Sunday, January 28, 2007

Too Much Foreplay for a CHAMP

I am currently running a newly completed Bottlehead Extended Foreplay III as a preamp and my newly constructed chipamp as my power stage into the LP#9's. The sound is excellent , however I listen to a fair amount of music as a fairly low volume level. The Extended Foreplay III C4S constant current source leaves behind a hiss - yes you can hear the current passing when it is hooked along side the ultra sensitive chipamp. This is not a problem when playing music at "audiophile" levels but when you are involved in a relationship it's really hard on the "audiophile" ears when the system is at a whisper as all you can focus on is the hiss.

Enter Paul Joppa. PJ is the king of the Bottlehead circuit design(s) and after posting a comment on the bottlehad forum PJ kindly responded with the following suggestion. He said to put a 66kOhm resistor in line with the signal coming from the FPIII just before going into the chip amp, then putting a 22KOhm across the signal input/output. This configuration would yeild a high impedance and about a 12db decrease in signal strength.

I did this initially with carbon comps and it does work. As before with the BSC however it leaves behind a film of yuck on the music. I decided to crack the piggy bank and order some tantalum resistors from Angela and put them in instead. Again - the lesson learned here is that when you want it right the pocket book has to open. The tantalum's did wonders and the music is back to its ultra clear quality, good imaging etc. And NO HISS from the FPIII.

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