Tube Amp Attenuator

[Buckminster Emptier]

Does anyone use one of these? I was thinking of buying one but the only ones I see on the market are for guitar amps. I can't find one that mentions it works for a bass amp in its description, and all the reviews I see online are from guitar players. It seems lntuitive  that it would work for both, but I can't seem to confirm that. 

 

I am thinking of buying it for  a Mesa TT800 by the way. It's sounds great when loud but doesn't overdrive when you turn it low. 

 

The one I'm looking at is JHS Black Box and it works by putting it in the FX loop, which is what sets it apart from the more expensive ones on the market. It really is a lot cheaper

Edited October 12, 2022 by Buckminster Emptier

[Skybone]

Attenuators should work for both guitar and bass amps, AFAIK, they only regulate the signal being sent from the power amp to the cab.

 

However, they should only be used on amps that have a Valve driven power amp section. A quick Google search of the Mesa TT800, shows that it's a Class D power amp, so therefore you don't actually need an attenuator. The TT only has valves in the pre-amp (3x 12AT7). 

 

The attenuator works to maximise the signal into the valve power amp, but reduces the signal into the cab, without damaging the transformers & power valves in the amp. It allows the power amp to be driven into distortion, which is a smoother and clearer sound than pre-amp distortion, which is "spiky" and can make the sound somewhat "mushy".

 

Basically, you don't need an attenuator unless you're using an amp with a valve power amp stage.

[BigRedX]

On the whole the reasons why power attenuators never mention the use with bass amps, is that most of them can't handle the output of a typical bass amp. They are generally designed for guitarists with all-valve 50-100W amps who don't need the ridiculous volume that they produce but do want the sound of the overdriven valves in the power-amp. We'll conveniently ignore the fact that speaker break-up which is also usually associated with this type of overdriven sound is at best reduced when a power attenuator is used.

 

To give you an idea of how hard power attenuators have to work when used with relatively low wattage amps here's a real-life example from my personal experience. I also play guitar and have a very nice Hughes & Kettner 50W all-valve combo, which I am able to run at sensible volumes using a Marshall Power-Break between the power amp and the speaker. The Power-Break is a large heavy device full of high-power resistors and inductors and a big temperature-controlled fan to cool them. Any sound with more than gentle overdrive (especially when I use either a phaser or flanger) will cause this fan to go into overdrive. Remember that this fan is powered completely by the output of the amplifier - nothing else. At the end of a typical 45 minute set the Power-Brake is close to being too hot to touch and has to be left until last so that it is cool enough to pack away. That's just from attenuating a 50W valve amp down to the same level of something around 20W. Now try and imagine what you would need for your typical bass amp.

 

And as has already been said the only benefit from having a power attenuator is to be able to run the output valves hotter than your normal playing volume would allow. Since the amp in question has a class D output stage you'll get no benefit from it. The JHS Black Box is designed to be used with valve amps that don't have a master volume control. It is not a power attenuator. I can't help but feel that if you ain't able to get a suitable overdriven sound out of your amp at low volumes, then you haven't set it up correctly. Maybe @agedhorse can help?

[fretmeister]

Definitely do not use it on a TT800.

 

As with all solid state power section amps the master volume is easy to control, and any preamp drive will be controlled by the gain control.

 

As said - they are for valve power sections ONLY, and the number of bass amps with valve power sections is really small, and even then the highest capacity attenuator I've ever seen for a guitar amp is 150W, which is far lower than you'd need for a big bass amp.

 

The main reason why you don't see them for bass amps is

 

1: Because even valve power section bass amps really don't need them

2: There's no market for them.

 

 

[agedhorse]

11 hours ago, fretmeister said:

Definitely do not use it on a TT800.

 

As with all solid state power section amps the master volume is easy to control, and any preamp drive will be controlled by the gain control.

 

As said - they are for valve power sections ONLY, and the number of bass amps with valve power sections is really small, and even then the highest capacity attenuator I've ever seen for a guitar amp is 150W, which is far lower than you'd need for a big bass amp.

 

The main reason why you don't see them for bass amps is

 

1: Because even valve power section bass amps really don't need them

2: There's no market for them.

 

 

Correct, these amps are WAY too much power for any commercially available power attenuator on the market.

