Ultrasimple MM/MC RIAA preamp 2

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data

Disabled Account
Joined 2007
Hay guys :)

I started reading this thread and very quickly became confused :confused:

I have a Ortofon 2M Red and I'm looking to try my hands at a MM jfet pre, which design here is best to go with?

I believe Mad's is the one that is suitable?

Edit:Guess I'll have to back track through the thread to get a clearer understanding...
 
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BikerBod

Member
Joined 2011
I built one of these

Its a bit of a mess but it sounds fantastic. I'm using this with an old Shure M75ED on a standard SL1200MKII. A real open punchy sound. I put together a very simple unregulated mains power supply using some huge reservoir caps and chokes and after a few tweaks here and there i have completely eliminated power supply induced mains hum. Here's hoping it works as well when its all neat and tidy!
 
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andyr

Member
Joined 2003
Mad_K said:
schematic:
Click to expand...

I notice in the schematic that you have used:
* 20K Drain resistor leading into the RIAA section, and
* 2M2 shunt resistor on the 2nd stage Gate.

I have seen a slightly different version of this circuit which had:
* 240K Drain resistor leading into the RIAA, and
* 510K shunt resistor on the 2nd stage Gate.

Are you able to tell me what effect these values have on the circuit? IE.:

* is there a benefit in increasing the Drain res to 200K or 240K? :confused:
(I can see this would probably reduce the signal level coming out of the RIAA - which is already low :) ).

* is there a benefit in increasing the 2nd stage Gate resistor to 2M2?

Thanking you in advance,

Andy
 
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genel

Member
Joined 2009
well,

Wish it used tubes ... :)


Mad_K said:
This morning I threw together my own version of the "Pacific Riaa Pre". I can now say that I have a completely Single Ended feedback-free amplifier chain (Pacific+BZLS+SOZ) :D And a really nice sounding chain it has become.. This crude little riaa pre is too good to be true. My intention is to tweak it like nothing has been tweaked before (cascoding etc), hence the "fast & furious" building style; it's very effective though (took me about 3 hours to make). All components are matched to the tightest tolerances and to get as close as possible to the ideal riaa values which are 22K4, 3K257 + 97n6, 100R + 33n5.

Well, enough rambling; do yourself a favour and try this circuit! ;)

Pictures:
Click to expand...
 
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ionian

Member
Joined 2010
Hi,
I am newbie to this work. I made a part list for this phono pre. But I don't know which is best for this project?

Which of these options should I choose?

RIA capasitors:
- Panasonic: ECQ-P1H333FZW (33nF, 50V, %1 Polypropylene) - Out of stock
- Panasonic: ECW-F6333HL (33nF, 630V, %3 Polypropylene) - DIGIKEY In stock
- Panasonic: ECQ-V1333JM (33nF, 100V, %5 Polypropylene) - DIGIKEY In stock. But %5 tolerance and 100V?
- Panasonic: ECQ-V1H333JL (33nF, 50V, %5 Polypropylene) - DIGIKEY In stock. But %5 tolerance?
- WIMA : FKP2C023301L00HSSD - (33nF, 63V, %2,5 Polypropylene) - MOUSER In stock. But 63V?.
- VISHAY: MKP-1837 (33nF, 160V, %1 Polypropylene) - But 160V?

Which options do you recommend?

What other options are there that you propose?
 
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ionian

Member
Joined 2010
My Paccific RIAA Phono Pre Amp

Realy true sound, incredible pure analog... Thanks everyone...

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preludefan

Member
Joined 2011
Mad_K said:
schematic:
Click to expand...

hi there Mad_K,

im very novice at building phono preamps and I want to try this circuit, what I find attractive about it is the simplicity, I do have a couple of questions however...

in one area, you have three capacitors paralleled and in another there are two, is there a specific reason you do this in terms of sound, or is it to keep the parts list simple?

also above the three paralleled capacitors, the resistor looks to be labelled "3k24" is this actually 3224 ohms or 3.2K ohms?

I was also looking to fit a simple valve buffer stage behind the circuit also, as I have a bit of a soft spot for them, however I believe that jfets have far lower noise than most valves... I was looking at a cathode follower, what is your opinion?

thanks for sharing this circuit!

mike
 
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rsavas

Member
Joined 2012
Hi Mike,

I probably can answer a few of your ?'s
3 cap's in parallel is to get a accurate value for the C, since the required value, is not a standard value that you can buy.
3K24 is 3240 ohms
A will leave opinions for using valves alone
Good luck building your jfet phono amp ckt.
 
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AndrewT

R.I.P.
Joined 2004
preludefan said:
................the resistor looks to be labelled "3k24" is this actually 3224 ohms or 3.2K ohms?...................
Click to expand...
resistor values use r, or k, or M, capacitors use p, or n, or u, or µ, or m,
In all of these, the multiplier can be inserted in lieu of the decimal place.

When any value is less than 1 always show the leading zero, eg.
type 0r1, or 0u22F especially when a decimal place is used as in 0.1ohms, or 0.22µF
Omitting the leading zero, leads to .1r or .22u and these can be misread as 1r and 22uF
 
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