phono preamp 'input buffers'.

[fap]

G'day all, just an enquiry about using a buffer circuit ahead of a standard phono stage. I'm trialling one of my own design, basically a modified FET source follower between my Shure M97xE and my DIY ESP P06 phono stage.

Subjectively, the buffer really seems to help with improved clarity and 'musicality'. Any thoughts on phono stage 'input buffers'? Regards, Felix.

[DF96]

If it provides gain then it isn't a buffer. If doesn't provide gain then it adds noise and, possibly, distortion. If it adds "musicality" then it almost certainly is adding a little second-order distortion and possibly adjusting the frequency response. You can easily change the sound of a MM cartridge by changing the load impedance.

[rayfutrell]

Tomlinson Holman used an emitter follower buffer when he was studying cartridge and preamp interaction. Here is a link to the paper.

http://www.davidreaton.com/PDFs/Holman_AES_paper.pdf

[AndrewT]

Is the esp phono stage inside your record deck?
The very shortest cables from arm outlet to first active device is mandatory for best performance.

[SemperFi]

Is the buffer's input impedance different from your phono stage? Could be the shure is seeing a more optimum load?

[Zoran]

the amplifying stages should be isolated with buffer stages, ae well as input.
the buffers should be from low capacitance input and low output resistance
to drive the riaa correction networks. that is from my experience... Nothing special, try spice...

[adason]

well designed phono stage will need no extra input buffer infront of it
buffer is designed to have high input impedance, phono preamp input is normally having 47kohm input resistance to traditionally load the cartridge
i have serious doubts about the benefit in what you are doing

[fap]

G'day all, thanks for all the comments. Regards, Felix.

[MRupp]

Originally Posted by fap

G'day all, just an enquiry about using a buffer circuit ahead of a standard phono stage. I'm trialling one of my own design, basically a modified FET source follower between my Shure M97xE and my DIY ESP P06 phono stage.

Subjectively, the buffer really seems to help with improved clarity and 'musicality'. Any thoughts on phono stage 'input buffers'? Regards, Felix.

Accuphase use input buffers in the MM stage of their new C-27 phono preamplifier (the MM circuit is a completely separate amplifier inside the box - you can actually see a simplified diagram in their brochure). This makes it easier for them to provide the high input impedance required for their MM stage. Maybe you have a similar effect and that is why you prefer the version with the input buffer in your circuit.

Edit: It should be easy to reverse engineer the buffer section that Accuphase use. And no, it does not compromise the noise performance of their MM stage, at least guessing by their published figures, and considering the input levels of MM cartridgs there is no reason to assume that noise would be an issue.

[SY]

Berning TF-10 (circ 1978) used pFET source follower buffers driving a grounded grid 12AX7 to avoid Miller input capacitance. As one might expect, it was not a noise-free solution.