Bottlehead Forum

General Category => Technical topics => Topic started by: Jamier on June 09, 2016, 09:10:21 AM

Title: Parafeed amps, noise and PS Cap Upgrades
Post by: Jamier on June 09, 2016, 09:10:21 AM

(This has probably been asked before)If parafeed SE amps shield the OT primaries from PS noise, is there any benefit to be had by upgrading the PS caps to films?

Title: Re: Parafeed amps, noise and PS Cap Upgrades
Post by: Paul Joppa on June 09, 2016, 09:19:34 AM

The potential benefit is smaller than with series-feed circuits, but still greater than zero.

Film caps are much larger than electrolytics, which makes it tempting to reduce the capacitance.  But the capacitance still plays a role, so I discourage changing the value - unless you recognize it's an experiment that might fail.  :^)

Title: Re: Parafeed amps, noise and PS Cap Upgrades
Post by: Jamier on June 09, 2016, 09:29:42 AM

This is a little off topic, but if you can reduce hum by altering, say, the input tube connection, then that noise would not be due to the PS, right (or wrong)?

Title: Re: Parafeed amps, noise and PS Cap Upgrades
Post by: Jamier on June 09, 2016, 11:56:18 AM

Altering is a bad choice of word(s). I should have said "improve" the input tube connection.

Title: Re: Parafeed amps, noise and PS Cap Upgrades
Post by: Doc B. on June 09, 2016, 12:10:45 PM

The proper wording is shorting the input. If the noise floor drops when the input is shorted the noise is coming from upstream of the amp.