Thx for the info. Since it doesn’t seem to worsendistortion that much, why doesn’t everyone do that? Are there other negative tradeoffs?
If you ever plan to try using your ACA boards in a parallel bridged mode, I recommend changing R11 to 20k and R12 to 90.0k. Increases the gain to about 4.5. I also like to bypass the 90.9k resistor with a 10pF silver mica capacitor.
@TungstenAudio no plans fir that. It’s just in use in a small den. Surprisingly it drives the elac DBR62’s to 75db at my listening position 2 meters away.
I did see references to your mods in several places and was going to investigate further. I see you live just a few miles away from me here in Seattle.
I did see references to your mods in several places and was going to investigate further. I see you live just a few miles away from me here in Seattle.
Not that I know of. The feedback network is AC coupled and so has no effect on the DC conditions at all.
I would guess the gain was set to give maximum undistorted output when fed from the nominal 2vrms max output level of most CD players/DAC's and so on.
By way of comparison something like a Quad 303 runs at 32db gain, the popular blameless Class B designs of Doug Self are around 27db and my own amp runs at 34db gain.
So the ACA is low by any standards.
no use of thinking that way, setting gain to set final THD
that way one is getting in situation of not having enough juice when, for instance, listening some piece with peaks well bellow 0db
in Pro World, they came long time ago to one sole possible ( and in their case, effective and good-enough) solution - they're using limiters
in home, ears are only viable criteria
that way one is getting in situation of not having enough juice when, for instance, listening some piece with peaks well bellow 0db
in Pro World, they came long time ago to one sole possible ( and in their case, effective and good-enough) solution - they're using limiters
in home, ears are only viable criteria
Gain available for distortion reduction (in dB) = Open loop gain (in dB) - Closed loop gain (in dB)
Therefore,
Reducing closed loop gain INCREASES gain available for distortion reduction
==============================================
Also,
Closed loop gain needs to exceed (output amplitude at clipping) / (input amplitude) . . . . or else you won't get the full available power to your speakers.
Flea power amps have low output amplitude at clipping, so they require less closed loop gain.
Therefore,
Reducing closed loop gain INCREASES gain available for distortion reduction
==============================================
Also,
Closed loop gain needs to exceed (output amplitude at clipping) / (input amplitude) . . . . or else you won't get the full available power to your speakers.
Flea power amps have low output amplitude at clipping, so they require less closed loop gain.
My kit appears to be missing the small bag of screws for attaching the heatsink rails to heatsink (at bottom right of pic). I dont mind replacing them myself if I knew the specs… anyone?
Thanks. And thanks everyone for answering my previous question too.
Just finished my ACA
Just finished my ACA -- adjusted bias and did the checks, hooked it up and it's sounding better and better. Stayed up way too late last night listening to music.
I know it's a little silly (and I'll check the thousand replies), but I was flummoxed about the choice of red or blue LED (I went with red) wondered if others were stymied with the choice?
I am getting the funny sound when I power up and a nasty almost metallic sound when I turn it off. I'll read further about that, but I guess I'm just so ecstatic about this build, and I've been reading since way before I registered and wanted to say I've joined the club and thanks so much for all I've learned from you all.
Sincerely,
David
Just finished my ACA -- adjusted bias and did the checks, hooked it up and it's sounding better and better. Stayed up way too late last night listening to music.
I know it's a little silly (and I'll check the thousand replies), but I was flummoxed about the choice of red or blue LED (I went with red) wondered if others were stymied with the choice?
I am getting the funny sound when I power up and a nasty almost metallic sound when I turn it off. I'll read further about that, but I guess I'm just so ecstatic about this build, and I've been reading since way before I registered and wanted to say I've joined the club and thanks so much for all I've learned from you all.
Sincerely,
David
Normal operation. C1 charging up. It is covered lots of times in the very long thread and in step 50 of the build guide Amp Camp Amp V1.6 Build Guide - diyAudio Guides
Good to have it working, go and enjoy! Alan
I disconnect a speaker wire at the speaker (easily accesible) before turning it off. I knowthe turn-off thump causes no damage, but I prefer it not to happen.
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If you’re really determined about getting rid of it, install a speaker protection jig.
Store has, xrk too and many others
Store has, xrk too and many others
Thanks guys. Ill wait a couple more days for diyastore support to reply to my email before I head to home depot.
LTSPICE model of ACA
Is there a model anywhere of the ACA that runs in the current version of LTSPICE?
Google didn’t come up with anything but I just started trying to learn that simulator and perhaps I’m using the wrong search terms.
Is there a model anywhere of the ACA that runs in the current version of LTSPICE?
Google didn’t come up with anything but I just started trying to learn that simulator and perhaps I’m using the wrong search terms.
I didn’t realize it was the chassis bolts you needed. Sorry. Your bolts need to come from HIFi 2000 or the hardware store.,
The below were for the PCB bolts
Mark
The below were for the PCB bolts
Mark
No reply from diyaudiostore. Ill be headed to hardware store later today and hopefully have this up and running later today or tomorrow. Will be using as a headphone amp for planars (Fostex T30 and TH500RP) direct from speaker taps. I dont have any very effecient speakers yet. Will do a FR BLH later.