5150 212 Combo - FX Loop low end Bleed Issue

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vahalien65
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5150 212 Combo - FX Loop low end Bleed Issue

Post by vahalien65 » Sat Jul 17, 2021 1:28 am

Hi, I got a new 5150 212 combo and I'm very happy with it overall. There is one issue with it though. When I try to add an ISP Decimator noise gate in the FX Loop, it doesn't gate the whole sound. Some low end still bleeds through (not extremely loud, but clearly). I tend to play at very low volumes so it is extremely noticeable (and unusable). I end up having to put the noise gate in front after my OD boost, which is OK but not always optimal. I'd like to have the option of having a noise gate in the FX Loop as well.

I tried searching online and couldn't find anybody mentioning this exact issue. All I could find was that people seem to say the amp fx loop seems to be serial and not parallel, so my understanding is that what I'm experiencing should not be happening in theory.

Does anybody have any idea what might be the issue or what steps to try? Thank you in advance, I really like the amp so I hope it can be sorted out somehow.

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JamesPaul
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by JamesPaul » Wed Aug 11, 2021 9:35 pm

vahalien65 wrote:
Sat Jul 17, 2021 1:28 am
Hi, I got a new 5150 212 combo and I'm very happy with it overall. There is one issue with it though. When I try to add an ISP Decimator noise gate in the FX Loop, it doesn't gate the whole sound. Some low end still bleeds through (not extremely loud, but clearly). I tend to play at very low volumes so it is extremely noticeable (and unusable). I end up having to put the noise gate in front after my OD boost, which is OK but not always optimal. I'd like to have the option of having a noise gate in the FX Loop as well.

I tried searching online and couldn't find anybody mentioning this exact issue. All I could find was that people seem to say the amp fx loop seems to be serial and not parallel, so my understanding is that what I'm experiencing should not be happening in theory.

Does anybody have any idea what might be the issue or what steps to try? Thank you in advance, I really like the amp so I hope it can be sorted out somehow.
Does the Decimator have this issue in another amplifier's FX loop? Possible bad Decimator?

You can try cleaning the FX jacks.

The Operating Guide does note "Only non gain effects devices (chorus, reverb, delay, etc.) should be used in the effects loop". I would not view the Decimator as a gain device, but it is not a time-based effect like the examples listed in the OG. There may be an incompatibility.

Edit: I found some threads on other forums discussing that the effects loop is just noisy and some discussing crosstalk in the effects loop tube. Some threads noted it occurs on 5150, 5150 II and 6505 amps. Most of them noted that they could hear a similar noise without anything in the effects loop. Can you hear it with nothing in the loop?
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

vahalien65
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by vahalien65 » Mon Dec 27, 2021 5:43 pm

Hi JamesPaul, thank you very much for your detailed reply. I've taken a look at your suggestions.
JamesPaul wrote:
Wed Aug 11, 2021 9:35 pm

Does the Decimator have this issue in another amplifier's FX loop? Possible bad Decimator?
I don't think it's the Decimator issue. I tried it on another amp, and seems to work fine. Is the Decimator in perfect condition? No, unfortunately, I do think its input/output jacks might be a bit dirty, yet the Decimator acts somewhat normally on another amp: it cuts the sound or does not depending on the threshold level. When I place it in the 5150 loop, it's very strange: what happens when I engage the Decimator in the FX Loop sounds exactly as if you had a Low-pass EQ at around 1k or so.
JamesPaul wrote:
Wed Aug 11, 2021 9:35 pm

The Operating Guide does note "Only non gain effects devices (chorus, reverb, delay, etc.) should be used in the effects loop". I would not view the Decimator as a gain device, but it is not a time-based effect like the examples listed in the OG. There may be an incompatibility.

Edit: I found some threads on other forums discussing that the effects loop is just noisy and some discussing crosstalk in the effects loop tube. Some threads noted it occurs on 5150, 5150 II and 6505 amps. Most of them noted that they could hear a similar noise without anything in the effects loop. Can you hear it with nothing in the loop?
I wonder why they suggest in the manual not to have any gain device used in the FX Loop. I agree with you that the noise-gate could be expected not to be placed in the FX Loop as a consequence.

