Oh, I fully agree! And I think the answer may be on the fact that, when flipping absolute phase you change the 'sign' of the even harmonics: second harmonic distortion is changed from positive to negative and the other way around, meaning you get different 'flavors', specially with amps that have more prominent 2nd harmonics.
There's an interesting parragraph about that in Papa Nelson's new article in First Watt.
So yeah, I'm sure it's worth testing. I was just mentioning that, in theory, absolute phasewould be reversed. That some recordings would be better served by positive 2nd harmonics while others by negative, I'm also sure.
So many things to try out! That's the beauty of this hobby! Big hug,
Rafa.
There's an interesting parragraph about that in Papa Nelson's new article in First Watt.
So yeah, I'm sure it's worth testing. I was just mentioning that, in theory, absolute phasewould be reversed. That some recordings would be better served by positive 2nd harmonics while others by negative, I'm also sure.
So many things to try out! That's the beauty of this hobby! Big hug,
Rafa.
Ps. To keep the external connections consistent, what I would recommend is soldering pin 2 to the left channel and pin 3 to the right. That way, if you switch from bridged to Balanced, you won't have to invert the speaker cables to preserve polarity.
Obviously, you can always invert the polarity anyway for these shifts in harmonics!
Obviously, you can always invert the polarity anyway for these shifts in harmonics!
indra1 - Let the salesmen of poetry and prose at the audio magazines write words about sound. I don't do that because I know better than to try to describe what my ears are hearing, in my room, with my speakers, with my other equipment, etc... because that will not be anything like what you will perceive with your ears, in your room, with your stuff, etc... You get the point.
The ACA is an absolutely wonderful amp and I listen to mine daily, I sincerely love it. M2x, however, is in a completely different league.
The ACA is an absolutely wonderful amp and I listen to mine daily, I sincerely love it. M2x, however, is in a completely different league.
Allright Jim, no problem. My request was actually rather technical, something to do with perception on the phase of H2, which (as NP mentioned) not everyone is able to hear. Your #7188 post show your ability to perceive H2 phase on a H3 dominated amp, quite rare actually. I think that what you can share will help to remind ACA users to try listening to both polarities at least once. 
Yes - my real point was to just try it yourself. Both of the amps in that situation were non-inverting so, in theory, flipping phase shouldn't have made a difference. But it did.
As it takes little time, is reversible if you don't like it, and can be done by everybody, try it and see what you think.
As it takes little time, is reversible if you don't like it, and can be done by everybody, try it and see what you think.
Yes Jim, since many years ago listening to both speaker polarities on a newly encountered system has become second nature for me. If you check, I reminded others to do so many times in Pass forum alone. But I defer to the eloquent way you express the experience, way more impact than I could ever hope to do.
The ACA page explains the trick to bridging but is it really a good idea with standard ACAs?
I know the amps will see half the load each, its recommended to double the bias current (meaning standard supply heatsink and supply needs an upgrade). without you have double the watts but each amp has to deliver twice the current so what do you actually gain from that?
User loudthud also mentioned in post #458 the distortion spectrum will shift fro second to third order and recommended doubling supply voltage to retain the 2nd order distortion... it sounds like you want a bridged ACA that still sounds like an ACA (sweet) you need 38V supply.
Would bias current automatically double with 38V supply?
if so then higher watt bias resistors are needed also.
its seems a bridged aca is better treated as a different amp than converting standard ACAs to bridged
I know the amps will see half the load each, its recommended to double the bias current (meaning standard supply heatsink and supply needs an upgrade). without you have double the watts but each amp has to deliver twice the current so what do you actually gain from that?
User loudthud also mentioned in post #458 the distortion spectrum will shift fro second to third order and recommended doubling supply voltage to retain the 2nd order distortion... it sounds like you want a bridged ACA that still sounds like an ACA (sweet) you need 38V supply.
Would bias current automatically double with 38V supply?
if so then higher watt bias resistors are needed also.
its seems a bridged aca is better treated as a different amp than converting standard ACAs to bridged
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In post 7038 I posted comparison of THD with single ended and balanced drive. With single ended drive, much of the 2nd harmonic character of the ACA is preserved.
No, Q2, Q3 and associated resistors control bias current. Many things need change to get the ACA to run on 38V and I'm not sure H2 THD will be the same phase as ACA v1.6. Unless you have lots of experience in this area, I don't recommend it. Instead, look at the PLH. It runs on about 40V and has a pot to adjust THD. Really an underrated design IMHO.
Well, Ive got about 47C on the case using Kapton.. SO I guess that works fine. Thanks 6L6
I put a few layers of cloth/teflon tape between the clamp and the mosfet to help spread any small pressure points a bit wider. Pretty pleased. I think my sinks are perfect size for 24V.
Yeah, everyone should build this. Too easy! Plus if you've been collecting parts long you'll probably have everything you need anyway. Thanks to Papa.
I'll update on the guitar amp after I add tone filters and a distortion generator.
Uriah
I put a few layers of cloth/teflon tape between the clamp and the mosfet to help spread any small pressure points a bit wider. Pretty pleased. I think my sinks are perfect size for 24V.
Yeah, everyone should build this. Too easy! Plus if you've been collecting parts long you'll probably have everything you need anyway. Thanks to Papa.
I'll update on the guitar amp after I add tone filters and a distortion generator.
Uriah
Bfpca - you called it.
Since I wasn't confident in testing this, I re-flowed everything first and that didn't resolve the problem. In frustration, I wiggled the input cable around, and that resolved the problem.
I'm using the Bluejeans LC-1 cables with Taversoe RCA plugs - this is the only RCA input jack that is having a problem, so I'm going to assume it's this input jack and not the cable.
How do I go about getting a replacement input jack?
Looks like I screwed up the solder joint - I have some solder that somehow bridges the small gap between the center pin and ground. I have tried to no avail to clean that mess up - in fact, I think I've now made it worse. So, where do I go to get the same RCA jack? (I know any one will likely do, but I would prefer to have the same one as all the other ones.)
Thanks for all the pointers helping me to root cause this!