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Old 27th September 2018, 09:27 PM   #6141
batty is offline batty  Australia
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Would the ACA be enough to drive 92dB senitivity speakers? I have build the Whammy and thinking of building the ACA.
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I have gone from 85 watts class AB amplification to an ACA.Gone on to the M2X.
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Old 27th September 2018, 09:38 PM   #6142
jwjarch is offline jwjarch  United States
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Quote:
Originally Posted by batty View Post
Would the ACA be enough to drive 92dB senitivity speakers? I have build the Whammy and thinking of building the ACA.
Should be more than enough. I'm using the Whammy with my ACA and ~85-86db 4ohm speakers and it gets loud enough for my tastes.

Build it! The ACA is a great little Class A amp!
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Old 27th September 2018, 10:07 PM   #6143
Sledge93 is offline Sledge93
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Mine is driving MMGs without any issue. They're advertised as being 86dB at 500Hz at 2.83v. I don't listen at ear splitting levels and I typically don't listen to orchestral music.
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Old 27th September 2018, 10:16 PM   #6144
astromo is offline astromo  Australia
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Quote:
Originally Posted by batty View Post
Would the ACA be enough to drive 92dB senitivity speakers? I have build the Whammy and thinking of building the ACA.
I built a pair recently with the plan to run them as balanced monos. They're feeding a pair of Ascension Timberwolfs that I got from Edward over in Adelaide.

I can't give you an impedance curve but here are the claimed specs:
Ascension Timberwolf 8893BSRTL speakers with the following specs sourced from the web at the time-
  • Power Handling: 220 WRMS
  • Nominal Impedance: 8 Ohms
  • Frequency Response: 25 - 40,000 Hertz +/-2dB with gradual roll-off giving usable response to low 20s
  • Sensitivity: 91 dB @ 1W/1m
  • Drivers: 2 x 225 mm fast kevlar cone bass drivers; 150mm high end papyrus cone SB Acoustics midrange with ultra flat response; Superb smooth ribbon tweeter capable of response beyond 50 kHz.

The ACAs do a great job. However they run out of puff (to my ears) driving the Beastie Boys, Brass Monkey, when compared with a 100 W pc Schiit Vidar. I typically use Brass Monkey to really test low end bass. But that's the only "negative" I can come up with - not that it's a real negative because most "normal" bass lines come across competently to me are not as extreme as the test track mentioned. Bear in mind too, that the room space is about 4 m x 10 m, wooden floors and the listening position is at about 2 m from the speaker fronts.

So, to answer you directly, I'd expect that your 92dB @ 1W/1m will sing with the ACAs and put a big smile on your face, just like the ones I built did for me.

Even so, I'm planning another amp build to move into 25 W pc territory ... yeah, I know - greedy.

Enjoy ..

Last edited by astromo; 27th September 2018 at 10:19 PM.
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Old 28th September 2018, 09:48 AM   #6145
Sub Sonic is offline Sub Sonic  Australia
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Quote:
Originally Posted by astromo View Post
I'm planning another amp build to move into 25 W pc territory ... yeah, I know - greedy.

Enjoy ..
Sounds like the F5 might be in your future :-)

SS
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Old 28th September 2018, 11:09 AM   #6146
astromo is offline astromo  Australia
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Originally Posted by Sub Sonic View Post
Sounds like the F5 might be in your future :-)

SS
Not one for this thread but I'm after XLR/Balanced audio goodness, so the Aleph J is how I was thinking. From what I can make out, there's no real losing game with a Pass Class A.
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Old 28th September 2018, 09:09 PM   #6147
jonbon is offline jonbon  Norway
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Built the aca and absolutely love it!

But looking at a 25w my self. Is f5 the way to go? Or aleph j? I maginenthe aleph sounds more tubey..
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Old 29th September 2018, 09:59 AM   #6148
Sub Sonic is offline Sub Sonic  Australia
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I’ve not heard the Aleph but I’d describe the F5 as being neutral sounding.
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Old 30th September 2018, 03:33 AM   #6149
Lorado is offline Lorado  Australia
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Default Using an integrated amplifier's pre-amp section for ACA's

Quote:
Originally Posted by semmyroundel View Post
Hi Rafa, and thanks for your explanation, I've finally got there- there is NO 15wpc stereo output, just mono, no good to me i'm afraid.
My speakers are all 8ohm which makes things easier, and interestingly, two are 86db, and one nice and sensitive at 95db.
So it looks like I might need a pre amp with gain (around 6db).
Someone mentioned a whammy, but I looked and that's a headphone amp, so how does that help me? Also it's a way more complicated build than the ACA.

