5150: What's the deal with the Effects Loop?

[mightywarlock]

So i just got a 5150, and it is all hissy, so I thought I would try my ISP Decimator G-string, but when I put it in the Effects Loop, all of a sudden there was this crazy buzz that would not go away. Unplug the G-string, and no buzz, just hiss.

 

Is this Effects loop bad?

or do 5150 loops not work?

[missingastring]

I think the 5150 loop is parallel, not serial. So basically, you're mixing effects into the dry signal, not putting them in series with the preamp.

[TheRymanChu]

it's a serial loop.

[PaoloJM]

5150 has a series loop.

 

 

How are you powering you pedal?

Seems like you might have a ground loop going.

[TheRymanChu]

From London Power:

 

Q: Is there a way to reduce the noise in my [Peavey] 5150's high gain channel without having to use a noise gate in the FX loop? My [Mesa] Triple Rectifier is pretty noisy, too.

 

A: Yes. The Rectifier models were derived from the 5150, which in turn was derived from a Soldano - poor Mike never gets proper credit! - and they all have masses of raw gain. So much, in fact, that you can easily lose some and not miss it.

 

The amps ship with 12AX7s, which are the high-mu members in their family of tubes. The 12AT7 has a slightly lower mu of 70; the 12AY7 is at 50 and the 12AU7 has a mu of just 20. All of these are pin-compatible, which means you can pull out a 12AX7 and plug in any of the others. As you go to lower-mu tubes, the noise diminishes very quickly. You might worry that too much gain will be lost at the same time, but the voicing of the preamps of these amp models is such that you always have a "gainy" sound.

 

Remember, each tube has two sections, so two gain stages are being shifted to the new raw gain value. On the other hand, because the stages are cascaded, their gains multiply. For example, two 12AX7s making up a four stage preamp have a theoretical raw gain of 100x100x100x100 or 100 million. If you replace one 12AX7 with a 12AU7, then the theoretical raw gain is reduced to 100x100x20x20 or 4 million. That's a 20-times difference, which in itself seems dramatic, but it is still 1,000 to 10,000 times more gain than it takes to have fully saturated distortion tones.

 

The real gain exhibited by real tubes in real circuits is far less than the theoretical values. Heavy attenuation and frequency shaping between the stages "throws away" much of that gain, and what makes an amp sound and feel gainy is just that frequency emphasis or voicing.

[PaoloJM]

 

Triple Rectifier is pretty noisy, too. A: Yes. The Rectifier models were derived from the 5150, which in turn was derived from a Soldano - poor Mike never gets proper credit! - and they all have masses of raw gain. So much, in fact, that you can easily lose some and not miss it. The amps ship with 12AX7s, which are the high-mu members in their family of tubes. The 12AT7 has a slightly lower mu of 70; the 12AY7 is at 50 and the 12AU7 has a mu of just 20. All of these are pin-compatible, which means you can pull out a 12AX7 and plug in any of the others. As you go to lower-mu tubes, the noise diminishes very quickly. You might worry that too much gain will be lost at the same time, but the voicing of the preamps of these amp models is such that you always have a "gainy" sound. Remember, each tube has two sections, so two gain stages are being shifted to the new raw gain value. On the other hand, because the stages are cascaded, their gains multiply. For example, two 12AX7s making up a four stage preamp have a theoretical raw gain of 100x100x100x100 or 100 million. If you replace one 12AX7 with a 12AU7, then the theoretical raw gain is reduced to 100x100x20x20 or 4 million. That's a 20-times difference, which in itself seems dramatic, but it is still 1,000 to 10,000 times more gain than it takes to have fully saturated distortion tones. The real gain exhibited by real tubes in real circuits is far less than the theoretical values. Heavy attenuation and frequency shaping between the stages "throws away" much of that gain, and what makes an amp sound and feel gainy is just that frequency emphasis or voicing.

 

 

 

Eh, he said the pedal was introducing noise, not that the preamp was noisy.

