GK 800RB newbie, is hiss common with these?

[DavidEdenAria]

Ive had this amp a while, actually havent dated it but its older...just now spending time with it and wow, so many great tones!

Thru a 4 ohm Acoustic 8x10 (braced modded inside) and bi amped thru an 8 ohm EV15L in TL-606 cabinet, like i said, a LOT of great tones but hiss is more present switching from my Eden Metro head (which is 400 watt into 4 ohms).

The Bi amp feature is really something else, especially with my 65 Epiphone Newport (neck mudbucker) an astounding array of tones available, even more when i kick in an EQ pedal...gets very close to a 'P bass sound'.

But its the hiss....i need to spend way more time and write down some settings as so much control with all of the EQ and volume-master volume and boost feature.

Is hiss common and/or something i need to do differently? Honestly i was amazed how loud the EV15L is with the 100 watt amp mixed in with the 8x10 on the 300 watt side.

Sorry, i know i need to spend more time and write down some settings...also using a Yamaha compressor with light compression but the hiss is the same whether i plug straight in or not...thanks in advance!

 

[Funk With Me]

Mine has always been pretty quiet. I’ve had it since ‘96, still chock full o’ sweetness.

 

[Funk With Me]

I currently own two SVTs (CL and MTI), a V4b, an Orange AD200Mk3, an EBS Reidmar 750, and a GK 800RB. I can honestly say that if I could keep only one, it would be the 800RB.

 

[Wasnex]

Ive had this amp a while, actually havent dated it but its older...just now spending time with it and wow, so many great tones!

Thru a 4 ohm Acoustic 8x10 (braced modded inside) and bi amped thru an 8 ohm EV15L in TL-606 cabinet, like i said, a LOT of great tones but hiss is more present switching from my Eden Metro head (which is 400 watt into 4 ohms).

The Bi amp feature is really something else, especially with my 65 Epiphone Newport (neck mudbucker) an astounding array of tones available, even more when i kick in an EQ pedal...gets very close to a 'P bass sound'.

But its the hiss....i need to spend way more time and write down some settings as so much control with all of the EQ and volume-master volume and boost feature.

Is hiss common and/or something i need to do differently? Honestly i was amazed how loud the EV15L is with the 100 watt amp mixed in with the 8x10 on the 300 watt side.

Sorry, i know i need to spend more time and write down some settings...also using a Yamaha compressor with light compression but the hiss is the same whether i plug straight in or not...thanks in advance!

The amp might need a tune up, or you might just need to learn how to set the amp's gain staging properly.

The amp has more gain controls than most. You have input gain (labeled volume), boost, and also separate masters for each amp. It's fairly easy to adjust the controls in a way that will produce excess noise.

I suggest turning up the volume control and lowering the boost and masters. Tone controls tend to be fairly noisy, so you want to hit them with nice strong signal. That way you can use less gain after the tone controls so the noise floor is lower.

The boost control is after the tone stack and adjusts the level that is sent to a FET that is designed to emulate a tube circuit. If you run the volume higher, you can turn down the boost and the signal at the FET is the same, however the signal to noise ratio will be better. If you run the volume lower and turn up the boost, you wind up amplifying more of the noise generated in the tone stack.

It's really a matter of balancing all of the controls. Keep in mind the level of signal your bass provides is also relevant.

 

[DavidEdenAria]

The amp might need a tune up, or you might just need to learn how to set the amp's gain staging properly.

The amp has more gain controls than most. You have input gain (labeled volume), boost, and also separate masters for each amp. It's fairly easy to adjust the controls in a way that will produce excess noise.

I suggest turning up the volume control and lowering the boost and masters. Tone controls tend to be fairly noisy, so you want to hit them with nice strong signal. That way you can use less gain after the tone controls so the noise floor is lower.

The boost control is after the tone stack and adjusts the level that is sent to a FET that is designed to emulate a tube circuit. If you run the volume higher, you can turn down the boost and the signal at the FET is the same, however the signal to noise ratio will be better. If you run the volume lower and turn up the boost, you wind up amplifying more of the noise generated in the tone stack.

It's really a matter of balancing all of the controls. Keep in mind the level of signal your bass provides is also relevant.

I have several basses and all hiss excessively....several other bass amps dont hiss like this one...volume wide open, Epi Newport is a powerhouse 'mudbucker' bass, no hum just hiss thru the 800RB...looked over caps carefully, no scratchiness from the pots but i will try cleaning all pots and jacks.

Ive read about similar issues with hiss in a search but i'll keep trying different settings.

 

[DavidEdenAria]

I currently own two SVTs (CL and MTI), a V4b, an Orange AD200Mk3, an EBS Reidmar 750, and a GK 800RB. I can honestly say that if I could keep only one, it would be the 800RB.

Yea, ive heard plenty of these live and on recordings thru the dacades...ive read the op-amps can get noisy which arent expensive but no way do i want to work on a printed circuit board amp!

 

[Wasnex]

I have several basses and all hiss excessively....several other bass amps dont hiss like this one...volume wide open, Epi Newport is a powerhouse 'mudbucker' bass, no hum just hiss thru the 800RB...looked over caps carefully, no scratchiness from the pots but i will try cleaning all pots and jacks.

Ive read about similar issues with hiss in a search but i'll keep trying different settings.

Definitely adjust the controls as I have suggested. I currently own a 700RB and it gets hissy if I run the masters and boost too high. It's a GK 112 combo with tweeter.

It's been long time since I ran an 800RB, but I remember it being noisy if I did not use proper gain staging. Keep in mind the 800RB came out before tweeters were very common in bass cabs. With proper gain staging, it's probably not going to be the quietest amp, but it should be usable unless it needs to be sent to a tech for some love.

I biamped my 800RB and ran the high amp through Ramsa WSA200. This is 12+horn PA cab. I definitely had some hiss, but was able to manage it by adjusting the controls.

 

[DavidEdenAria]

Definitely adjust the controls as I have suggested. I currently own a 700RB and it gets hissy if I run the masters and boost too high. It's a GK 112 combo with tweeter.

It's been long time since I ran an 800RB, but I remember it being noisy if I did not use proper gain staging. Keep in mind the 800RB came out before tweeters were very common in bass cabs. With proper gain staging, it's probably not going to be the quietest amp, but it should be usable unless it needs to be sent to a tech for some love.

I biamped my 800RB and ran the high amp through Ramsa WSA200. This is 12+horn PA cab. I definitely had some hiss, but was able to manage it by adjusting the controls.

I definitely will adjust controls and spend more time with it....it is a powerhouse, tons of bottom end and punch, almost too much with some basses! Need to Eq and try some compression...its minty shape, no leaking or bulging caps and worth replacing op-amps or whatever if the case may be..thanks!

 

[DavidEdenAria]

Ok, spent more time with it comparing to other bass amps and there deinitely seems like an excessive amount of hiss going on.

So, whats the solution? Replacing the Op Amps? If so what kind of money am i looking at and who to take on the task?

There are no leaking caps that i can see, no hum...just hiss...a shame but thats likely i bought it for low dough 'as is'...no other issues i can detect.

 

[Wasnex]

Ok, spent more time with it comparing to other bass amps and there deinitely seems like an excessive amount of hiss going on.

So, whats the solution? Replacing the Op Amps? If so what kind of money am i looking at and who to take on the task?

There are no leaking caps that i can see, no hum...just hiss...a shame but thats likely i bought it for low dough 'as is'...no other issues i can detect.

Having more hiss than a modern bass amp is not necessarily an indication of a problem. Having more hiss than an 800RB should have is a problem. As I mentioned my 800RB had a bit of noise, but I was able to adjust the amp so it was not a problem for live performances.

What are your Volume, Boost, and Master settings? Start with the Master and Boost at about 9:00. Try running the Volume up till it causes distortion when you pluck hard. Back it off just enough to get a clean signal. Now increase the Boost until the amp develops the compression and/or grind you want. Turn the Masters down if necessary. After you get the feel the way you want, set the Masters for the desired volume.

Are you Biamping? My 700RB has a switch for the woofer that bypasses the LPF so the woofer amp runs full range. When the LPF is engaged it adds quite a bit of hiss, but it's not a problem because the woofer does not efficiently reproduce high frequencies. How much of a difference does engaging the crossover make with your 800RB?

Are you using a cab with a tweeter? If yes, how hot are you running the tweeter? Is turning down the tweeter an option and is it helpful?

If the amp is unusable, sending it to a tech who is experienced with 800RBs would be my recommendation. If you could fix it yourself, you wouldn't be asking this sort of question. Randomly replacing ICs is not the right strategy IMHO. I technician will go through the amp and find the source of the problem and replace the faulty components.

 

[DavidEdenAria]

Having more hiss than a modern bass amp is not necessarily an indication of a problem. Having more hiss than an 800RB should have is a problem. As I mentioned my 800RB had a bit of noise, but I was able to adjust the amp so it was not a problem for live performances.

What are your Volume, Boost, and Master settings? Start with the Master and Boost at about 9:00. Try running the Volume up till it causes distortion when you pluck hard. Back it off just enough to get a clean signal. Now increase the Boost until the amp develops the compression and/or grind you want. Turn the Masters down if necessary. After you get the feel the way you want, set the Masters for the desired volume.

Are you Biamping? My 700RB has a switch for the woofer that bypasses the LPF so the woofer amp runs full range. When the LPF is engaged it adds quite a bit of hiss, but it's not a problem because the woofer does not efficiently reproduce high frequencies. How much of a difference does engaging the crossover make with your 800RB?

Are you using a cab with a tweeter? If yes, how hot are you running the tweeter? Is turning down the tweeter an option and is it helpful?

If the amp is unusable, sending it to a tech who is experienced with 800RBs would be my recommendation. If you could fix it yourself, you wouldn't be asking this sort of question. Randomly replacing ICs is not the right strategy IMHO. I technician will go through the amp and find the source of the problem and replace the faulty components.

Thanks...i will try the amp again thru a few different cabs and different settings...its certainly not unuseable...i have a noise gate i can try as well.

I do work on tube amps but generally stay away from printed circuit boards but yea, the amp does not hum, i cant detect anything else wrong...i think the amp is late 90's but not sure...no bulging or leaking caps, this amp is very clean (it was in a rack) and worth repairing if something were to occur...i may just use the 300 watt side for now.

 

[Wasnex]

Thanks...i will try the amp again thru a few different cabs and different settings...its certainly not unuseable...i have a noise gate i can try as well.

I do work on tube amps but generally stay away from printed circuit boards but yea, the amp does not hum, i cant detect anything else wrong...i think the amp is late 90's but not sure...no bulging or leaking caps, this amp is very clean (it was in a rack) and worth repairing if something were to occur...i may just use the 300 watt side for now.

From the attached service manual

I suspect the noise is either from the EQ or the Crossover. Should be easy enough to use this diagram to localize the source of the problem. From what I remember, the EQ is fairly noisy in this amp...or maybe mine needed to be service as well. Anyway, the noisy EQ is why I am suggesting that you run the Volume as high as possible.

I work on my tube amps also, but don't really have the necessary test equipment, etc to deal with most solid state repairs. I think it would be easy to localize the hiss with an O'scope.

I have repaired a couple of my old solid state devices, and removing components with a soldering iron and spring loaded solder sucker has been challenging. I should probably buy something like a Hakko FR-301 desoldering tool...but they are not exactly cheap.

 

[DavidEdenAria]

From the attached service manual
View attachment 4021419

I suspect the noise is either from the EQ or the Crossover. Should be easy enough to use this diagram to localize the source of the problem. From what I remember, the EQ is fairly noisy in this amp...or maybe mine needed to be service as well. Anyway, the noisy EQ is why I am suggesting that you run the Volume as high as possible.

I work on my tube amps also, but don't really have the necessary test equipment, etc to deal with most solid state repairs. I think it would be easy to localize the hiss with an O'scope.

I have repaired a couple of my old solid state devices, and removing components with a soldering iron and spring loaded solder sucker has been challenging. I should probably buy something like a Hakko FR-301 desoldering tool...but they are not exactly cheap.

Great info and thanks for the link!

 

[DavidEdenAria]

Having more hiss than a modern bass amp is not necessarily an indication of a problem. Having more hiss than an 800RB should have is a problem. As I mentioned my 800RB had a bit of noise, but I was able to adjust the amp so it was not a problem for live performances.

What are your Volume, Boost, and Master settings? Start with the Master and Boost at about 9:00. Try running the Volume up till it causes distortion when you pluck hard. Back it off just enough to get a clean signal. Now increase the Boost until the amp develops the compression and/or grind you want. Turn the Masters down if necessary. After you get the feel the way you want, set the Masters for the desired volume.

Are you Biamping? My 700RB has a switch for the woofer that bypasses the LPF so the woofer amp runs full range. When the LPF is engaged it adds quite a bit of hiss, but it's not a problem because the woofer does not efficiently reproduce high frequencies. How much of a difference does engaging the crossover make with your 800RB?

Are you using a cab with a tweeter? If yes, how hot are you running the tweeter? Is turning down the tweeter an option and is it helpful?

If the amp is unusable, sending it to a tech who is experienced with 800RBs would be my recommendation. If you could fix it yourself, you wouldn't be asking this sort of question. Randomly replacing ICs is not the right strategy IMHO. I technician will go through the amp and find the source of the problem and replace the faulty components.

Ok, i plugged the 800RB into the pair of TL606 EV15L cabs stacked.

Running 300 watt side 'only' full range, i am able to achieve very good tones and response with minimal hiss....a bit but i am able to compensate...actually with the 'boost' wide open and the master way down the hiss is no different than the master on 10, if i adjust EQ a bit.

This is where it gets tricky (and i need to spend more time), there is so much EQ interaction available but this amp packs a huge wallop down low thru the EV15Ls...so much i need to adjust the bass way down but the 'low mid' and 'hi mid' are absolutely working wonders with the 65 Epiphone Newport with its neck only 'mudbucker'...the voicing seems almost spot on for this bass whereas back in the 60's not much was out there in bass rigs to contour the tone of these beasts.

Im stoked....this amp gets LOUD very quickly with the EV15L in the ported TL 606 cabs and the definition is excellent...plenty of top end from the Pressure Wounds.

The 'boost' on the 800RB is awesome! Now im gonna see how close i can get to a P bass sound with the Newport for kicks, A/B to a 'P bass' thru my Metro amp rig.

 

[Wasnex]

Ok, i plugged the 800RB into the pair of TL606 EV15L cabs stacked.

Running 300 watt side 'only' full range, i am able to achieve very good tones and response with minimal hiss....a bit but i am able to compensate...actually with the 'boost' wide open and the master way down the hiss is no different than the master on 10, if i adjust EQ a bit.

This is where it gets tricky (and i need to spend more time), there is so much EQ interaction available but this amp packs a huge wallop down low thru the EV15Ls...so much i need to adjust the bass way down but the 'low mid' and 'hi mid' are absolutely working wonders with the 65 Epiphone Newport with its neck only 'mudbucker'...the voicing seems almost spot on for this bass whereas back in the 60's not much was out there in bass rigs to contour the tone of these beasts.

Im stoked....this amp gets LOUD very quickly with the EV15L in the ported TL 606 cabs and the definition is excellent...plenty of top end from the Pressure Wounds.

The 'boost' on the 800RB is awesome! Now im gonna see how close i can get to a P bass sound with the Newport for kicks, A/B to a 'P bass' thru my Metro amp rig.

I think you misunderstood....turn both the Boost and the Masters down, and <CRANK> the Volume!!!!!

Please, look at this diagram and follow along.

The green part of the circuit should not be very noisy. The blue part should be very noisy, but the noise will be constant at the output of the blue circuit regardless of how you adjust the Volume control.

The Boost circuit is the red block. The level presented to the red box determines how much compression or grind the amp generates. This circuit does not care whether you run the Volume high and the Boost low, or the Boost high and the Volume low. The circuit only cares about the level.

Try to grasp the idea that there is specific signal level at the input of the red box that you are shooting for. When you hit this target signal level, the red box produces the desired amount of compression or drive.

However since we are trying to improve the signal to noise ratio, we want to turn the Volume up and the Boost down. Turning down the Boost turns down everything...hiss and the bass. Turning up the Volume primary increases the signal level of the bass. By running the Volume as high as possible and then adjusting the Boost control to taste, you should be setting the amp for the highest signal to noise ratio, and still get the desired compression or grind.

The final part of the puzzle is the Master controls...simply adjust them for the desired output level. If you have the Volume and Boost controls set properly, the amp should be able to hit max power well before the Masters are maxed out.

 

[DavidEdenAria]

I think you misunderstood....turn both the Boost and the Masters down, and <CRANK> the Volume!!!!!

Please, look at this diagram and follow along.

View attachment 4023039


The green part of the circuit should not be very noisy. The blue part should be very noisy, but the noise will be constant at the output of the blue circuit regardless of how you adjust the Volume control.

The Boost circuit is the red block. The level presented to the red box determines how much compression or grind the amp generates. This circuit does not care whether you run the Volume high and the Boost low, or the Boost high and the Volume low. The circuit only cares about the level.

Try to grasp the idea that there is specific signal level at the input of the red box that you are shooting for. When you hit this target signal level, the red box produces the desired amount of compression or drive.

However since we are trying to improve the signal to noise ratio, we want to turn the Volume up and the Boost down. Turning down the Boost turns down everything...hiss and the bass. Turning up the Volume primary increases the signal level of the bass. By running the Volume as high as possible and then adjusting the Boost control to taste, you should be setting the amp for the highest signal to noise ratio, and still get the desired compression or grind.

The final part of the puzzle is the Master controls...simply adjust them for the desired output level. If you have the Volume and Boost controls set properly, the amp should be able to hit max power well before the Masters are maxed out.

I think you misunderstood....turn both the Boost and the Masters down, and <CRANK> the Volume!!!!!

Please, look at this diagram and follow along.

View attachment 4023039


The green part of the circuit should not be very noisy. The blue part should be very noisy, but the noise will be constant at the output of the blue circuit regardless of how you adjust the Volume control.

The Boost circuit is the red block. The level presented to the red box determines how much compression or grind the amp generates. This circuit does not care whether you run the Volume high and the Boost low, or the Boost high and the Volume low. The circuit only cares about the level.

Try to grasp the idea that there is specific signal level at the input of the red box that you are shooting for. When you hit this target signal level, the red box produces the desired amount of compression or drive.

However since we are trying to improve the signal to noise ratio, we want to turn the Volume up and the Boost down. Turning down the Boost turns down everything...hiss and the bass. Turning up the Volume primary increases the signal level of the bass. By running the Volume as high as possible and then adjusting the Boost control to taste, you should be setting the amp for the highest signal to noise ratio, and still get the desired compression or grind.

The final part of the puzzle is the Master controls...simply adjust them for the desired output level. If you have the Volume and Boost controls set properly, the amp should be able to hit max power well before the Masters are maxed out.

Ive tried it with the master volume dimed as well the master set low with volume cranked, the amount of hiss doesnt differ much and im not getting enough drive with the boost set low but i will work on it!

I will try more settings as you suggest...makes me wonder if something is going on internally but i will use a bit of compression added in and try different settings.

Remember the Epiphone 'mudbucker' is an entirely different pickup, very touch sensitive to picking (and thats with the poles lowered), it is a LOUD pickup...next up will be a P bass with a Duncan 'vintage P' pickup...im happy with the sound right now, hiss is acceptable...its not like im recording, hiss is below the noise threshold once the bass is played.

 

[DavidEdenAria]

Also, the EV15L are a guitar speaker with a lot of top end...though 'agedhorse' likes these speakers a lot for their clarity in bass use as long as they dont exceed medium volumes...im wondering now if they are bringing out more hiss...another thing, the 'hi boost' doesnt do much at all no matter where the treble is set.

