Posted by GarMan [ 66.48.160.161 ] on January 09, 2005 at 20:43:29:
In Reply to: Re: Grounded Grid Preamp Breadboarded posted by manualblock on January 07, 2005 at 21:56:36:
John, there were a few reasons why I selected this design:
It's different from most preamp designs out there. I've heard and/or built preamps in the common cathod, mu follower and SRPP topographies and was interested in hearing how this one would be different.
It's simple with relatively few part counts. Three tubes in total and six resistors per channel in the amp stage. I think I've also mentioned the PS which uses low cost parts such as 120V transformers and low value filter caps.
It's been reviewed very well. Bruce has a very loyal following on his own message board and most everyone who's build or heard it have very positive things to say about it.
But the most important reason why I selected this preamp was its low gain of only 12dB (4x). Prior to building this amp, I was toying with the idea of building an unity gain buffer (12SN7 cathode follower)as a preamp. With most power amps having an input sensitivity of less than 500mV, it doesn't make sense to put a high gain stage between source and amp. The gain provided by this preamp lets me listen pass the 12 o'clock position, and even into the 3 or 4 o'clock with low sensitivity speakers.
BTW, I'm still toying with the idea of the unity gain buffer.
Gar.
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