Tube amplifiers switcher technical question

[PentodeLicious]

TL;DR Do all the different speaker cabinets and different amplifiers speaker outputs ground should be connected to each other, all the time???

I recently purchased an Amp/Cabinet selector for all my heads.
Out of respect for the maker I will keep its name to myself.
Connected all my amps.
What a disappointment. major tone sucking and compression.

Opened the unit, all the parts are cheap.
Wires are cheap.
I upgraded the whole wiring with a decent speaker cable.
A small improvement but still major tone sucking.

I noticed that all the amp inputs jacks and the speaker output jacks are connected to the same ground, All The Time!
No matter what position the speaker selector is at.
No matter if the amp is connected to a different cabinet, it shares ground with all the other amplifiers speaker output ground.
If I understand correctly, each amp speaker output ground should be separated from other amplifiers speaker output grounds.

Could this be the tone sucking/compression reason?
Is this safe?

 

[william vogel]

TL;DR Do all the different speaker cabinets and different amplifiers speaker outputs ground should be connected to each other, all the time???

I recently purchased an Amp/Cabinet selector for all my heads.
Out of respect for the maker I will keep its name to myself.
Connected all my amps.
What a disappointment. major tone sucking and compression.

Opened the unit, all the parts are cheap.
Wires are cheap.
I upgraded the whole wiring with a decent speaker cable.
A small improvement but still major tone sucking.

I noticed that all the amp inputs jacks and the speaker output jacks are connected to the same ground, All The Time!
No matter what position the speaker selector is at.
No matter if the amp is connected to a different cabinet, it shares ground with all the other amplifiers speaker output ground.
If I understand correctly, each amp speaker output ground should be separated from other amplifiers speaker output grounds.

Could this be the tone sucking/compression reason?
Is this safe?

Because they are tied together (plugged in)it would be complex to switch both ground and signal independently of each amp/speaker combination. It is possible. Generally noise would result from the groupings vs tone. Are you sure that the signal inputs are connected although not connected to the speaker?

 

[PentodeLicious]

Because they are tied together (plugged in)it would be complex to switch both ground and signal independently of each amp/speaker combination. It is possible. Generally noise would result from the groupings vs tone. Are you sure that the signal inputs are connected although not connected to the speaker?

Yes i'm sure, all the jacks grounds are soldered together.
Basically one wire runs thru all the jacks ground.

 

[PelliX]

Could this be the tone sucking/compression reason?

Unlikely. Have you measured the resistance of the switcher without anything attached? Gutshots?

Is this safe?

Yes. After all, your speaker negative, aka ground is at the same potential as the chassis of your amps. When the amps are connected using an earthed plug their chassis' are all at the same potential, too.

 

[PentodeLicious]

Unlikely. Have you measured the resistance of the switcher without anything attached? Gutshots?



Yes. After all, your speaker negative, aka ground is at the same potential as the chassis of your amps. When the amps are connected using an earthed plug their chassis' are all at the same potential, too.

Yes I measured the resistance.
When the amp is selected the resistance is 0. when it is not it sees a 600 Ohm Load.
Unfortunately no guts shot.nothing exciting though...

Just did another test now in proper volume.
Same amp thru switcher & without. same cables (I have a jumper)

Thru the switcher it sounds almost like somebody placed a Low pass filter. Almost nothing over 6Khz.
That was it for me.
I am taking the switcher out.
Back to cable swinging.
When I have the time I'll build my own box.
What a waste of money...

 

[PelliX]

Thru the switcher it sounds almost like somebody placed a Low pass filter. Almost nothing over 6Khz.

And it's really just "switching", no other circuitry involved?

When I have the time I'll build my own box.
What a waste of money...

No option of returning it?

Opened the unit, all the parts are cheap.

Just curious, what kind of parts are you referring to?

 

[AML]

TL;DR Do all the different speaker cabinets and different amplifiers speaker outputs ground should be connected to each other, all the time???

I recently purchased an Amp/Cabinet selector for all my heads.
Out of respect for the maker I will keep its name to myself.
Connected all my amps.
What a disappointment. major tone sucking and compression.

Opened the unit, all the parts are cheap.
Wires are cheap.
I upgraded the whole wiring with a decent speaker cable.
A small improvement but still major tone sucking.

I noticed that all the amp inputs jacks and the speaker output jacks are connected to the same ground, All The Time!
No matter what position the speaker selector is at.
No matter if the amp is connected to a different cabinet, it shares ground with all the other amplifiers speaker output ground.
If I understand correctly, each amp speaker output ground should be separated from other amplifiers speaker output grounds.

