Using Ruby circuit as a preamp?

[armstrom]

I've done some searching on the board but I couldn't find any discussion regarding what I would like to do.

I know this isn't really an amp forum, but since my questions relate to the Ruby I figure this is the best place to ask...
My plan is to use a modified version of the ruby circuit as a preamp to a 15W power amp stage (TDA2005 chip). The following modifications will be made to the ruby circuit:

1) Replace the volume pot with a big muff tone control (This is the pot between the JFET buffer and the LM386 input)
2) Install a "Master Volume" pot on the output similar to the 25Ohm rheostat used in the Lil'Gem design

The output of the master volume will run directly to the input of my power amp board (no preamp circuit in the middle).

Here are some questions I have:
1) Will the big muff tone sap too much of the input signal? I'm hoping not since I will be eliminating the non-master volume that is normally located there (10k pot)
2) What size pot should I use as my master volume control? Since the LM386 will be driving a much higher impedance load than a 4Ohm speaker the output current should be much lower, allowing me to use a "standard' pot rather than the high current rheostat called for on the lil'gem. I just want to make sure I select the correct size pot to have a "normal" volume control range. In other words, i don't want to have the output be very low from say 0 to 7 and then have it come rushing up from 8-10 with little room for adjustment.

Thanks in advance for any help!
-Matt

[frequencycentral]

Strange - I did it the other way round. I used a Subcaster as a preamp to a 386 based power amp. Only 1 watt though!

Maybe you might consider a Subcaster or Valvecaster for the preamp? There are a few mods you can do to clean it up if you want to.

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EDIT: Ooops, just realised you contributed to the Valvecaster thread, so you obviously have considered this already. just wondering why you decided against it?

[armstrom]

Actually, I haven't decided against the valvecaster. I will build both circuits and decide which one to use based on how they sound This amp is being built for a harmonica player so I'm not sure which would work best.  I like the wide range of gain available from the LM386. My concern is that the valvecaster won't have enough gain. I asked in the valvecaster thread how much gain I should expect but never really got a reply. Keep in mind there will be no other preamp before the power amp (all the reports I've heard are of people using the valvecaster as a distortion pedal feeding the existing preamp section of a guitar amp.

-Matt