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Amp Camp Amp - ACA
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Old 12th January 2018, 01:45 AM   #3671
Skip Pack is offline Skip Pack  United States
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From the beginning of my ACA build, I planned to bridge two amps on each channel because I have 16 ohm speakers. As I tested each large heatsink with two amps as a stereo single-ended amp (not bridged), I found that they powered my 95 db sensitive speakers very well. Don't hesitate to listen to those nice 3 watts just because it doesn't seem like enough to work well. I really like the now-finished bridged amps, but it probably wasn't necessary to bridge them -- the difference is very subtle.

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Old 12th January 2018, 01:47 AM   #3672
zekeblue is offline zekeblue
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Originally Posted by Zen Mod View Post
approx. 3 clean watts , with 24Vdc rail
Thanks for chiming in. Big drop from 8 watts. Higher impedance is supposedly easier to drive. Does that mean better results in terms of sufficient power given the same wattage? ie, would 3 watts at 16 ohms seem like more power than 3 watts at 8 ohms given the same speakers?

Thanks again.
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Old 12th January 2018, 02:02 AM   #3673
Zen Mod is online now Zen Mod  Serbia
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Amp Camp Amp - ACA
no apples and oranges ..... meaning - you can't find two speakers same in everything , except in impedance

even if you translate what's needed in db/W/m figures , there are few more factors in speakers world - most important being impedance module - in other words - how speaker is easy to drive

so , listening test is only way to compare things like that
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Old 12th January 2018, 03:25 PM   #3674
zekeblue is offline zekeblue
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Quote:
Originally Posted by Zen Mod View Post
no apples and oranges ..... meaning - you can't find two speakers same in everything , except in impedance

even if you translate what's needed in db/W/m figures , there are few more factors in speakers world - most important being impedance module - in other words - how speaker is easy to drive

so , listening test is only way to compare things like that
I was meaning in theory anyway, to tease out the effect of impedance alone. But I've got the sense of it I need. Thanks to you both.
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Old 23rd January 2018, 08:57 PM   #3675
__BriKs__ is offline __BriKs__  France
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Hello,

I built ACA and love it! Have the opportunity to test it on a high end system (same kind of speaker as Nelson Pass Kleinhorn in smaller).
Conpetitor amp was a Pioner M22, the ACA (ACA 1.1 with single 120W meanwell 24V PSU) and the ACA was good!
Off course M22 is best on low medium and bass especially when huge power is required, then I would love design my own amp based on ACA active current source.
I think this is due to the poor reactivity of my psu (also poor wattage for 2 channel), would like to try with a 350W fly back psu.
But the idea is to lower the output impedance, since I'm far away to be an electronic audio expert, after reading the whole thread I decide to explore lowering output impedance this way:
modify the ACA design and reuse the lovely active current source, in fact transform the active source to active sink using a common drain instead of common source. Then the gain of output stage goes to unity and design a low noise, low distorsion JFET voltage gain stage with common nsource topology.

Then I ask to you if this kind of idea worth try or if I'm totally wrong ?

For my presentation I'm a french electrical engineer who after lurking some Nelson Pass design for years decide to go in bath and build some amps!
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Old 23rd January 2018, 09:20 PM   #3676
2 picoDumbs is offline 2 picoDumbs  Australia
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No idea is totally wrong.

You need to determine whether the problem is not enough voltage swing or damping factor. Current clipping is unlikely to be a problem in stock form.
If you can't figure that out, just mod both. You'll need bigger heatsinks though.

Alternatively build an F6. I've modded mine to have almost identical distortion character to ACA but at around 0.05% and damping factor is over 20 in mine.
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Old 24th January 2018, 11:36 AM   #3677
__BriKs__ is offline __BriKs__  France
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OK, the idea is wrong for the lack of low medium/bass of the ACA I built.
Then maybe it's not the good topik for such questions.

Here a picture of my ACA 1.1, I did the PCB with kicad and manufacture it to seeedstudio (5 pcb for 75$).
I made a mod to avoid OFF pop: I connect speaker directly between the power resistor on one side and the other side is AC coupled with two big caps between power rails. In a such way voltage rise and fall same potential at the two pole of speaker. And this serve also as a power tank for whole circuitry. I also add a common mode 1mH self and a big 3900F tank for each channel.

I also upload the ltspice shematic with THD run of the idea I would like to test, THD measurment seems to show good results from the unity voltage/current gain output stage.
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File Type: jpg aca.jpg (823.5 KB, 669 views)
File Type: jpg amp.jpg (305.7 KB, 628 views)
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Old 25th January 2018, 09:35 PM   #3678
Toobsox is offline Toobsox  Canada
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Default Really Basic Switch Question

Hello.

I am building an ACA and Im jammed up about toggle switch ratings. My power supplies are 24v 6a. What should my power switch be rated at? Is this something I should be worried about?

Thanks.
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Old 2nd February 2018, 07:18 AM   #3679
moppy is offline moppy  Malaysia
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I have completely built the ACA partner with BOZ pre. I found the sound is not loud enough. The BOZ volume control I'm using is ALPS 20k. Let say at 6 o'clock the volume is zero, when I turned up till 1 o'clock the sound is not loud. My speaker is a DIY by own. The speaker is 88db @ 8ohm. Anyway to make it louder? The sound is great.
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Old 2nd February 2018, 07:51 AM   #3680
ZacharyP is offline ZacharyP  United States
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Quote:
Originally Posted by moppy View Post
I have completely built the ACA partner with BOZ pre. I found the sound is not loud enough. The BOZ volume control I'm using is ALPS 20k. Let say at 6 o'clock the volume is zero, when I turned up till 1 o'clock the sound is not loud. My speaker is a DIY by own. The speaker is 88db @ 8ohm. Anyway to make it louder? The sound is great.
More details about the speakers are needed.
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