Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: xcortes on January 31, 2011, 01:15:25 PM

Title: BCP-16 in FP3 or Sex
Post by: xcortes on January 31, 2011, 01:15:25 PM

According to Mike:

Quote

if you have a preamp with a cathode follower output stage--- give LC coupling a try. This is what [we] did in the Abbie preamp and it sounds really great. Very transparent, fast, deep bass. Use the grid choke in lieu of the shunt resistor to ground.

I have a pair. Where would you try it first, in the FP3 or in the Sex amp (between stages, of course).

Thanks

Title: Re: BCP-16 in FP3 or Sex
Post by: 2wo on January 31, 2011, 05:11:22 PM

I would say try it in the FP3, pretty much so you can tell us how it works ;). You already know that it will work in the SEX

Title: Re: BCP-16 in FP3 or Sex
Post by: Doc B. on February 01, 2011, 06:02:15 AM

How are you going to put it in a FPIII? You can't put it between stages, they are directly coupled.

Title: Re: BCP-16 in FP3 or Sex
Post by: xcortes on February 01, 2011, 06:05:33 AM

An old post on the MQ forum by Mike said: "if you have a preamp with a cathode follower output stage give LC coupling a try. Use the grid choke in lieu of the shunt resistor to ground"

Since the FPIII has a cathode follower output and a shunt resistor to ground I thought I could try it there. Is there something I'm not seeing?

Title: Re: BCP-16 in FP3 or Sex
Post by: Doc B. on February 01, 2011, 08:33:10 AM

Not sure I grok "shunt resistor" in this context. Does he mean the output load resistor? Or the cathode load resistor? If used on the cathode you will likely need to add some series resistance, and even then I don't know if the BCP-16 could handle the cathode current. If he means replacing the 470K output load resistor, I think that it would make more sense to replace the input grid load resistor of the amp that follows the cathode follower.

Title: Re: BCP-16 in FP3 or Sex
Post by: xcortes on February 01, 2011, 08:35:19 AM

Thanks. I guess I'll use them in the Sex. Particularly since I don't know how long the FP3 will last in this system :^)

Title: Re: BCP-16 in FP3 or Sex
Post by: ssssly on February 01, 2011, 09:45:51 PM

Quote from: Doc B. on February 01, 2011, 08:33:10 AM

Not sure I grok "shunt resistor" in this context. Does he mean the output load resistor? Or the cathode load resistor? If used on the cathode you will likely need to add some series resistance, and even then I don't know if the BCP-16 could handle the cathode current. If he means replacing the 470K output load resistor, I think that it would make more sense to replace the input grid load resistor of the amp that follows the cathode follower.

Hmmm that sounds interesting. Might have to try this at some point. What's the current across that resister?