Frank's Ultimate Tube Preamp.

[fdegrove]

Hi,

Ahh yes, the timbre of a tube is most important...

Hearing aid batteries on the low side again?

Shows how resolving your system is or should one say your "mind"?

Do whatever you like within your limitations, Joel, I can't care less, just don't hamper people with a bit more ambition than yourself, will you?

Show us you can let the RDH go and fly on your own wings, its high time for you to do so IMHO.

All the best,

[planet10]

Originally posted by fdegrove
You more than deserve the compliment though....it took me hours to clean up those handdrawn scans shown in the last to pics.

It took a lot less time to draw them... next time just mail me the scans -- or if your 'puter guy continues to turn them around so quick, it might be faster to snail-mail me photocopies

dave

[Brett]

Originally posted by planet10
No magic, a good tool, and lotsa practise

That's what I tell all the girls.

[fdegrove]

Hi,

t took a lot less time to draw them... next time just mail me the scans -- or if your 'puter guy continues to turn them around so quick, it might be faster to snail-mail me photocopies

But I'll be rewarding you for your work, one way or an other Dave.

Mighty nice of you to offer this kind of service...I might take you up on it, whenever the creative juices get flowing again I'll remember your offer..in the mean time, if I can help you with anything I will, promise.

That's what I tell all the girls.

Morning stiffness, Brett?

I'd love to implement Allen Wrights' RIAA idea into this phono stage, it's probably simple enough even for my non-mathematical mind but I fail to see how to implement it correctly here.

Any additional info on calcs is welcomed...Thinking out loud...is this lack of corrective RIAA measure the reason why MC carts with a rising top end didn't bother me all that much?
Puzzling.

Cheers,

[EC8010]

Is there a typo in the drawing of Post #85? Should the series resistor from the first stage to the second actually be 100k rather than 100R?

The MC step-up seems familiar. Did I see an early version in Wireless World donkey's years ago?

[analog_sa]

Is there a typo in the drawing of Post #85? Should the series resistor from the first stage to the second actually be 100k rather than 100R?

Seems fine to me. This seems to be a non-criticl value, it may even work with 100k.

[fdegrove]

Hi,

Is there a typo in the drawing of Post #85? Should the series resistor from the first stage to the second actually be 100k rather than 100R?

Oh dear, I do need a pair of glasses...

EC8010 is absolutely correct the 100R resistor in the phono pre goining from the anode of the first triode halve just after the 47nF/400VDC must be 100K not 100R.

It is of utmost importance for the RIAA correction.

I'll update the circuit asap and repost it.

The MC step-up seems familiar. Did I see an early version in Wireless World donkey's years ago?

Actually it was inspired by Eisenson of Audio Dimension, a similar cicrcuit was published by Christer Oehrnell in HI-FI news & RECORD Reviev in the June 1983 issue.

Quite likely it was published in other magazines as well.

Thank you for spotting the error.

Cheers,

[analog_sa]

Hi Frank

I seem to be a bit confused. Could you please let us know how you calculate the values for the riaa components. It seems to me the output resitance of the first stage should not matter for riaa accuracy in a feedback arrangement but i haven't really given it a good thought. If it does indeed matter than the cathode bypass on the first stage cannot be optional as it changes the output resistance of the stage.


cheers

peter

[GaryB]

Originally posted by fdegrove

I'd love to implement Allen Wrights' RIAA idea into this phono stage, it's probably simple enough even for my non-mathematical mind but I fail to see how to implement it correctly here.

Frank,
Its actually pretty easy to implement Allen Wrights suggestion of an extra pole (or is that zero?). I don't have his article handy, but I believe his suggestion is to flatten the curve out at 50khz, instead of letting things drop forever.

To do that in your circuit you need to put a resistor in series with the 0.0033uf cap. A value of around 965 would do the trick. I believe the nearest standard value is 976, which should be fine for most folks.

---Gary

[fdegrove]

Hi,

To do that in your circuit you need to put a resistor in series with the 0.0033uf cap. A value of around 965 would do the trick. I believe the nearest standard value is 976, which should be fine for most folks.

Gary,

Thanks, I think Dave and his buddy will be happy with that.

Correct, 976R is the nearest value from the E96 series.

Peter,

I seem to be a bit confused. Could you please let us know how you calculate the values for the riaa components. It seems to me the output resitance of the first stage should not matter for riaa accuracy in a feedback arrangement but i haven't really given it a good thought.

First and foremost, it's been ages since I looked at all that RIAA stuff.
Still, the first pole is formed by the 47nF and series R 100K, the next two are frequency dependent networks as you would do in a classic circuit, say a la Dyna or Marantz, the difference is that the signal is fedback from the anode of the second triode.

If it does indeed matter than the cathode bypass on the first stage cannot be optional as it changes the output resistance of the stage.

It does matter and in this incarnation of the circuit the cathode bypass is not optional.
The dotted lines had more to do with the value and nature of the caps.
See, at first I used 2.2uF Wima filmcaps for that...later on I fitted 4.7uF Roederstein MKP 1831s which sounded better and allowed for more extended bass response in conjunction with a 0.68uF iso the 0.47uF after the first anode.
You need a very quiet TT combo for that with a really dead tonearm or the woofer cones will flap like hell.

Cheers,