ultrasimple mm/mc riaa preamp

[fdegrove]

Hi,

This is why probably many tube RIAA stages can sound "quieter" than some ss RIAA stages.

That's where tubes shine...

Hmmm...350mV peak?
Guess you need a single sided record for that kind of modulation.

Time to build a MC Hammer, Ashok.

[jewilson]

Do not get me wrong I enjoy the sound of tubes, and own tube gear however; I also enjoy the sound of transistors equipment. Having said that, I just have not heard a tube designed phono-preamp that had noise figures that were at the same levels as the best transistor gear. I know Frank say he has gear that will do it and I have no reason to disbelieve him. But the only way I know how to do that would be build a hybrid FET or Bipolar cascaded with tubes amp. Also, don't have that much expertise in tube area like I do in transistors.

Well back to the over issue, if we get away from the low voltage parts it very easy to raise the overload in the passive RIAA. However, if I use a tube amp with a passive RIAA, I'll have to raise the impedance of the network to match the tubes. I guess I could just parallel cathode followers, what do you think Frank.

Still I just don't get to consumed about overold since I'm using Moving Coils.

[fdegrove]

Hi,

However, if I use a tube amp with a passive RIAA, I'll have to raise the impedance of the network to match the tubes. I guess I could just parallel cathode followers, what do you think Frank.

Well, I think that passive RIAA and tubes are no problem whatsoever...using CFs to drive the circuit is an idea that I haven't seen implemented yet....

With all the controversy about CFs over the past years, I'd postpone it for a good while though...

You're however correct IMHO, the impedance of the network needs to be raised to match the tube and operating voltages you use.

It's never simple and clear-cut but at least tubes are quite forgiving beasts.

The idea of using a FET as an input isn't new, Arthur Loesch had thought of that too but that puts us into hybrid amps, not my field of expertise...As if Id' have any...

Still I just don't get to consumed about overold since I'm using Moving Coils.

Same here....But my circuits takes any cart happilly, I can make MC Hammer make swallow the output of a MM cart if must be but that wasn't the design goal and it won't likely be to good sounding either.

Which brings us to Thorsten Loesch and his objection about the PS rail not being able to cope with the voltage swing, IOW it will clip and sound as flat as pancake...Not to mention the occasional clipping.

Haven't actually checked if the opamps can take it, but if they're run at higher voltages this should theoretically give some potential to work with....
I'm no expert there either, so it's just a suggestion best taken at face value.

BTW, I don't think my circuit could match the SNR figures of a SS design or hybrid design..
It passes the music though and I don't think I'm missing even the blackest of silence or the sublest nuance.
The circuit by itself is only indicative as you may have guessed, painstaking execution is everything...

Not that the circuit can't be bettered either but I trust you can use your own creativity here.

Cheers,

[ashok]

I have both SS and Tubed RIAA amplifiers. Both good and the SS has better distortion figures and much lower noise.

BUT the tubed RIAA is miles ahead in 'sound' and the "poorer" S/N ratio is not noticeable at all. You can see that easily when the stylus settles in the groove ! Even otherwise I do not get a noticeable "hiss" from the tube amp when I am not playing anything.
I'll never use the SS preamp again!
Cheers.

[CheffDeGaar]

I couldn't resist posting a little theory :

Look at this one from PatsLab (Love that name, reminds me of something )



and compare to this one posted on the forum, drawn by our one and only Jocko Homo :



They feel quite similar to me...

Adding to that the same type of gentle humour on PatsLab as we are used to with Jocko...

Adding to that that we all know that Fred and Jocko know each other, and that :

Originally posted by Fred Dieckmann
"I'll tell Beau you find his name funny at lunch next week. You are lucky you are in Sweden. Mr. Platz is about 6'5" and played college football for the Arkansas Razorbacks.........

But I'm surely fooling myself

[Christer]

Cheff,

It could be pure coincidence and Freds joke about my comment
would be typical of Fred whether he had anything to do with it or
not I suppose. However, now when you have brought our attention
to it there are quite a number of coincidences. Jocko often write
"the Jay-omega axis" and similar in text, which I think would be
pronounced very much like "J. O'Mega". Jocko seems to like AD825,
and he stepped in to the discussion to defend the circuit, not as
much as some others, perhaps, but anyway. The answer Elso got
sounds very much like one of Fred's several styles of writing, now
when I think about it. The legal notice on Pats lab would be logical
since they had a lot of problems with and complained about people
misusing their designs by copying and claiming as their own etc.

It is of course very easy to find coincidences when one is looking
for them, but I am getting a feeling you may be on to something here.
Your theory is almost too good not to be true.

[jewilson]

CheffDeGaar,

You might be on to something here; there are some eerier similarities in what ones here from Jocko and Fred. In addition, some of his schematics seem to be drawn similar style as the ones on Pat’s Lab. However, when you read over the information it does sound more like Fred. Now we all know that Jocko-Homo “devo” and Fred are not the same person, Jocko seems just a little more mellow. We will have to do some more detective work.

[CheffDeGaar]

Originally posted by jewilson
In addition, some of his schematics seem to be drawn similar style as the ones on Pat’s Lab.

Yes, I had noticed, but forgoten to mention , altough it has been the first thing to strike me. Same software (Micro Cap), but most, same type of annotations. Adding the liberal use of current sources with leds in the regulator for the clock...
But I have made so many mistakes in my life...

[Christer]

Cheff,

I suggest we hereby appoint you as chief, sorry I mean cheff, of
the inverstigation committee into the origin of Pat's Lab.

[Ropie]

Hello,

Could anyone who has built Thorsten's El Cheapo phono pre please explain the grounding to me. Are all the ground points simply starred together? Where are they then connected? And what does the turntable ground wire connect to?

Thanks in advance.