So I have some of these. Not sure where I got them, but it was around the time I was building a chipamp. If I use these instead of mica and thermal grease on the 7824 (u1) and 7924 (u2), do I still need the thermal grease. Also does anyone know what material these are made of? They feel like ceramic kind of heavy and thick.
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It's hard to tell with one out-of-focus picture, but since it's much more common than beryllium oxide, it's more likely aluminum oxide (alumina), which isn't dangerous at all. You should still use a thin coating of heatsink compound, to make them mate well to the semiconductor and heatsink. If they are beryllium, that's even better from a heat-transfer standpoint.
After struggling for almost 2 months, my PearlII is finally up and running.
Due to the monumental oversight of not installing a jumper at Rx, I was
having trouble setting the dc offset to zero. I had fixed that and I could
set it to zero, but it was not stable. Today, I finally got a chance to put
some solid time investigating what was going on. Removing C7 did the trick.
DC offset in both channels is now stable and < 100mV.
It sounds pretty good. Balanced and sweet. It is almost as if its not there....
a quality I find remarkable in any component.
I'm looking to upgrade my turntable, any recommendations? Something in
the range of a Debut III or RP1 would work nicely... or if you guys have
any other experiences. I have a 2M Red and possibly DL103 on the way.
Edit: Thanks nar, hesener and wayne for the help. Appreciate it!
Due to the monumental oversight of not installing a jumper at Rx, I was
having trouble setting the dc offset to zero. I had fixed that and I could
set it to zero, but it was not stable. Today, I finally got a chance to put
some solid time investigating what was going on. Removing C7 did the trick.
DC offset in both channels is now stable and < 100mV.
It sounds pretty good. Balanced and sweet. It is almost as if its not there....
a quality I find remarkable in any component.
I'm looking to upgrade my turntable, any recommendations? Something in
the range of a Debut III or RP1 would work nicely... or if you guys have
any other experiences. I have a 2M Red and possibly DL103 on the way.
Edit: Thanks nar, hesener and wayne for the help. Appreciate it!
Last edited:
Hi ra7,
glad you are up and running! sometimes it's those simple things.....
as for turntable upgrades, I guess you have a vast choice that will also depend on your budget. myself I am running a LP12 (rather old), with the Ittok2 arm, and a "talisman" pickup from clearaudio. works fine!
have fun
glad you are up and running! sometimes it's those simple things.....
as for turntable upgrades, I guess you have a vast choice that will also depend on your budget. myself I am running a LP12 (rather old), with the Ittok2 arm, and a "talisman" pickup from clearaudio. works fine!
have fun
hey hesener,
I got a great deal on a Technics SL1300 MKII. It has the well documented problem of a malfunctioning cueing mechanism, but what a turntable!! It is about 30 lbs, very heavy. The built in strobe shows the speed to be dead steady. It feels very solid. I was able to hook up the Ortofon 2M Red I had waiting around for a few months.
The sound is just breathless! The power and dynamics are phenomenal. Trumphets sound like they've been unleashed! You just want to keep turning it up. This is going to satisfy me for a few years and the focus can now be securing more records.
The PearlII is just invisible. It gives you whatever is in front of it. It doesn't lack any qualities, nor does anything jump out and try to impress you. Simply brilliant. Dead quiet too.
I got a great deal on a Technics SL1300 MKII. It has the well documented problem of a malfunctioning cueing mechanism, but what a turntable!! It is about 30 lbs, very heavy. The built in strobe shows the speed to be dead steady. It feels very solid. I was able to hook up the Ortofon 2M Red I had waiting around for a few months.
The sound is just breathless! The power and dynamics are phenomenal. Trumphets sound like they've been unleashed! You just want to keep turning it up. This is going to satisfy me for a few years and the focus can now be securing more records.
The PearlII is just invisible. It gives you whatever is in front of it. It doesn't lack any qualities, nor does anything jump out and try to impress you. Simply brilliant. Dead quiet too.
Hi h-wan,
sorry for my late response. please check post 675, in the schematic there (the simulation schematic) you will find a resistor R3=0.01, it is this one that I changed to 22 Ohm in my Pearl II. The other one (6800 ohm originally) should stay with this value (and not 5600 ohm), as wayne pointed out my simulation did not consider a couple things.
listening to it right now, sound has improved over a few months now, it is a fine sounding phono stage I must say. Enjoy!
sorry for my late response. please check post 675, in the schematic there (the simulation schematic) you will find a resistor R3=0.01, it is this one that I changed to 22 Ohm in my Pearl II. The other one (6800 ohm originally) should stay with this value (and not 5600 ohm), as wayne pointed out my simulation did not consider a couple things.
listening to it right now, sound has improved over a few months now, it is a fine sounding phono stage I must say. Enjoy!
