Bottlehead Forum

Bottlehead Kits => S.E.X. Kit => Topic started by: proud indian on December 08, 2014, 11:00:12 PM

Title: Passive
Post by: proud indian on December 08, 2014, 11:00:12 PM

I want to build a passive amp, that will stand before the sex. What would be the ideal value of the pot?

Thanks

Shreekant :)

Title: Re: Passive
Post by: Zimmer64 on December 09, 2014, 12:59:06 AM

Hi,

I am working on a similar little project and will use a 100k Alps pot and a 6 position selector switch.

Best

Michael

Title: Re: Passive
Post by: proud indian on December 09, 2014, 01:21:19 AM

Ok we are on similar lines, as I too have a 6 selector switch that I picked up from Decware a long time ago. I have a stepped attenuator of 100k, but wanted to make sure that the value is right for the sex amp.

Thanks,

Shreekant :)

Title: Re: Passive
Post by: Paul Joppa on December 09, 2014, 08:15:53 AM

Passive "preamps" must make a compromise. On the one hand, the source components (especially those with tubes) want to see a high impedance, such as 100K ohms.  For a reference, Reduction, Eros, and Quickie-with-PJCCS all work best with at least 50K, though we have found them sonically satisfactory at 15K minimum.

On the other hand, if the passive is to drive interconnects of any length, its impedance should be low.  For a reference, Reduction, Eros, and Quickie-with-PJCCS all have an output impedance of 4K ohms, and we advise cables of 1 meter, or low-capacitance cables of 2 meters, maximum.

The most widely used value is a 10K potentiometer, which has a worst case source impedance of 2500 ohms at the -6dB setting, assuming the source components have a very low internal impedance. A 16K potentiometer would have a 4K worst-case source impedance.

Hope that helps.

Title: Re: Passive
Post by: proud indian on December 09, 2014, 01:35:25 PM

Thanks Paul. But to make it simple for me, which value would you suugest, if I were to run my cd player (oppo) into my sex amp directly. Would you suggest 10, 25, 50 or 100k. My interconnects are short......max 18 inches.

Thanks,

Shreekant :)

Title: 25K (nt)
Post by: Paul Joppa on December 09, 2014, 02:40:56 PM

nt

Title: Re: Passive
Post by: proud indian on December 09, 2014, 02:42:43 PM

Thanks

Title: Re: 25K (nt)
Post by: Zimmer64 on December 09, 2014, 07:14:19 PM

Quote from: Paul Joppa on December 09, 2014, 02:40:56 PM

nt

Paul,

What does nt stand for?

Michael

Title: Re: 25K (nt)
Post by: Ferrous Bueller on December 09, 2014, 07:25:45 PM

Quote from: Zimmer64 on December 09, 2014, 07:14:19 PM

Paul,

What does nt stand for?

Michael

NT stands for "N"o "T"ext.

His answer was in the subject (25K) nt, not the body of the post.

HTH

Title: Re: Passive
Post by: Zimmer64 on December 10, 2014, 06:20:34 AM

Thanks. Should clean my glasses occasionaly...  :o