Simplistic NJFET RIAA

kenev · 2010-09-23 8:49 am

Hi there,

I have decided to build this RIAA preamp, but there seems too much to read already written in this thread.

I know there is a pdf file published by psgr, but the two links I found searching in this thread are dead. Can anyone direct me to a valid link for this pdf file or re-uoload the file?

Thank you

Salas · 2010-09-23 8:56 am

That's the updated circuits link you can click below. What cart, and what is the gain of line and main amp, speakers SPL? The PDF has good general instructions but prefer the polished circuits in the link. I am not sure if the pdf is hosted still. PM me to send you if you can't find it.

http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-495.html#post2308275

CaNNA3IS · 2010-09-23 10:55 am

Salas said:
It had very low voltage headroom in the cascode and on second stage your numbers show me. That is why you got sound when you added B+. Your leds appear strong, maybe at 8.1V, take one out from each quad, short its pads. You should be left with 3 glowing leds per channel. Your 2nd stage fets are stronger, or your R6 is 22R. 1k1 is a good R7 value. If with stronger fets its not bad, but make R6s into 100R trimmers (middle leg connected to ground leg, top leg to source pin). Don't throw away your old R6s, recycle them as in the picture so they are helpful with Q6's dissipation. Set trimmers at 33R, connect to the 37V (exactly set) shunt, turn the R6 trimmers for 8V at Q2's drain to ground. Should be doing OK with those numbers hopefully. Also tell me the new numbers on Q1 & Q5's drain to ground after that. Use coaxial shielded cable for input. What is your test cartridge and what load did you use for Rload? Also is your C3 a combination of polysterenes and what is the value of its main component?

My cartridge is a Goldring eroica lx. 0.5mV 100ohm load recommended.
I saw you suggested 1k instead of 100R for load earlier and i will try it with the next bunch of resistor i will order. Yes those are Remix polysterens or stiroflex. 47n, 15n+1n,100n. I don't know how it sounds correlating to russian pio or silver micas but i will when occasion offers. I have a lot so the simplest way was to use theese stiros.
Getting back to my shunt problem my TX is a 20VA 2x15V toroidal, so can its weakness in current cause some deviation to normal playing?
Relevant modification will be place when i get home again.

Karesz

Salas · 2010-09-23 11:07 am

Depends on each cart and system. You gotta listen to some loads because subjective tone has to do with TT set up, speakers HF in room etc. 100R looks OK electrically for an 8 Ohm coil cart like yours. A DL-160 would sound good from 1k to 8k2 for instance when a DL-103R from 150-180R. Try 15.4n instead of 16.1n C3 in total also before you lighten its load to 1k. I hope all it will work OK first with those changes. Having 20VA must still be OK since you consume 8.4W. Is your Vin to reg 42V when working?

CaNNA3IS · 2010-09-23 11:24 am

Salas said:
Depends on each cart and system. You gotta listen to some loads because subjective tone has to do with TT set up, speakers HF in room etc. 100R looks OK electrically for an 8 Ohm coil cart like yours. A DL-160 would sound good from 1k to 8k2 for instance when a DL-103R from 150-180R. Try 15.4n instead of 16.1n C3 in total also before you lighten its load to 1k. I hope all it will work OK first with those changes. Having 20VA must still be OK since you consume 8.4W. Is your Vin to reg 42V when working?

Without load it was 41V if i remember well but i will check the accurate value.

Salas · 2010-09-23 11:43 am

A bit marginal for a 37V Mosfet reg with 4V Vgs in series CCS. I would find it better with a 2x17V Tx in series for 34VAC.

RCruz · 2010-09-23 12:07 pm

The Space Egg Corp said:
Hi thanks for recommending ARMAGEDDON to me.
QUOTE]

Hi Simon

I built a Geddon and basically it is a 500VA toroid reducing from 220Vac to 110Vac.

The reduction in voltage also brings lower torque to the motor but it also reduces noise so you can hear better detail.

Check what type of motor is installed in your TT before building this rig because it does not work with all motors. (Both my TT (Rega and Ariston) use a premotec 24 pole AC motor)

kenev · 2010-09-23 3:55 pm

Salas said:
That's the updated circuits link you can click below. What cart, and what is the gain of line and main amp, speakers SPL? The PDF has good general instructions but prefer the polished circuits in the link. I am not sure if the pdf is hosted still. PM me to send you if you can't find it.

http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-495.html#post2308275

Thanks Salas,

I was already aware of the quoted, link but a friend told me that (as you also state) that the pdf is a good general paper.

My cart is VdH MC10 Super (0.65 mV), preamp has 15 dB of gain, I play with a couple of (mainly sensitive) amps and my speakers are horn loaded at 96 dB/W/m.

Salas · 2010-09-23 4:04 pm

The normal MC circuit will do fine. Good luck with the build, and don't hesitate to ask if stumbling. Are you the guy you came asking for birch plywood sources years ago when I was working for that pro sound company by the way?

kenev · 2010-09-23 5:54 pm

Salas said:
...Are you the guy you came asking for birch plywood sources years ago when I was working for that pro sound company by the way?

Correct!

psgr · 2010-09-23 6:52 pm

Salas,
"Ouden pro tou telous makarize"
I will see what I can do over the weekend.