Starting on the Pearl II
Hello,
new over here. Wanted to get back into some soldering and the Pearl II looks like a nice project as I'm back into vinyl these days. I'll start with the power supply (the one in the Pearl II article) and when I've got that working I will give the Pearl II a try. I know how to read schematics and solder things together but I'm a noob when it comes to the way the thing actually works, so I guess I'll be visiting here to get some help when needed.
In the end the goal is to get a phono preamp that sounds better than the built-in one of my Sony TA-FA70ES (also FET type I believe). And to have a lot of fun building it of course.
Some questions about the power supply:
1. I ordered Vishay 056 electrolytics, are these good ones (also for the Pearl II itself) or are there better "sounding" ones out there (without going into very expensive exotic types)?
2. Mains is 230V over here, should I therefore lower the fuse to 250mA, or just keep it at 500mA?
3. I ordered Diotec B40R rectifiers. In the specifications I read "max admissable load capacitor 5000 microfarad". Will I get in trouble with the 10000 mu electrolytics in this power supply? If so, which rectifiers would you recommend (I have a 2x 24V 50VA toroidal)
Thanks in advance!
Hello,
new over here. Wanted to get back into some soldering and the Pearl II looks like a nice project as I'm back into vinyl these days. I'll start with the power supply (the one in the Pearl II article) and when I've got that working I will give the Pearl II a try. I know how to read schematics and solder things together but I'm a noob when it comes to the way the thing actually works, so I guess I'll be visiting here to get some help when needed.
In the end the goal is to get a phono preamp that sounds better than the built-in one of my Sony TA-FA70ES (also FET type I believe). And to have a lot of fun building it of course.
Some questions about the power supply:
1. I ordered Vishay 056 electrolytics, are these good ones (also for the Pearl II itself) or are there better "sounding" ones out there (without going into very expensive exotic types)?
2. Mains is 230V over here, should I therefore lower the fuse to 250mA, or just keep it at 500mA?
3. I ordered Diotec B40R rectifiers. In the specifications I read "max admissable load capacitor 5000 microfarad". Will I get in trouble with the 10000 mu electrolytics in this power supply? If so, which rectifiers would you recommend (I have a 2x 24V 50VA toroidal)
Thanks in advance!
Hi and welcome, enjoy the ride! my pearl II is even now still getting better alittle bit - or thats just my ears adapting to whatever, I dont know ;-)
On your questions
1) I used Epcos electrolytics, I think this is non-critical. On the Pearl II PCB itself is another regulator and then another cap after that one, that should be the most important one. If you can, look for the lowest ESR you can find.
2) Again, not really important I think, this is to prevent catastrophic failure, I would leave as is
3) Larger rectifiers will certainly help. If you have the space, use UF4007 (not 1N4007) or "Stealth" diodes from Fairchild, e.g. FFP04S60S or other similar high-speed "soft" rectifiers. Then have a 100nF foil cap from "+" to "-", followed by 10mH inductors and then the main electrolytic cap.
Are you going to use the PCB from Pass Labs? If so, there is a GND connection between the power supply ground plane and the amplifier ground plane (a VIA) that you should fill with a wire and some solder, to make sure there is a good contact there.
have fun!
On your questions
1) I used Epcos electrolytics, I think this is non-critical. On the Pearl II PCB itself is another regulator and then another cap after that one, that should be the most important one. If you can, look for the lowest ESR you can find.
2) Again, not really important I think, this is to prevent catastrophic failure, I would leave as is
3) Larger rectifiers will certainly help. If you have the space, use UF4007 (not 1N4007) or "Stealth" diodes from Fairchild, e.g. FFP04S60S or other similar high-speed "soft" rectifiers. Then have a 100nF foil cap from "+" to "-", followed by 10mH inductors and then the main electrolytic cap.
Are you going to use the PCB from Pass Labs? If so, there is a GND connection between the power supply ground plane and the amplifier ground plane (a VIA) that you should fill with a wire and some solder, to make sure there is a good contact there.
have fun!
One can also bypass the onboard 78XX / 79XX and use external reg. like the one seen in original Pearl, but bipolar (+/-24V)
This regulation is used in most UGS and UP projects, I tested it, it's real stable and seems highly praised; another option could be the use of a shunt reg.
Regards,
nAr