[TheRymanChu]

From TC Electronic:

 

Can I connect a G-Major in a Peavey 5150 effect loop ?

 

Answer: The Peavey 5150 or 5150mkII heads have hi-z effect loop (instrument level).

 

The G-Major inputs (low impedance) require line level signal. The impedance mismatch results in an insufficient level of signal in the G-Major input generating a high floor noise, and/or a too high level in the return of the 5150 which could cause some distortion.

[TheRymanChu]

Might have a dirty jack or need a resolder. I was just trying to say that the pre from the 5150 is naturally hot and hissy. I had to look up the TC stuff, cuz I thought it said the 5150 was parallel, but I was wrong.

[MadKeithV]

 

when I put it in the Effects Loop, all of a sudden there was this crazy buzz that would not go away.

 

 

Sounds like a ground loop to me - unless you're using battery power for the ISP.

[missingastring]

I really thought it was parallel. Go figure.

[TheRymanChu]

5150 Puts out:

 

Effects Send:

Load Impedance: 47K ohms or greater

Nominal Output: -10 dBV, 300 mV RMS

Effects Return:

Impedance: Very High-Z, 470K ohms

Designed Level: -10 dBV, 300 mV RMS

Preamp Output:

Load Impedance: 47K ohms or greater

Nominal Output: +10 dBV, 3 V RMS

System Hum & Noise @ Nominal Level:

(Clean channel):

(20 Hz to 20 kHz unweighted)

Greater than 74 dB below rated power

 

ISP G-String can take:

Input Impedance: 500K ohms - Maximum Input Level: +12dbu - Effective Noise Reduction: greater than 60db - Dynamic Range: greater than 100db

 

Not a mismatch. The ISP should be able to take what 5150 is putting out. Are you using the right jacks in the ISP?

 

It's late here. I apologize if I didn't help.

[nakedzen]

Try running the Decimator with a battery instead of a power supply, I used to get crazy hum with mine.

 

Good cables, new tubes, good pickups and less gain also help reduce hiss. Personally I haven't had a need for a noise gate for years.

[NinjaRaf]

I have had the same issue with mine since I got it. I just resorted to using it the ns-2 up front, and not messing with the loop. Anything I put in the loop causes more noise, so I just pretend its not there.

[OverDriven]

 

Parallel. You sir are correct.

 

 

Huh??? The 5150 has a series loop, not parallel. And it sounds like you have a ground loop problem somewhere. Are you going from FX send > ISP input > ISP output > FX return?

[petejt]

Triple Rectifier is pretty noisy, too. A: Yes. The Rectifier models were derived from the 5150, which in turn was derived from a Soldano - poor Mike never gets proper credit! - and they all have masses of raw gain. So much, in fact, that you can easily lose some and not miss it. The amps ship with 12AX7s, which are the high-mu members in their family of tubes. The 12AT7 has a slightly lower mu of 70; the 12AY7 is at 50 and the 12AU7 has a mu of just 20. All of these are pin-compatible, which means you can pull out a 12AX7 and plug in any of the others. As you go to lower-mu tubes, the noise diminishes very quickly. You might worry that too much gain will be lost at the same time, but the voicing of the preamps of these amp models is such that you always have a "gainy" sound. Remember, each tube has two sections, so two gain stages are being shifted to the new raw gain value. On the other hand, because the stages are cascaded, their gains multiply. For example, two 12AX7s making up a four stage preamp have a theoretical raw gain of 100x100x100x100 or 100 million. If you replace one 12AX7 with a 12AU7, then the theoretical raw gain is reduced to 100x100x20x20 or 4 million. That's a 20-times difference, which in itself seems dramatic, but it is still 1,000 to 10,000 times more gain than it takes to have fully saturated distortion tones. The real gain exhibited by real tubes in real circuits is far less than the theoretical values. Heavy attenuation and frequency shaping between the stages "throws away" much of that gain, and what makes an amp sound and feel gainy is just that frequency emphasis or voicing .

