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!
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 ..
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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
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.
Using an integrated amplifier's pre-amp section for ACA's
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
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
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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.
Hi Alan
First thank you for trying to help me.
I am sorry I have not replied before now but I went down with stress and Star Trek was about all I could manage.
I am a bit better now so I have tried measure the voltages as shown.
The output from the phone fluctuates a bit but on average 0.37v.
Out ACA without speakers 1.4v.
Out ACA with speaker 1.17v.
This gives an amplification of 3.2 and not that far from your 3.6 and probably well within measurement uncertainty.
So I guess the conclusion is that my ACA is OK which is good news.
I connect the ACA to my desk speakers and used my phone as input. Really low output. Then I used the output on my pc (not laptop) and that changed everything. Suddenly I got a sound level that was usable.
So... how do I know if a preamp is usable?
How much gain is required?
None of my present gear works and I before buying (or building) a preamp I would like to be sure I am doing the right thing.
A nice sunday to all you ACA'ers
Hi, does this mean that you can effectively get a 8w+8w amplifier ?
I had this idea of buying two parts kits and installing them side by side in the same chassis, each being driven by one RCA, naturally they wouldn't be balanced, but at least I'd get double the power.
Or am I missing something?
Hi, thanks for that reply-taken in the helpful vein that it was intended.
But, and it's a big but, this is a DIYaudio forum is it not? Why would I want to buy $280-$400 worth of pre amp?
I was hoping to find a way of doubling the power in stereo, that would be sufficient for me.
As I've said, I'm hoping that the bare bones 8wpc will suffice once built, as I'm hard pressed to follow an electronics wiring diagram, even the tripath amp that i built (and it works fine except on tuner) I built by sight and layout. Once parallel paths had been created on the circuit board, I was no longer able to test the resistors on the board, only prior to soldering.
Such is my limited ability.
Anyway, I still appreciate the reply, it's all good.
Thanks and yes, it seems clear that I'll have to try it without doubling up, as Nelson said: "the first watt is the most important" I shouldn't lose sight of that I guess.
BTW, for those in Europe, that 2u chassis is only €84 from modu shop plus 15 for delivery.
Granted, you have to tap the threads, but that's part of the fun of DIY
I agree with this. If the ACA doesn't have enough grunt for your tastes, there are plenty of Pass Class A options to choose from.
My personal philosophy was to use the ACA to dip my toe in the water and establish my sense of capability. Then, of course, I've been bitten. So, the next step that I'm planning is an Aleph J. From the sounds of what you're after, the Pass amps on offer that can deliver in the 25 W pc range would probably fit your bill.
My thinking is that my learner ACA monoblocks will head down to my studio and drive some bookshelfs and get low down drive separately from a sub. The Aleph J will ultimately be the main unit in my living room where there's more space to fill.
That said I could happily live with the ACAs where they are (those 15 W monos drive wonderfully well) but, meh, why do that? Why stop at just 1 build?
The answer is yes or no*.
Mono 'bridged' or 'balanced' mode (2 ACAs) gets more power out for 8 to 16 ohm impedance speakers so say 14 - 15 watts. They can effectively swing more volts.
'Parallel' mode (again 2 ACAs) gets more power into lower impedance speakers. 4 ohms or so. Could be 15 watts. This is because there is double the current available.
* So the answer depends on the speaker impedance as much as anything.
There are puts and takes for either mode and it is covered here https://cdn.shopify.com/s/files/1/1006/5046/files/ACA_Monoblock_Operation_RevA.pdf in the build guide.