Could this be the tone sucking/compression reason?
Is this safe?

Unsafe only if you connect an amplifier that is designed such that neither speaker output wire should be grounded. Which might be the case if you connected some Class D amplifiers. But - as mentioned above - just about every guitar-oriented valve amp has a grounded speaker wire.

I have a switcher - from de Lisle - and there's no tone suck.

And tell me more about this "decent speaker wire" you used. If the original wire was specced for the current correctly, there was no improvement (unless in the desoldering and resoldering you fixed a poor solder joint). Even 100W into a 8-Ohm load sees maybe 5A.

 

[PentodeLicious]

And it's really just "switching", no other circuitry involved?



No option of returning it?

well it is on PCB and also there are rotary switches, 330 ohm resistor also soldered to ground that get closed circuit for all other positions other then the selected amplifier.

I am in a different country, I also opened it thinking I could make it stop the tone sucking.So no I cannot return it.

Just curious, what kind of parts are you referring to?

parts i'm referring to: the rotary switches and the cables used for the inter connections.

I have a switcher - from de Lisle - and there's no tone suck.

Well maybe I should get a de lisle then.
I'll try to sell this one first.
Though I think i'm gonna make one on my own.

And tell me more about this "decent speaker wire" you used. If the original wire was specced for the current correctly, there was no improvement (unless in the desoldering and resoldering you fixed a poor solder joint). Even 100W into a 8-Ohm load sees maybe 5A.

Regarding the wire:
I use 14 AWG "pure" copper speaker wire.
It is a wire I used for a 2 amps to 1 cabinet switch I made for my amps.
The switch is transparent.

You'll be surprised how cables differ in quality even though they are in "spec".
For example I have two 3 meters speaker cable 16AWG from different brands.
Supposedly same specification, they even look identical.
Sonic wise?
Night and day.
One sucks all the high frequency content and sounds muffled.like a low pass filter.
The other sounds open and delivers the "full" frequency spectrum.
Both costs the same.

I built a few Hi Fi speakers and a good wire makes night and day difference for hi end systems.
Spending thousands of dollars on a supposedly the best speaker wire that ever exist is rubbish IMO.
But using the "Correct" spec speaker cable gauge and length does not promise you there will be no degradation in sound compared to higher than "necessary" spec cable.

 

[PelliX]

parts i'm referring to: the rotary switches and the cables used for the inter connections.

Assuming the contacts in the switches are OK I doubt they're playing much of a role here. The cables... I find it hard to believe that the wire itself is the cause of the issue, or even the routing. We're talking about low impedance high current signal.

For example I have two 3 meters speaker cable 16AWG from different brands.

The longer the haul, the more influence any resistance and so on may have. Inside a switcher box type construction I'll assume we're talking about maybe 10cm, roughly?

 

[PentodeLicious]

Assuming the contacts in the switches are OK I doubt they're playing much of a role here. The cables... I find it hard to believe that the wire itself is the cause of the issue, or even the routing. We're talking about low impedance high current signal.

Well there was a slight improvement after I changed the inter connection cables.
but did not get rid of the problem completely.
So yes i'm with you, there is something else.
Technically wise the resistance is 0 so all should be fine.but...
After a few amp builds I did I know, sometimes it looks right on the scope but sounds bad in real life...

The longer the haul, the more influence any resistance and so on may have. Inside a switcher box type construction I'll assume we're talking about maybe 10cm, roughly?

Ofcourse.
yeah not longer.

 

[PelliX]

After a few amp builds I did I know, sometimes it looks right on the scope but sounds bad in real life...

Fair enough, but if the high frequencies are being attenuated, I would assume this would be visible by feeding a signal in and scoping the output?

Random idea, the switcher box isn't perhaps being influenced by some insane magnetic field near to it?

 

[PentodeLicious]

Fair enough, but if the high frequencies are being attenuated, I would assume this would be visible by feeding a signal in and scoping the output?

Random idea, the switcher box isn't perhaps being influenced by some insane magnetic field near to it?

The difference is obvious.
You don't need a scope to see it.

And no insane magnetic field next to it.
Just my overwhelming good looks

 

[Cal Nevari]

TL;DR Do all the different speaker cabinets and different amplifiers speaker outputs ground should be connected to each other, all the time???

