GK rails in a pedal?

[johnk_10]

mine was super noisy and it was made by John. Which is why I got rid of it.

that's a surprise to me, since i've never had that compaint about one. you should have contacted me.

 

[Blu bro]

Could you do a recording so we can get a gauge of noise? I think everyone’s tolerance in their head is different

I will try to record something soon (will only be through my phone though coz I don’t have a set to do it properly- but you will get an idea)

 

[Mosfed]

that's a surprise to me, since i've never had that compaint about one. you should have contacted me.

I was past that a long time ago. Hope your business is going well.

 

[Peaveylover]

that's a surprise to me, since i've never had that compaint about one. you should have contacted me.

+1 for John K's work. I have several of his handmade pedals and none exhibit any noise or problems.

 

[Blu bro]

Here is a small clip showing- what I consider to be a high noise floor

Hightail Spaces

I have never posted footage before, so I hope this works

 

[Wasnex]

Here is a small clip showing- what I consider to be a high noise floor

Hightail Spaces

I have never posted footage before, so I hope this works

97meg file. I couldn't view it without downloading, which took awhile.

Isn't the point of the pedal to SIM the drive you get from a pushed RB series amp? I don't really see the reasoning for turning down the Input Level for a clean sound and then cranking up the Output to the point where the hiss is excessive. If you want clean, just bypass the pedal.

I don't find it odd that you can't max the Output control without getting excessive hiss. I can't think of a single pedal that I run with the Output maxed. Some of my vintage amps are like this as well. Crank up the Master too much and you get way too much noise.

 

[Blu bro]

97meg file. I couldn't view it without downloading, which took awhile.

Isn't the point of the pedal to SIM the drive you get from a pushed RB series amp? I don't really see the reasoning for turning down the Input Level for a clean sound and then cranking up the Output to the point where the hiss is excessive. If you want clean, just bypass the pedal.

I don't find it odd that you can't max the Output control without getting excessive hiss. I can't think of a single pedal that I run with the Output maxed. Some of my vintage amps are like this as well. Crank up the Master too much and you get way too much noise.

I understand what you are saying but even with everything at 12 o’clock it has a big noise floor- I only showed the output maxed as an example.

I want to run the pedal as clean when I play normally but drive when I dig in. As an always on pedal if possible.

I agree that if you max the gain you should expect a noise floor but that is not the way I am using the pedal.

 

[DownUnder_Funk]

Interesting. In my recording using higher gain settings I had very little noise. Maybe it’s your specific pedal

 

[kleinenenten]

I understand what you are saying but even with everything at 12 o’clock it has a big noise floor- I only showed the output maxed as an example.

I want to run the pedal as clean when I play normally but drive when I dig in. As an always on pedal if possible.

I agree that if you max the gain you should expect a noise floor but that is not the way I am using the pedal.

Do you have that same hiss (but quieter) without the pedal? Your noise sounds the same as mine, which is just my regular amp hiss being amplified by the pedal. It’s not adding any noise, but since it’s distorting and amplifying the signal, it makes the hiss more apparent when not playing. I cannot hear the hiss when I am playing.

 

[Blu bro]

Do you have that same hiss (but quieter) without the pedal? Your noise sounds the same as mine, which is just my regular amp hiss being amplified by the pedal. It’s not adding any noise, but since it’s distorting and amplifying the signal, it makes the hiss more apparent when not playing. I cannot hear the hiss when I am playing.

No I don’t. My rig is very quiet. It is very noticeable when I turn the pedal on.

I play both with “in ears” and amps (depending on the gig) and the hiss is noticeable in both cases.

 

[kleinenenten]

No I don’t. My rig is very quiet. It is very noticeable when I turn the pedal on.

I play both with “in ears” and amps (depending on the gig) and the hiss is noticeable in both cases.

Do you use tweeters? About a year ago, I thought something was wrong with one of my amps/cabs. I have two nearly identical setups, and one was hissing. What I found out was that the hissing cab was actually the one working correctly, and that the other cab needed a new diaphragm for the tweeter. In other words, the tweeter was essentially “off”, causing less hiss. If your cab doesn’t have a tweeter, perhaps the high pitched amp hiss isn’t noticeable under normal circumstances? Just speculating here, because as some one who hates noise and gates extensively, I have had to learn that amp hiss is unavoidable when turned up “loud enough”. The pedal’s gain could be “loud enough”.

 

[Wasnex]

I understand what you are saying but even with everything at 12 o’clock it has a big noise floor- I only showed the output maxed as an example.

I want to run the pedal as clean when I play normally but drive when I dig in. As an always on pedal if possible.

I agree that if you max the gain you should expect a noise floor but that is not the way I am using the pedal.

What affect does adjusting the Input Level and Boost have on the noise?

Is the Output noisy if the Input Level and Boost are turned all the way down?

