OK, just got through the thread and am studying the schematic ( ain't tubes, so I'm guessing at a lot of stuff ).

Am I correct in assuming that the input cap. spec would be primarily determined by C3 & C4 ?

And that the cartridge sees the summation of the two caps, i.e., a total of 11pf ?

Thanks in advance for any help.

Cheers, Crazy Bill

P.S. I haven't got a clue how to figure the output impedance of the stage from the schematic. Anybody care to throw a number out there ? Or give a quick tutorial on how to do it ?

Oh forgot to answer the question on current draw.

It should not be too bad. I am guessing something like 50-70ma with 12-15V rails.

Yes, placid BP will work nicely here. :)

I would try leaving those caps off to begin with.

The output resistor selection will depend on you cables and load. For a capacitive load or cables i would use 21R If you cables are not very capacitive then I would just install jumpers.

Cheers!
Russ

Hey Russ,

I'm back and ready to go at this thing. Just ordered the Hi-Z full kit. Checked my Fidelity Research FR66s tonearm and my grounds are isolated, so I'm good to go.

While I've got a Placid BP in house that I bought for my still as yet unbuilt Ventus, I want to start w/ a battery supply and go from there. However, I've never done anything like that, so I'm only guessing at what I'm doing, but here goes.

If an alkaline D-cell is rated for, lets say 10,000 mah, will that mean I should expect, based upon your low end estimate of 50 ma for current draw, an estimated 200 hours or so of run time from the battery bank ?

So I don't blow anything up, am I assuming correctly that if I series 20 alkaline D-cells, and reference the node between the 10th and 11th cell to ground, I'll have my +- 15V supply. ( I'm obviously no whizbang at this stuff. )

And last for now ( and this is open for anyone ), I know I'm going to have to change my phono cable. The FR66s came w/ silver coax, ( rca's and din ) but I'm sure that's no good for balanced, as I would think I would need a high quality twin coax cable to wire balanced. Anybody have any ideas about a raw cable that I could use to construct a new balanced phono cable. I'm presently going to use this kit w/ an Audio Technica AT150MLX, so I want to keep the cable capacitance as low as possible.

Alternatively, I also have 60 ft of 29 gauge 5 nines silver in house that I could construct my own cable from. I'm a little concerned about the standard twisted pair ( no pun intended ) shielded cable being too high in capacitance for MM cartridges. Anybody have any thoughts on a low capacitance shielded cable design that I could construct myself.

As always, thanks in advance for any help,

Cheers, Crazy Bill

Hello Brian,

I had done some studying on battery ps, and was aware that performance was not optimal, but I was looking for the easy way out ( throw away and replace the batteries ) instead of recharging. But you talked me out of it.

Now I've got to decide between NiMH and LiPO batteries. I know the LiPO's would offer the ultimate performance, but I may settle on the NiMH for various reasons. Which begs a couple of questions.

You spec 12-15v bipolar supply. Are there any sonic or performance advantages to keeping that supply as close as possible to the 15v. Also, can I exceed that 15v rating a bit. If I go the LiPO route w/ 5 in series for each rail, I'll be @ 16v/rail. I don't know anything about SS circuits, except that I've read that they don't overload gracefully like tubes do, but that they fail catastrophically when exceeding their ratings.

I'd like to not smell any smoke

As always, thanks for any help.

Crazy Bill

Thanks Levon.
I reckon I'll keep that 4 in series, but I'm having a hard time finding an appropriate holder for them. I guess I could always DIY one.
thanks again for your help.