(re)searching for a better preamp

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#225
this is my SMD board that plugs into the power supply and DC servo board
 

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#226
#230
rudi said:
HI Safetyman

have a look how i did it

See My Post here
Click to expand...

Rudi, thanks for being so ready to assist. I saw your project and it gave me goose pimples. 😀 Nah, I don't think I am ready for that yet. I am going to try and get the AD815 SIP chips from B.G. Micros and implement Carlos's design. Looks more achievable for me. 😀

juma said:



Hi safetyman,

This is how I did it:
http://free.hostdepartment.com/j/jrexton/pre1.jpg
http://free.hostdepartment.com/j/jrexton/preampheat2.jpg
http://free.hostdepartment.com/j/jrexton/

You don't need a PCB, just a steady hand and fine tip on your soldering iron.

Cheers
Click to expand...

Juma, thanks for the assist too. Really nice. Maybe one day, I'll learn enough to build something as nice as what you have done. 🙂
 
#232
safetyman said:


Rudi, thanks for being so ready to assist. I saw your project and it gave me goose pimples. 😀 Nah, I don't think I am ready for that yet. I am going to try and get the AD815 SIP chips from B.G. Micros and implement Carlos's design. Looks more achievable for me. 😀
Click to expand...

Hi safetyman. Up until two weeks ago I were a bit sceptical whether or not I can make my own PC board. It took me a day or so to get the technique right now it takes me 3 hours to make the PCB and build it and have it playing. And soldering SMD’s are really very simple

I am testing various DC servo arrangements now so I have gone through some prototypes already. (But they all sound the same – amazing)
 
#234
I assume that you talking about the bypass caps on the opamp. I have used 100nf but honestly i don't think you need them. the opamps run on the same power as the AD815, i will have my dual opamp version ready this afternoon. my feeling is that it will be better (not sonicly but electrically) than using two, less strain on the PSU

i have used a value of 820k with a 1uf film cap for the DC servo and it sounded worse, loss of clarity but only marginal. the values suggested works the best. The guy that designed it for me does this everyday for a living and he had very good reason for using those values.
 
#235
Thanks for the reply

The 820K resistor was for R7 right?

With the value in your schematics(servo) the servo is set at .2Hz and below?

If I use a 174k resistor and a 3.5uf cap,do I change R9 or is R9 just a load for the output of the op amp?
How was the value for the resistors calculated?
 
#236
rudi, how did you mount the heatsink on to the AD815 chip? BTW, which version of the LM317 and LM337 is the correct one. There seems to be many, with different letters behind them? :xeye:

rudi, thanks for the encouragement... how the hell am I going to attempt what you did when I don't even know what is a DC servo? 😀 When I can get someone to help me make boards, I am going to try your X-Caliber... that's for sure. 😉
 
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