Is EW seeking to redeem itself -- RIAA amp with SSM2220's

[jackinnj]

first decent article under the new stewardship -- a discussion of RIAA amplifiers, SN, use of transformers or low noise devices like the SSM2220 or LM394.

there is hope that the editors will spare themselves eternal perdition in gehenna --

 

[lineup]

first decent article under the new stewardship -- a discussion of RIAA amplifiers, SN, use of transformers or low noise devices like the SSM2220 or LM394.

there is hope that the editors will spare themselves eternal perdition in gehenna --

Any weblinks, to news article you refer to?
I guess is E-lectronics W-orld or something like that.

I know there are some interesting ultra low-noise circuits
in an old PDF I have got.
Some application notes on the LM194, which was previous to the improved LM394,
but used for same things in same way.

lineup

 

[EC8010]

I'd given up on EW, perhaps I might have a look...

 

[peufeu]

...and now National puts phono amp schematics in their app notes !

 

[jan.didden]

Re: Re: Is EW seeking to redeem itself -- RIAA amp with SSM2220's

[snip]Some application notes on the LM194, which was previous to the improved LM394,
but used for same things in same way.

lineup

Just the other way around, the 194 is a tighter spec'd 394 (or the 394 is a looser spec'd 194 ;-). They come from the same die, the best ones are stamped 194, the rest is stamped 394. That's how these things work.

Jan Didden

 

[jan.didden]

first decent article under the new stewardship -- a discussion of RIAA amplifiers, SN, use of transformers or low noise devices like the SSM2220 or LM394.

there is hope that the editors will spare themselves eternal perdition in gehenna --

Jack, is that the Nov or Dec issue?

Jan Didden

 

[jackinnj]

it's actually October -- it comes over on the slow boat.

"The Sound of Silence" Transformer or Solid State?" by Burkhard Vogel, October 2006 p 28.

 

[EC8010]

Ah, too late for me to double EW's circulation by buying a copy.

 

[poobah]

Who woke up the cat?

 

[jneutron]

first decent article under the new stewardship -- a discussion of RIAA amplifiers, SN, use of transformers or low noise devices like the SSM2220 or LM394.

there is hope that the editors will spare themselves eternal perdition in gehenna --

How is the LM394 circuit different from the one printed in EDN on March 3, 1982?

Cheers, John

 

[jan.didden]

it's actually October -- it comes over on the slow boat.

"The Sound of Silence" Transformer or Solid State?" by Burkhard Vogel, October 2006 p 28.

I know Burkhard Vogel - usually writes pretty good stuff. Missed it, arghh.

I had a 5 year sub on EW but let it lapse after madame Josifskofki (or similar) took over and appeared to be set to make it into a 'me too' EDN. Are they coming back from that rourte?

Jan Didden

 

[jneutron]

followup schematic

I made a schematic for the march 3 1982 article from EDN, page 111. It uses an LM318 opamp as the basis. Couldn't scan it as I used felt tip pen on it while I was making the circuit..

From what I can recall, they tied both input pins to the -15 volt rail to disable them, and replaced the input pair with the lm394 low noise pair, connecting them to the balance/comp pins.

The 100K and 10K are specified as low noise.

Cheers, John

 

[jackinnj]

Re: followup schematic

I made a schematic for the march 3 1982 article from EDN, page 111. It uses an LM318 opamp as the basis. Couldn't scan it as I used felt tip pen on it while I was making the circuit..

From what I can recall, they tied both input pins to the -15 volt rail to disable them, and replaced the input pair with the lm394 low noise pair, connecting them to the balance/comp pins.

The 100K and 10K are specified as low noise.

Cheers, John

I think that's the same schematic as in Nat Semi ap note 222 and 229 -- the EW article uses all sections of the LM or SSM as a "base spreader" -- not as a differential amplifier.

 

[jneutron]

Re: Re: followup schematic

I think that's the same schematic as in Nat Semi ap note 222 and 229 -- the EW article uses all sections of the LM or SSM as a "base spreader" -- not as a differential amplifier.

My 1990 copy of the PMI "Audio Handbook" goes into more detail, with some nice schematics using the SSM 2210 and SSM 2220.

They present a 500 pV/sqr Hz amplifier using 3 SSM 2210's and an OP-27 (strangely, they use an led as a zener feeding the input pair constant current source?).

They also show a 320 pV/sqr Hz amp using 3 SSN 2220's and an OP-27E. Again, with that led..

Cheers, John

 

[EC8010]

Re: Re: Re: followup schematic

Strangely, they use an led as a zener feeding the input pair constant current source?

Not strange at all. LEDs make very quiet voltage references. I use far more red LEDs as voltage references than as indicators.

 

[jneutron]

Re: Re: Re: Re: followup schematic

Not strange at all. LEDs make very quiet voltage references. I use far more red LEDs as voltage references than as indicators.

Ah, nice to know. For some reason, I had thought led's were very noisy. I believe it was probably from something that Risch had written and I did not think to question..😕

Cheers, John

 

[grimberg]

EC8010,

Is the red LED a personal preference or does it have different electrical properties? The reason I ask is that we can find red LEDs in the market with red lenses or clear ones. I know that clear lens LEDs emit different colors by using different metal combinations, but I am not sure if their behavior in a circuit is noticeably different.

 

[EC8010]

It's an electrical difference. LEDs produce light by momentarily exciting electrons into a higher energy orbit. As the electron falls back from this unstable orbit, it releases a photon of light. The higher the orbit, the higher the energy, the shorter the wavelength of light emitted. What this means in practice is that blue LEDs (short wavelength) require a higher voltage than red (long wavelength).

I have found by experimentation that LEDs with higher forward voltages have higher slope resistance, so I favour cheap red LEDs as voltage references. Cheap, because they're older technology and tend to be lower forward voltage and slope resistance than more modern efficient LEDs. There's been quite a bit of discussion about this on the tubes forum. The upshot is that experiment shows that for lowest slope resistance, you want a red LED that doesn't produce much light per mA of current. If anyone can come up with a physical explanation for why this is so, I'd be glad to hear it.