Need HELP with my very first rack effects unit - Jemsite
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post #1 of 6 (permalink) Old 09-17-2012, 05:57 PM Thread Starter
Join Date: Apr 2012
Location: Dallas, Texas
Posts: 13
Need HELP with my very first rack effects unit

I just purchased a Yamaha FX770 rack effects unit. I know its older than dirt, but it was mint condition and only $ I though what the heck. I currently use pedal effects, and run all my time-based pedals through the serial loop of my Hughes & Kettner Tubemeister-18 with no problems. I was curious how a rack effects unit would compare to my pedals, so I disconnected my pedalboard and plugged the Yamaha's mono output into the fx loop of my amp, and plugged my guitar into the front of the Yamaha. But I could not figure out how to return the loop to the Yamaha...and it did not require a return cable to play through the amp.


The unit sounded good through the clean channel of my amp, but when I switched to the Lead (distortion) channel I heard NO distortion. There was a very slight increase in volume, but no distortion. I thought perhaps I had run the connection wrong, so I tried swapping the plugs to different jacks, but the only way I would get ANY sound was the original way I had it connected. I also tried plugging my guitar into the front of my amp, but once sound.

I plugged my guitar back into the front of the Yamaha, and plugged the output of the Yamaha into the front of my amp and...VOILA'. I could now use the amp's distortion, however, the quality of the effects turned to complete $hite!!

Can I run a rack effects unit in the same manner that I run pedals?

Here is a partial link (since I dont have the required posts to add a proper link) to a photo of the rear connections of the Yamaha FX770 for reference.


Any help is greatly appreciated.

kidfixer is offline  
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post #2 of 6 (permalink) Old 09-17-2012, 08:19 PM
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Location: Bozeman, MT
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Re: Need HELP with my very first rack effects unit

I have no experience with this unit, but a quick search indicates that the input is high impedance, so the input is intended to be fed directly from the guitar rather than from the Send of an amps effects loop (low impedance). It looks like there is both an input level knob (adjust for no clipping) and a output level control -- did you experiment with both? It might be possible to use it for effects only inside the amp's effect loop (effects send into Yamaha; Yamaha output into effects return) by turning off the Yamaha's amp sims and experimenting with the input level, but the high impedance input is likely to present problems in most effects loops.

I expect things sounded nasty with your amps dist channel because you had the units amp sims enabled. That's like having 2 preamps chained together which usually creates problems. I also see an insert loop which apparently is an analog output that precedes the amp sims. So another way to connect it while bypassing the internal amp sims would be to run the Yamaha's Insert Loop Send into the amps effects return.

BTW -- do you have the manual for this thing?
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post #3 of 6 (permalink) Old 09-18-2012, 09:26 AM
Join Date: Dec 2000
Location: Melbourne, FL 32940
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Re: Need HELP with my very first rack effects unit

I've been running rack units since 1989, so I've hooked things up in all kinds of strange ways.

First you need to understand amps, combos or heads and rack power amps.

A Combo amp or Head, is made up of two parts, the Preamp and the Power amp.
The effects loop is placed between the two.
In order

1. Preamp, the Bass, Mid, Treble, Presence and Distortion
2. FX Loop Send
3. FX Loop Return
4. Power amp, the Volume (The Noise Maker!)

If you only use the FX Loop Return, you are bypassing the Preamp section of the amp, this is why there was no distortion when you switched channels.

This is where I have a beef with Combos and Heads.
The Preamp section of a Combo or Head limits the amount of tone that can be run to the power amp, a bottleneck is created.
This is why they get muddy when you try to add to much EQing to get the tone your after.
Effects and some pickups can cause the same problems on some amps too.

I learned this years ago with my 5150 Head.
I was trying to run my ADA MP-1 and Rocktron Pro-Q (EQ) in the front of the amp.
I was trying to add more bass and it just mudded out on me.
So I bypassed the Preamp and plugged in to the FX Loop return.
I had to use my ADA to control the volume level.
The knobs on the front of the 5150 were useless, no 5150 Preamp.
Then I was able to get more bass without the muddyness now that the preamp bottleneck was out of the way.

This is what rack power amps are, good clean power without any tone.
A good rack power amp should do nothing but blast whatever you are running in to it without coloring the tone at all.

If you want to run this rack unit with your amp, plug the guitar in to the front of the amp.
Plug the FX Loop send in to the input on the rack unit.
Then the output of the FX unit to the return on the amps FX Loop.

You should start with the level control knob on the FX unit down all the way.
If you can bypass the FX Loop do it to listen to how load the amp is.
Then enable the FX Loop and turn the level knob up unit it sounds like the same volume as with no FX Loop.
This way you won't over drive the I/O and end up with line distortion.

If the FX unit has input and output level knobs, run the up until you see the meters at a normal level.
Then turn the output up to match the amps volume level.

On some amps the way it's wired, you need to keep adjusting the input level because the preamp level keeps going up as you turn the volume up on the amp.
This causes the input to the FX unit to clip.
If this happens to you, turn the input level on the FX unit down to compensate for the greater input from the preamp.

Let me know if you have more questions.
sebastian is offline  
post #4 of 6 (permalink) Old 09-18-2012, 01:10 PM
Join Date: Jun 2003
Location: Florida
Posts: 593
Re: Need HELP with my very first rack effects unit

Sebastian is the man! You should get him to recommend a setup for you... That's what I did and have been loving it every since.
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post #5 of 6 (permalink) Old 09-18-2012, 02:22 PM
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Posts: 916
Re: Need HELP with my very first rack effects unit

You probably have it already, but here's a link for the manual:

Recommended connections are on p. 11.
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post #6 of 6 (permalink) Old 09-18-2012, 09:09 PM Thread Starter
Join Date: Apr 2012
Location: Dallas, Texas
Posts: 13
Re: Need HELP with my very first rack effects unit

Originally Posted by sebastian View Post


Let me know if you have more questions.

Great info, thanks, man!! However, I think I'm just gonna toss this thing aside. I dont believe it was designed to be used in the capacity that I'm attempting to use it in. Plus, it seems like you really have to invest some time in tweaking all the parameters to get a sound you like. I didn't particularly like ANY of the factory patches that came pre-loaded from Yamaha. My current selection of pedals kick the snot out of it as far as quality of sound. Then again, the cheapest pedal I have cost four-times what I paid for this thing

Maybe I'll try to pick up a dedicated effects unit like the TC Electronic G-Major, or one of the Lexicon MPX units.

If anyone wants this Yamaha FX770, you can have it for free...just cover S&H.
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