Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => The Fix => Topic started by: Paul Joppa on February 23, 2014, 06:01:13 PM

Title: Driving a low-impedance amp
Post by: Paul Joppa on February 23, 2014, 06:01:13 PM

The question has come up (in a PM) about using the Fix with a solid-state amp which has a low input impedance.

The performance of the Fix really deteriorates with a load less than 100K ohms. You can try it without harm, but I anticipate the range of adjustment will become much smaller, as well as the frequency calibrations being off.

The best "solution" is to add a buffer such as the Quickie, which also restores the lost 4dB of gain. This is not an entirely satisfactory solution in all circumstances, but I don't know of a better practical approach.

Title: Re: Driving a low-impedance amp
Post by: Jim R. on March 09, 2014, 06:19:48 AM

Paul,

What if you have the opposite problem -- opreamp that has 150/500 ohm Zout? Or even lower?

-- Jim

Title: Re: Driving a low-impedance amp
Post by: Paul Joppa on March 09, 2014, 12:56:38 PM

Quote from: Jim R. on March 09, 2014, 06:19:48 AM

Paul,

What if you have the opposite problem -- opreamp that has 150/500 ohm Zout? Or even lower?

-- Jim

"The source impedance should no greater than than 4K (the output impedance of Eros, Reduction, and Quickie with PJCCS) and the load should be no less than 100K"  150 ohms is certainly no greater than 4000 ohms!  :^)  Seriously, it works most accurately driven from a source with zero impedance and driving a load of infinite impedance.

Title: Re: Driving a low-impedance amp
Post by: Jim R. on March 09, 2014, 01:40:24 PM

Thanks for the response -- not sure I can get to those extremes, but my 6j5 preamp and paramour IIs and paramounts should be good enough. ;-)

-- Jim