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Old 21st March 2018, 05:18 PM   #3851
mg16 is offline mg16
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Join Date: Nov 2001
Location: western pa
Default Parallel inputs and outputs ACA

I am wondering if anyone here has built the ACA, and used 2 boards per channel, paralleling the inputs and outputs, for double the current into a 4 ohm load. Naturally, larger heatsinks, and PSU would be required.
I have read over 100 posts regarding the ACA here, and have not come across any discussion regarding this yet, so I am posting this.
I have read Nelsons' Zen amp article,(also have built one successfully), and he states you can parallel inputs and outputs of the Zen stereo amp, turning it into a monoblock, with twice the current, in order to drive 4 ohm speakers.
I have already populated 4, ACA PCB's, (Chinese copies from Ebay). Would have rather bought them here, but they are sold out unfortunatly.
I have a 330VA , 18+18 vac transformer, 60,000uf worth of 35 volt capacitors, and a
chassis with dual 12" by 4.5" heatsinks with 1.5 inch fins, from an old project.
I would be using the amp with a pair of small, 4 ohm, monitor speakers,(Infinity Infinitesimal v.1).
The 2k2 resistors are soldered in to give 1.4 amp bias per board as described here.
With 2 boards per heatsink, 24 vdc supply, 2.8 amps bias, I would be dissapating 67 watts per heatsink, with about 10 watts delivered to the speaker if I calculate correctly.
In my small room, this would hopefully be enough.
Would this be feasible?
Any opinions warmly welcomed.
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Old 21st March 2018, 05:52 PM   #3852
MrBoat is offline MrBoat  United States
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Originally Posted by Eric View Post
The ACA needs a power supply that will provide about 80-100w of total power. General rule of thumb for Class A amps is you want a power supply that provides a minimum of 7.5x output power into 8ohm load. ACA = 5w per channel * 2 channels * 7.5 = 75w, then go a bit higher if you can.

Your power supply will provide 24v * 8.8A = 211w of power.
Thanks for the answers/explanations, everyone.

I was more concerned with sharing a single source for two amps. I did not know if this particular type of amp needs isolated sources outside of the popular fashion of mono-blocks.

I actually liked the idea of using the bricks which seemed like a tidy solution when all is said and done. This supply, I just happened to already have on hand and just remembered I had it.
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Old 21st March 2018, 07:58 PM   #3853
Eric is offline Eric  United States
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Amp Camp Amp - ACA
The general perspective is to isolate channels from one another so output demands from driving one channel don't impact the other channel. This is probably more appropriate with larger, higher output power amps. Right now, I'm powering my stereo ACA chassis with a single Dell 90w power brick. Works great.
My DIY Basement Theater, Aleph-X Amps, Avro Open Baffle Speakers, LDR based BA-3 pre, Pearl II, highly modded Technics SL-1200, F4, M2, Aleph-J, MoFo, a40, several ACAs, FHXL, Tang Band 1772 bass-reflex
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Old 21st March 2018, 08:45 PM   #3854
mg16 is offline mg16
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Default ACA more power

Would just using one board per channel, and biasing it for 2.8A, be better than 2 boards per channel, paralleled, each running at 1.4A? Taking into account increased heat sink area, PSU capability, etc.?
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Old 23rd March 2018, 10:15 PM   #3855
MEPER is offline MEPER  Denmark
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I just got components home from DigiKey for the ACA. I got the 10uF/25v Elna silmic II and to have something to compare with I also got the standard Panasonic 10uF/25v. Then for the project I have a Jensen 10uF/100v alu foil (a "real" capacitor).

I made some some measurements at 10 kHz to check how the 3 capacitors performs. The Elna Silmic II performs worst. The Panasonic a bit better but no match for a real capacitor. Think the data talks for itself.

But people thinks the Silmic "sounds" good?
There will be some "phase error".....
Attached Images
File Type: jpg Elna_Silmic_II_10uF_25v.jpg (176.2 KB, 581 views)
File Type: jpg Panasonic_10uF_25v.jpg (177.9 KB, 565 views)
File Type: jpg Jensen_10uF_100v_alu_foil.jpg (186.0 KB, 572 views)
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Old 24th March 2018, 01:26 PM   #3856
MEPER is offline MEPER  Denmark
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The Elna Silmic II 10uF/25v is physical very small (4 x 10 mm). I think the larger versions has better measurement. E.g. like the 100v version:
RFS-100V100MH4#5 Elna America | Capacitors | DigiKey

I have made measurements before on a Silmic II 22uF which was -80 degree at 10kHz. It was one with higher voltage rating.
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Old 24th March 2018, 01:30 PM   #3857
Zen Mod is online now Zen Mod  Serbia
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Amp Camp Amp - ACA
well , it sounds good ;
I'm routinely bypassing with 1uF MKC , and for my ears that's it , when I must have a cap
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
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Old 26th March 2018, 10:41 AM   #3858
Jason is online now Jason  Australia
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Amp Camp Amp - ACA
I'm happy to announce that after an inordinately long gestation period the new Amp Camp Amp kit is finally here.

Amp Camp Amp Parts Kit – diyAudio Store

The parts kit is now more affordable ($129), and the new stereo chassis is the same price as before ($149). The parts kit ships from the USA, and the chassis direct from Hifi2000 in Italy. There will be much more posted about this over the coming days, including a new build guide from 6L6 and some special tips and tricks for advanced users.

The old PCBs (1.0 and 1.0b) won't fit into the new (Mini Dissipante based) chassis, as the MOSFETs would hit the heatsink brackets. To get around that, we came up with a new 2U UMS specification (yet to be published), Nelson redesigned the circuit board (V1.1) to suit that and now we have a very good looking 2U UMS format for small amplifier projects. If you have one of the old ACA boards, it may still be possible to use the new chassis using jumper cables to the MOSFETs (not yet tested, don't shoot me if I'm wrong!), but for now please consider the old boards and new chassis relatively incompatible. We'll have the new 1.1 boards available for individual sale in a month or so.

More information to come...
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Old 26th March 2018, 03:27 PM   #3859
Tom V is offline Tom V  United States
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Order #DAS-4534 confirmed! I'm in!

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Old 26th March 2018, 03:38 PM   #3860
exw9 is offline exw9  United States
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me too, got my order in this morning! very excited

Last edited by exw9; 26th March 2018 at 03:45 PM.
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