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PostPosted: Mon Dec 11, 2017 7:29 am 
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Mark III

Joined: Sun Feb 02, 2014 11:51 am
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Hi,

Maybe a dumb question about the MULTI-SOAK on the TC100. If I understand this correctly, the excess power (100W less the power soak setting) would be “soaked up” and only the remaining power would go to the speaker. For example, at a SOAK setting of 20W, there would be 20W going to the speaker and 80W being “soaked”. Is that correct?

A second dumb question about the TC family..... what is the difference betwee the SOAK option and the interplay between the CHANNEL MASTER and OUTPUT knobs? In other words, if one wanted to drive the power tubes on a TC-50 but not play so loud, could one just turn up the MASTER to 3 o’clock and turn the OUTPUT down low for bedroom listening?

I suppose it all depends on where these knobs are in the power chain, which is what I do not really know. Just curious if anyone could explain it. Thanks much.


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PostPosted: Tue Dec 12, 2017 1:05 am 
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Mark III

Joined: Sat Apr 25, 2015 1:22 am
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I'll try to keep this as simple as I can. May not be perfect but you should get the idea.
The channel masters, or master as it's called, is just for the pre amps. The output is for the power amp. So master controls the little tubes volume and that gets sent to the big tubes, where the output controls their volume. Now for the soak, it comes after the output and it has a big resistor to soak up all the volume before finally sending what's left to the speakers. Now the why. Why do this at all when it seems like there is already plenty of volume controls. There are really two big reasons, the main reason is to be able to overdrive your power tubes and be able to control that overdrive's volume. That can't be done on tube amps unless you have an attenuator. This is because the only way you can overdrive your power tubes is by volume, it has to be loud, there's no way around it. You gotta crank up the volume. That resistor in the power soak is there to be able to control that ear splitting loudness of a 100 watt tube amp turned up so loud that the power tubes are freaking out and clipping the signal. It turns all that extra volume you choose to soak into heat.

So you can't just turn up the channel master and turn down the output to get power tube overdrive, the only way is to turn up the output as it is the one that controls the power tubes and the overall volume of the amp. And lots of volume is the only way to get that power tube drive. That is until mesa put another resistor, or volume control, after the power tubes, to harness their power, and they called it a power soak.

This isn't a perfect description but I hope that helps give you a general idea of what's going on.

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PostPosted: Tue Dec 12, 2017 7:14 am 
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Mark III

Joined: Sun Feb 02, 2014 11:51 am
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Hi,

Thanks for the explanation. So... the channel MASTER controls the signal level going to the power section of the amp. And the OUTPUT knob controls how much amplification (work) is being done by the power section. So, cranking the channel MASTER will put a stronger signal into the power section, but will not have any affect on what the power section is doing with the signal. The OUTPUT knob controls how much the power section will amplify the signal. And, to your point about needing to really have the power tubes working, I take that to mean they need to be pushing high amounts of current out the back end to the speaker to really be working. In other words, setting a very, very low MASTER level and turning up the OUTPUT will maybe provide bedroom levels at high OUTPUT setting, but there really isn’t any current (voltage?) being pumped out of the power tubes and they will not sound optimal. Is that right?

The power soak feature allows the power tubes to pump out a lot of current (voltage?) but not all of it goes to the speakers, so this prevents ear bleed.

Sorry, just kind of rewording things to try to solidfy it in my little brain.

On the Mark V, if one turns off the EFX loop, the channel MASTER becomes the final stage. Does this mean that the OUTPUT knob is essentially “set to MAX” (or bypassed, I guess) when the EFX loop is off?


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PostPosted: Tue Dec 12, 2017 6:25 pm 
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Mark III

Joined: Sat Apr 25, 2015 1:22 am
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In a nutshell, yea, that's the idea. Have you ever heard people say that you really gotta crank a tube amp to get it to sound good? Or tube amps sound best loud? That's why, because that's the only way you can get those power tubes working hard and influencing more in the overall tone. So mesa put another volume control, the soak, right after the power tubes and before the speaker. Attenuators do the same thing essentially and they are placed in basically the same place, after the power tubes and before the speakers. Now you can run the amp in its sweet spot and be able to control the volume. If you don't have a power soak, or an attenuator, you have to have the amp extremely loud to reach that sweet spot or to reach full on overdrive. There's no other way around it.

