• FORTE Model 1 • INput impedance

[rekupax]

Hi all!
Anyone knows what resistance one should use as passive amp for the Forte Model 1 Power amp?
I've just connected 2 Volts CD-Player through 50 kOm potentiometer (500 - 2M Ohms total resistance) --- signal in incredibly low!

Anyone tried?

Forte sounds a way better without my MBL preamp, so getting right attenuator would make me happy!

 

[labjr]

Hi all!
Anyone knows what resistance one should use as passive amp for the Forte Model 1 Power amp?
I've just connected 2 Volts CD-Player through 50 kOm potentiometer (500 - 2M Ohms total resistance) --- signal in incredibly low!

Anyone tried?

Forte sounds a way better without my MBL preamp, so getting right attenuator would make me happy!

I think the model 1 input impedence is 47K and input sensitivity was like 1 volt or less for full power output so shouldn't be a problem with a CD player. Make sure your pot is hooked up right.

 

[AndrewT]

2M total resistance measured!
How have you wired up the pot and how did you measure that resistance?

A 47k input impedance would work better with a 10k log pot.

 

[rekupax]

schematic i used was like this:

i didn't measure any resistance yet, i read it in manufacturer's datasheet.
"Total Resistance 500Ω ~ 2MΩ"

thanks, i'll try 10k pot tonight and compare!

 

[rekupax]

schematic pic
http://i46.tinypic.com/2rcu6ub.jpg

 

[jacco vermeulen]

The Forté Audio Model 1 has a bipolar input.
Not an easier way for a passive pre to swap for a matched JFET pair ? (equivalent to the Model 1A)

 

[Nelson Pass]

I think you can drop them in.

😎

 

[rekupax]

!! thank you all, i've solved the problem (cables were pseudo-balanced, rewired now). WORKS!
but now it's too powered. i can use just about 20 degrees angle rotation for non-extreme volume adjustment. ( 50K potentiometer )
i finally enjoy the sound ))

how MBL pre can be so poor in a circuit?... it's vintage though

cheers!