Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: luthierwnc on August 21, 2023, 10:05:19 pm

Title: Left-field phase inverter question
Post by: luthierwnc on August 21, 2023, 10:05:19 pm
Hi all and thanks for looking.  I'm redoing the pedalboard for a home-brewed Matchless HC-30.  I use a Radial Twin Cities A/B-Y pedal for either or both channels.   

In messing around with the order I tried putting the time-based effects on the cleaner triode-channel after the Twin Cities.  I didn't like the results.  That could be for lots of reasons but i wondered if one was that the triode effects were phase-cancelling the signal coming in on the pentode side of the inverter.  I've attached the schematic showing how that works.  With all effects before the splitter it sounded better.
What do you think?  Thanks, Skip

Title: Re: Left-field phase inverter question
Post by: shooter on August 22, 2023, 03:03:24 am
Quote
I didn't like the results.
the jacked in tubes are out of phase with the "normal"
Quote
A/B-Y pedal for either or both channels.
didn't see how the pentode was "cut off" but it's early.  Did you like it by itself?
Title: Re: Left-field phase inverter question
Post by: luthierwnc on August 22, 2023, 12:16:59 pm
Thanks Shooter,  Wonderful sounding amp -- although it is not for bedroom playing.  The pentode side is more commonly used for leads or crunchy rhythms.  The coupling capacitor array subs for a tone-control circuit.  The triode side is more conventional.  They can be run together.  Most people just use a jumper.  But it didn't work well with my poor-man's wet/dry arrangement.  I figure delay on one side is anti-delay on the other.  I'll rewire the new board for either/or rather than both and go from there.  Cheers, Skip
Title: Re: Left-field phase inverter question
Post by: luthierwnc on August 22, 2023, 06:21:09 pm
Update:  It wasn't a phase issue.  I'm not sure what it actually was but these things can take diverse signals on either end of the inverter.  Here's the current line-up.  It will get smaller since a few things are redundant or less than great.  sh

Title: Re: Left-field phase inverter question
Post by: pdf64 on August 23, 2023, 08:04:23 am
  … anti-delay …
Yikes, what’s anti delay?

It’s worth bearing in mind that anything that affects frequency response in either side’s signal path will also affect phase response, it’s the 2 sides of the same coin.
Title: Re: Left-field phase inverter question
Post by: luthierwnc on August 23, 2023, 11:06:16 am
Hi pdf64,  I always seem to get you the weird ones.  I was concerned that the effects on one channel were causing phase problems for the other.  It was probably a pedal set wrong.


It turns out those amps are often used that way with the pentode side supplying the grit and the triode channel for polite effects.  Some guys will use a volume pedal on the triode-side to set the effects level.  I put a little Spark Booster set at unity mostly as a buffer and will probably ditch all but the Chimey Boost on the EF86 side since that channel has plenty of hair.  Trouble is; you have to play that amp loud -- even at half power it peels paint.


Thanks for getting back to me, Skip 
Title: Re: Left-field phase inverter question
Post by: pdf64 on August 23, 2023, 11:22:15 am
Hi pdf64,  I always seem to get you the weird ones… 
The weird ones can be the most interesting  :icon_biggrin: