What Goes in the Loop?

[kd]

Is it common to run all your pedals in the loop or do you run some in the loop and some in front of the amp?

Thanks,
Ken

[guitardude57]

I would run any boost or distortion in front......and modulation and time effects through the loop.

[Structo]

I think the best scenario is to build or buy a Dumbleator type tube buffered loop and to run your time based or modulation type effects in that loop.
For instance on my amp (D'Lite) and D'lator I run Chorus, Modulation, Delay and Reverb in the loop.

If you don't run a buffered loop, you can run a pedal like reverb on the passive jacks on the amp but it is not optimum to do that.

I don't currently run anything into the front end although I do sometimes use a Analogman Sunface with Sundial for fuzz.
The OD on the Dumble is pretty darn good and really performs well for a overdrive type effect.

[kd]

Thanks guys.

Ken

[Bob-I]

Is it common to run all your pedals in the loop or do you run some in the loop and some in front of the amp?

Thanks,
Ken

Pedals don't really handle the power of the loop well. Unless you buffer it using a Dumbleator or some other device you'll overdrive it and kill the signal.

I run a TC electronics Nova Delay in the loop, because it has a line level input and works well in the loop.

[JD0x0]

I've been wanting a D-lator for a while but im not sure i really NEED one. I only use a Tech 21 D.L.A. in the loop with 3in patch chords. The pedal has a boost/cut built in which is useful for control signal to the power amp similar to the dlator. but the delay does not reduce the signal to the front of the pedal like a Dlator.

should i spend the cash on a C-lator from ceriatone or possibly just build in a volume pot before the loop to cut the signal and then use the boost in the pedal for recovery?

[guitardude57]

My loop is D-lator built in the amp. Had the extra tube there anyway.

I haven't owned a distortion pedal in 25 years, always had good sounding tube amp crunch happening.

Along with a couple of good sized racks of effects and a Ground Control Rack Switcher operating everything. The foot controller switches amp channels, amps, and all the effects............works pretty darn good.

So the ODS works with this set up nicely.

If you have the room in your amp for 1 more 9 pinner and a small handful of parts....put in the tube loop..... Or make the D-lator, the extra gain there makes things very nice. With or without effects. It is must have.

I believe the '97 ODS layout shows the set up.

[kd]

I should have said I have a Dumbleator in the amp loop. I don't know much of anything about loops and was going to plug all the pedals into it. I'll try the overdrive type pedals in the front of the amp. Been busy and haven't had a lot of time to experiment. Thanks to everyone for the input.


Ken

[guitardude57]

You typically want distortion devices in front. So since the clean and OD is in front of the loop where it belongs, put time and mod effects in the loop. You may not even need the distortion pedals since the OD is good by itself. Some use them for just a solo boost.....

You will want to balance the ins/outs (if you have level pots) for as close to unity gain as you can. That way all the signals will be clean and true without overload.

I have level controls, and all the rack stuff has level LEDS to make sure not to overload any inputs. I also mounted a loop off switch, to check for effects on, versus off levels.

Have fun!

[Structo]

Yes having a bypass switch on the loop is a nice feature to have to check levels.

[talbany]

An amp with an effects loop is best designed to run with the power amp completely clean, getting the distortion from the preamp, at least when using delay effects. Otherwise you are better off doing a wet/dry rig if you want to crank the amp to the point where the output stage distorts.

A buffer should only be necessary if the amp's effects loop output source impedance is high (such as a "passive", or unbuffered loop), or if the effect's input impedance is low (some line-level effects have low input impedances, around 10K ohms or less, so they may need a buffer if the amp's effects loop source impedance is high), or if you are driving long cables and are experiencing a loss of highs.
__________________
Beware - you don't match impedances when dealing with low-level signals like you do when using a power amp and a speaker.

In a low-level signal application, you want maximum voltage transfer, not maximum power transfer, so the "ideal" situation is a zero output impedance from the driving source going into an infinite impedance for the receiving end.
An example being say you have a send impedance of 100 ohms is very low, so it is near "ideal", and the 1Meg input impedance of say a Boss device is very high, so they are a good match because you will not lose any appreciable amount of voltage - if the effect puts out a 1V signal, you'll get 0.999 volts at the input to the Boss.

The output impedance of the Boss is 1K, which is still fairly low, so driving into the return of the loop, which presents a 220K load (Mounted on the S R Jacks) you'll only lose a small amount of voltage - if the Boss puts out a 1V signal, you'll still get 0.995 volts at the FX return, so they are well-matched.

If you have an FX loop with a high output impedance or an effect with a low input impedance, you'll need to use a buffer between the loop output and the effect input. Likewise, if you have an effect with a high output impedance or an amp with an FX return with a low input impedance, you'll need to use a buffer between the effect output and the amp loop return.

In general, if the source impedance is at least 10 times lower than the load impedance, you're okay, because you'll get 90% of signal transfer. The lower the source impedance, the less high end you'll lose due to cable capacitance or load capacitance on the input of the effect, so the closer you get to a zero ohm source impedance, the better.

The problem that usually occurs with instrument-level effects like pedals in loops is that you have to attenuate a large signal swing down to the level of a guitar pickup signal so you don't overload the pedal effect (which is designed to go inline with the guitar and amp input) and then amplify it back up to a large level to drive the return side. This will greatly amplify any hiss at the output of the effect and any noise present in the chain, which is why it is best to use line-level effects in an amplifier fx loop whenever possible.

Ironically, most tube manufacturers use tube buffers for the send and receive of an fx loop (to keep the all-tube "purists" happy), but you can get a much better noise floor with modern low-noise opamps in the loop circuitry. Since the effects are 99.9999% (series loop) solid-state anyway, it really shouldn't matter, tone-wise, if the loop is solid-state (as long as it is relay-bypassed when not in use)..

Tony

[llemtt]

Ironically, most tube manufacturers use tube buffers for the send and receive of an fx loop (to keep the all-tube "purists" happy), but you can get a much better noise floor with modern low-noise opamps in the loop circuitry. Since the effects are 99.9999% (series loop) solid-state anyway, it really shouldn't matter, tone-wise, if the loop is solid-state (as long as it is relay-bypassed when not in use)..

+1

but sometimes it's a lot easier to put a tube buffer in a tube amp than ICs and their supply

anyway yours is one of the best summary of loops/buffers/impedance I read

cheers
teo

[ChrisM]

I use HV MOSFETs for my buffered loops. I prefer them to ICs just because I find them easier to implement and build with.