If the pedal works like the actual GK Boost circuit, there is a FET that distorts when it is pushed to a certain signal level. Think of the FET as having a fixed signal threshold. Signals pushed progressively above the threshold become compressed and then distorted. Both the Input Level and Boost affect the level sent to the FET. In other words both are before the FET. The Output control should be after the FET.

It's only possible to send a certain level of clean signal through the FET before distortion occurs. So if the hiss is generated before the FET you may be able to increase the S/N Ratio by adjusting/balancing the Input Level and Boost. Try turning up the Input Level relatively high and the Boost relatively low, and vice versa.

If the hiss is generated in or after the FET stage, then there is no way to compensate. The Output basically should take the signal passed by the FET and make it louder.

It's possible the FET or one of the other gain stages in the pedal is faulty or biased improperly.

For the record, I don't own an 800RB but I do own a 700RB. My circuit analysis was based on the 700RB schematic. Also my 700RB is a bit hissy when I really crank it up.

 

[johnk_10]

the boost is the only part of the circuit that i've found to add hiss.

 

[Wasnex]

the boost is the only part of the circuit that i've found to add hiss.

I searched through the thread a bit and found these schematics.

It appears there is some power amp emulation after the Boost circuit.


Also I saw that you and Domdec314 were building this pedal. I searched for TB user Domdec314 and it crossed to @Dominic DeCosa, who appears to be the builder of the OP's Dicosimo pedal. So are the JK and Dicosimo versions of the pedals pretty much the same?

 

[TomB]

the boost is the only part of the circuit that i've found to add hiss.

This replicates the boost function on the GK RB's and MB amps, at least in my experience. The Boost function on these GK models adds quite a bit of hiss, along with its other virtues. This is especially noticeable through a post-EQ DI to headphones. It's never been a problem in a live setting, though sound techs have noted it.

 

[Dominic D]

Also I saw that you and Domdec314 were building this pedal. I searched for TB user Domdec314 and it crossed to @Dominic DeCosa, who appears to be the builder of the OP's Dicosimo pedal. So are the JK and Dicosimo versions of the pedals pretty much the same?

I've built a handful of these pedals, but I stopped building them because of the hiss. I personally can't hear it unless the pedal is maxed and my amp or audio interface are pushed way past normal levels. However, enough people had a problem with it so I stopped.

 

[johnk_10]

I searched through the thread a bit and found these schematics.
View attachment 3928086
View attachment 3928087
It appears there is some power amp emulation after the Boost circuit.

it's not a power amp simulator, it's just a Jfet booster (like in the GK amp).

 

[Wasnex]

it's not a power amp simulator, it's just a Jfet booster (like in the GK amp).

Perhaps I am making too much of the dual rail, push pull output section. AFAIK most pedals do not use push pull circuitry.

 

[Blu bro]

What affect does adjusting the Input Level and Boost have on the noise?

Is the Output noisy if the Input Level and Boost are turned all the way down?

If the pedal works like the actual GK Boost circuit, there is a FET that distorts when it is pushed to a certain signal level. Think of the FET as having a fixed signal threshold. Signals pushed progressively above the threshold become compressed and then distorted. Both the Input Level and Boost affect the level sent to the FET. In other words both are before the FET. The Output control should be after the FET.

It's only possible to send a certain level of clean signal through the FET before distortion occurs. So if the hiss is generated before the FET you may be able to increase the S/N Ratio by adjusting/balancing the Input Level and Boost. Try turning up the Input Level relatively high and the Boost relatively low, and vice versa.

If the hiss is generated in or after the FET stage, then there is no way to compensate. The Output basically should take the signal passed by the FET and make it louder.

It's possible the FET or one of the other gain stages in the pedal is faulty or biased improperly.

For the record, I don't own an 800RB but I do own a 700RB. My circuit analysis was based on the 700RB schematic. Also my 700RB is a bit hissy when I really crank it up.

The hiss seems to be directly linked to the out put. If input and boost knobs are on zero I still get an audible hiss.

I have tried to compensate the input with the boost knob but because the hiss is clearly linked to the output knob I can’t get around the hiss no matter how I set the pedal.

I am happy to replace parts within the pedal if somebody has an idea what could be at fault?

Thanks for all the time time and effort that you are putting into your replies @Wasnex

 

[Wasnex]

The hiss seems to be directly linked to the out put. If input and boost knobs are on zero I still get an audible hiss.

I have tried to compensate the input with the boost knob but because the hiss is clearly linked to the output knob I can’t get around the hiss no matter how I set the pedal.

I am happy to replace parts within the pedal if somebody has an idea what could be at fault?

Thanks for all the time time and effort that you are putting into your replies @Wasnex

It could be faulty component (which I sort of suspect) or it could be the design. Hard to say without comparing to another like pedal.

@johnk_10 is the main schematic correct? Me electronics skills are rudimentary and a bit rusty, but I would assume the signal should enter between the junction of D2 and D3 for proper push pull operation.

As drawn

I assume it should be connected this way.