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Jer's 400 PLWO Thread
- Thread starter jbeckva
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(see??).
In simplest terms:
In a feedback system with gain in it, each pole will contribute phase lag from 0 to 90 degrees based on frequency (from low to high frequency). At the same time it is introducing phase lag it is attenuating gain at 6dB/octave (for every doubling of frequency, the amplitude is halved). Eventually the gain will reach zero dB or 1 or unity. A single pole system will have up 90 degrees of phase lag when the gain reaches 0dB and is very stable.
As above, a feedback system with 2 poles will introduce 0 to 180 degrees of phase lag based on frequency. At the same time it is introducing phase lag it is attenuating gain at 12dB/octave (for every doubling of frequency, the amplitude is quartered). Eventually the gain will reach zero dB or 1 or unity. A two pole system will have up to 180 degrees of phase lag when the gain reaches 0dB and is conditionally stable. If the phase lag is 135 degrees at unity gain, the system will be stable. If the system has 180 or more degrees of phase lag at unity gain, the system will be unstable.
The trick to having one slow transistor is that it forms the single pole system and rolls off the gain in the system early, before the system second pole occurs creating that stable system.
Of course there are always other system parasitics adding phase lag so a 2 pole system is usually never just a two pole system.
Exec summary: Kill your all system gain before you have 180 degrees of phase lag and you will be all set.
In a feedback system with gain in it, each pole will contribute phase lag from 0 to 90 degrees based on frequency (from low to high frequency). At the same time it is introducing phase lag it is attenuating gain at 6dB/octave (for every doubling of frequency, the amplitude is halved). Eventually the gain will reach zero dB or 1 or unity. A single pole system will have up 90 degrees of phase lag when the gain reaches 0dB and is very stable.
As above, a feedback system with 2 poles will introduce 0 to 180 degrees of phase lag based on frequency. At the same time it is introducing phase lag it is attenuating gain at 12dB/octave (for every doubling of frequency, the amplitude is quartered). Eventually the gain will reach zero dB or 1 or unity. A two pole system will have up to 180 degrees of phase lag when the gain reaches 0dB and is conditionally stable. If the phase lag is 135 degrees at unity gain, the system will be stable. If the system has 180 or more degrees of phase lag at unity gain, the system will be unstable.
The trick to having one slow transistor is that it forms the single pole system and rolls off the gain in the system early, before the system second pole occurs creating that stable system.
Of course there are always other system parasitics adding phase lag so a 2 pole system is usually never just a two pole system.
Exec summary: Kill your all system gain before you have 180 degrees of phase lag and you will be all set.
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So I'm clear on it, what is a "pole" ... is it the +/- halves of the circuit or is it the predriver and outputs forming two separate "poles"?
Got the 410's back in... either the left channel is just enough in line between the outputs and predriver, or the predrivers are some bad eggs out of the carton.. I found a good test - the beginning of "Subdivisions" by Rush... the synths for some reason really bring the issue out in the open. Not after switching back to the 410's tho...
Got the 410's back in... either the left channel is just enough in line between the outputs and predriver, or the predrivers are some bad eggs out of the carton.. I found a good test - the beginning of "Subdivisions" by Rush... the synths for some reason really bring the issue out in the open. Not after switching back to the 410's tho...
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Rule #1 that I have joked with Lee about many times, check your test equipment first. It is more 3 times more likely to have something wrong with it than the unit under test 
So I'm clear on it, what is a "pole" ... is it the +/- halves of the circuit or is it the predriver and outputs forming two separate "poles"?
Got the 410's back in... either the left channel is just enough in line between the outputs and predriver, or the predrivers are some bad eggs out of the carton.. I found a good test - the beginning of "Subdivisions" by Rush... the synths for some reason really bring the issue out in the open. Not after switching back to the 410's tho...
Got the 410's back in... either the left channel is just enough in line between the outputs and predriver, or the predrivers are some bad eggs out of the carton.. I found a good test - the beginning of "Subdivisions" by Rush... the synths for some reason really bring the issue out in the open. Not after switching back to the 410's tho...
It is complicated but think of a pole as a filter. Generally (but not always) a pole is associated with a low pass or lag function in the circuit. Contrast that with a zero which is generally (but not always) associated with a high pass or lead function in the circuit.
When I say the transistor is a pole, I mean you have hit the frequency when the transistor starts turning into a filter and its ability to amplify current is reducing as frequency increases. There are no perfect transistors out there and they all have a Ft. Fast transistors have a high Ft and slow transistors have a low Ft.