And yea, you got the mark v thing right. Maybe someone else can chime in and be a little more technical with this. :lol: This is just my little brain understanding it. There always someone smarter.

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PostPosted: Wed Dec 13, 2017 7:14 pm 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
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I may add some more info. Master (channel or global) is just that, final volume level of the preamp that will be applied to the power tubes. This is on the high side (high voltage side). Amps with built in or external attenuators are always found on the low side (low voltage but moderate current on the speaker side of the OT).

Amps with a global master volume: This is generally associated with the FX loop and is the output from the gain circuit before the Phase inverter. This allows for a higher preamp output signal from each channel if so desired as it will be attenuated to pass through the FX loop (in use or not) (case for Mark V with the FX loop active). The solo volume control is also part of the global master volume and is driven by the same tube. For amps that can disable the entire FX loop (had bypass) such as the Mark V and Roadster (to name a few) will send the output signals from each channel without attenuation and thus become independent master volume controls that are directly connected to the phase inverter (FX circuit is completely bypassed as well as the last gain stage used for the global master volume and solo feature).

There are some amps that do not have a global master volume control or solo feature but do have an FX loop. Generally the circuitry for the FX loop is always active even if the send/return is unconnected or the switch is turn off that controls a relay to break the signal path to divert signal through the series FX loop. In some cases there may be additional controls such as a global master and solo like on the TC-50. The JP-2C and the RA100 do not have the global master and solo but do have the FX loop circuits in use at all times.

As for the Multi soak, good description Samuel. Most power brakes or attenuators (resistive or reactive) that are external like the Two Notes Torpedo or Rivera Rock Crusher (just to name a few) are placed between the amp and the speaker. They will do the same thing in reducing the output volume level on the speaker but yet allow for the tubes to become saturated at their sweet spot just at the point of clipping and compressing the sound. Having a load attenuator allows the tubes to be driven harder without the burden of requiring ear plugs. Similar to the effect of moving from a 412 cabinet down to a single 112 cabinet having the same impedance. The amp will still be running at the full wattage but the effective output at the speaker will be much lower and in some cases may be enough for silent use. The Royal Atlantic 100 has the multi soak feature but it is more or less resistive loading. What is different about the TC100 is that it is reactive so there should a reduction in thermal changes from the attenuator. RA100 uses a cooling fan and load resistor that is near the power tubes and shares the same tube protector cage. I did not notice that on the TC100 images but it does have two extra transformers or chokes near the OT. I am eager to get my hands on one and compare it to the RA100. I wonder if the cab clone will still work with the attenuators in use? I would assume it would.

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PostPosted: Wed Dec 13, 2017 9:03 pm 
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mace wrote:
Thanks for the explanation. So... the channel MASTER controls the signal level going to the power section of the amp. And the OUTPUT knob controls how much amplification (work) is being done by the power section.


No.

Channel MASTERS attenuate the signal between the preamp output and the effects loop send.

The master OUTPUT attenuates the signal from effects loop return to the power amp input.

The POWER SOAK attenuates the signal between the power amp output and the speaker input.

Quote:
So, cranking the channel MASTER will put a stronger signal into the power section, but will not have any affect on what the power section is doing with the signal.


No. Cranking the channel MASTER will send a stronger signal into the power section and will cause the overall output (volume) to be louder.

Quote:
The OUTPUT knob controls how much the power section will amplify the signal.


No. The OUTPUT knob controls how much signal is sent into the power section. The easiest way to think about it is that an amplifier produces a relatively constant amount of amplification, and the variable is how much signal you feed into it. More signal in = more signal out (to a point *).

The MASTER and OUTPUT knobs both basically do the same thing (attenuate signal/adjust volume), but sit in a different part of the signal path in order to serve a different purpose in the overall design. In most Mesas the individual channel MASTERs are there balance the individual channel volumes whereas the OUTPUT is used to raise/lower amplifier's overall volume.

It's a relatively intuitive design. If the amp is too quiet you're likely to raise the OUTPUT rather than turning up all three MASTERS, however if your channel two is too quiet you'll probably raise the channel 2 MASTER rather than turning up the overall OUTPUT.