 

[mouthmw]

Definitely adjust the controls as I have suggested. I currently own a 700RB and it gets hissy if I run the masters and boost too high. It's a GK 112 combo with tweeter.

Yeah, that's just not right. GK RB series work best with power section cranked up more, it's the input section that shouldn't be cranked too much.

I had 700RB-II and gigged it a lot, and now I have 2001RB that I've gigged for around 5 years. I used to crank the woofer around 15:00 on 700RB-II, with boost over 13:00 and have input at around 10:00. No hiss.

My 2001RB is a more powerful beast, as I use it in bridged mode always. My woofer is around 13:00 most of the time (I did crank it up to 15:00 once or twice), my boost is around 10:00 and my input is mostly at 09:00, sometimes 10:00. No hiss.

Something is definitely not right with the components if the amp hisses.

 

[Wasnex]

Ive tried it with the master volume dimed as well the master set low with volume cranked, the amount of hiss doesnt differ much and im not getting enough drive with the boost set low but i will work on it!

I will try more settings as you suggest...makes me wonder if something is going on internally but i will use a bit of compression added in and try different settings.

Remember the Epiphone 'mudbucker' is an entirely different pickup, very touch sensitive to picking (and thats with the poles lowered), it is a LOUD pickup...next up will be a P bass with a Duncan 'vintage P' pickup...im happy with the sound right now, hiss is acceptable...its not like im recording, hiss is below the noise threshold once the bass is played.

FYI, the boost control is simply a potentiometer just like the block diagram shows. All it does is vary how much of the signal it let's pass. If you hit it with a really hot signal, you turn to Boost control down to attenuate the signal more. If the signal is weak, you turn the Boost control up so the signal is attenuated less.

I certainly don't mean to say that you should run the actual signal level hitting the Boost at a lower level. In fact I am saying you want to hit the Boost circuit with exactly the same signal level. So you need to fiddle with the Volume and Boost controls to make this happen. Turn the Volume as loud as you can without getting distortion, and then set the Boost where it produces the desired effect.

Something to keep in mind: The gain factor from the front end of the preamp to the speaker out should remain exactly the same. We are just moving some of the gain from middle and back end of the amp which is a bit noisy, to the front end of the preamp, which should be much quieter. If this doesn't make any difference, it's possible your amp needs some love. It's also possible our expectations are just a little too high. It's a very old design, and I remember the one I ran in the late 90s was a bit noisy as well.

Anyway it sounds like you are almost dialed in .

 

[Wasnex]

Yeah, that's just not right. GK RB series work best with power section cranked up more, it's the input section that shouldn't be cranked too much.

I had 700RB-II and gigged it a lot, and now I have 2001RB that I've gigged for around 5 years. I used to crank the woofer around 15:00 on 700RB-II, with boost over 13:00 and have input at around 10:00. No hiss.

My 2001RB is a more powerful beast, as I use it in bridged mode always. My woofer is around 13:00 most of the time (I did crank it up to 15:00 once or twice), my boost is around 10:00 and my input is mostly at 09:00, sometimes 10:00. No hiss.

Something is definitely not right with the components if the amp hisses.

I definitely don't like running the Volume so high that it causes distortion before the Boost circuit. That is not how this amp should be run IMHO.

I currently have my Boost at 11:30, my Tweeter at 12:00 and my Woofer at 14:00. If I run the Masters much higher than this, the amp gets a little hissy, but not what I would call problematic for live work. It probably would not fly in a recording studio though. I don't think I would ever run the woofer Master past 15:00. The Woofer amp is noisier when the Woofer X-Over switch is engaged. Not a surprise...extra circuitry adds noise.

The Boost control is just an attenuator on this amp as well. So you can keep the level hitting the Boost circuit the same by increasing the Volume while decreasing the Boost control, or by increasing the Boost control while decreasing the Volume. But the best S/N ratio is with the Volume set fairly high.