[Pyriel0]

I just got a Firstwatt F1 amp yesterday and I my setup right now is pc->buffalo->F1->K1000. I have to turn my pc volume way down(35 db down in foobar2000) to be able to listen at a normal level. I want to put new resistors in the ivy to make it put out less voltage.

I'm using the standard setup atm which should be 190ohm resistors and 4vrms for the balanced outputs. The amp gain is 14db. How do I figure out the ohms for the resistors that I need? If I cut the resistance in half, will it knock off 28db of gain since it would be dropping the + and - signal for the same channel? I'm thinking that 90-100ohm = -28db in this setup and 140-150ohm = -14db. Is this right?

I am looking at PTF56100R00TYEK
but at $6 a pop and I need 4 at a time, it is a little too much for trial and error.

Thanks

 

[nikongod]

Based on everything else the K1000 likes and hates, the F1 is at best not a great amp for them. For the application it was designed for Im sure its great, but your trying to ride a motorcycle in a car race.

The F1 has absurdly high voltage gain into anything but 8-16ohms as you have noticed, and relies on the speaker and its unusually hight output impedance to load down its output to an acceptable level.

As a temporary fix, wire a 10 to 18ohm/15W resistor across the output terminals in parallel with the headphones which will drop the effective voltage gain of the amp to the stated levels, but you can do so much better for the K1000 with an amp with a lower output impedance. For so many reasons this is a band-aid fix at best but it should keep you going until you can get an amp that will run the K1000 right.

If you bought this amp to drive the speaker it was designed for keep it. If you dont have a single driver speaker with no crossovers/zoebels/notch filters sell this amp and buy something else.

 

[Pyriel0]

I would rather modify the buffalo output because if a resistor across the output of the amp blows, then my headhpones will too. If I just make the voltage from the source smaller then the headphones are safe all the time.

This amp drives the K1000 great after listening to it compared to my old amps. I was using 2 shanling ph100's, one on each channel. They were close to 0 output impedance and 1.2 watts at 120 ohms when bridged/running balanced. The F1 is easily better than them.

 

[Don Quichotte]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif Based on everything else the K1000 likes and hates, the F1 is at best not a great amp for them. For the application it was designed for Im sure its great, but your trying to ride a motorcycle in a car race. The F1 has absurdly high voltage gain into anything but 8-16ohms as you have noticed, and relies on the speaker and its unusually hight output impedance to load down its output to an acceptable level. As a temporary fix, wire a 10 to 18ohm/15W resistor across the output terminals in parallel with the headphones which will drop the effective voltage gain of the amp to the stated levels, but you can do so much better for the K1000 with an amp with a lower output impedance. For so many reasons this is a band-aid fix at best but it should keep you going until you can get an amp that will run the K1000 right. If you bought this amp to drive the speaker it was designed for keep it. If you dont have a single driver speaker with no crossovers/zoebels/notch filters sell this amp and buy something else.

I'm no techie, so I can't agree or disagree with what you said, but to say that it surprises me would be a serious understatement! Every single post I've read concerning the Firstwatt / K1000 pairing characterized this combo at least as "very good", up to "the best I've heard my akg's" in some cases. What is the explanation for this incongruence? Please don't take me wrong, I repeat that I don't know enough to have a personal opinion on technical bases, but your opinion is too contrasting with what I've heard, and I'm about to commission somebody to build me an F2 for my K1000's, so I'm highly interested.

What would you recommend for the K1000 instead? (preferably a DIY option)