How to Balance the Phase Inverter
ฝัง
- เผยแพร่เมื่อ 13 ก.ย. 2024
- Using an oscilloscope, and two probes, you can perform the balance of a phase inverter via this process. It should work with any amp, Connect two inputs to each side of the output of the phase inverter, before it goes into the power amp tubes, on each half.
~-~~-~~~-~~-~
Please watch: "Marshall Dual Video 8"
• Marshall Dual Video 8
~-~~-~~~-~~-~
Where are you making your scope connections?
Great video! I'm about to start work on my own #124 as well and it was interesting to see this. What type/model scope are you using there to measure things?
It's a rigol ds1054z.
I am just getting into building an amp. I have two chassis' but they are a little complicated ,so thinking about building a champ out of these or starting from scratch. I nee to get me a few more tools for the work and a little more knowledge. I may see if I can get me some graphs and such. Looks like you are getting along pretty well with yours.Can't seem to find the schematic for the twiddle dee-I guess it is a secret!!!!!!!
+why not me it's available on the ampgarage.com forums, with plenty of other dumble, trainwreck and other amps, I think I posted or mentioned that in one of the earlier videos I did on the build
+Buddysimo Simonetta sorry buddy, didn't see you already had the answer :)
Thanks
thanks.
How much out or not equal is supposed to be correct for a gtr amp then?
Well that's a subject of debate. Some say a few volts of imbalance are best for guitar. Hifi wants perfect balance. I say listen with your own ears and go with that
I have comments questions and concerns: (1) What if you just have an old oscilloscope with no math or fft? (2) You explained, but you did not actually show adjusting the waveform. It would have been invaluable just to see that process from a visual learning standpoint. Especially for us who do not have the benefit of math or fft and need to manually do this. (3) Kill the autofocus! :-/
I only mentioned FFT as one way, you can also just use the oscilloscope to see the two outputs of the PI and adjust until they're as close to identical as possible. I did explain this but you're right that I didn't show it 'happening' but that was because I didn't really want to move this 'out' you can see the waveforms of the two probes, one on each side that I then used that pot to adjust them until they were slightly imbalanced. enough to get those 2nd order harmonics. You can also definitely just set it to very equal output, OR set it by ear but use the scope to see where that's at. Also some people just use the AC output on a DMM and look at trying for a few volts imbalance on purpose, maybe 6VAC difference in the AC output of the signal. As for the autofocus, it's the bane of my existence, because I somehow often find a way to turn it back on on accident... never intentionally.
LOL, every time I watch a video where somebody is using a digital oscilloscope for audio equipment it seems to add complexity, confusion and general annoyance compared to an analog oscilloscope!
I personally had an analog oscilloscope and sold it.
Nice but if you want really want to kiss, keep it simple stupid, forget the o scope for balancing, just inject a 1k tone @150mv. Dummy load the output and turn up the volume. Now hook the scope probe to output jack and either turn it up until it just about to starts to clip, or half that peak to peak signal and use an ac rms voltmeter and take a reading on each phase inverter cap and adjust until both sides are equal. You could use the scope and move to each side and adjust for equal. Most scopes read peak, peak to peak. It will vary sometimes like slowing decrease in level on each side so check them several times but you’ll get it.
If you don’t have a scope, turn it up to the normal level you place and adjust it again with an ac rms meter. I prefer to go half way to clipping and adjust because I found the balance will change as volume changes so 1/2 way is a happy medium. This isn’t rocket science folks, get it as close as possible and move on with your day.
I have heard of this technique as well. There are as many techniques as there are musicians :) I think if that one works for you, you're set. Thanks for sharing.
That "almost perfect" doesnt work for anything exept guitar amps. A complete null is needed for Hi Fi.
+Ned Sheats absolutely correct, on a guitar amp it's entirely offers :) hifi it's horrible
Gah phone autocorrect, I meant "On a guitar amp it's entirely optional, on hifi it's horrid :)
@@FrenchieFilms Not every nonlinearity sounds good even in guitar amps. IMO when something doesn't sound worse when fine-tuned it is worth it to make it look better "on paper". It is the best to know where nonlinearity will provide musical distortion and let tubes/RC filters/chokes do their job there. Because at the end of the signal chain all of these forgotten/"insignigicant" nonlinearitis will sum up to higher noise or lo-fi sound and nothing can be done there... So in my opinion it is the best to emphesise what sounds good rather than think that electric guitar tone is lo-fi and forgiving :) Great video.
True. A ton of this is learning what matters and when etc.
N
N!