Author Topic: Amp/signal splitter  (Read 381 times)

Buffalo Tom

Amp/signal splitter
« on: September 04, 2020, 06:51:27 AM »
Hi. Is this good design for a signal splitter to feed multiply guitar amps. Will breadboard it today and try but any inputs on the design is gratefully received. Idea is one input buffer followed by a separate buffer to drive each transformer. Should I include a series resistor (100ohm?) after C2,C3,C4?. Do I need any resistors, caps after OA1 and before the non inverting inputs on the following op-amps?

It's a rack mount unit and I have built a internal AC power supply for it. I have 24VDC coming from there and planning to use 24V for relays and lamps and +/-12V for the op-amps. Also its 5 outputs but only showing 3 on the schematic.


antonis

Re: Amp/signal splitter
« Reply #1 on: September 04, 2020, 07:15:07 AM »
I don't think Zobel networks are necessary there, Tom..
(maybe it should be better to be placed across transformers primaries..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Buffalo Tom

Re: Amp/signal splitter
« Reply #2 on: September 04, 2020, 08:49:05 AM »
I don't think Zobel networks are necessary there, Tom..
(maybe it should be better to be placed across transformers primaries..)

Thanks Antonis

Those 2k resistors in series with 1.6 nF is from the Lundahl datasheet.. Will try both with and without them. The 10nf cap is something Ive seen on transformer isolated outputs on Cornish gear. Will experiment with and without that cap too and see if it makes any difference.

Here is the power supply just finished  ;D


And here is what Iím planing to use as rail splitter. Values stolen from the Keeley mixer.




antonis

Re: Amp/signal splitter
« Reply #3 on: September 04, 2020, 03:04:03 PM »
R9 forms LPF only for positive rail..
(place another one for negative rail)

And better, move both of them after D1.. :icon_wink:

P.S.
100R should exhibit 1V drop for 10mA rail current... :icon_wink:
(you might have to lower their value and oversize C11 & C12 respectively..)
« Last Edit: September 04, 2020, 03:08:18 PM by antonis »
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Buffalo Tom

Re: Amp/signal splitter
« Reply #4 on: September 05, 2020, 05:45:07 AM »
Thanks Antonis for taking time with me  :)

R9 forms LPF only for positive rail..
(place another one for negative rail)

And better, move both of them after D1.. 

Like this?  :icon_wink:


Most of the rail splitter schematics I found don't use R9 but It was included to the positive rail in the Keeley schematic I copied.. http://www.robertkeeley.com/manuals/Keeley_Parallel_Mixer.pdf

Quote
P.S.
100R should exhibit 1V drop for 10mA rail current... :icon_wink:
(you might have to lower their value and oversize C11 & C12 respectively..)

Interesting but Im not sure I understand this... What values are suatable? Maybe Im better without R9 and R12?

antonis

Re: Amp/signal splitter
« Reply #5 on: September 06, 2020, 06:15:07 AM »
R9 could or couldn't be included.. Its presence depends on how much regulated is +24V..
(e.g. in case of +24v taken from a truck battery, it should be useless..)

R9 & C11 form low pass filter of about 34Hz cut off frequency while there is a voltage drop across R9 (is set in series with +12V) proportional to current draw by load..
e.g. in case of a 1k2 load resistance, between +12V & GND, there is a 10mA current flowing across it.. That current also flows through R9 resulting into 1V voltage drop..

If you wish to preserve 34Hz cut off frequency, it should be better to make R9 value 10R (ten times smaller) and make C11 value 470μF (10 times bigger)

P.S.
Same stand for R12 / C12..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..