Pete

The Space Egg Corp · 2010-09-24 9:23 pm

Thanks Merlin

merlin el mago said:
Let me know wich is your arm pivot to spindle distance: 213.25 mm or 215.70 mm? so I can post your arm potractor

Hi Merlin

I joined Vinylengine as Ricardo suggested, but I am unable to download anything from their site, it's the only site I have EVER had this problem with and is a total mystery why.
I have the SME manual now from some where else, but still don't have the Thorens TD160b MKII manual.
It is available from Thorens site but they want you to PAY £10 TO DOWNLOAD IT !!!!! unbelievable !!! :cuss:

I see there were, as you say, two pivot to spindle distances made, I think if there is a serial # on the arm it must be at the bottom. I will see this at the weekend if I remove the arm, and strip down the turntable. I will also look at the arm mounting board and measure this.
I am going to re-paint the plinth, and I also have to deal with a broken lid and hinges.

Cheers Simon... :up:

...

nicoch58 · 2010-09-24 10:44 pm

try firefox /opera

The Space Egg Corp · 2010-09-24 11:57 pm

Before and after ARMAGEDDON

RCruz said:
The Space Egg Corp said:

Hi thanks for recommending ARMAGEDDON to me.
QUOTE]
I built a Geddon

Click to expand...

Hi Ricardo

Managed to find all the semiconductors for the preamp today, so have added them to my now quite long parts order.

Yes I noticed in searching the site you had made the Geddon and am interested in what you think of it.

I am deciding at the moment how to power the preamp, would like inbuilt transformer/s for convenience but also wondered if I did a Geddon I may well be able to power the preamp from that as well, have got plenty of time to decide and may just do it on experimenting.

I used to build stuff and do the case last, but now I like to get the case sorted out first and then build what goes in it.

Still haven't managed to get a manual for the TD160b MKII, I joined Vinylengine but cannot download anything and it's the only website I have ever been on that does this, don't know why.

I hope to strip down the turntable at the weekend for plinth painting and cleaning, and will check out the motor and electronics then.

Cheers Simon

merlin el mago · 2010-09-25 12:35 am

The Space Egg Corp said:
Hi Merlin

I joined Vinylengine as Ricardo suggested, but I am unable to download anything from their site, it's the only site I have EVER had this problem with and is a total mystery why.
I have the SME manual now from some where else, but still don't have the Thorens TD160b MKII manual.
It is available from Thorens site but they want you to PAY £10 TO DOWNLOAD IT !!!!! unbelievable !!!
I see there were, as you say, two pivot to spindle distances made, I think if there is a serial # on the arm it must be at the bottom. I will see this at the weekend if I remove the arm, and strip down the turntable. I will also look at the arm mounting board and measure this.
I am going to re-paint the plinth, and I also have to deal with a broken lid and hinges.

Cheers Simon......

Hi Simon,

You have PM

Cheers,
Felipe

The Space Egg Corp · 2010-09-25 2:10 am

Tracked Down The Components Today

Salas said:
Geddon gurus would know that I suppose.

Hi Salas

Thanks for the Geddon link it was better than mine.
It takes me awhile to find things as I have GPRS internet which is... :snail:

Found all the semiconductors for the preamp and regulator today. :up:

Even found the 2SK170's. :yes:

I don't suppose the sufixes matter that much, what do you think? I found:-
BC550c or BC550
BC546b or BC546bg
BF245c version

The IRFP9140 for some reason that I can't understand why is VERY expensive, am I missing some thing about this part ?
The IRFP9240 is almost the same and a third of the price !
I am thinking that with the power involved a IRF9510, 4A 100v 43w 1.2ohm, mounted on a decent T220 sink which I have lots of would be fine, especialy with 2 regulators. Am I missing some thing other than power handling ?

Cheers Simon.

Salas · 2010-09-25 2:45 am

550C fine. 546B fine. BF245C has strong IDSS. Degenerate it to 5mA with a resistor in line with its S pin. The 9140 they find some times when the 9240 is not available, interchangeable. Other TO-220 acceptable if their capacitive characteristics will no lead to oscillations in the particular circuit. The 9510 has low gfs so I would use it only in the CCS as it is also faster and try 9540 in the shunt position.

The Space Egg Corp · 2010-09-25 3:30 am

International Rectifiers In Stock

Salas said:
The 9510 has low gfs so I would use it only in the CCS as it is also faster and try 9540 in the shunt position.

Thanks Salas

Just looked and happen to just by chance have five IRF9540 already.
So I guess I should use them in all 4 positions.
I think it's recommended I make one regulator per channel.
Would you also do 2x of rectifiers & reservoir caps ?

Cheers Simon

Salas · 2010-09-25 3:57 am

If possible yes, double rectification. Prefer 9510 on CCS. Check for oscillations with a scope on B+. You should see a straight line if all is OK.

The Space Egg Corp · 2010-09-27 1:21 am

Valve Phono ?

Salas said:
P.S. What kind of CCT is your valve phono? I have made some valve phonos too.

Hi Salas

Was just looking back at the thread, and I didn't answer your question.
I had said I am making a valve mic & stereo valve mic preamp, but hadn't mentioned a valve phono. BUT
I have 95% made a valve phono, it is a hybrid and uses a BC549 before each half of a military CV2492 per channel (2 gain stage, 1 valve per channel).
As I say, it's 95% done. Case, turret tag boards, PSU, valve holders etc. are all done. BUT
I stepped on one of the CV2492's (with Adidas on at the time I'm glad to say !!!) and have not yet located a replacement pair of valves.
I'm not accident prone by the way, but s*#t happens !!!
I'm interested to know what tube phono's you made and what you think.
Would you reccomend one to make (I bet you made the most minimal one going !).
Have too many things on the go as it is, but a recommended super minimal tube phono would be a cool thing to get going.
I saw the photos of your regulator case on the site, is that one of the tube phonos on the coffee table next to it ?
Looks very minimal and cool in it's aly box if it is.

Cheers Simon

Simplistic NJFET RIAA

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