I would be listening to line-level sources, so.......
Despite the fact that I feel I might be left a bit short (yes I know these are just numbers, but I'm used to powerful amps, my main setup at home is a Quad 909 with 99 pre amp, driving Spendor A6 speakers), I'm now tempted to build this amp in its 8w stereo guise and listen to it (it'll have to be on the sensitive speakers).
Shame Nelson didn't design a more powerful version.
Thanks everyone who chipped in though, it's all been helpful.
Oh by the way Rafa, en Espanyol si te apetece, te entiendo.

If you already have an integrated amplifier with pre-amp out and power amp in connectors, you can take out the jumpers and just use the pre-amp section. I bought a second-hand NAD C356BEE with two pre-outs and one main-in, and I am going to use one of the pre-outs connected to the ACA's.
"
11
PRE OUT 1:
The PRE OUT 1 sockets can be used to drive an additional
power amplifier. Use a twin RCA-to-RCA lead to connect the left and
right “Audio Input” of the Power amplifier or processor to the PRE OUT 1
sockets.
Always turn the C 356BEE and associated external power amplifiers OFF
before connecting or disconnecting anything to the PRE OUT 1 sockets.
The PRE OUT 1 output signal will be affected by the C 356BEE’s volume
and tone control settings.
12
PRE OUT 2:
Connections to an external power amplifier or processor,
such as a surround-sound decoder. In normal use, this should be
connected to the MAIN IN sockets with the links supplied. To connect
your C 356BEE to an external processor or amplifier, remove first these
links. Use a twin RCA-to-RCA lead to connect the left and right “Audio
Input” of a power amplifier or processor to the PRE OUT 2 sockets.
Always turn the C 356BEE and associated external power amplifiers OFF
before connecting or disconnecting anything to the PRE OUT 2 sockets.
The PRE OUT 2 output signal will be affected by the C 356BEE’s volume and tone control settings."


Just make sure the pre-amp can deliver enough Volts to drive the ACA's. In my case 8-10 Volts should be ample.



PREAMPLIFIER SECTION
LINE LEVEL INPUT, PRE OUT
THD 20 Hz – 20 kHz, CCIF IMD, SMPTE IMD, DIM 100
<0.005 % at 2 V out
Signal-to-Noise Ratio
>106 dB (IHF; A-weighted, ref. 500 mV out, unity gain)
>114 dB (A-weighted, ref. 2 V out, Volume maximum)
>92 dB (ref. 100 mV out, unity gain)
Channel separation -1 kHz
>80 dB
10 kHz
>68 dB
Input impedance (R and C)
22 kohms+ 100 pF
Maximum input signal
>6 Vrms (ref. 0.1 % THD)
Output impedance - Pre out
80 ohms
Tape out
Source Z + 1 kohm
Input sensitivity
166 mV (ref. 500 mV out)
Frequency response
±0.3 dB (20 Hz - 20 kHz, Tone defeat ON)
±0.3 dB (20 Hz - 20 kHz, Tone defeat OFF)
Maximum voltage output -IHF load
>10 V (ref. 0.03 % THD)
600 ohms load
>8 V (ref. 0.03 % THD)
TONE CONTROLS
Treble
±5 dB at 10 kHz
Bass
±8 dB at 100 Hz


One of the advantages is that I can use the NAD remote control for my ACA's!


Cheers,
Walter

Last edited by Lorado; 30th September 2018 at 03:34 AM. Reason: spelling error
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Old 30th September 2018, 04:33 AM   #6150
NealJ is offline NealJ  United Kingdom
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Amp Camp Amp - ACA
Quote:
Originally Posted by semmyroundel View Post
So it looks like I might need a pre amp with gain (around 6db).
Someone mentioned a whammy, but I looked and that's a headphone amp, so how does that help me? Also it's a way more complicated build than the ACA.
I'm using an Objective2 headphone amp as a preamp for my ACA with 86dB 8ohm speakers. The desktop mod from HeadnHiFi is nice and has RCA outputs you can use to connect to the ACA. Admittedly this is a little more complicated build than what you want, so why not try using the same concept with a CMoy headphone amp? It's very simple to build and extremely cheap.

I've no idea how it would sound, but it might give you an idea and you could use it as a confidence builder to try something like an O2 or whammy later. I've got some opamps so I'll build one and try it.
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