Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Quickie => Topic started by: DoS on January 11, 2013, 09:58:20 AM

Title: One channel for guitar pre? DC voltage?
Post by: DoS on January 11, 2013, 09:58:20 AM

I was thinking that the Quickie is so simple I could use it as a guitar pre (buffer, not looking for boost). But I was also wondering how much voltage it runs on because of battery packs used for pedals might work for the Quickie too.

Title: Re: One channel for guitar pre? DC voltage?
Post by: Paul Joppa on January 11, 2013, 10:10:27 AM

It runs on 36 volts (four 9-v batteries in series), plus two 1.5v D-cells for the filaments.

Title: Re: One channel for guitar pre? DC voltage?
Post by: DoS on January 11, 2013, 02:39:01 PM

Thanks. Hm...

Can you decrease gain by changing voltage for them?

Title: Re: One channel for guitar pre? DC voltage?
Post by: earwaxxer on January 11, 2013, 03:22:36 PM

I have found that the Quickie can be run as low as the mid 20's and believe the white paper for the 3s4 shows such, with a bit less gain. I think mine quit somewhere around 15 volts.

Title: Re: One channel for guitar pre? DC voltage?
Post by: Paul Joppa on January 11, 2013, 04:34:54 PM

If the proper operating point is maintained, the gain will not vary.

I did my best to maintain the proper (i.e. properly scaled to maintain the important non-dimensional parameters for the mathematicians here - you know who you are!) down to 24 volts, and up to around 72 volts, without circuit changes; its optimized around 30 volts but its a very broad optimum.

The gain does vary with the load resistance, which includes the plate load resistor - that's why the gain increases by 6dB with the PJCCS. Numerous other parameters also vary with that resistance, but they're all within what I think is a tolerable range. As long as it's not clipping, the details are a matter of taste IMHO.