Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: balancedtriode on October 25, 2012, 12:43:28 PM

Title: FPIII fillament supply resistor Q
Post by: balancedtriode on October 25, 2012, 12:43:28 PM

Hey guys, I am in the process of building a partial  FPIII kit I got of ebay I also just ordered the extended upgrade, I am in the process of choosing a resistor for the heater supply and I seem to like the 0.1 ohm mundorf as an option. (I like their products)
http://www.partsconnexion.com/resistors_mundorf.html (http://www.partsconnexion.com/resistors_mundorf.html)
non-inductive wire-wound is what I should use right? (I think I read it was the right type some where but I am not sure, also I should mention that I am building it with three 6sn7's hence the resistor value.)
thanks,
-Coltrane

Title: Re: FPIII fillament supply resistor Q
Post by: Paul Birkeland on October 25, 2012, 12:58:42 PM

Hello Coltrane,

The 0.1 ohm resistor is a good value for three 6SN7's.  The type of resistor is not important, as the heater supply is way out of the signal path in the Extended Foreplay. 

A 20 watt resistor will be tough to fit in the space provided, MILLS-64395 at Parts Connexion would probably fit if you had to have something fancy there.

Title: Re: FPIII fillament supply resistor Q
Post by: balancedtriode on October 25, 2012, 03:08:47 PM

PB,
Which resistors are important in the signal path?
I am trying to decide where to allocate my funds, any info would help.
Thanks,
Coltrane.

Title: Re: FPIII fillament supply resistor Q
Post by: Paul Birkeland on October 25, 2012, 03:22:14 PM

Hello again C,

I'd get Vishay RN55D resistors (Mouser is a good source) for the Sweetest Whispers, and potentially get some empty Goldpoint switches to replace the Lorlins (one 4P3T-1D and two 1P12T-1D).

In the Extended model, there are four 237 Ohm resistors on the active loads that are somewhat important, using RN55D's here is a good idea too.

There are some series input resistors that feed the attenuators of various impedances, I'd use what's in the kit to see which values you like.

The output coupling capacitors are another nice place to invest in some good parts.

There are also some small 0.22uF capacitors in the power supply, rated at 250V.  You won't have a ton of room to put exotic parts here, but the 250V film capacitors from Parts Express fit nicely.

I hope this is helpful, you could certainly put nice parts everywhere in the circuit, but these should be the ones that help the most.

-PB

Title: Re: FPIII fillament supply resistor Q
Post by: balancedtriode on October 26, 2012, 03:46:10 AM

thanks for the info!!!!!
do you know roughly what the spacing on the board is for the 0.22uf?
thanks again,
Coltrane

Title: Re: FPIII fillament supply resistor Q
Post by: Paul Birkeland on October 26, 2012, 05:36:34 AM

It is 0.8"/20mm.