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Old 27th September 2010, 07:34 PM   #5021
Salas is offline Salas  Greece
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Quote:
Originally Posted by merlin el mago View Post

To finish only needs the 15nF RIAA caps.
15n+330pF test, or 15n alone test.
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Old 27th September 2010, 07:57 PM   #5022
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Originally Posted by Salas View Post
15n+330pF test, or 15n alone test.
I have 330pF SM so I will test, thank you.
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Old 27th September 2010, 07:59 PM   #5023
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Originally Posted by Salas View Post
No way for MC carts. This is for MM carts only that have high inductance and react with hundreds of pF and tens of Kohm. The pre pre loads the MC and expects 47K MM input.
Thank you, so he will go surely for Shinkoh or Vishay "nude" TX2575 for 47K load
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Old 27th September 2010, 10:57 PM   #5024
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One simple improvement would be to change the reg's Zener to a resistor (I will give you the value if you tell me your Vout and mV across the 10R under the 2SK170 at Zener's base), another is to tweak your C3 capacitor's value on the phono to your best HF alignment liking. But if you find the tonality OK in your system and you have no buzz or hum you are basically done. Don't you sink the Mosfets BTW? Using R1 10R in the regs? Also cabling to them Mos is not good, at least apply the 220R gate stoppers directly on their G pins.
After letting the reg settle for 15 mins and come up to temperature I measured:

Vout = 24.95 V
Vr4 = 56.0 mV

This is with the pres connected and open circuit audio inputs and outputs.

Also, I am using R4=10R as per the pdf schem.

The cabling to the MOSFETs are a product of having a tight layout, which I hadn't visualized as being quite so tight... I was planning on mounting them on sinks that run parallel to the board, using stand-offs to mount the sinks. What problems do I cause by having leads to the MOSFETs? Are there other components than the gate R's that I could mount directly on the Mos's to help?

Thanks.
Tani.
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Old 27th September 2010, 11:13 PM   #5025
Salas is offline Salas  Greece
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Substitute the Zener with a 4K3 1/2W resistor. Has a noise benefit VS normal quality non TC comp Zeners (usually unobtanium in low quantity, aerospace spec, expensive), and its audible in my experience, adding resolution. If it will not hit 25V exactly since my calculation with your local CCS current shows it should overshoot the stock 4K3 value a bit, either add a small trim value in series (68R maybe), or forget about it, no big deal. Let me know if you could hear this change.

You may be cutting some reg bandwidth because of the cable's inductance but you are lucky it did not oscillate. Thankfully its a tolerant design. The least length to Mosfet's gate and pin attached gate stopper are the only worthy parameters to take care of.
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Old 28th September 2010, 03:20 AM   #5026
Salas is offline Salas  Greece
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This is another area I am looking to expand capabilities, though options are low in good DJing carts and I'm sure that none come close to audiophile offerings. Any cart suggestions are enthusiastically welcomed, however back cueing (yes we spin 'em backwards) and high tracking ability are a must. I doubt that these are design features of a sub-millivolt MC, unfortunately.

Regards,
Tani.
Did you consider the Grado DJ carts? They are supposed to back cue, don't know how well they will scratch though. DJ pro fora must have more info about durability and uses. There is also an AT model that some say has some sonics and the durability ATP2-xN. Amazon bargain on the AT. I don't think they will handle anywhere near an ORT Nightclub E though.
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Old 28th September 2010, 04:01 AM   #5027
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Scratching is not an issue as it's not really my style and certainly not the style of this project... it'll be a rotary mixer without cross-fader, making fast cuts impossible.

I wasn't aware of the Grado carts and although I knew of the AT's, I didn't know that they were regarded highly. That offer from Amazon is good enough to get them and see for myself... thanks for the link.
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Old 28th September 2010, 04:07 AM   #5028
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If the Grados suffice must be the better ones for sonics. The AT has the better durability. Now with the trimmer stuff, maybe it can fair better than they think. Because the Grado has very low inductance and loads flatter on all mixers. Xone to Gemini it will come across as smoother easier.
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Old 28th September 2010, 04:33 AM   #5029
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Sorry Salas, I'm not following exactly. Given I can adjust the input loading with a trimmer, which do you think would be the best cart to try first? Are you recommending that more could be gotten from the AT due to the trimmer compared to the Grado? That is, the Grado won't react as much to input load changes due to it's lower inductance... ?
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Old 28th September 2010, 04:38 AM   #5030
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Yep, I say maybe the AT is better than they think by just slapping it on 47K mixers when the Grado has a benefit to shine easier. Its moving iron, not moving magnet, hence the low inductance. The AT is not for the DMC championship either but the Grado looks like taking only the odd back cue. The AT is certainly steadier.

P.S. Got to find trip mats! Way cool.
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