Vox AC30/ 6 (TBX). Add an MV ?

[Justin Thomas]

What Mr. Thud points out makes perfect sense WRT guitar amps because you absolutely couldn't place a single volume control at the end of the signal chain on, say, a Peavey 5150 and hope for anything like a clean tone from a guitar plugged into it.

Who needs a 5150? Hell, a couple 5879s in series to an LTPI is more than adequate to destroy any semblance of clean tone if you don't put some Chaos Mitigation Strategeries in there! And this thing started as a projector! So that's why it has a TMB tone stack & a total of three Volumes - one for each amplifying stage (5879, 5879, & the LTPI amplifies a lil bit)[actually each side of the PI has an individually adjustable Volume control a la @g1 because FUN! & "why not?"] And it's still not particularly clean unless everything is at 50% or less.

I initially built it with NO controls whatsoever. That was fun! I'm sure the neighbors disagreed. I like to start out simple & complicate it as I go along.

Jusrin

[Chuck H]

Strictly speaking, this is not true. In a non-Master Volume amp, the Volume control is (almost always) located between the first and second preamp tubes. This is done so that if you are just plugging your guitar into the amp without any kind of distortion, clean boost or overdrive pedal, you can turn the Volume control down and always have a clean signal as long as the signal level at the power amp input is not overdriving the power amp. Remember that it has been said that in a non-MV amp, the power tubes are the first to clip or distort the signal.

Right. This^^^^^^^^^^^^^^^^^^^^^^^^^^

Guitar amps are no longer "reference" amps. Though the earliest designs and some much later continued to emulate this. What Mr. Thud points out makes perfect sense WRT guitar amps because you absolutely couldn't place a single volume control at the end of the signal chain on, say, a Peavey 5150 and hope for anything like a clean tone from a guitar plugged into it. This is an extreme example of course but what I hope to illustrate is that THEORETICAL operation and intuitive operation in practice can be very different. Yes you could send a small enough input signal to a wide open 5150 preamp that it would not clip. But for too many reasons that should not even need explaination for anyone that's ever played an electric guitar through an amplifier this is not practical.

[loudthud]

Why not? The volume control could be located at any point along the signal path.

Strictly speaking, this is not true. In a non-Master Volume amp, the Volume control is (almost always) located between the first and second preamp tubes. This is done so that if you are just plugging your guitar into the amp without any kind of distortion, clean boost or overdrive pedal, you can turn the Volume control down and always have a clean signal as long as the signal level at the power amp input is not overdriving the power amp. Remember that it has been said that in a non-MV amp, the power tubes are the first to clip or distort the signal.

[Chuck H]

FWIW in my diagram above each horizontal row represents the signal flow through the amplifier. In case that wasn't obvious.

[Sea Chief]

How does a shut off valve on your water main work? Why would you need one if you've already got a tap (faucet) to control the flow of water? Am I painting a mental picture for you?

No, your only making me go more mental, Greg. I can see the analogy of a tap/ water pipe is useful for explaining electricity (current etc), but as an analogy for a far more complicated guitar amp of two distinct sections you plug something into with a vol knob on, I'm not with you (why would you need this extra one? I've no idea why: sorry I'm really not on board with your point).

SC

[Greg Robinson]

Tbh I've never considered how turning the gtr vol down can actually make the amp vol diminish.

Now I am thinking how on god's earth this happens. So I've got another connundrum to consider.

I might hazzard a guess though, that it diminishes the signal going from the guitar into the preamp. IE if it's 0.5mV at gtr vol 10, then it's 0v at gtr vol 0. If it's a pot on the guitar, it can only affect whatever's emanating from it. I have no idea though.

SC

How does a shut off valve on your water main work? Why would you need one if you've already got a tap (faucet) to control the flow of water? Am I painting a mental picture for you?

[Sea Chief]

I've politely pm'd this guy if he could not post on my thread.

Maybe instead of his unkind request mods, you could kindly suggest he just doesn't post- it's easy for him do nothing at all.

Thanks, SC

[loudthud]

Moderators: I don't think he's going to get it. Please close this thread.

[Sea Chief]

If you turn the volume control on your guitar down, it mutes the output of the amp right? It's not only "before" the power amp, but the preamp too. So why is a volume or "gain" control in the preamp muting the power amp a difficult concept for you to understand?

Tbh I've never considered how turning the gtr vol down can actually make the amp vol diminish.

Now I am thinking how on god's earth this happens. So I've got another connundrum to consider.

I might hazzard a guess though, that it diminishes the signal going from the guitar into the preamp. IE if it's 0.5mV at gtr vol 10, then it's 0v at gtr vol 0. If it's a pot on the guitar, it can only affect whatever's emanating from it. I have no idea though.

SC

[Sea Chief]

Ignored.

[loudthud]

As to how the MV -only- affects the power amp section in your diagram.. this is WAY in advance of where my understanding is. I haven't on god's earth got a clue as to why or how an MV can affect just the power amp, if it's placed before it (& if that's where your diagram suggests it is placed).

You don't seem to understand signal flow. Do you expect the signal to go backwards through the Master Volume and affect the Preamp ? Do you know what a Voltage Divider is ?

Are you refusing to answer the questions because you don't know the answers ?

Are you one of these AI Robots that just posts stuff to get a reaction from people.

[Greg Robinson]

If you turn the volume control on your guitar down, it mutes the output of the amp right? It's not only "before" the power amp, but the preamp too. So why is a volume or "gain" control in the preamp muting the power amp a difficult concept for you to understand?

[Sea Chief]

No. Hifi are meant to be clean. Guitar amps can be both.
noth

Of course I understand this, distortion wasn't part of the enquiry at all.

I'm back a step nosaj. I'm trying to get my head around the idea of a single volume control, affecting the power amp, located in the preamp. As of yet, I can't visualise a power amp section, without having a volume control: the power amp seems to me to be at the end of the path, with the very last part being the output to the speakers. So I always thought the volume control would be located here, just before the speakers, affecting what is ultimately SENT to the speakers. I also know that you put an attenuator HERE, between the power amp.. & the speakers, further confirming (wrongly as I now am told) that Volume knobs just go right here.

So, is my hifi two-box separated preamp & poweramp, with it's volume control on the preamp, a good example for comparison (regardless of distortion which is irrelevant)-?

SC

[nosaj]

No. Hifi are meant to be clean. Guitar amps can be both.
noth

[Sea Chief]

Can anyone tell me if my two separate SS hifi boxes (preamp & poweramp), is a useful 'tool' to compare to the preamp/ poweramp stages in a Tube guitar amp?

Thanks, SC