 

Hmmm....interesting

[JerryP]

If you're running the pedal in front of the amp and in the loop you have a ground loop. Try the pedal in the loop only and don't run the guitar thru it. The IPS racks had the same problem.

Jerry

[JoshuaLogan]

Hmm, I hope I don't have a problem like this. I was planning on getting a 5150 and hooking up the Axe-FX to it via 4 cable method to add nice cleans and fx to the 5150.... that's {censored}ty if the FX loop is noisey/problematic....

[NinjaRaf]

 

If you're running the pedal in front of the amp and in the loop you have a ground loop. Try the pedal in the loop only and don't run the guitar thru it. The IPS racks had the same problem. Jerry

 

 

Does that work the same with the ns-2? I tried running my ns-2 in an x pattern, and I have done this before with the head version, and with a crate BV120, and it killed all noise. With this combo, though, it produces more noise...as does anything at all in the loop. Up front its fine though.

[JerryP]

I don't know about the Axe-FX or the Boss unit. The 5150 has it's loop jacks and input jacks at different ground potentials so if the unit you are trying to use has the grounds all tied together you will get a ground loop.

Jerry

[mightywarlock]

 

Sounds like a ground loop to me - unless you're using battery power for the ISP.

 

 

yeah, sounded like a ground loop, but using a brand new battery. Only happens when plugging into effects loop.

[mightywarlock]

 

Huh??? The 5150 has a series loop, not parallel. And it sounds like you have a ground loop problem somewhere. Are you going from FX send > ISP input > ISP output > FX return?

 

 

yep. guitar in, guitar out to front. decimator out to effects return, effects send to decimator in.

[mightywarlock]

 

If you're running the pedal in front of the amp and in the loop you have a ground loop. Try the pedal in the loop only and don't run the guitar thru it. The IPS racks had the same problem. Jerry

 

 

The ISP Decimator "G-String" only works when you have the whole shebang wired up right...guitar in, guitar to front, decimator in from send, decimator out to return.

 

can't choose one or the other. otherwise it won't even power on.

i think......

 

i took my boss ns2 to the studio last night and at least i was able to use that as a noise gate, but not being able to use the ISP is somewhat dissapointing. I sold my regular decimator to get the g-string, and as of yet have not been able to use it.

 

hey Jerry, is this something you can help with in one of your mods?

[MadKeithV]

From JerryP's description it sounds like the 5150 itself has a ground loop "built in" to the FX loop. I think there's a mod you can do to your connecting cables (the one from FX send to decimator in), disconnecting the "shield" of that cable, but I haven't tried that myself.

[OverDriven]

 

The ISP Decimator "G-String" only works when you have the whole shebang wired up right...guitar in, guitar to front, decimator in from send, decimator out to return. can't choose one or the other. otherwise it won't even power on. i think...... i took my boss ns2 to the studio last night and at least i was able to use that as a noise gate, but not being able to use the ISP is somewhat dissapointing. I sold my regular decimator to get the g-string, and as of yet have not been able to use it. hey Jerry, is this something you can help with in one of your mods?

 

 

It's simply not going to work like that. It looks like the G-string and the 5150 don't play nice. I would say it's more of a problem with the G-String than the 5150. They should have designed it to work with any amp that has different ground potentials at the input and loop.

 

I would say your only option is to either use one decimator in the loop like you used to or somehow have the amp modded to bring the input and loop to the same ground. What was wrong with using the regular decimator, just out of curiosity?

[mightywarlock]

I "Thought" the G-string was going to be better. It costs almost double, so thought I would get better tone and such.

 

 

So far, it is the most useless pedal I have spent money on. I can't use it with the 5150, which is one of the reasons i bought it...and i sold my regular isp to get it.

 

Dumb move on my part, since I apparently didn't know how it would work, and also dumb move to get it from the store i got it from, as they wouldnt let me return it for anything but store credit the very next day.

 

oh well...guess i will just have to live with the noise, and I still have my boss ns2...in front for now...