 

Also, some attenuators are NOT isolated from common signal ground, which means that on a bridged (BLT) amp, it's possible to short 1/2 of the amp and damage it. No tube guitar amp has this configuration, so a common ground won't hurt anything (except may be a little noisy)

[Buckminster Emptier]

On 11/10/2022 at 23:47, Skybone said:

Attenuators should work for both guitar and bass amps, AFAIK, they only regulate the signal being sent from the power amp to the cab.

 

However, they should only be used on amps that have a Valve driven power amp section. A quick Google search of the Mesa TT800, shows that it's a Class D power amp, so therefore you don't actually need an attenuator. The TT only has valves in the pre-amp (3x 12AT7). 

 

The attenuator works to maximise the signal into the valve power amp, but reduces the signal into the cab, without damaging the transformers & power valves in the amp. It allows the power amp to be driven into distortion, which is a smoother and clearer sound than pre-amp distortion, which is "spiky" and can make the sound somewhat "mushy".

 

Basically, you don't need an attenuator unless you're using an amp with a valve power amp stage.

The mesa tt 800 has two channels, one is a all tube amp, one is a class d amp. It says it has a tube driven gain stage. Isn't that a tube amp? 

Edited October 14, 2022 by Buckminster Emptier

[Buckminster Emptier]

On 12/10/2022 at 02:39, BigRedX said:

On the whole the reasons why power attenuators never mention the use with bass amps, is that most of them can't handle the output of a typical bass amp. They are generally designed for guitarists with all-valve 50-100W amps who don't need the ridiculous volume that they produce but do want the sound of the overdriven valves in the power-amp. We'll conveniently ignore the fact that speaker break-up which is also usually associated with this type of overdriven sound is at best reduced when a power attenuator is used.

 

To give you an idea of how hard power attenuators have to work when used with relatively low wattage amps here's a real-life example from my personal experience. I also play guitar and have a very nice Hughes & Kettner 50W all-valve combo, which I am able to run at sensible volumes using a Marshall Power-Break between the power amp and the speaker. The Power-Break is a large heavy device full of high-power resistors and inductors and a big temperature-controlled fan to cool them. Any sound with more than gentle overdrive (especially when I use either a phaser or flanger) will cause this fan to go into overdrive. Remember that this fan is powered completely by the output of the amplifier - nothing else. At the end of a typical 45 minute set the Power-Brake is close to being too hot to touch and has to be left until last so that it is cool enough to pack away. That's just from attenuating a 50W valve amp down to the same level of something around 20W. Now try and imagine what you would need for your typical bass amp.

 

And as has already been said the only benefit from having a power attenuator is to be able to run the output valves hotter than your normal playing volume would allow. Since the amp in question has a class D output stage you'll get no benefit from it. The JHS Black Box is designed to be used with valve amps that don't have a master volume control. It is not a power attenuator. I can't help but feel that if you ain't able to get a suitable overdriven sound out of your amp at low volumes, then you haven't set it up correctly. Maybe @agedhorse can help?

The amp I'm talking about is the Mesa TT 800. It has two channels, one is class D and one is driven by all tubes. For that channel both pre amp and power amp and effects loop all driven by tubes isn't that what it means to have a tube driven gain stage? 

Edited October 14, 2022 by Buckminster Emptier

[Buckminster Emptier]

On 12/10/2022 at 19:08, agedhorse said:

Correct, these amps are WAY too much power for any commercially available power attenuator on the market.

 

Also, some attenuators are NOT isolated from common signal ground, which means that on a bridged (BLT) amp, it's possible to short 1/2 of the amp and damage it. No tube guitar amp has this configuration, so a common ground won't hurt anything (except may be a little noisy)

Your manual for the TT 800 says it has two channels, one is class D and one is all tube. Is this not correct? If it's not then your manual is extremely misleading. These guys are saying it is strictly a class D amp, that's not what the manual says. 

 

I understand now that it has too much power for an attenuator. It's too bad really because I can't get the signal to distort without turning it way the he'll up. Is this any different at 4 ohm?  I'm running at 8 ohms. The only time I can get it to distort is through headphones. I thought the point of the Boogie channel is that it is a tube amp, you're sposed to get an overdrive gritty sound. I can only get that with it turned very loud so I assumed an attenuator would help.

