[mewrei]

I'm looking over the schematics of the AMB M3 and I'm trying to figure out if the required 100uF and 330uF aluminum electrolytic capacitors are even in the signal path (debating whether to get some nice boutique capacitors like some Elna's or just go with high-grade Nichicon KW's, and save some money)

I'm not an electrical engineer (hobbyist at this point, not gotten to the electronics sections of my major), so I'd like to verify this information before I dump a bunch of cash into boutique capacitors.

Thanks

 

[m1abrams]

Quote:

Originally Posted by mewrei /img/forum/go_quote.gif I'm looking over the schematics of the AMB M3 and I'm trying to figure out if the required 100uF and 330uF aluminum electrolytic capacitors are even in the signal path (debating whether to get some nice boutique capacitors like some Elna's or just go with high-grade Nichicon KW's, and save some money) I'm not an electrical engineer (hobbyist at this point, not gotten to the electronics sections of my major), so I'd like to verify this information before I dump a bunch of cash into boutique capacitors. Thanks

The M^3 is a Direct-coupled, so there are no caps in the signal path. However that is not exactly true, IF you have the bass boost feature you do have 2 caps in the feedback so those two caps cbb can benefit from "boutique" parts.

The ones you mention are not in the signal path so just stick with the recommended parts.

 

[mewrei]

Alright, thanks man

 

[MisterX]

Looks like someone forgot about C1, C2 and C3....

 

[mewrei]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif Looks like someone forgot about C1, C2 and C3....

Are those in the signal path? I guess Cbb and C1-3 would be good for boutique caps. I'll have to brush up on good boutique film capacitors.

 

[diditmyself]

The effect of C1 and C3 in the audible spectrum is minor. I don't think audio grade caps are something to strive for here. Besides audio grade pF caps are scarce and don't fit the board. Use NPO ceramics as recommended.

I think the same goes for C2, but I'm not clever enough to be sure how much this cap influence the sound, and if it's "active" in the audible range. From simulation and listening tests with other amps I think you shouldn't worry too much about it.

The bass boost cap is more important, but a "cheap" standard polypropylene is probably good enough.

Regarding the electrolytics, they're also in a way part of the signal path, but in a 3-ch class A amp they play such a minor role I doubt anyone can hear the difference between caps.

Amb really knows his stuff, and I think it's wise to follow his recommendations.

 

[Beefy]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif Looks like someone forgot about C1, C2 and C3....

But there's signal path, and there's signal path

At no point does the entire signal pass through an inter-stage coupling cap, which is where you really need something nice. Then again, the bass boost capacitor is right there in the feedback loop and is pretty critical, but I wouldn't ever use that myself......

Quote:

Originally Posted by mewrei /img/forum/go_quote.gif Are those in the signal path? I guess Cbb and C1-3 would be good for boutique caps. I'll have to brush up on good boutique film capacitors.

Well, its marginal. They are compensation caps for tuning the amps response, and other tuning functions. Stick with the default recommendations. With respect to Cbb, if you are truly serious about sound quality, then leave it out.

 

[amb]

When the bass boost is set to off, the pot (or switch, whichever option is used) shorts out Cbb so it has no effect. Only when bass boost is enabled does it become an influence. If you find yourself using bass boost often, then using boutiquey caps for Cbb makes sense. Otherwise, a good (but not necessarily super fancy or pricey) polypropylene film cap would work well here.