Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: Toxophilite on June 22, 2016, 11:39:28 pm
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I just went to the dark side and picked up a nice Roland Jazz chorus 77 for a decent price
I've always liked these amps but the JC 120 was just too big
As I almost always play clean I don't really need a tube amp for that
Now if I want i can have one of my deluxes cranked for distortion and use some amp switching too
THis one with 10' speakers and stereo amps is just perfect. LOUD and clean and not noisy
It has stereo line outs but I'd like to add an effects loop
Even just having one line in going to the second channel/amp would be cool because then I could run my space echo(Re-150) from the effects loop and run the echo into the second channel and get a smaller version of the two amp thing I normally do
Anybody have experience with these or have done this same thing ?
The only schematics I can find online are older pre effects loop JC-120 schematics
I was kind of hoping to find a schematic for one of the newer models so I could just copy what they did
but I'll be happy with whatever works if someone has a good idea
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here's the schematic
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Figured it out with help from my electronics engineer brother in law
I'l record it here in case anyone ever wants to do the same
run line out from the 'mono' line out (27) with dummy plug in line out 10
This gives you a dry signal
Install another jack and run just the echo(Re-150 can split the dry and echo signal) back in through that jack via a 47K or 100K resistor (I think I'll go with the 100K) and a .1mfd cap to block any DC
run that to leg 3 of IC-4 and hey presto stereo echo!
next I'm going to try and shim the outside edges of the speakers maybe 1/2" where they mount on the baffle to give them a slight outward slant to achieve a wider spread on the chorus and echo the farther you are away from the amp
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Though it works very well and I'm loving it.
I did notice (while recording the amp with both speakers miked) that with the space echo in the new 'effects loop' the dry sound on the echo side is slightly quieter than before. I can see it in the wave file for that channel
Without the echo unit attached both channels are pretty well equal
I'm curious if this is because the added echo input at that stage makes for less dry (somehow it only wants so much level and normalizes it.)
or could it have to do with the size of mixing resistor I'm using
I went with a 82k so i can use roughly the same settings on the echo Volume-wise as I have for years
However I could use a 47K like the chorus is using
any idears??
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My quick look suggested that matching gain and levels would be difficult.
The nominal maximum output of the Echo is somewhat below the levels used around the JC's power amp inputs.
My big-rock idea would be to throw in some op-amps for buffer and boost.
You may get there with resistor diddles.
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Thanks!
The difference is a db or two, noticeable but not horrendous
I can turn the echo volume (on the RE-150) right down and it makes no difference to the non-echo sound in the wet channel. However if i unplug the patch chord from the echo output the levels in the JC-77 balance out again between the channels.The chords are still plugged into the back of the JC I just pull the echo output one out of the Space echo.
Plug it back in and even with the volume of the echo turned down to nothing the non echo signal drops again
interesting
Here's the Roland schematic just in case
Here's my extremely dumb question spawned by ignorance ..,
Would I be better off going higher or lower on resistor size?