I have no idea what to do about this. It's disappointing that the noise gate is not as effective as it could have if it could be placed in the FX Loop.

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JamesPaul
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by JamesPaul » Fri Jan 07, 2022 7:24 pm

vahalien65 wrote:
Mon Dec 27, 2021 5:43 pm
Hi JamesPaul, thank you very much for your detailed reply. I've taken a look at your suggestions.
JamesPaul wrote:
Wed Aug 11, 2021 9:35 pm

Does the Decimator have this issue in another amplifier's FX loop? Possible bad Decimator?
I don't think it's the Decimator issue. I tried it on another amp, and seems to work fine. Is the Decimator in perfect condition? No, unfortunately, I do think its input/output jacks might be a bit dirty, yet the Decimator acts somewhat normally on another amp: it cuts the sound or does not depending on the threshold level. When I place it in the 5150 loop, it's very strange: what happens when I engage the Decimator in the FX Loop sounds exactly as if you had a Low-pass EQ at around 1k or so.
JamesPaul wrote:
Wed Aug 11, 2021 9:35 pm

The Operating Guide does note "Only non gain effects devices (chorus, reverb, delay, etc.) should be used in the effects loop". I would not view the Decimator as a gain device, but it is not a time-based effect like the examples listed in the OG. There may be an incompatibility.

Edit: I found some threads on other forums discussing that the effects loop is just noisy and some discussing crosstalk in the effects loop tube. Some threads noted it occurs on 5150, 5150 II and 6505 amps. Most of them noted that they could hear a similar noise without anything in the effects loop. Can you hear it with nothing in the loop?
I wonder why they suggest in the manual not to have any gain device used in the FX Loop. I agree with you that the noise-gate could be expected not to be placed in the FX Loop as a consequence.

I have no idea what to do about this. It's disappointing that the noise gate is not as effective as it could have if it could be placed in the FX Loop.
I do not know if this is accurate, but one of the threads/topics I found stated something about the effects return on these amps feeeding directly into the phase inverter was why they recommended no gain devices. Again, I do not view the Decimator as a gain device. But maybe there is some other negative dynamic which could occur.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

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Enzo
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by Enzo » Sat Jan 08, 2022 1:37 am

Look at the schematic. On a 5150, the FX return goes to a recovery gain stage and THEN into the phase inverter.


Just like on a Classic 30, or JSX, or XXX, or just about anything.

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JamesPaul
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by JamesPaul » Sat Jan 08, 2022 11:47 pm

Are you implying I cannot believe everything I read on the Internet? :shock: :lol:

In my defense, I did begin my paragraph with a disclaimer.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

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Enzo
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by Enzo » Sun Jan 09, 2022 12:16 am

Oh, they can't put anything on the internet unless it is true. Ask my wife, the French model...

VSW
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by VSW » Sun Jan 09, 2022 4:19 pm

Enzo wrote:
Sun Jan 09, 2022 12:16 am
Oh, they can't put anything on the internet unless it is true. Ask my wife, the French model...
Absolutely! 👍
Vaughan

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dak
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Re: 5150 212 Combo - FX Loop low end Bleed Issue

Post by dak » Mon Jan 10, 2022 4:06 am

If I am looking at the right schematic, pre- and post effect loop amplification share one 12AX7. Channel separation across a twin tube is not nearly the same level than what you can achieve with a solid-state twin circuit. Assigning twin tubes for that reason is sort of an art that wants to be done carefully and usually involves picking signals that are correlated anyway and not at significantly different gain stages (to avoid internal feedback) in the same chain.

FX send and return tend to be a reasonable choice when they are used for send and return of an effect not involving large volume changes indeed instead of unrelated purposes or completely unrelated signal routing.

Silence is sort of the worst thing to reproduce when the other side of the tube is working with an active signal.

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