You could look at it like the transistor eventually becomes the capacitor in a low pass filter.
Cancel that!
Realized that with the DBX 200 I had a scratchy switch.. Yep, always the "test setup"... lol..
Realized that with the DBX 200 I had a scratchy switch.. Yep, always the "test setup"... lol..
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Had a pretty busy night and morning myself. Doing a conversion for a local 400. New PS caps, new Joe board, New outputs and drivers. No Joe LED board, ya might send me 2 whites Joe and a white 700. Got 3 amps comin this week.
Fired up the board tester and fixed the board I had pulled out of fitz43's Larry 700 and the one I swapped out for Gibsonians disaster. I'll keep them local just in case.
Fired up the board tester and fixed the board I had pulled out of fitz43's Larry 700 and the one I swapped out for Gibsonians disaster. I'll keep them local just in case.
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Ok, time for an update on this guy... First, we've actually went ahead and made this LOOK like a WOPL (whatever that may be). I went with kind of a "Dune" type theme.. with a black finish with a lil' bit of feathering thrown in for some texture, and the bezels now sporting a nice gold tone. I went with the lettering in gold as well, except the "500".. which blood red, ala "300" style seemed like a good idea at the time...
So now it's ready to go? To WHOM??? Well... the original owner, Northwinds, of course. I figured a lil bit of phoenix "karma" would be a good thing, and I got a few Black Sabbath LP's in the deal, so hey... Ron... PM me your address and I'll get it in the mail to ya. Yeah those dang meters... they're "better" but still a lil stick now and then. Looks like something a swiss watchmaker might fix, but that's not me LOL.
Enjoy Ron... I know I am right now listening to it. Very good sounding tunes...
So now it's ready to go? To WHOM??? Well... the original owner, Northwinds, of course. I figured a lil bit of phoenix "karma" would be a good thing, and I got a few Black Sabbath LP's in the deal, so hey... Ron... PM me your address and I'll get it in the mail to ya. Yeah those dang meters... they're "better" but still a lil stick now and then. Looks like something a swiss watchmaker might fix, but that's not me LOL.
Enjoy Ron... I know I am right now listening to it. Very good sounding tunes...
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HOLY SHIT!!!!!! Pardon my French but that looks wild!!!
I appreciate it Jer, I plan on sending you some more good tunes very soon. This was just totally cool to watch from a rode hard and put away wet dead as a stick carcass to a functioning asskickin firebreathing monster. The personal touch is perfect, back from the dead and time to shred
Thanks to all for bringing this back from the dead and thanks most of all to you Jer, that's a heck of a thing you did and I won't forget it
Oh man, rack handles would indeed look badass on this. I did not even know they had them for these
Going to dust off the CT-24 and polish up the CV's, I have a feeling things will be getting loud around here again with 500 horses under the hood
I appreciate it Jer, I plan on sending you some more good tunes very soon. This was just totally cool to watch from a rode hard and put away wet dead as a stick carcass to a functioning asskickin firebreathing monster. The personal touch is perfect, back from the dead and time to shred
Thanks to all for bringing this back from the dead and thanks most of all to you Jer, that's a heck of a thing you did and I won't forget it
Oh man, rack handles would indeed look badass on this. I did not even know they had them for these
Going to dust off the CT-24 and polish up the CV's, I have a feeling things will be getting loud around here again with 500 horses under the hood
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HOLY SHIT!!!!!! Pardon my French but that looks wild!!!
I appreciate it Jer, I plan on sending you some more good tunes very soon. This was just totally cool to watch from a rode hard and put away wet dead as a stick carcass to a functioning asskickin firebreathing monster. The personal touch is perfect, back from the dead and time to shred
Thanks to all for bringing this back from the dead and thanks most of all to you Jer, that's a heck of a thing you did and I won't forget it
Oh man, rack handles would indeed look badass on this. I did not even know they had them for these
Going to dust off the CT-24 and polish up the CV's, I have a feeling things will be getting loud around here again with 500 horses under the hood
I appreciate it Jer, I plan on sending you some more good tunes very soon. This was just totally cool to watch from a rode hard and put away wet dead as a stick carcass to a functioning asskickin firebreathing monster. The personal touch is perfect, back from the dead and time to shred
Thanks to all for bringing this back from the dead and thanks most of all to you Jer, that's a heck of a thing you did and I won't forget it
Oh man, rack handles would indeed look badass on this. I did not even know they had them for these
Going to dust off the CT-24 and polish up the CV's, I have a feeling things will be getting loud around here again with 500 horses under the hood