 

 The manual goes on and on about its over driven signal, but I don't get that much. I have a rickenbacher. When I dig in it will distort a little but I think that's actually the bass pickups and not your amp. 

Edited October 14, 2022 by Buckminster Emptier

[Buckminster Emptier]

On 12/10/2022 at 07:48, fretmeister said:

Definitely do not use it on a TT800.

 

As with all solid state power section amps the master volume is easy to control, and any preamp drive will be controlled by the gain control.

 

As said - they are for valve power sections ONLY, and the number of bass amps with valve power sections is really small, and even then the highest capacity attenuator I've ever seen for a guitar amp is 150W, which is far lower than you'd need for a big bass amp.

 

The main reason why you don't see them for bass amps is

 

1: Because even valve power section bass amps really don't need them

2: There's no market for them.

 

 

According to the TT 800 manual the boogie channel is a tube power amp. Isn't that what it means when it has a tube driven gain stage?

Edited October 14, 2022 by Buckminster Emptier

[Buckminster Emptier]

Well then how do you get the goddamn thing to overdrive?  That's the whole reason I bought it, its advertised as having a tube gain stage that gives it the grit of classic Mesa tube amps. I find that to be very misleading. It's an $1200 amp and it has two almost identical channels, neither of which distort or have any kind of overdrive to them. What's the point? 

I've really had it with this amp. Now I'm gonna have to sell it and loose a few hundred on the purchase. 

Is there a bass amp with actual overdrive, not dark glass digital cow poop but real overdrive?

Edited October 14, 2022 by Buckminster Emptier

[Buckminster Emptier]

On 12/10/2022 at 02:39, BigRedX said:

On the whole the reasons why power attenuators never mention the use with bass amps, is that most of them can't handle the output of a typical bass amp. They are generally designed for guitarists with all-valve 50-100W amps who don't need the ridiculous volume that they produce but do want the sound of the overdriven valves in the power-amp. We'll conveniently ignore the fact that speaker break-up which is also usually associated with this type of overdriven sound is at best reduced when a power attenuator is used.

 

To give you an idea of how hard power attenuators have to work when used with relatively low wattage amps here's a real-life example from my personal experience. I also play guitar and have a very nice Hughes & Kettner 50W all-valve combo, which I am able to run at sensible volumes using a Marshall Power-Break between the power amp and the speaker. The Power-Break is a large heavy device full of high-power resistors and inductors and a big temperature-controlled fan to cool them. Any sound with more than gentle overdrive (especially when I use either a phaser or flanger) will cause this fan to go into overdrive. Remember that this fan is powered completely by the output of the amplifier - nothing else. At the end of a typical 45 minute set the Power-Brake is close to being too hot to touch and has to be left until last so that it is cool enough to pack away. That's just from attenuating a 50W valve amp down to the same level of something around 20W. Now try and imagine what you would need for your typical bass amp.

 

And as has already been said the only benefit from having a power attenuator is to be able to run the output valves hotter than your normal playing volume would allow. Since the amp in question has a class D output stage you'll get no benefit from it. The JHS Black Box is designed to be used with valve amps that don't have a master volume control. It is not a power attenuator. I can't help but feel that if you ain't able to get a suitable overdriven sound out of your amp at low volumes, then you haven't set it up correctly. Maybe @agedhorse can help?

It's not like it's some mystery of how to set the amp up. You plug the amp into the speaker cabinet. It's set up. 

I can crank the gain  all the way to 10 and I have to turn it up to a volume so loud the amp head shakes off the cabinet to get even the smallest amount of grit on the signal. 

Edited October 14, 2022 by Buckminster Emptier

[itu]

Your amp may have tubes/valves, but it does not mean it has a tube power amp. TT800 has a class D power amp.

 

A head consists of a preamp and a power amp. Preamp is for signal modification (gain, eq...) and power amp is for driving the cabinet. Your amp has powerful solidstate power amp, it is not to be attenuated with that external attenuator. You can just turn the volume down.

 

Tube power amp is working so, that it starts to distort at its limits. Because that amount of power is quite a lot, many g-word players crank their amps to 10, but use the attenuator in between to get a reasonable sound level. Other power amp types sound worse at those limits and that's the reason your amp can be simply turned down. The effect is not the same. But you can drive the preamp to its limits.

