Which DIY phono-stage gives great results?

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Helmuth

Helmuth

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Joined 2008
#1
Hi,

I have to try other phono-stage designs.

My own I build back in the eighties , it was a low noise design 87dB. I think it can sound much better only never came to make a better one.


To save time would you be so nice and advise me your DIY phono-stage that is very satisfying. And is recommended to copy.

Regards, Helmuth
 
#3
vgeorge said:
Salas one, would be my recommendation.
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Hi Vgeorge,

With what turntable and cartridge are you using Salas his design?

Do you mean this one.
115025d1220347982-simplistic-njfet-riaa-salasriaa2sk170bl.jpg

I made in 2005 something similar to that one I had not enough amplification and difference in amplification between left and right i didn't solve the problems because with two Jfets I could not raise amplification to 28dB.
This one is similar to the Salas one maybe the second Fet has to be replaced to by a two stage bipolar transistor end-stage to get higher amplification. And raise the power supply to 40 volt.
21575d1076787732-ultrasimple-mm-mc-riaa-preamp-2-mad_k-pacific.jpg


Or this one.
An externally hosted image should be here but it was not working when we last tested it.



All these designs have Jfets to get low noise but they use 680K and 1meg resistors. Resistors make noise to.
POWER SPECTRAL DENSITY
The Power Spectral Density simply describes how much noise power would generated by a resistor in a 1 Hz bandwidth.

S = 4 k T R (V2/Hz)

where

S = the noise Power Spectral Density
k = Boltzmans constant (1.38∙10-23)
T = temperature in Kelvin (Room temp = 27 °C = 300 K)
R = resistance

With raise of bandwidth and Resistance and temperature the noise level of the resistor raises.
This means with the given designs after the first correction one would need a buffer stage so we can use lower resistors.
http://www.ecircuitcenter.com/Circuits/Noise/Noise_Analysis/res_noise.htm

The last design looks nice with J1 and J2 that make a srpp I believe. Only J3 shout be used as buffer with gate to R5. And a opamp lme49860 to get the right amplification, Only a thought.
 
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#7
vgeorge said:
I use a Shelter 901 with a VPI Aries turntable.
What do you use and you need a higher gain?
Read here : http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-248.html#post2308275
You can find an MC pre-pre if you need it.
Also if I could, I would avoid opamp buffers.
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I can see you have done serious investment in de phono equipment. And do conclude your looking for the best. There is a huge chance that I will adopted Salas design.

I see that Salas is surprised and pleased with the results of the design. It is simple I like that (like a mentioned I did some thing similar with a 2n3819). For my own design I listened to it worked it did not sound special as far I tested it.

There for a first impression can of a sound can be misleading, when listened to it for a long time.

Regards helmuth
 
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#8
SY said:
If you want to go the tube route and some expense/complication doesn't scare you, take a look at His Master's Noise over in the Articles section.
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I have interest but I do not see a advantage in using a tube to a Jfet. Not based on any experience though.

Why would the tube version be better SY?

The design you're advising is complex and with transformer input also expensive. The measurements are amazing good.

Triode dick has a tube phone stage on the web. No measurements.
PhonoDudeamp.GIF
 
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#10
Helmuth said:
Why would the tube version be better SY?
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Overload margins and linearity, and the transformer input gives high common mode rejection and galvanic isolation. As you noted, despite the absence of any feedback loops and a simple passive equalization, the performance is very good. And yes, as you noted, not terribly cheap to build, especially if you want good transformers. Just throwing it out as a suggestion- as you see, there are a lot of good options using all different sorts of design approaches.
 
#14
Dare I suggest in this discrete company, an opamp design? I'd grab the National application note on preamps made using the LME49710. It's hard to top those designs in any measurable way; IMHO, the real issues in preamp design have to do with passive component quality (caps), layout and wiring, as much as the circuit. Gain distribution and overload issues also need to be examined, but they're not as much of a problem in most systems as some would have you believe.
 
#15
Conrad Hoffman said:
Dare I suggest in this discrete company, an opamp design? I'd grab the National application note on preamps made using the LME49710. It's hard to top those designs in any measurable way; IMHO, the real issues in preamp design have to do with passive component quality (caps), layout and wiring, as much as the circuit. Gain distribution and overload issues also need to be examined, but they're not as much of a problem in most systems as some would have you believe.
Click to expand...

I am thinking about a 2sk170 input and lme49860 output simple and as you state probably unbeatable specs.
 
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