Princeton is back... this time its Reverb

[Triffid]

So the topic as of late is reverb

A while back i ripped the distortion channel out of the my fender princetion 112 plus schematic (with much of everyones help, thanks again) and ended up with pretty cool sounding effect... here is the schematic link...

//www.mrgearhead.com/faq/schematics/fender/Princeton%20112%20Plus%20Sche3BB.pdf

I would like now to pull the reverb section.  My amp that i currently play doesn't have this and i have been missing it.  I am will to rip out the spring unit from my princeton to do this.   I see the section where the reverb is (center right in schematic).  Its seems to be pretty simple using  a couple tl072's.  I know i'll also need to add a voltage divider for the opamps.  I guess i am not quite sure where i should "cut and paste", more or less,  to preserve a good sounding reverb.  I have my guesses... but i'm not sure.  The effects loop that is to be connected is not important to me... I will be making an external box.  

Feel free to tell me that it would be easier just to create one from scratch with ggg's stage center reverb.

Thanks in advance for any help provided.

[Triffid]

Ok, i got home to look at the accutronics unit in my princeton.. it is of type... 8EB2C1b.

from accutronics web site...
8 for Type 8
E = 800 Ohm Input Impedance
B = 2575 Ohm Output Impedance
2 = Medium (1.75 to 3.0 sec) decay time
C = Input Insulated / Output Grounded
1 = No Lock
B = Horizontal Open Side Down

Will this work with the stage center reverb from ggg?  Or do i have to build the reverb from the princeton schematic?  I though ggg recomended around 300 ohm input impedance for the stage center.

Thanks again for any help

[Johnny G]

i cant remember the exact spec on the accutronics tank i used for the center stage reverb (and dont want to have to open up the boc i made to have a look) but im fairlly sure mine had over 300 ohms of resistance.

what i did was to put a trim pot instead of a fixed resistor in the feedback loop of the opamp thats sending a signal to the tank. that way i could increase or decrease the amplification of the signal being sent to it.

i also put in a simple high pass tone control before the signal gets sent to the tank which i found to be really useful for getting some interesting effects.

i can do everything from U-571 type noises to having a really interesting clean sparklly sound with only the higher frequencies having reverb on them. if you want i still have the schem for my edited version around here somewhere that ill put up here

i was also flash and put in a relay switching system so theres just a push button on the front and theres a normal TS jack input that can be used for a foot switch

[Triffid]

Thanks for the help.

I am looking at the schematic at ggg...
http://www.generalguitargadgets.com/diagrams/stage_center_reverb_sc.gif

are you talking about the mix pot?  Or can you tell me which resistor you talking about?

Thanks again

[Triffid]

Oh, i see... your talking about r7 right... the 470 k resistor?

[Triffid]

Does this seem right... with a bipolar 9v supply instead of the +-16 volts for the opamps?

http://castagno.org/test.png

Any help is appreciated

[Triffid]

wow... am i black listed or something?  Maybe i should just build the stage center then

[Triffid]

Well, i'm not sure anyone cares at this piont. but i went ahead and breadboarded up the stage center reverb and used it with the accutronics springs from my princeton.   It sounds pretty good except i get a pretty good size hum when i turn the depth all the way up, not that that depth is very playable anyway.  I seem to enjoy a very small portion of the reverb this thing has to offer.  I am willing to chalk up the hum to the bread board for now... next step is to get a bipolar supply (max1044) and box this baby up.  I will also try the tone stack before the output to the reverb unit from the previous suggestion... thanks

http://castagno.org/reverb.jpg

oh... i also added a 50k pot instead of the 33k resistor on the final opamp before output to control the volume with true bypass