Tube Amp Archive

Posted: **Fri Jan 17, 2020 9:40 am**

I was reading the FAQ of Two Rock and came across the information below:

https://www.two-rock.com/f_faq/

All of our amps that have reverb have a reverse phased output section. What this means is that the signal is in the negative swing as it leaves the amplifier. Traditional wiring of speakers takes the “+” positive terminal and connects it to the tip of the speaker jack, and the “-“ negative terminal and connects it to the sleeve of the speaker jack. When the speaker gets the signal in this configuration the speaker will push first and the pull. If the wiring of the cabinet is “Out of Phase” with the amp then the speaker will pull first and then push. We wire all our cabinets and combos that pair with our reverb amps with the “-“ speaker terminal going to the tip of the speaker jack and the “+” positive going to the sleeve. This way the signal that is in the negative swing as it leaves the amp see a negative polarity at the speaker. Causing it to push first and then pull. Making sure that the amplifier matches the cabinet will result in the amp/speakers working together. This will increase the dynamic range and tone of the system. It will not hurt the amp to have the speaker running in an opposite polarity then the amp. It will just sound slightly muffled and not have the headroom. Amplifiers that have no reverb will want to be wired in the traditional manner.

I am fairly tempted to trying the "reverse" configuration they mention, but wanted to make sure it will be safe for the amp. Also curious on member's view, as this seems very unconventional.

Posted: **Fri Jan 17, 2020 9:47 am**

Seems like a long-winded way of saying that when you pair a speaker with a two rock combo amp combo, their speaker wiring polarity is opposite normal convention.

Posted: **Fri Jan 17, 2020 10:50 am**

This is techno-babble bullshit I'm afraid. Speakers do not have polarity and to refer to them as positive and negative terminals is incorrect and misleading. The reason they are marked + & - is to indicate the phase which is only relevant if there is more than one speaker when they should be wired in phase to prevent cancellation of the sound waves. It makes no difference whatsoever which side of the output jack is connected to the + or the - terminal as long as they are all connected the same way if there is more than one speaker.

Posted: **Fri Jan 17, 2020 3:43 pm**

From what I remember of my past experiences with HAD, all of the speaker output jacks in this style amp are wired out of phase. It was known that you needed a speaker cable that reversed the + and - wires for the speakers to sound in phase. I'm not sure why this was implemented, but I've known about it for years.

Posted: **Fri Jan 17, 2020 4:05 pm**

Scumback Speakers wrote: ↑Fri Jan 17, 2020 3:43 pm From what I remember of my past experiences with HAD, all of the speaker output jacks in this style amp are wired out of phase. It was known that you needed a speaker cable that reversed the + and - wires for the speakers to sound in phase. I'm not sure why this was implemented, but I've known about it for years.

Thanks for chiming in. Very interesting. I will give it a try, but instead of a reverse cable I will just swap the + and - of the speaker around.

Posted: **Fri Jan 17, 2020 4:17 pm**

I use a phase reversal switch on my cabs and/or amps

Posted: **Fri Jan 17, 2020 4:35 pm**

Colossal wrote: ↑Fri Jan 17, 2020 4:17 pm I use a phase reversal switch on my cabs and/or amps

Like this? Where do you usually install the switch? on the back of the cab next to the input jack?

Posted: **Fri Jan 17, 2020 4:59 pm**

I may be missing something here but I can't see what the point of this is? If you have more than one speaker then they need to be in phase with each other to avoid cancellation but it makes no difference whatsoever which side of the output jack is connected to the + or - side of the speaker(s) - it will sound exactly the same.

Posted: **Fri Jan 17, 2020 5:25 pm**

Considering the vast array and almost infinite variety of fx pedals available these days, and the random nature of any particular rigs polarity, surely if overall signal / system polarity made any audibly discernible difference, then a polarity flip pedal would be a common thing?

Posted: **Fri Jan 17, 2020 6:24 pm**

Bombacaototal wrote: ↑Fri Jan 17, 2020 4:35 pm
Colossal wrote: ↑Fri Jan 17, 2020 4:17 pm I use a phase reversal switch on my cabs and/or amps
Like this? Where do you usually install the switch? on the back of the cab next to the input jack?

Hi Raphael,

Yes, that is how I wire the switch. On cabinets, yes, I install the switch next to the input jack. It works great and if you get the phase match wrong, just click the switch. The sonic difference between an amp that is in and out of phase with its speaker is VERY obvious.

Paul and Pete, I am referring to the relationship between an amp and the cabinet it is attached to. If you miswire a multi-speaker cab, that is a separate problem.

FWIW, note that Matchless includes(ed) a phase reversal switch on their amps. I've been doing this for years.

