Changing phase
Moderators: pompeiisneaks, Colossal
Changing phase
I bought an old Sano "stereo" tube amp with a stereo input. It splits the signal into 2 volume controls and a separate tube circuit for each. Kind of like an old Marshall. I have a mono to stereo guitar cord ordered from China and hoped to experiment by blending the channels, however, I read on another forum that the 2 channels are out of phase, with each other. I can't find a schematic anywhere for this amp ( 1960's Sano Hi fi ) so I'm guessing that 1 side has an extra tube half, before blending them together. The logic by the forum author was that an accordion has 2 transducers and doesn't mind the out of phase condition? Anyway, when the cord arrives, if this is true, I want to be prepared. Is there any cost effective way to shift the phase of 1 channel? I see a Barber launch pad that has a phase shift option, but $179 is more than I want to spend. Also, I'd have to rig up some kind of patchwork cords to work around it.
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Stevem
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Re: Changing phase
The best way to go is to make the channel that has the most gain stages into being like the channel that has the least gain stages, it's probibly not a 45 minute deal though!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Changing phase
The accpmordion phase thing sounds dubious. Without a schematic, I'd open her up and trace out the stages to see. I don't suppose you'd like to wire the guitar in stereo?
Tube junkie that aspires to become a tri-state bidirectional buss driver.
Think I found something
I found a Radial Big Shot aby box that has a true bypass output and a reversed phase out put (transformer coupled ) that can be used simultaneously. All I need now is a 1/4 dual mono to stereo cord, which Musicians Friend sells, and I should be ready to go. I'm thinking that I can run a different od or effects boxes in each line also, for added versatility.
Re: Changing phase
Most probably a NFBless amp with each channel entering in one side of the PI.
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Leo_Gnardo
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Re: Changing phase
I've worked on some old Sano amps with "stereo" accordion inputs. Most of the time I wind up modding that input pair so the user can select a tone thru hi & low frequency preamps & I don't recall them being out-of-phase. The input is intended to be made via a 4-pin mic connector from "stereo" accordion. To clarify, "stereo" really isn't stereo, it is one mic pointed at bass reeds and another mic on the rest of the reeds of the accordion.
I'll admit I haven't seen ALL the amps Sano turned out, maybe this amp does have a phase funny in its preamp but I wouldn't assume until trying it out.
It is possible the "phase flip" story leaked over from Fender and some other amps where there's one more phase flip in one pre compared to the other and summing same signal thru both pre's yields a dodgy "out of phase" tone.
One good thing out of all this, you got the right gadget when you got the Radial Big Shot. You might find it more useful when you Y into two amps at once. Only drawback is the internal transformer comes unstuck if you drop the box. Some of my customers broke theirs, what a PIA they can't make 'em tougher. You might consider glomming some glue onto yours in case of the inevitable.
I'll admit I haven't seen ALL the amps Sano turned out, maybe this amp does have a phase funny in its preamp but I wouldn't assume until trying it out.
It is possible the "phase flip" story leaked over from Fender and some other amps where there's one more phase flip in one pre compared to the other and summing same signal thru both pre's yields a dodgy "out of phase" tone.
One good thing out of all this, you got the right gadget when you got the Radial Big Shot. You might find it more useful when you Y into two amps at once. Only drawback is the internal transformer comes unstuck if you drop the box. Some of my customers broke theirs, what a PIA they can't make 'em tougher. You might consider glomming some glue onto yours in case of the inevitable.
down technical blind alleys . . .
Stereo Question
If there are two inputs on an older tube power amp from a Magnavox console stereo would those outputs be out of phase? btw this amp sounded really nice with an emulator but a filter cap needs, all need to be replaced so it sits on the shelf for now. I may build something else with the trannies though instead...
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martin manning
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Re: Changing phase
The two channels are essentially duplicate circuits, sharing a few components and a common power supply, so they are in-phase.
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Stevem
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- Joined: Fri Jan 24, 2014 3:01 pm
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Re: Changing phase
I looked up my notes on a excelsior Accordian amp the I went thru some years ago and it too was called stereo, but really was not!
The two channels, treble and bass both had the same number of gain stages, but the last gain stage that the bass channel went thru before the PI section was just set up for less gain by it passing thru a 12Au7 and not a 12ax7!
The two channels, treble and bass both had the same number of gain stages, but the last gain stage that the bass channel went thru before the PI section was just set up for less gain by it passing thru a 12Au7 and not a 12ax7!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Changing phase
Thanks for the replies. I will give both channels a try as soon as that mono to stereo cord arrives. This one has a 1/4 inch stereo input instead of the earlier Sano's with the 4 pin connector. Playing through the guitar input, last night it sounded very good for about half an hour. Then the sound thickened up and got a little hair on it. Was perfect. I played a few hours, turned it off, then played it again, an hour later and never recaptured that thick sound. Sounded a lot like Molly Hatchets version of "Dreams" Damn, I need to find out what happened and make it keep happening. The el34's feel pretty loose, maybe they warmed up and built some resistance? For an hour or so, I had the sweetest amp that I've ever heard.