Quikie as unity gain buffer?

[jln]

What IS the Quickie gain, and is it practical to change component values to make a unity gain buffer amp?
I'm looking for a clean quiet inexpensive buffer to drive rather long (12') interconnects until I settle and fund a nice line stage.
Tx
jln

[Paul Joppa]

In stock form the nominal gain is 2.2 and the output impedance is 2000 ohms. Driving those numbers down with a smaller plate load will increase distortion substantially and I don't recommend it.

A 2:1 stepdown transformer would reduce gain to 1.1 and impedance to 500 ohms, which might be what you need.

A 1:1 transformer could be configured as a 2:1 autoformer and might do the job. But it would depend on the winding details - many such transformers are bifilar wound and would be quite unsuitable. Look for an electrostatic shield between windings or some claim of capacitive isolation. 600:600 ohm transformers are commonly available but many will not have enough inductance. You might have to experiment, since few if any transformers will be specified for this application. Ask Mike on the Magnequest forum; his "tapped choke" might fill the bill. It's not listed officially but is widely used - he may have coil stock on hand.

[jln]

Thanks for taking the time to think this over.
As I feared this gets more complicated and expensive than I would like.
Perhaps it would still serve my purpose in the stock configuration with a gain of 2.2.

[Paul Birkeland]

Add the Speco output transformers to the Quickie as described in the guide for headphone upgrades, just take the output off the orange wires instead of the red ones. 

This will add $15-20 to the cost of the preamp, not too bad really... 

[jln]

Not too bad at all.
I might give that a try.
What about adding an attenuator to Quikie? Is that feasible?
Many thanks,
jln

Add the Speco output transformers to the Quickie as described in the guide for headphone upgrades, just take the output off the orange wires instead of the red ones. 

This will add $15-20 to the cost of the preamp, not too bad really... 

[JC]

What do you intend to use as a source, and what will be at the other end of the interconnects?  It seems to me that the volume control will attenuate the signal pretty much to "0", while CB's suggestion of using the transformers will give you a good  output impedance to drive the interconnects.

I'm afraid I must be missing something.

[Paul Birkeland]

What about adding an attenuator to Quikie? Is that feasible?
Many thanks,
jln

The Quickie comes with an attenuator.

[vanofmonks]

Ask Mike on the Magnequest forum; his "tapped choke" might fill the bill. It's not listed officially but is widely used - he may have coil stock on hand.

Hi PJ, I have a nickel pinstripe tapped choke from MQ, so I will give this a try in the next week or 2 and let you guys know.

Chris