wenstore has yet again made a confusing change to the way it is listed... I ordered 2 with fets but they havent shipped and if i can get boards only cheaper i might do that asnthey want to refnd my orders because they failed to,charge shipping and asked me to re-order...
Arg... No longer listimg boards for 50$ each
Arg... No longer listimg boards for 50$ each