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Old 12th March 2012, 02:35 AM   #1821
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Thanks Kor952 and RJM. I will try to find the right info for the cartridge for R1 and R2.

I ripped out all the wires, reversed the transistors and took out the RCA jacks. I connected the power supply and the boards power up, but I haven't had a chance to test them further (damn that weekend yard work).
I have to order some insulated RCA jacks and maybe some better hookup wire. (Has anyone ordered from Percy Audio, Michael Percy Audio Ordering Information)

Inspired by Orion's nice build, I may look around for a better case than my Hammond extruded aluminum box while I am at it. Perhaps I should get one big enough for the B-Board buffer stage too.

By the way, desoldering was a pain for me. I had a lot of trouble getting the transistors off, since they have three pins and it was difficult to get all three pads hot at once. I also had trouble getting the solder out of the holes on the small pads. I have a nice Weller iron and copper solder wick, but it seemed like I was going to burn up the board getting the solder off. Any tricks that I am missing?

John
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Old 12th March 2012, 02:52 AM   #1822
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Yeah sorry for that. It s from the output of the vsps (connected to nothing) and the cartridge connected on the input
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Old 12th March 2012, 03:54 AM   #1823
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According to the Needle Doctor website, the cartridge impedance for the Concept MC is 11 ohms. According to the Phonoclone calculator, R1 should be 11 ohms and R2 should be 275 ohms. Those are what I will order.
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Old 12th March 2012, 04:33 AM   #1824
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dimkasta

Short the inputs and remeasure the output noise. That's your baseline reference.

The second image shows the output with the cart plugged in? That's 1V rms! What the heck...

60 mV channel difference on 1.5V is an imbalance of 0.3 dB (4%). That's about typical for a cartridge output, but a little high if this is just the VSPS circuit. Right now I'm not sure where your signal is coming from.

john

That's about right for the resistors, it doesn't have to be exact. Desoldering is a total pain, and burning components is a real risk. Especially anything with more than two leads. If I have to do a lot I'd sooner trash the board and start over. No nice way to sugar coat this: learn to do the job right the first time so you never have to desolder anything.
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Last edited by rjm; 12th March 2012 at 04:37 AM.
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Old 12th March 2012, 05:16 AM   #1825
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Quote:
Originally Posted by jcowling View Post
Thanks Kor952 and RJM. I will try to find the right info for the cartridge for R1 and R2.

I ripped out all the wires, reversed the transistors and took out the RCA jacks. I connected the power supply and the boards power up, but I haven't had a chance to test them further (damn that weekend yard work).
I have to order some insulated RCA jacks and maybe some better hookup wire. (Has anyone ordered from Percy Audio, Michael Percy Audio Ordering Information)

Inspired by Orion's nice build, I may look around for a better case than my Hammond extruded aluminum box while I am at it. Perhaps I should get one big enough for the B-Board buffer stage too.

By the way, desoldering was a pain for me. I had a lot of trouble getting the transistors off, since they have three pins and it was difficult to get all three pads hot at once. I also had trouble getting the solder out of the holes on the small pads. I have a nice Weller iron and copper solder wick, but it seemed like I was going to burn up the board getting the solder off. Any tricks that I am missing?

John
For removing items like transistors, cut the legs off from the component first so you can then desolder one at a time. I tend to use solder wick and then a solder sucker. I have bought parts from Michael Percy in the past with no problem.

Regards
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Old 12th March 2012, 08:23 AM   #1826
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Damn I feel like the rainman...

The second 3rd and 4th images are with cartridge reading a 300 hz tone from a test record.
3rd and 4th is "zoomed out" in time to get many samples for the measurements
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Old 12th March 2012, 08:30 AM   #1827
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That's all right then. 0.3 dB imbalance from a MM cart is about par.

If you could just remeasure the output noise with the inputs shorted we'd be all set.

/R
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Old 12th March 2012, 01:45 PM   #1828
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OK I will later today when I get home.

By the way, I might be able to borrow a high precision DMM next week.
Is it worth precisely matching each and every component for both channels and power rails?
Or just the RIAA parts?

PS. New mouser package just arrived... oh my... it s gonna be a fun evening
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Old 12th March 2012, 05:18 PM   #1829
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Ok here we go. Measuring the output, with input shorted... please don t laugh

Click the image to open in full size.

I m starting with changing the transformer with a torroid. Then changing the rectifiers, then the reg caps back to nichicon.
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Old 13th March 2012, 03:08 PM   #1830
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New update.

625-GBPC602-E4 Vishay Bridge Rectifiers cause almost twice the ripple (50Hz) in comparison to 4x MUR860G.

The Hammond 182P12 really hates smallish fuses. 250mA fuses were blown to electro-heaven without a chance. 1A fuses last ~5-6 power cycles.
I will try bigger ones today, but it really defeats the purpose of the fuse (causing it to protect merely from hard shortcircuits)
A soft start might be a good idea and should not increase the cost significantly.
Or perhaps using a big 5A on the primary side for general protection against shortcircuit, and a 250mA on each of the secondaries for protecting the phono.


If one of the small ones blows, it will cause single rail reg power, but should not be a prob since X-reg cross exchanges voltages from both rails as references, so if one goes down, then both should go down.

Any thoughts?

By the way, the sonic improvement with the big torroid was amazingly huge.

Last edited by dimkasta; 13th March 2012 at 03:11 PM.
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