Building a Pearl 2

Jump to Latest
M

McQuaide

Member
Joined 2011
Eric said:
There are several resistors that work in combination to alter gain. Soldering some female sockets into the Cx location provided the easiest way to experiment with different values with a minimum of soldering, so this is the path I chose. I saw in the pearl thread that you installed a switch on R14. This is a more flexible solution once the experiment is over. I like your build very much!

Perhaps it's time to go back and experiment again with resistor values. That, or just get a MC cartridge...
Click to expand...


Thank you! The front panel adjustments worked out quite well. I'm going to get rid of the resistor in Cx and up the value of R14, and see what happens.
 
M

McQuaide

Member
Joined 2011
6L6 said:
Stick a zobel across the input.

680ohm in series with 1000pF

If it's LC ringing from the cartridge interacting with the input, that's going to calm it down. Usually more an issue with high-output MC, but it's worth a try.
Click to expand...

Hi Jim, as you may recall my SAE1000 cartridge started the zobel thing, and I do have one on my new build. That was more of a blast of white noise as opposed to just too much gain. :)
 
M

McQuaide

Member
Joined 2011
Eric said:
I use an Audio Technica 5mV MM cartridge which initially caused distortion for me as well. There are two solutions- I had to implement both to make my distortion go away:

First Gain Stage:
Change R21 through R24 from 10R to 20R. This reduces the current through the first stage to about 5.3mA.

Second Gain Stage:

Parallel R16 (100k) with resistor in Cx location can alter the gain for high output MM cartridges.

Approximate resulting second stage gain for net values of feedback
R16 originally 100k, Cx originally open:

150k (replace R16 with 150k, Cx = empty) about 43,5dB (increases output by 3.5dB)
100k (Cx = empty) about 40dB gain (original output level, R16=100k)
66k (Cx=200k) about 36dB gain (decreases output by 4dB)
50k (Cx=100k) about 34dB gain (decreases output by 6dB)
33k (Cx=50k) about 30dB gain (decreases output by 10dB)

Hope this helps!
Click to expand...

I have R14 at ~1.2k now with everything else stock and all is well. There is still more gain than with my previous build, but not too much for the preamp. Since my power amps are low-powered it's good to have actually.
 
R

Russellc

Member
Joined 2003
Paid Member
McQuaide said:
Hi Jim, as you may recall my SAE1000 cartridge started the zobel thing, and I do have one on my new build. That was more of a blast of white noise as opposed to just too much gain. :)
Click to expand...

Yup, I had same problem with same cartridge. I don't remember if I asked this back then or not, but if I decide to replace cart with low output MC, thinking Hana, will I need to remove zobels, or will they be benign?

Thanks,
Russellc
 
W

Wellerman

Member
Joined 2011
I've been reading about lowering noise from the LM317/337 by adding a bypass capacitor from adj to gnd. I want to use the LM 317/337 in stead of my current 7824/7924's. I have a couple of questions:


1. Does the esr of the adjustment cap matter? I sometimes read about ringing with low esr caps in this position. I have Nichicon PW 10uF 35V (0.6 Ohm) and 63V (2 Ohm).
2. Would increasing the value of the adjust cap (to say 22 uF) help even more in reducing noise? Datasheet says about 15dB reduction with 10uF, I've read about 20dB where they used 22uF. I've got 22uF Panasonic FC on hand (0.95 Ohm) or lower esr 22uF FM (0.34 Ohm)
3. Same question about capacitor on the output. 25uF mentioned in the datasheet, I often see higher values of around 220uF. Would a low esr type be harmul here (I've got 100uF 50V Panasonic FC on hand (0.162 Ohm)?

4. The datasheet mentions protection diodes. Would these do any harm in the form of adding noise to the output?
 
Eric

Eric

Pass DIY Addict
Joined 2000
sites.google.com/bucknell.edu/ericshometheater/erics-home-theater
Paid Member
I built the Tracking Pre-Regulator in Part 4 of the Off-Piste article and with my measurement equipment, the measured noise floor is about -75dB or -78dB. The TPR is fed by an upstream CRCRC filter and I was expecting to see something closer to -100dB based on what the article indicates, so I'm not quite sure what is going on...
 
M

McQuaide

Member
Joined 2011
Pearl 2 puts receiver into protection mode

My Pearl 2 is connected to a Denon SR5010 HTR that I'm using as a preamp (zone 2 analog HDAM preamp which sounds great). But, powering the Pearl on or off with the Denon powered on puts the Denon into protection mode.

Both of my Pearl 2 builds do this. I assume it's passing DC or some kind of spike to the receiver. Anyone else experience this? :confused:
 
Q

qwertyl

Member
Joined 2003
qwertyl1.wixsite.com/diyaudio
McQuaide said:
My Pearl 2 is connected to a Denon SR5010 HTR that I'm using as a preamp (zone 2 analog HDAM preamp which sounds great). But, powering the Pearl on or off with the Denon powered on puts the Denon into protection mode.

Both of my Pearl 2 builds do this. I assume it's passing DC or some kind of spike to the receiver. Anyone else experience this? :confused:
Click to expand...

Pearl 2 has cap on the output, so there should not be any DC coming out of it...
 
You must log in or register to reply here.
Top Bottom