for Zen Mod
No problem with ascii, just use the "PHP" button and
great thread guys, me ordered the missing parts for this thingy today...
cheers, LC
No problem with ascii, just use the "PHP" button and
PHP:
l Audiophile MC Pre-Pre
=======================
Folks, with just few resistors, one JFET, one output cap you can build a
step-up device.
12 Volts regulated or accumulator buffered supply
|
|
2k2
|
|---------0.47uF-----out------------>
| |
(drain) |
---in---------(gate)JFET 100k
| (source) |
100R | |
| 47R |
| | |
-ground--------------------------------------------------
The basic topology is that of the second step-up amplifier by "Maison de
L Audiophile" of Paris/France.
The first 100R is the cartridge load, which must be adapted for the
cartridge you use. Using a paralleled 1nF cap also makes the circuit immune
against RF noise. The 47R resistor in the source is not necessary, if the
JFET has an IDSS(on) of 2mAmps or less.
As the signals are very sensitive, the voltage must be very clean, a 100 000
uF electrolytic cap for blocking power supply noise, computer grade
favourably, is advisable. Suitable JFETS are 2SK170, 2SK240 (double JFET),
2SK97 (double JFET), sorry only these japanese types are suitable, the
European BC264 and BF254 and so on do not work here (I tried !).
All resistors must be big metall resistors, e.g. Beyschlag 1Watt, or
tantalum resistors. No carbon resistors allowed here, tubes addicts.
The output cap is preferably polystyrene or polypropylene or paper-in-oil,
as you like it, as they are different in sonic balance.
Pacific RIAA Pre - 24V Version
==============================
o-----------------------------------o------------+24V
| |
R2 R6
| |
| D---o---C7---o
D---o---C1--R3--o--------o------o---G OUT
o---o---G | | | S---o o
IN | S---o R4 | R5 | |
o | | | | | | |
| | | o--o--o o--o--o | | |
| R1 | | | | | | | | |
| | | C2 C3 C4 C5 C6 | | |
| | | | | | | | | | |
o---o-------o--------o--o--o--o-----o---o-------o--------o--- 0V
R1 = 100k C1 = 0.47 micro
R2 = 2.4k C2 = 15 nano (ideal C2 + C+ +C4 = 99.3 nF)
R3 = 27k C3 = 15 nano well my copy says 100nF
R4 = 3k C4 = 68 nano
R5 = 100k C5 = 22 nano here its 30nF total
R6 = 2.4k C6 = 6.8 nano
C7 = 2.2 micro
We build the Pre using both the Fet Pre Pre and the Pacific. PSU is 3 X PP3
NIMH Recharables. The Pre Pre get's it's PSU via a dropper resistor and a
2,200uF Decoupling Cap (Black Gate or similar) so that 12V are supplied to
the Pre-Pre.
Later Thorstengreat thread guys, me ordered the missing parts for this thingy today...
cheers, LC
Yep I canmpmarino said:Batteries might 'be cheating' but could you imagine this pre on batteries hooked up to a 12+12 marine battery mini A - into a set of Altec 19's.
Mark you know, whatever I can imagine. I can do Loads of ppl told me that I was c****, he-he. My philosiphy goes like this: If you can/will build it, go ahead. If not, shut the f*** up!There are a few of the last category here on the board who think they contribute with something usefull!!
Sorry if I stepped on anyones toes
Harsh guy, signing outSteen
As steen is doing the hard job, I can concentrate on serious listening.
For unhappy few who did not buid the pre : a cat is a very good test instrument. Playing "interview with a cat"/Marcel Brodhaerth, for exemple. Watch the reaction of the cat.
If I am too much OT, tell me , I will be quiet, very quiet, vanishing...
manu
For unhappy few who did not buid the pre : a cat is a very good test instrument. Playing "interview with a cat"/Marcel Brodhaerth, for exemple. Watch the reaction of the cat.
If I am too much OT, tell me , I will be quiet, very quiet, vanishing...
manu
Nope I am not doing any hard job, yet!! I just put together the circuit and relied on Mr. Pass's judgement and adjusted the input pots to half resistance He-he that was the easy solution, but what do you expect from the Lucky L..... guy?? Fast and Furious
I will give it a more serious walkover later!!
Steen
He-he that was the easy solution, but what do you expect from the Lucky L..... guy?? Fast and Furious I will give it a more serious walkover later!!Steen
steenoe said:Nope I am not doing any hard job, yet!! I just put together the circuit and relied on Mr. Pass's judgement and adjusted the input pots to half resistance
Steen
Do you have both the input pot from papa drawing and another one at the input for selecting the volume?
Not that there is anything wrong about it, I'm just curious.
steenoe said:I have no idea why you find this surprising???? Please elaborate on that. I was surprised by the sound of a simple circuit like that, but I dont think that is what you are aiming at?? What is your (ahem) aim??
Steen
Well, i tend to take your opinion about sound and in particular Pass circuits seriously. From your unbridled enthusiasm i got the impression this is the best you've ever heard. Should i not be surprised?
Zen Mod
Thanks for posting all the old info.
Manu said:
No problem, just don't get too serious
Hey...I was offline for a few hours and WOw I see that Steen is already listening to his preamp! Congratulations! Steen, are you using the exact Nelson's schematic? Did you change any resistor value?
Judging from Steen's experience, this is really going to be a "diamond" preamp!
We can only
to Nelson!Thank you guys for the support...now I have to hurry....gotta build that pre!!
Regards,
Vix
Attachments
Hi,
Sorry Manu. Your experience counts as well. I was mostly interested to know how will Jfet Boz sound with F4. Steen was the first one to try that.
(Ok, Nelson was first....)
By the way, Nelson, are you listening to this combination right now? (even if you have something better, please don't tell us, at least not now!
)
Regards,
Vix
Sorry Manu. Your experience counts as well. I was mostly interested to know how will Jfet Boz sound with F4. Steen was the first one to try that.
(Ok, Nelson was first....)
By the way, Nelson, are you listening to this combination right now? (even if you have something better, please don't tell us, at least not now!
)Regards,
Vix
analog_sa said:
I wont go as far as to say its the best I ever heard.
Was I too enthusiastic? I dont know! The easy way for you to find out, is to simply build one for yourself
Takes almost 2 hours to get one in the air Its not my fault that Mr. Pass sends out all those very well sounding circuits Vix, I used the values as in the schematic except for the source resistor. Funny enough I was out of 10r's too, so I had to use two 27r's in parallel.
I will try and finetune the circuit this weekend.
Steen
mpmarino said:Here's my little mess
I get about 5.1v across the jfets. I went thru about 7 of them to get them close. Are they normally that badly matched??
Anyway - can't try it tonight it's a bit too late
Nice work Marino. Not as messy as mine though
At some point I had a pair of J-fets with 4,3V and 5,6V, VDS. Quite a difference.
Steen