Frank's Pre Still In Vogue?

[Original Burnedfingers]

quote
You guy's are talking phono (MM, MC) preamps or just line stages here?

We are talking line stages. If we were talking MM or MC phono preamps I would have recommended your design of preamp with your multiple power supplies.

From personal experience with the Aikido I don't think that a regulated supply would be of a benefit because of the cancellation of the power supply noise in the Aikido circuit.

With your circuit Frank I could tell a difference just using a shunt VR regulated design. To me this means a difference with a good regulated design in my opinion.

[SY]

Originally Posted by 6BG6GA

With your circuit Frank I could tell a difference just using a shunt VR regulated design. To me this means a difference with a good regulated design in my opinion.

That's the tradeoff- the Aikido has good power supply rejection, but at the expense of more tubes. A more basic circuit will have worse PSR, transferring the complexity to the power supply. Take your choice.

The PSR of the topology Frank uses can be greatly improved, in fact made better than the Aikido, but there's a parts-count penalty for doing so.

[thefragger]

Originally Posted by SY

The PSR of the topology Frank uses can be greatly improved, in fact made better than the Aikido, but there's a parts-count penalty for doing so.

You can't just stop at that... how would you recommend accomplishing this task?

[fdegrove]

Hi,

What SY says is correct for the MM preamp part. That's the part that benefits most from a band aid such as a well regulated supply.

Not the MC part and certainly not the White CF which sports excellent PS rejection by design and a 0.1 gain loss...

Unless you'd want a buffered volume control to drive longish capacitive ICs and want to build my ultimate CD volume control using "sucker" parts (just kidding), there is little point in going overboard on the PSU for that section.

The line level preamp will be as transparant as the sum of the parts used. A mild insertion loss (gainwise) but that's all there is to it.
A transparancy from the volume control nowhere near anything you ever heard. There you go, high end audio for not exactly peanuts but at least you know which way to look.

Ciao,

[SY]

Originally Posted by thefragger

You can't just stop at that... how would you recommend accomplishing this task?

Just to be clear, we're talking about the line amp. If the cathode of the voltage amp is held at AC ground and the plate load is made high (a CCS, a gyrator, or a good plate choke, for example), the PSR of the first stage can be increased. For example, if you use two red LEDs to bias the cathode and a CCS with a 50M impedance (easy to do), you'll get about 75dB more PSR. The CF will then be the limitation, with a PSR of roughly 26dB. That can be improved by bootstrapping via another tube section or a MOSFET.

[thefragger]

Originally Posted by SY

Just to be clear, we're talking about the line amp. If the cathode of the voltage amp is held at AC ground and the plate load is made high (a CCS, a gyrator, or a good plate choke, for example), the PSR of the first stage can be increased. For example, if you use two red LEDs to bias the cathode and a CCS with a 50M impedance (easy to do), you'll get about 75dB more PSR. The CF will then be the limitation, with a PSR of roughly 26dB. That can be improved by bootstrapping via another tube section or a MOSFET.

I need to do more reading after my midterms are over!

[Yaho]

For example, if you use two red LEDs to bias the cathode and a CCS with a 50M impedance (easy to do)

SY, I hear you but I can't understand what you are saying. Would elaborate for me? What i am hearing is to trap 2 diodes for each cathode instead of a Rk. Am I hearing you right? If so what type of LEDs?

Further, what do you mean by 50M impedance?

That can be improved by bootstrapping via another tube section or a MOSFET

I am not getting what you are saying. ..Your lips move but I can't hear what your saying I ... have become...


Thank you!

[AJT]

hey yaho, you build the thorsten line amp many years ago did you not? how did you find the sound?

[SY]

Originally Posted by Yaho

SY, I hear you but I can't understand what you are saying. Would elaborate for me? What i am hearing is to trap 2 diodes for each cathode instead of a Rk. Am I hearing you right? If so what type of LEDs?

Further, what do you mean by 50M impedance?

http://syclotron.com/ImPassePreamplifier.pdf

Hopefully, this will be a clearer explanation.

[Yaho]

hey yaho, you build the thorsten line amp many years ago did you not? how did you find the sound?

Indeed! You have a great memory! It sounds very neutral. I like it a lot. Here is the link.
RIAA and Linestage for life time

I now want to build a different one. The joy of being a diyer!

BTW, I ended up using a step attenuator instead of the 100k input log.

Hopefully, this will be a clearer explanation.

Me too! It's not about your explanation, it's about my ignorance in the subject matter. I am reading it.

BTW. Are you the author of this article? Wow, incredible!

Thanks Sy!