[Brinkman]

Anyone know the input (load) capacitance of the Piccolo, the Ripper, and the Cornet2?

If I DIY a box for the Piccolo, I am considering a third rotary switch with selectable load capacitance values.

See this interesting article here for why one might like to know.

Best.

[el34]

I was looking at this issue too, also check out Mr. Hagerman's excellent page at
http://www.hagtech.com/loading.html which graphs the electrical response
of cartridge inductance with various loadings.  I built a cornet (original board.)
Somewhere I read that the input capacitance of a 12ax7 is about 100pf.  Cabling
will add 50pf to 100pf a foot.  So I got me some low capacitance cable, (12.2pf/ft)
but I haven't worked out yet how I'll wire it into the cable (It's larger, and the
center conductor is a solid copper wire, which could easily snap off if not well supported.)

I've got to get back to this and experiment but I'm guessing with my 580mh mm cartridge
it would be useful to adjust the terminating resistance in the 10k to 200k range and see
how it sounds.

[Brinkman]

I haven't really fooled around with Audacity yet, but I'm thinking that the Ripper would come in mighty handy if one wanted to analyze the frequency response of their cartridge.

For instance, you run the turntable (while playing test record pink noise) into the Piccolo, and the Piccolo into the Ripper (bypassing the Ripper's RIAA) and analyze the signal response, via the USB out, with Audacity.

With variable resistive loading (and possibly variable capacitive loading), the Piccolo and Ripper combo could be used to optimize cartridge loading.

[hagtech]

The input capacitance on the CORNET is lower than just about any other 12AX7 input phono stage.  You can only do better using a cascode section. 

The input capacitance of the tube is less than 10pF.  However, as a high gain tube, the negative feedback from the plate causes a Miller multiplying effect, bring it up to 100pF or more.  That is, on a typical gain stage.  Not so in the CORNET.  A little trickery eliminates the problem.  Part of the CORNET magic.  Lots of little things add up.

I measured the CORNET when I first designed it, comes out to 40pF or so with all of the built-in parasitics.

jh

[Brinkman]

Thanks Jim!

Would it be safe to assume the octal Cornet is similar in this respect?

[hagtech]

Yes.

jh

[Brinkman]

I found an old Hagtech post that answered one of my other questions so I thought I'd quote it here for posterity, along with the prior posts to this thread.

The input capacitance on the CORNET is lower than just about any other 12AX7 input phono stage.  You can only do better using a cascode section...
I measured the CORNET when I first designed it, comes out to 40pF or so with all of the built-in parasitics.

Jim also said the same input capacitance could be assumed for the Octal Cornet.

And from a separate thread, in regards to the Ripper input capacitance:

Input capacitance probably same as BUGLE, roughly 15pF.

jh

This only leaves the Piccolo...

[hagtech]

PICCOLO should be low, but not as low.  But it doesn't matter so much with MC carts.  You should not need to use a PICCOLO with an MM cart.  A pure guess would put the capacitance in the region of 100pF.

jh