Effects in the loop of #124

[Rob Livesey]

Hi Chaps,

Without going to the expense of a Dumbleator, has anyone tried any rack effects or other such devices, especially reverbs and delays in the basic loop of a #124 style amp?

What were your findings and can anyone recommend something to try?

Cheers,
Rob.

[Normster]

In my limited experience (reverb and delay pedals only) the passive loop works OK as long as the cable runs are reasonably short and the volume is moderate. Unfortunately, I've only tried two setups.

With an Arion digital delay in the loop and short cables, the amp sounds great until I turn the volume up past 10:00 and hit PAB. At those settings the pedal goes into digital clipping when digging in on the low notes . Very nasty sounding.

Also tried running 50' of cable using a Maxxon analog delay. No clipping at any volume, but the cable takes its toll on clarity. It's not too bad, mind you...but the difference is noticeable.

Sorry, no experience with rack effects.

[odourboy]

Hey Rob,

I can share my (somewhat limited) experiences. I'm sure some of the seniors members here will have something to add.

There's several things a Dumbleator will do for you:
1) Provides substantial buffering against signal loss (highs in particular) from cable runs to/from your devices and low input impedance on said devices.
2) Provides attenation so you don't overload devices at higher signal levels and gain on the return path to restore the signal level to where it should be for the power section of the amp.
3) Colors the tone in a pleasing manner.
4) Inverts the signal (this is important if you buy into the statement that signal phase to the speaker matters with a D-style amp)

So, all that said, I have used a few buffered reverb and delay units with an unbuffered loop on very short (12"), low capacitance cables at moderate volumes with no signal loss that my 40+ year old ears could detect.

Hope that helps.

[Structo]

I installed the Ironsounds buffered FX loop in my D'Lite and it works great with my delay and Boss RV-5 reverb.
I use standard 12 foot guitar cables to and from the pedals.

[dogears]

Rob, are you asking if the special "network" in #124 has any bearing on things? If so, the network is bypassed when effects are used so the basic in/out jacks present in all Dumbles is what you are using. And in my experience, you need a buffered loop. You'll drive the hell out of effects otherwise (as Norm points out)

Hi Chaps,

Without going to the expense of a Dumbleator, has anyone tried any rack effects or other such devices, especially reverbs and delays in the basic loop of a #124 style amp?

What were your findings and can anyone recommend something to try?

Cheers,
Rob.

[Funkalicousgroove]

If you are trying to do it on the cheap you can use a mic Impedance adapter to change the signal to Lo-z to drive your effects, then recover with a cheap Mic Preamp-

[dimitris]

Dogears wrote:Rob, are you asking if the special "network" in #124 has any bearing on things? If so, the network is bypassed when effects are used so the basic in/out jacks present in all Dumbles is what you are using.

Maybe I’m missing something obvious but looking at ods_124060 photo i think that the opposite is happening. It seems to me that the brown wire from master volume is soldered to the ring lug of the return jack and the green wire from 0.02 cap is soldered to the tip lug of the same jack. So these two wires are connected when the loop is not used. When the loop is used this connection breaks and the signal goes from the ring of the return jack to the tip of the send jack through the resistor/cap network
Again if I’m missing something please feel free to correct me.

[ayan]

Dogears wrote:Rob, are you asking if the special "network" in #124 has any bearing on things? If so, the network is bypassed when effects are used so the basic in/out jacks present in all Dumbles is what you are using.

Maybe I’m missing something obvious but looking at ods_124060 photo i think that the opposite is happening. It seems to me that the brown wire from master volume is soldered to the ring lug of the return jack and the green wire from 0.02 cap is soldered to the tip lug of the same jack. So these two wires are connected when the loop is not used. When the loop is used this connection breaks and the signal goes from the ring of the return jack to the tip of the send jack through the resistor/cap network
Again if I’m missing something please feel free to correct me.

You are absolutely correct, Dimitris. What goes out to the FX SEND jack is the affected, thinner signal. Therefore the network only comes into play when the loop is used.

Gil

[odourboy]

Dogears wrote:Rob, are you asking if the special "network" in #124 has any bearing on things? If so, the network is bypassed when effects are used so the basic in/out jacks present in all Dumbles is what you are using.

Maybe I’m missing something obvious but looking at ods_124060 photo i think that the opposite is happening. It seems to me that the brown wire from master volume is soldered to the ring lug of the return jack and the green wire from 0.02 cap is soldered to the tip lug of the same jack. So these two wires are connected when the loop is not used. When the loop is used this connection breaks and the signal goes from the ring of the return jack to the tip of the send jack through the resistor/cap network
Again if I’m missing something please feel free to correct me.

You are absolutely correct, Dimitris. What goes out to the FX SEND jack is the affected, thinner signal. Therefore the network only comes into play when the loop is used.

Gil

So I've got it wrong in this schematic then?

https://tubeamparchive.com/viewtopic.php?t=4354

[ayan]

Maybe I’m missing something obvious but looking at ods_124060 photo i think that the opposite is happening. It seems to me that the brown wire from master volume is soldered to the ring lug of the return jack and the green wire from 0.02 cap is soldered to the tip lug of the same jack. So these two wires are connected when the loop is not used. When the loop is used this connection breaks and the signal goes from the ring of the return jack to the tip of the send jack through the resistor/cap network
Again if I’m missing something please feel free to correct me.

You are absolutely correct, Dimitris. What goes out to the FX SEND jack is the affected, thinner signal. Therefore the network only comes into play when the loop is used.

Gil

So I've got it wrong in this schematic then?

https://tubeamparchive.com/viewtopic.php?t=4354

'fraid so. All you have to do is relocate the wire coming from the master to the other end of the network, to match the picture, and it will be fine.

Cheers,

Gil

[dogears]

Thanks for clarifying Gil. I could have sworn you told me it was there when the loop was not used.

Whoops!

[odourboy]

Thanks Gil. Makes more sense as well. FWIW, I've updated the schematic.

[ayan]

Thanks for clarifying Gil. I could have sworn you told me it was there when the loop was not used.

Whoops!

And I may just have said that - I sincerely don't remember - but if Idid I was wrong! Fortunately, the picture is very clear and 100% unambiguous.

Gil

[ic-racer]

I looked at the pictures again and I see now what is going on and changed my own schematic accordingly. Good thing I read this thread

In terms of Rob's amp, I wonder how it is wired. The Overtone layout must have an error because it shows the 220K and 270pf cap shorted out with a jumper.

[ayan]

Thanks Gil. Makes more sense as well. FWIW, I've updated the schematic.

Super cool!

Gil