 

Please study the preamp section and what it does. Start from setting the vol to, say 1 or even less. Then crank the gain and bass' vol to 10. There's some distortion for sure.

 

Remember: eq section is also like set of bandwidth limited volumes. If all eq pots are at 0, the preamp level is low. Turn all pots to noon, and start tweaking.

[agedhorse]

I am going to respond assuming that you have grossly misunderstood the manual rather than being intentionally disrespectful. 
 

The manual is crystal clear and accurate in its description of what the amp is and how it works. There is also a block diagram in the back that clearly shows the signal paths throughout the amp. There are also extensive specifications published at the end of the manual.

 

The TT-800 is a 2 channel preamp, with a Boogie channel and a Subway channel. Both channels are tube driven and have tube gain stages. There is switching between the two channels, which then drive an 800 watt RMS class D power amp. 
 

If you are looking for an overdriven tone, I would suggest the Boogie channel to start, be sure the gain switch is in the high gain position, start with the channel master at the 9:00 position, all of the eq controls at noon, the high pass filter set to the 10:00 position, and turn the gain up until you hear the overdriven tone. Once you get this, use the channel master volume to set the overall volume of the overdrive tone. This is a starting point.

 

If you have a low output bass or the setup of the bass had greater pole clearance than stock, or you have a light touch, you may not get as much overdrive as another bass with higher output. This channel has roughly the same gain structure as the Bass 400.

 

That said, if this is confusing to you, or you continue to have difficulty understanding this amp, it simply may not be the right amp for you. It’s not as simple as other amps on the market (including the other amps in the Subway line)

 

Another thing you can do is follow the sample settings page, but for overdriven tones, these settings were developed with specific bass types more commonly associated with overdriven and distorted tones.

 

Hope this helps.

[Skybone]

From the Mesa Boogie website:

Amp Type: Tube Preamps & Class D Power Amp.

 

Mesa Boogie TT800

 

[BigRedX]

There you go.

 

agedhorse has answered your question perfectly.

Edited October 14, 2022 by BigRedX

[Downunderwonder]

@Buckminster Emptier best don some mittens and read all the above a few times before going back to your manual and joining the dots.

[jonno1981]

Great guidance above. 
I wonder if your bass is too low an output to push the amp to overdrive. 
If you can get hold of one/borrow etc. I’d try running a preamp in front of it and see how much of a difference that makes. It’s clear you’ve got a sound in your head you’re trying to get to. 
If not a darkglass fan, sansamp or something similar. 

[fretmeister]

On 14/10/2022 at 07:40, Skybone said:

From the Mesa Boogie website:

Amp Type: Tube Preamps & Class D Power Amp.

 

Mesa Boogie TT800

 

To be fair that says “Power Amp Tubes, Class D Power Amp”

 

I can see that being confusing to someone who doesn’t know that a Class D is not a tube amp.

 

@agedhorse That is a bit misleading. I’ve been playing for 36 years and I would wonder which of those 2 things was wrong as I know one of them must be. But inexperienced players may not realise there’s a contradiction there. It should really say “Power Amp Section” or some other description that doesn’t mention tubes.

[agedhorse]

8 hours ago, fretmeister said:

To be fair that says “Power Amp Tubes, Class D Power Amp”

 

I can see that being confusing to someone who doesn’t know that a Class D is not a tube amp.

 

@agedhorse That is a bit misleading. I’ve been playing for 36 years and I would wonder which of those 2 things was wrong as I know one of them must be. But inexperienced players may not realise there’s a contradiction there. It should really say “Power Amp Section” or some other description that doesn’t mention tubes.

You have to remember that we are primarily a tube guitar amp company and the marketing/website folks use a template that describes the output stage by what tubes are used (or no tubes at all, which would then be in the case of all the new bass amps "class D" because nobody uses power amp tubes in class D amps). When we used class AB output stages in bass amps, it was described as MOSFET - class AB

 

It's assumed that players purchasing this level of equipment will understand this, and have done their homework by doing at least a little bit of research. There are numerous reviews, videos, forum discussions and even the owner's manual is available on line. In the back of the owner's manual is a tutorial on what class D is and how it works. We even discuss switchmode power supplies.

 

I don't think it's misleading, and in fact in the entire 8 years of the Subway line this is the first time this has come up.