Best,
Dave

Posted: **Fri Jan 17, 2020 6:41 pm**

"Absolute phase" is really relative phase to a point in time at which the phase measurement is referenced (Noon GMT on Tuesday, the first sample in a time-domain window of sample data for instance, or maybe the middle sample in a vector).
Relative phase can also be measured with respect to another waveform of the exact same constant frequency, as the difference in phase measurement between the two waveforms at any one point will be the same at all other points, as long as the two frequencies stay identical.
Phase is important because it is one of the 3 parameters needed in an equation that completely describes a sinusoid. Without phase information, the waveform is ambiguous.

y(t)=a⋅cos(b⋅t+ϕt0), where ϕt0is the phase at time t=t0.

https://www.psaudio.com/pauls-posts/absolute-phase/

when you hit your bottom e string hard you want your speaker to push the air outwards not inwards with the transient.

edit: it seems with an open back cab, usually combos, having the air going backwards isn't an issue as it will shoot out the open back, I think Fender did this on purpose, sealed cab's would definitely want to be in absolute phase I'd say.

M

Posted: **Fri Jan 17, 2020 6:46 pm**

Colossal wrote: ↑Fri Jan 17, 2020 6:24 pm
The sonic difference between an amp that is in and out of phase with its speaker is VERY obvious.

Paul and Pete, I am referring to the relationship between an amp and the cabinet it is attached to. If you miswire a multi-speaker cab, that is a separate problem.

FWIW, note that Matchless includes(ed) a phase reversal switch on their amps. I've been doing this for years.

Best,
Dave

An amplifier cannot be "out of phase with it's speaker", an amplifier produces an alternating current electrical signal, a speaker converts that signal into sound vibrations (variations in air pressure). For example if you feed 1000Hz signal into an amplifier that will result in the speaker cone vibrating forwards and backwards from it's resting position 1000 times every second, if you reverse the wires on the speaker it will still vibrate 1000 times per second and produce exactly the same sound!

Posted: **Fri Jan 17, 2020 6:47 pm**

PaulD wrote: ↑Fri Jan 17, 2020 6:46 pm
Colossal wrote: ↑Fri Jan 17, 2020 6:24 pm
The sonic difference between an amp that is in and out of phase with its speaker is VERY obvious.

Paul and Pete, I am referring to the relationship between an amp and the cabinet it is attached to. If you miswire a multi-speaker cab, that is a separate problem.

FWIW, note that Matchless includes(ed) a phase reversal switch on their amps. I've been doing this for years.

Best,
Dave
An amplifier cannot be "out of phase with it's speaker", an amplifier produces an alternating current electrical signal, a speaker converts that signal into sound vibrations (variations in air pressure). For example if you feed 1000Hz signal into an amplifier that will result in the speaker cone vibrating forwards and backwards from it's resting position 1000 times every second, if you reverse the wires on the speaker it will still vibrate 1000 times per second and produce exactly the same sound!

see above

Posted: **Fri Jan 17, 2020 7:02 pm**

PaulD wrote: ↑Fri Jan 17, 2020 6:46 pm
Colossal wrote: ↑Fri Jan 17, 2020 6:24 pm
The sonic difference between an amp that is in and out of phase with its speaker is VERY obvious.

Paul and Pete, I am referring to the relationship between an amp and the cabinet it is attached to. If you miswire a multi-speaker cab, that is a separate problem.

FWIW, note that Matchless includes(ed) a phase reversal switch on their amps. I've been doing this for years.

Best,
Dave
An amplifier cannot be "out of phase with it's speaker", an amplifier produces an alternating current electrical signal, a speaker converts that signal into sound vibrations (variations in air pressure). For example if you feed 1000Hz signal into an amplifier that will result in the speaker cone vibrating forwards and backwards from it's resting position 1000 times every second, if you reverse the wires on the speaker it will still vibrate 1000 times per second and produce exactly the same sound!

I understand what you are saying but I disagree. Install the switch on a 1x12 cab and do an A/B and report back. If you cant hear the absolute night and day difference, well, I can't help ya

There was discussion on this very issue regarding the Trainwreck Express. Do a search...

EDIT: https://ampgarage.com/forum/viewtopic.p ... ss#p140207

Posted: **Fri Jan 17, 2020 10:01 pm**

Colossal wrote: ↑Fri Jan 17, 2020 6:24 pm
Bombacaototal wrote: ↑Fri Jan 17, 2020 4:35 pm
Colossal wrote: ↑Fri Jan 17, 2020 4:17 pm I use a phase reversal switch on my cabs and/or amps
Like this? Where do you usually install the switch? on the back of the cab next to the input jack?
Hi Raphael,

Yes, that is how I wire the switch. On cabinets, yes, I install the switch next to the input jack. It works great and if you get the phase match wrong, just click the switch. The sonic difference between an amp that is in and out of phase with its speaker is VERY obvious.

Paul and Pete, I am referring to the relationship between an amp and the cabinet it is attached to. If you miswire a multi-speaker cab, that is a separate problem.

FWIW, note that Matchless includes(ed) a phase reversal switch on their amps. I've been doing this for years.

Best,
Dave

Thanks Dave, I will do this to all my cabs! Very good idea.

How would you wire it to the amp?

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