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I did this in order to reduce gain that was causing audible distortion out of my Pearl 2 with a 5.0mV MM cartridge. Not all recordings produced overload, but some did.
I changed R21 through R24 from 10R to 20R. This eliminated the distortion that was coming through on some records. Some here have pointed out that this is a sub-optimal solution (because it starves the input stage) and a better approach is to adjust output through R14. Mark has a nice diagram of his implementation of a switchable value for R14 here.
When I get some time next week, I'm going to return R21-R24 to normal and give the switch a try and see what happens.
Edit: I don't know this for sure, but I'm thinking that varying levels of hiss that people are reporting is a function of overall gain structure across the playback chain, coupled with speaker sensitivity.
I changed R21 through R24 from 10R to 20R. This eliminated the distortion that was coming through on some records. Some here have pointed out that this is a sub-optimal solution (because it starves the input stage) and a better approach is to adjust output through R14. Mark has a nice diagram of his implementation of a switchable value for R14 here.
When I get some time next week, I'm going to return R21-R24 to normal and give the switch a try and see what happens.
Edit: I don't know this for sure, but I'm thinking that varying levels of hiss that people are reporting is a function of overall gain structure across the playback chain, coupled with speaker sensitivity.
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Maybe a 50/50 solution between R14 and source resistors would be worth trying. If my devices were already in that lower 10-40 spread, I’d probably think twice. I am getting some of that same distortion you mentioned Eric, which is my primary reason for looking at gain adjustment. Otherwise I agree with you on the volume control Jim.
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Experiment and see what happens. I first tried playing around with the second gain stage, but it was before Mark posted his nice solution, and I no longer remember what resistor values I tried or where I put them. Have to go back through my notes and see if I captured it.
I would try playing with R14 first. If this doesn't do it, then go for R21-24.
I would try playing with R14 first. If this doesn't do it, then go for R21-24.
Thanks for the tips Eric! I just swapped the 1K out for 3.32K at R14 and it’s sounding really good so far. A couple nights ago I put a 220mF lytic and 0.1mF film bypass on the ground side of R14. After getting a rock solid 0mV at the test point and consulting with Wayne, I went ahead and removed the output cap and bypass. Really enjoying all the tweaks, and the sound keeps getting better and better!
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Glad to hear the R14 mod improved your distortion. I found some of my old notes and it looks like I had tried inserting new resistors into the Cx position in order to reduce the gain of the second stage. The values that I tried didn't have the impact I was looking for to reduce the intermittent overload distortion I was hearing, so I abandoned this approach.
With your results, I'll return the input stage to normal and and play with different values of R14 and see what happens. Thanks for sharing the results!
With your results, I'll return the input stage to normal and and play with different values of R14 and see what happens. Thanks for sharing the results!
I'm on my second Pearl 2 (traded the first away and wanted to do a fresh build) and this new one also has a huge amount of gain. With a .2mV cartridge I have to go to a low gain setting on R14 so as not to overload my O2 headphone preamp. When going into the BA-3 preamp, it's fine with high gain.
This is how I added switchable gain and resistive/capacitive loading on mine. I used microphone cable which has 2 wires and a foil shield/drain wire. The drain wire is grounded at the PCB side.
I now have the cap on R14 as well, and with zero DC offset I plan to pull the coupling caps out.
Curious to hear your feedback once you pull coupling caps - keep us posted!
I pulled out the coupling caps today. Forgot to add a jumper to C13 (duh) so had to go back in, I used a piece of solid core copper wire. Also note that when you offboard R14 it makes a convenient spot to add the extra cap. DC offset is zero point zero. There is more DC in just holding the probes in the air.
However, I plan to be very careful about the power-up sequence with this configuration as the Pearl 2 was known to put my AVR into protection mode on startup even with the coupling caps in place. I put a voltmeter on the output and saw a momentary 19VDC on power-on, enough for the lightning bolt to flash on my Fluke meter
. It settles back to zero in a few seconds.I listened to one track and it sounded really crisp on the highs. Given that people constantly discuss/argue about the sound of coupling caps, I have to think a piece of solid copper in place of a cap must have a significant influence. I'll post when I put some more time on it.
Dropbox did the same thing, although they want less than $400. I now have my images on Office 365, which costs me $100/year and includes 1TB of storage each for me and family. No one should think they can get a service for free forever. If I stopped paying for O365 I would expect all the images I post on forums would get whacked.
McQ - Why not just host your own images, you don't rely on anyone then and its actually cheaper than what your paying? I pay £3.99 a month, which covers website hosting and includes my ongoing URL registration fees. Unlimited data storage and my own email addresses eg name@sitename.co.uk If the hosting company goes under, you just upload your data to a different hosting company and change a few settings to keep your email addresses working. All your links for images on forums etc will still work if you change companies, as its your site that you are linking to and that can be hosted anywhere.
I wouldn't trust any third party.
I wouldn't trust any third party.
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I pulled out the coupling caps today. Forgot to add a jumper to C13 (duh) so had to go back in, I used a piece of solid core copper wire. Also note that when you offboard R14 it makes a convenient spot to add the extra cap. DC offset is zero point zero. There is more DC in just holding the probes in the air.
However, I plan to be very careful about the power-up sequence with this configuration as the Pearl 2 was known to put my AVR into protection mode on startup even with the coupling caps in place. I put a voltmeter on the output and saw a momentary 19VDC on power-on, enough for the lightning bolt to flash on my Fluke meter
I listened to one track and it sounded really crisp on the highs. Given that people constantly discuss/argue about the sound of coupling caps, I have to think a piece of solid copper in place of a cap must have a significant influence. I'll post when I put some more time on it.
Nice! That was my impression too. Subtle improvement, but the HF seemed to have a bit more depth and definition.
Or until the thread is archived, where images/links are not stored. I don't know how it's handled here, but I have come across sites where the archive has no reference to images.
It's also a bit limiting, you couldn't store all your personal images here, and if you want items to be viewed across several sites, it probably wouldn't work anyway.
With the images on your own site, you just hot link from as many places as you want and the image is only stored on your site.
Whenever you upload an image to a forum or a image hosting site, it becomes their property, check the small print. It avoids them being sued for loss of data should things go wrong. In some cases by agreeing the terms you also hand over intellectual property rights for anything in the image.
If everyone stored their project images here, there would soon be changes to rules, as server space would be eaten up. That's why Photobucket started charging, images were taking up huge amounts of storage space and advertising was not generating enough revenue to cover the costs.
I argued all this on AoS forum, about two years before the Bucket fiasco. Fell on deaf ears and worse, after the event folks just signed up to a different service as though nothing had happened. Their links, like elsewhere are still for the most part broken, many have lost images for good.
It's inevitable that it will happen again at some point, I just think the £50 a year it costs, to DIY, AUDIO image storage, is money well spent, for peace of mind and total control.
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