Insert 'box of hall' reverb into a polytone mini brute amp ?
Posted: 23 Nov 2012, 11:02
Hello guys, I posted this on the amp forum, but theres no answer so i thought maybe here someone would have an idea..
I would like to add a reverb to a polytone amp (without reverb) i grabbed used a few weeks ago. As advised, i'm changing all electrolytic caps into it at the moment and i thought that as it's opened, it would be a great time to add reverb to it.
However, i am not sure how i could do that: mainly, where should i take the signal into the preamp path, and where should i reinject it into the amp?
The schematic of the preamp of the polytone i have is here:
my amp only has the circuit in the big red square : preamp and master volume control. no distortion or reverb.
here is the box of hall schematic for reference :
Looking at the schematics i believe i could try to plug the box of hall into that amp like this, but i would really like to have the opinion of more advanced people about it:
- Drop the input section of the Box of hall : 3,R4 C4 and IC1B. replace R22 on the polytone schematic by R5 on the box of hall schematic, and cotinue with the box of hall circuit : ICIC, belton brick, damp and reverb controls, and finally, R8 would connect to UA3 on the polytone schematic: to C15 and R18 in the feedback loop of the UA3 opamp.
The questions i have are :
- the box of hall sends the reverb back into the original signal and blend it using the - input of the op amp. the polytone uses the + input, could that change something? or cause problems?
- The box of hall taps the signal to the reverb part of the circuit in the feedback loop of IC1B while i would take it before R16 in the polytone schematic. would that be a problem? (if i remember correctly, the feedback loop of a opamp without a resistance has a high impedance which i wouldn't have if i take the signal where polytone suggests it.
- the main power bus on the polytone is 15V, would it be of to put a TL072 at 15V, that would allow me to save a voltage divider section.
- I guess i could easily find a voltage regulator that does 15V -> 5V, right?
Thanks for your advices, i've made a super ugly copy paste of the two schematics to give you a better idea of what i tried to explain.
Any advice is welcome
I would like to add a reverb to a polytone amp (without reverb) i grabbed used a few weeks ago. As advised, i'm changing all electrolytic caps into it at the moment and i thought that as it's opened, it would be a great time to add reverb to it.
However, i am not sure how i could do that: mainly, where should i take the signal into the preamp path, and where should i reinject it into the amp?
The schematic of the preamp of the polytone i have is here:
here is the box of hall schematic for reference :
- box of hall reverb belton.png (10.7 KiB) Viewed 524 times
- Drop the input section of the Box of hall : 3,R4 C4 and IC1B. replace R22 on the polytone schematic by R5 on the box of hall schematic, and cotinue with the box of hall circuit : ICIC, belton brick, damp and reverb controls, and finally, R8 would connect to UA3 on the polytone schematic: to C15 and R18 in the feedback loop of the UA3 opamp.
The questions i have are :
- the box of hall sends the reverb back into the original signal and blend it using the - input of the op amp. the polytone uses the + input, could that change something? or cause problems?
- The box of hall taps the signal to the reverb part of the circuit in the feedback loop of IC1B while i would take it before R16 in the polytone schematic. would that be a problem? (if i remember correctly, the feedback loop of a opamp without a resistance has a high impedance which i wouldn't have if i take the signal where polytone suggests it.
- the main power bus on the polytone is 15V, would it be of to put a TL072 at 15V, that would allow me to save a voltage divider section.
- I guess i could easily find a voltage regulator that does 15V -> 5V, right?
Thanks for your advices, i've made a super ugly copy paste of the two schematics to give you a better idea of what i tried to explain.