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Old 4th December 2008, 01:05 PM   #441
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by Thomo
You can laugh as much as you like:

The fets and transistor were the wrong way round

Making music right now. I have a hum, but that's just poor placement of the reg. I shall attempt a shunt reg today. I'll also fit the Russian Silver Mica's and paper in oils.

Thanks for your help, yet again.
Good work Lee

I recently upgraded my present setup with a Rayreg on the 101b preamp.

This made a lot of difference because the MM phono pre is powered by the new regs.

My TT is killing the CDP already.... can not wait to try the salas riaa and shunt.

Ricardo
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Old 4th December 2008, 01:46 PM   #442
Thomo is offline Thomo  United Kingdom
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Here's a couple of pics of my pre/phono.

http://www.diyhi-fi.co.uk/images/sys...ont%20View.jpg

http://www.diyhi-fi.co.uk/images/sys...Top%20View.jpg

The wiring will be tidied up when the parts are finalised and the shunt reg is in.

Lee.
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Old 4th December 2008, 02:00 PM   #443
Salas is online now Salas  Greece
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Nice space and box. If you continue to have hum problems after finishing, remember that most possibly is gonna be due to no use of shielded coax for signal. Especially on input from TT. If you face any ground loops ask me too. Also, you must decide what kind of buffer you want to employ so not to have 2. Remember, you already have Q5 doing this. You may do the B1 I have shown above, directly at your Riaa tail and compare the Q5 or your external buffer. If you gonna use an external one, just toss Q5 and R19, link Q2 drain to C4 in, and take output from current out point. So you have one redundant stage less. More transparent.
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Old 4th December 2008, 06:47 PM   #444
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by salas
Also, you must decide what kind of buffer you want to employ so not to have 2. Remember, you already have Q5 doing this. You may do the B1 I have shown above, directly at your Riaa tail and compare the Q5 or your external buffer. If you gonna use an external one, just toss Q5 and R19, link Q2 drain to C4 in, and take output from current out point. So you have one redundant stage less. More transparent.
Hi Salas

So you mean there is no need for any output buffer after the riaa ? Can it feed the power amp directly ?

Ricardo
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Old 4th December 2008, 06:52 PM   #445
Salas is online now Salas  Greece
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Your Meridian 101 will be fed in some 10K impedance input, if I recall correctly. So you will need a buffer functioning stage, or a stand alone buffer. Rule of thumb is to drive at least 10 times more input impedance than the value of your Riaa's second stage drain resistor. Keeps the signal level high and the distortion low.
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Old 4th December 2008, 06:54 PM   #446
Salas is online now Salas  Greece
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Quote:
Originally posted by RCruz
Can it feed the power amp directly ?

Ricardo
What is the sensitivity and input impedance of your amp?
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Old 4th December 2008, 07:02 PM   #447
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by Thomo
Here's a couple of pics of my pre/phono.

http://www.diyhi-fi.co.uk/images/sys...ont%20View.jpg

http://www.diyhi-fi.co.uk/images/sys...Top%20View.jpg

The wiring will be tidied up when the parts are finalised and the shunt reg is in.

Hi Lee

Finally I can see your pre

It looks quite good.

What type of buffer is it ?
Do you need that buffer between the CDP and the power amp ? Can the DOS feed the power amp directly ?

Ricardo
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Old 4th December 2008, 07:11 PM   #448
Salas is online now Salas  Greece
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Can it be a Pedja Rogic circuit from Serbia? I think that I can see a TO-220 Mosfet there.
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Old 4th December 2008, 07:17 PM   #449
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by salas


What is the sensitivity and input impedance of your amp?
I do not have that info but here is what I found:

"103 power amp input impedance 11k.

Optimally you can use a 101 pre with a 0.775v/0db sensitivity power amp."

Of course my setup consists on Meridian 101b pre + 103 power amp.

Hope this helps.

I am now wondering if I can use only a riaa +pot + power amp and do the same with the CDP: CD with DOS + pot + power amp.

That would be a blast.

Ricardo
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Old 4th December 2008, 07:57 PM   #450
Salas is online now Salas  Greece
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The Riaa has to stay about 600mV peak to peak (0.21V RMS) so to sound clean without pressing its second stage and elevate distortion.
That is where I keep it for chosen cartridges and suitable gain structure. Many records have higher modulation parts and can be roughening it if we push the gain. Have done experiments on that for the given circuit. It lends a nice volume rotation range that way with most records, not far away from most average CD recordings.
The impedance of Meridian 103, asks for a buffer stage and a gain of 4 after the Riaa so to be driven correctly. The Riaa version that Lee makes, and your 46dB more sensitive but exactly the same topologically that I have posted for you, includes a Q5 buffer stage. So you can use your 101 for pre, and its low impedance input will not drag down the Riaa.
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