Advantages of controlling volume via fx loop?

David Mullis · From: Rock Hill, SC

I read in another post about how you could hook your volume pedal in via the pre-eq patch. I had thought about doing this a while back, as well as running my stomp boxes through the FX loop. The only advantages I see in doing this are, you don't have all of that stuff in line with your guitars signal going to the amp. Any other avantages or disadvantages to doing this?

Thanks
David

Mike Brown · From: Meridian, Mississippi USA

I assume that you are referring to the PRE EQ PATCH on Peavey amps? If so, here is an article that I recently submitted to the Ozark Steel Guitar Newsletter concerning this patching procedure. Note; this is pre eq, not post eq.

THE PRE EQ PATCH
“WHY IS IT CALLED A VOLUME PEDAL PATCH?”
By Mike Brown

Since Peavey Electronics first introduced the Session500 steel guitar and fiddle amplifier back in 1980, we have been the only company to offer an interesting solution to the problems that are encountered when using potentiometer based pedals for controlling the volume of the amp. Although our “volume pedal” or “pre eq patch” point has been a standard feature on every steel amp since the Session500, players may not be aware of this unique method of “inserting” their volume pedal into the circuit on the various models that have been introduced since that time. On the Session500, this insert point was labeled “PEDAL-IN & OUT”. On the Vegas 400 and the Nashville 400, it was labeled “PRE EQ PATCH-IN & OUT”. On the Session400 Limited, this insert point is labeled “PRE EQ PATCH-SEND & RETURN”. On our latest models, the Session2000 and Nashville1000, this insert point is labeled “PRE EQ PATCH-SEND & RETURN”. Although they are all labeled with different names, the purpose and results are the same.

A typical volume pedal patch is made between the guitar and the amplifier input. However, doing so could cause the tone of the guitar to change as the pedal is moved up and down with changing volume requirements, because this patch introduces a varying resistance as seen by the guitar pickups. The Peavey pedal patch allows the user to insert a volume pedal into the active pre-amp circuit, thus increasing the performance of the volume pedal. Because the volume pedal is patched in after the first pre-amp stage, no signal degradation occurs regardless of the pedal volume setting. The volume pedal changes only the volume without affecting the tone or character of the guitar voice.

This is how the circuit works. When an instrument signal is routed through either the high gain or low gain inputs (10db gain difference between the two types), it is routed through a first order high-pass filter that blocks DC into and out of the first operational amplifier (IC chip) for protection. A 20 hertz low pass filter is in place to provide better signal to noise ratio of the circuit. In this first stage of the circuit, we have designed in various electronic component circuits to reduce noise so that it won’t be amplified through the remaining signal path. When the audio signal hits the pre gain control potentiometer, the level of the signal that is to be routed through the remainder of the circuit is dependent upon the setting of this control. At this point in the circuit, the signal is routed out of the OUT jack via shielded cable, through the volume pedal and back into the circuit through the IN jack using a second shielded cable. NOTE; When the volume pot is in the fully up position (no sound), the wiper of the pot is sent to ground. When the volume pot is in the fully down position (sound), the signal is then audible through the circuit). The pedal volume pot acts in the same fashion as the PRE GAIN control on the amplifier. The IN jack is of the “normaling” type, which remains closed until a ¼” plug is inserted for the returned signal. At this point in the circuit, additional noise filtering is applied and a 1.56Mhz. low pass noise filter is employed to shield radio frequencies from entering the circuit. In addition, a high pass filter blocks frequencies below 10 hertz.

At this point in the circuit, a second first order high-pass filter blocks DC current into the second gain stage before signal is routed through the remainder of the preamplifier.

This “pedal patch” is exclusive to Peavey steel guitar amplifiers and it works! If you have any questions, please contact me toll free in the U.S. at 1-877-732-8391 or by e-mail at mikebrown@peavey.com

David Mullis · From: Rock Hill, SC

Thanks Mike, I figured no signal loss would be a plus. You cleared that up and then some

I'll give it a try later on and let you know how I like it.

Take Care
David

Mike Brown · From: Meridian, Mississippi USA

Chip Fossa · From: Monson, MA, USA (deceased)

Hello Mike,
Great explanation on the use of the EQ Patch.
All these years I've owned this Vegas 400 and never quite knew what it was for.

Anyway, would a typical hookup be like this:

steel[out] to vol.pedal[in] * vol.pedal[out]
to EQ Patch[in] * EQ Patch[out] to Input 1[in]?

I'm right now working on some pull rods and
pedal throws and so I can't wait to get the steel back up and running and try this out. Same goes about what Jim Smith had to say about putting things in before and after the effects loop and where you gave that great Peavey Amp chronology. Very informative, and thank you for that.

ChipsAhoy

Mike Brown · From: Meridian, Mississippi USA

Chip, the correct patching procedure is as follows;
Output of guitar straight to the input of the amp(bypassing the volume pedal), using two more shielded cables, patch the first from the SEND,OUT or TO(depending on the Peavey amp model) to the input of your volume pedal. Using the the third cable, patch from the output of your pedal to the IN, RETURN or FROM jack(depending on the Peavey amp model). This completes the "3 cord hookup", "volume pedal patch" or "pre eq patch" procedure.

If you there is any confusion with these procedures, please let me know. I'm here to assist you.

MB

Chip Fossa · From: Monson, MA, USA (deceased)

Thanks Mike for straightening me out. Easy enough to follow. Can't wait to give this a whirl; just a matter of getting the steel
back together.

Doyle Huff · From: Broken Arrow, OK USA

Mike, can you do this with a Profex 2?

Wayne Morgan · From: Rutledge, TN, USA

Hi Mike Brown, you are most helpful in any matter that comes up in electronics, I know you are in the business, but you go beoynd the call, to help people with their problems,,and I thank you for being the nice guy you are. You are one of the Steel Family Treasures.

Regards,
Wayne

------------------
Wayne Morgan
BMI D10 8x8, Nash 400,'63 Fender Super Reverbe,and '71 telecaster custom

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