* More Signal In = More Signal Out is true until you reach the limits of an amplifier, at which point feeding more signal in drives the amplifier into distortion (aka, overdriving the amp). At this point More Signal In = More Distortion at the same overall output.


Quote:
And, to your point about needing to really have the power tubes working, I take that to mean they need to be pushing high amounts of current out the back end to the speaker to really be working. In other words, setting a very, very low MASTER level and turning up the OUTPUT will maybe provide bedroom levels at high OUTPUT setting, but there really isn’t any current (voltage?) being pumped out of the power tubes and they will not sound optimal. Is that right?


No. It doesn't work that way. To get the power tubes really working the amplifier has to be loud as f*ck. If it's not getting the cops called on you and you don't live on a farm in the middle of nowhere then they're not working all that hard.

The one exception to this is a power soak. It attenuates the signal between the power amp and the speakers. Attenuation in this part of the signal path is the only way to reduce overall volume without reducing the stress on the power tubes. Every other method of reducing volume (in the case of the TC-50/100, the GAIN, MASTER and OUTPUT knobs) causes the stress on the power tubes to be reduced.

Quote:
The power soak feature allows the power tubes to pump out a lot of current (voltage?) but not all of it goes to the speakers, so this prevents ear bleed.


This is correct. The Power Soak in a TC turns energy into heat via big resistors that can take the full output of the amp without burning up.

Quote:
On the Mark V, if one turns off the EFX loop, the channel MASTER becomes the final stage. Does this mean that the OUTPUT knob is essentially “set to MAX” (or bypassed, I guess) when the EFX loop is off?


In simplistic terms, yes. In reality, it's removing a bunch of additional circuitry and gain stages from the signal path... so, in this case running the OUTPUT wide open is different from removing it completely since it's also removing gain stages from the signal path, which is why running the master OUTPUT wide open also tends to add a lot of extra noise when compared to bypassing the effects loop.

I tried to keep that simple. Hopefully it makes sense.

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Ignore the hype and trust your ears. Play more, buy less = better tone.

|| McCarty | Les Paul | Custom 24 ||
|| Cantrell Wah | Rotovibe | Phase 90 | Grid Slammer ||
|| Triple Crown 50 | Recto 2x12/4x12 ||

|| Jazz Bass | Bass Strategy | PH410 ||


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PostPosted: Fri Dec 15, 2017 7:20 am 
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Mark III

Joined: Sun Feb 02, 2014 11:51 am
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Thanks for the explanation. That helped clear things up. Now that I read it, I remember seeing that info in the manuals, but somehow it wasn‘t totally clear (or I forgot).

What does the phase inverter do and why is it needed?


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PostPosted: Fri Dec 15, 2017 11:38 am 
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mace wrote:
Thanks for the explanation. That helped clear things up. Now that I read it, I remember seeing that info in the manuals, but somehow it wasn‘t totally clear (or I forgot).

What does the phase inverter do and why is it needed?


It splits the signal in two and inverts the phase on one side. Both sides drive the output transformer and the process is what makes a class A/B amplifier a push/pull circuit.

The process is technically complicated to explain and if you want the details you're better off Googling the answer since those guys can explain it way better than I can.

_________________
Ignore the hype and trust your ears. Play more, buy less = better tone.

|| McCarty | Les Paul | Custom 24 ||
|| Cantrell Wah | Rotovibe | Phase 90 | Grid Slammer ||
|| Triple Crown 50 | Recto 2x12/4x12 ||

|| Jazz Bass | Bass Strategy | PH410 ||


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PostPosted: Fri Dec 15, 2017 4:57 pm 
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Mark III

Joined: Sun Feb 02, 2014 11:51 am
Posts: 178
screamingdaisy wrote:
mace wrote:
Thanks for the explanation. That helped clear things up. Now that I read it, I remember seeing that info in the manuals, but somehow it wasn‘t totally clear (or I forgot).

What does the phase inverter do and why is it needed?


It splits the signal in two and inverts the phase on one side. Both sides drive the output transformer and the process is what makes a class A/B amplifier a push/pull circuit.

The process is technically complicated to explain and if you want the details you're better off Googling the answer since those guys can explain it way better than I can.


Yep.

https://mesaboogie.zendesk.com/hc/artic ... 0Smith.pdf


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