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Old 16th October 2012, 08:06 PM   #8201
Salas is online now Salas  Greece
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Originally Posted by buzzforb View Post
THanks,,
Ill go ahead then.
The mezmerize like routing and switch system was the main pig for p2p, I am done with it at least. Phono tweak time starting from next week probably.
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Old 16th October 2012, 08:20 PM   #8202
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Dense as ever, are youvsayinf you will stay with that type output, avoiding large coupling cap, or are yiu ultimately moving to pure phono stage.
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Old 16th October 2012, 08:28 PM   #8203
Salas is online now Salas  Greece
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That pic is from the mate's line pre. I put single supply b1 in the ones we are going to check out already, a couple of 1uF simple supreme caps I got, the pot to the 6v6 buffer is 50k, no need I go symmetric supply and dcb1.
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Old 16th October 2012, 08:33 PM   #8204
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That is convenient, as I have the same pre to feed Thanks again Salas. Sorry for stalking you everywhere.
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Old 17th October 2012, 01:40 AM   #8205
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Originally Posted by Rush View Post
159155
Divide your resistance then your uF into the above number and you have the 3 BD down roll off frequency. Multiply the 3 DB down frequency by 10 and that is how far the phase shift effects the frequency response.
So, 159155/1000000/.1 = 1.59 Hz x 10 = 15.9 Hz. All good, below 20 Hz
If, 159155/500000/.1 = 3.18 Hz x 10 = 31.8 Hz.

As the resistance goes down, the cap size goes up for the same roll off.

Rush
Another question on the 1Meg res value, Rush, if you don't mind.

Given the "rule of thumb" which says that Zout of one component (or gain stage) should be <1/10th - and preferably <1/20th - of the Zin of the following gain stage ... if we assume Zin for a JFET is ~15Meg then using a Gate resistor of 1Meg gets us much closer to the low-end limit than 500K does (1/15th as against 1/30th).

Is this a problem?

Thanks,

Andy
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Old 17th October 2012, 01:41 AM   #8206
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Terrific - thanks, Rush ... now I understand your choice.

What caps cost $34 for 0.1uF? I have used Relcap RTX at about $9 in this position ... I presume yours sound a lot better?


Regards,

Andy
For that with MPF103 fets one or you made a simplistic also?
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Old 17th October 2012, 01:48 AM   #8207
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Originally Posted by Salas View Post
For that with MPF103 fets one or you made a simplistic also?
Hi Salas - you mean the circuit using MPF102s that I posted a Q about, last year? (You have a good memory.)

No, I haven't built a Simplistic ... I have made substantial modifications to that initial circuit over the past 3 years, so that it retains the basic construct (2 x JFET gain stages with a passive composite RIAA network in between) but everything about the gain stages is different! (Including changing to 2SK170s, to get me more gain.)


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Andy
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Old 17th October 2012, 01:56 AM   #8208
Salas is online now Salas  Greece
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What PSU you use for it?
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Old 17th October 2012, 02:02 AM   #8209
andyr is offline andyr  Australia
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What PSU you use for it?
Salas, I'm using 2 x 12v/2.2AH SLAs per channel (which deliver a total of 26v when fully charged).

Regards,

Andy
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Old 17th October 2012, 03:29 AM   #8210
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Originally Posted by andyr View Post
Another question on the 1Meg res value, Rush, if you don't mind.

Given the "rule of thumb" which says that Zout of one component (or gain stage) should be <1/10th - and preferably <1/20th - of the Zin of the following gain stage ... if we assume Zin for a JFET is ~15Meg then using a Gate resistor of 1Meg gets us much closer to the low-end limit than 500K does (1/15th as against 1/30th).

Is this a problem?

Thanks,

Andy
I am not the master of JFET knowledge, I leave that up to Salas.
You can pick what ever size output cap you have or want and figure the resistor backwards within reason, 1 meg being the highest value resistor.
The roll off frequency should be less than 2 Hz.
The phono sounds the best it has after this mod, due to .... who knows why? I'm going with better coupling caps as the reason.

Rush
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