I recently purchased an Amp/Cabinet selector for all my heads.
Out of respect for the maker I will keep its name to myself.
Connected all my amps.
What a disappointment. major tone sucking and compression.

Opened the unit, all the parts are cheap.
Wires are cheap.
I upgraded the whole wiring with a decent speaker cable.
A small improvement but still major tone sucking.

I noticed that all the amp inputs jacks and the speaker output jacks are connected to the same ground, All The Time!
No matter what position the speaker selector is at.
No matter if the amp is connected to a different cabinet, it shares ground with all the other amplifiers speaker output ground.
If I understand correctly, each amp speaker output ground should be separated from other amplifiers speaker output grounds.

Could this be the tone sucking/compression reason?
Is this safe?

Interesting question that I will defer to others to answer; however, I did want to mention the Radial Headbone VT, which is a great product IMHO (see my review for details). This switcher provides transparent switching without changing the tone of either the guitar or amps. Not sure if this is what you have already, but if not you might want to check it out. Best of luck!

Headbone VT - Radial Engineering

The Headbone VT is a specially designed switching device that lets you toggle between two different tube amp heads while using a single speaker cabinet.

www.radialeng.com

 

[2L man]

Simple connection box has one or two sturdy/high current input jack(s). Then two isolated output jacks which do the series circuit. And two or more jacks which do parallel connection.

Amplifier has a wire or resistor from output to "ground" which prevent output potential climb if/when output transformer primary leak HV to secondary. So this box can be plastic and/or all jacks can be plastic in metal box.

If there is a need to swap one speaker/cab phasing two DPDT lever switches are needed. 10A rated are quite cheap. One is used for series outputs. Another DPDT for parallel outputs but then only one speaker/cab can have opposite phase. However this allow three parallel to be used which should be plenty.

Double pole rotary shitch which current rating is high enough is expensive. DP might be enough for both output phase swaps but now priefly thinking I did not get one DP function for series and parallel output phase swaps and if it is so then rotary switch has way too low current rating or very expensive choice!

When there is a few hundred ohm resistor parallel with input the idea is that it tries to prevent amp oscillation when rotary switch setting is changed. To prevent oscillation it is best to switch HV off few seconds before rotary is turned.

 

[Ronquest]

sometimes it looks right on the scope but sounds bad in real life...

Sometimes (most times) it looks bad on the scope but sounds good...

 

[AtomicRob]

You might have already tried it, but I'd recommend running some isolated tests to see what factors actually matter. Start with only one amp and one cab, nothing else plugged in. Does it suck tone even then? If so then it's not related to interaction between the amps or a ground loop. If it doesn't suck tone with one-to-one, try two amps and one cap. Etc.

BTW is this a purely passive unit - no power? If there's a power supply in it I'd be looking closely at that too... ground loops can definitely cause tone suck in weird ways. With only one amp, one cab, and nothing else plugged in you can't have a ground loop, but if the unit itself has a power supply that could be causing it.

 

[PentodeLicious]

You might have already tried it, but I'd recommend running some isolated tests to see what factors actually matter. Start with only one amp and one cab, nothing else plugged in. Does it suck tone even then? If so then it's not related to interaction between the amps or a ground loop. If it doesn't suck tone with one-to-one, try two amps and one cap. Etc.

BTW is this a purely passive unit - no power? If there's a power supply in it I'd be looking closely at that too... ground loops can definitely cause tone suck in weird ways. With only one amp, one cab, and nothing else plugged in you can't have a ground loop, but if the unit itself has a power supply that could be causing it.

The unit is passive.
It's a good idea to test single amp.
However the whole purpose is to connect all my amplifiers to it.
But yes i'm intrigued so I will do the single amp test you suggested.

 

[PentodeLicious]

observation:
one amp & one cab -> high frequency response much better, still compressing. tone sucking is still there. much more subtle but still noticeable.

 

[PentodeLicious]

YESSSS!!!
Removed all the resistors. Tone sucking is gone!!!
Tested a/b with cable straight to the amp.
Of course cable straight a bit more high frequency response but overall the switch is now workable!
Who would of thought.
Maybe the interaction of the resistors with the common ground.
Who knows.
There is a lot of voodoo going on with tube amplifiers
Anyone who builds one knows.

 

[snakej200]

That’s crazy I’ve got a Delisle 8x8 deluxe switcher and it doesn’t tone suck at all. Only issue I’ve ever had is you HAVE to have an amp head hooked up to the #1 amp spot otherwise you’ll get this weird ground issue. Otherwise it’s awesome