Queensland Audio Club © 2019

December 2016 – Keith Louis Eichmann (KLEI) and Paul Baker (Falls Audio). 

Thank you all for coming to the get together on the 10th of December at Reedy Creek.  

A great time was had by all.

The following is some info for the two amplifiers ran that day.  

Both amplifiers were designed and build by me (Falls Audio).

The first amp (Falls Audio KT66 PP) which we ran most of the day.  

This is a push pull output stage consisting 2 X Mullard KT66 AB mode with cathode bias.

This is driven by a 5692 (RCA) twin triode phase splitter which is driven by a E80F( Mullard ) pentode in the input stage.  

Rectification is done by a 5R4G rectifier tube. Tthe first two stage have a tube regulator stage that feed them a stable voltage.  

The output of this amp is about 35 watts RMS 20 to 35khz + & – 3db.

The second amplifier (Falls Audio GM70 SET/DHT) which was run was the GM70.  

This amp was only in the development stage when heard.  

This consisted of a GM70 in single ended fixed bias driven by a EL34 in triode mode with was driven by 6BL7 in SRPP which was driven by a WE328 in triode mode.  

This amp in that configuration put out 25 watts RMS.

The GM70 amp has had more work done to it since that afternoon and is now starting to really perform well.  Filament hum still a problem that is there.  

I hope to rid it of this shortly.  

Hopefully by the time we have another get together it will be the star of the day.

I know some of you were asking about the open baffle speakers designed by me (Falls Audio).  

These use a four way first order crossover.  

I tried second and third order but did not the results I wanted.

Choosing the correct drivers is very important.  

The woofer must have a high Q  to work successfully in an open baffle.  

Each of the other drivers must has a wide band width in order to work properly .

As you all heard they sound pretty good.

Thanks,

Paul Baker - Falls Audio