I tested and sorted my jfets for Idss today. Wow, that was simple and fast. 
The best matches were selected and installed.
Hopefully my chassis will arrive in the next day or two, and I can start making some real progress. As far as I can tell, (although there is always one last thing...) I have all the parts on hand or in transit to complete the project.
The best matches were selected and installed. Hopefully my chassis will arrive in the next day or two, and I can start making some real progress. As far as I can tell, (although there is always one last thing...) I have all the parts on hand or in transit to complete the project.
I will be using a pair of Par-metal '20 series' enclosures 12"w 8"d 3"h .
http://www.par-metal.com/product-ttp-20series.php
The PSU will be in it's own case, the phono boards in the other.
http://www.par-metal.com/product-ttp-20series.php
The PSU will be in it's own case, the phono boards in the other.
The holes you see are the pem nuts installed by par-metal to attach the top part to the lower.
To answer your question, most of the holes will be made with a hand drill. However, if my buddy who has a press is available, I will use it. The square hole for the power entry will be cut undersized with a jigsaw or nibbler, and filed clean.
LEDs for showing power will probably be very small holes in the front panels and the led behind.
To answer your question, most of the holes will be made with a hand drill. However, if my buddy who has a press is available, I will use it. The square hole for the power entry will be cut undersized with a jigsaw or nibbler, and filed clean.
LEDs for showing power will probably be very small holes in the front panels and the led behind.
It's been a while since I have discussed my PSU specifically - the reason for the departure from the published PSU is that my transformer has 30v secondaries, which when rectified will produce more than 40v. This is a problem because the on-board regulators (7824/7924) have a maximum input of 40v, and as any excess voltage will get turned into heat, I am hoping to be under that by a good margin. Hence the CRCRC; it't not because I want the noise performance (although it's a nice side effect...) I'm just trying to throw away some volts.
It's funny you should mention the Cardas solder, as that's what it is soldered with.
I also use Cardas solder, Tri Eutectic. I've been happy to switch from lead to this one, even if joints are not so shiny, it seems to do a better job sonically and seems to be more consistent over the years too ( Just rewired my speakers network and I found old lead solder tends to get softer.)
Technique to solder properly is however more difficult to master. On a circuit board, the less solder, the best
Regards,
nAr
Hi, guys. I gathered parts for the Pearl Two a little while ago, but haven't started building until now. I have a question for the tribe. What is the best way to incorporate variable gain for MM and MC ? I'd like about 40-45 dB for MM operation, (Clearaudio Maestro) and 60-65 dB for MC operation, (Koetsu Black). Wayne has already stated that 10 dB more gain is available by reducing R14 from 1k to 300 ohms, (easy - shunt switch !), but I'm wondering how to reduce gain to 45dB. Will increasing R14 to 3k ohm reduce second stage gain by 10 dB, or would it make more sense to insert a switchable voltage divider between the RIAA network and Q4 ?
Any ideas that you guys have, or better, have tried and proven workable would be welcome !!
Any ideas that you guys have, or better, have tried and proven workable would be welcome !!
In my conversation with Wayne at Burning Amp, I was curious about the same thing -- but not in the way you are thinking...
IIRC, he said that it won't overload until about 10mv input. ! ! I'm not sure there is a good cartridge on the market with that kind on output. The various Rega MM cartridges, which are about the strongest I know of, put out 7mv.
Basically, that means don't worry about it. If there were overload problems, that would be a good excuse to make the changes you want. You probably could rig up some kind of multi-pole switch to control the gain by changing the values of R14 & 15, but why? There is going to be no real noise performance advantage by doing so.
Build it stock and see how it works with both your carts. I will bet that you won't find any reason to change it.
IIRC, he said that it won't overload until about 10mv input. ! ! I'm not sure there is a good cartridge on the market with that kind on output. The various Rega MM cartridges, which are about the strongest I know of, put out 7mv.
Basically, that means don't worry about it. If there were overload problems, that would be a good excuse to make the changes you want. You probably could rig up some kind of multi-pole switch to control the gain by changing the values of R14 & 15, but why? There is going to be no real noise performance advantage by doing so.
Build it stock and see how it works with both your carts. I will bet that you won't find any reason to change it.
Up to 10 mv input ? No s&@t. !! That's a LOT of overload margin.
The other issue is to not overload the following linestage. 3.5 mv times 55 dB is 2.0 V's, (probably OK), but running over 2.0 V into a linestage is not good practice, particularly if the follow-on stage is an A-D converter for digital file generation.
0.15 mv (think Denon or Fidelity Research) times 55 dB is only 85 mv. I think a shunt resistor to increase second stage gain still makes sense - 65 dB of gain would deliver 270 mv - better for very low output moving coils.
The other issue is to not overload the following linestage. 3.5 mv times 55 dB is 2.0 V's, (probably OK), but running over 2.0 V into a linestage is not good practice, particularly if the follow-on stage is an A-D converter for digital file generation.
0.15 mv (think Denon or Fidelity Research) times 55 dB is only 85 mv. I think a shunt resistor to increase second stage gain still makes sense - 65 dB of gain would deliver 270 mv - better for very low output moving coils.
