ACA too much treble/high end?
Hi all -- I finished my ACA about a month ago. It's my first amp build. I really enjoyed the project. But to my ears, it's got way too much treble/high end. I'm using it with my Project Debut Carbon TT and original Elac B6's. I tried it both with a project pre and bought a bellari pre with tone control. To make it sound OK, I have to really EQ the bass up and the treble down. It's sounded this way pretty much the whole time it's been running and I've been using it an hour or two everyday. It's plenty loud enough so that's not an issue. I don't have any way to measure, so don't exactly what's coming out of the speakers as far as frequency is concerned. Could it be anything I did when building the amp? Any other thoughts or suggestions? Thanks for your help/input.
Hi all -- I finished my ACA about a month ago. It's my first amp build. I really enjoyed the project. But to my ears, it's got way too much treble/high end. I'm using it with my Project Debut Carbon TT and original Elac B6's. I tried it both with a project pre and bought a bellari pre with tone control. To make it sound OK, I have to really EQ the bass up and the treble down. It's sounded this way pretty much the whole time it's been running and I've been using it an hour or two everyday. It's plenty loud enough so that's not an issue. I don't have any way to measure, so don't exactly what's coming out of the speakers as far as frequency is concerned. Could it be anything I did when building the amp? Any other thoughts or suggestions? Thanks for your help/input.
There isn't much that could cause excess treble, in fact the design of the ACA means that even if the input coupling cap and/or the output cap were incorrect in value by factors of ten or a hundred, the top end response would remain flat.
That said, an incorrect value input cap would cause the low frequencies to suffer although in a different way to what might be expected. Same applies to the output cap.
If these two components are correct in value then the response is pretty much guaranteed to be correct.
The 'sound' of the ACA is quite speaker dependent due to the high output impedance but it wouldn't cause such pronounced effects.
If you have another amplifier that you think 'sounds right' then there might be a way to compare the response of the ACA with that one using just a meter and test tones.
That said, an incorrect value input cap would cause the low frequencies to suffer although in a different way to what might be expected. Same applies to the output cap.
If these two components are correct in value then the response is pretty much guaranteed to be correct.
The 'sound' of the ACA is quite speaker dependent due to the high output impedance but it wouldn't cause such pronounced effects.
If you have another amplifier that you think 'sounds right' then there might be a way to compare the response of the ACA with that one using just a meter and test tones.
I suspect that even a mono ACA might have issues with the (ugly) impedance of this loudspeaker.
That giant impedance peak at about 2kHz will be heard.
dave
Thanks Planet 10 and Mooly for the info. The ELAC speakers sounded pretty good with my previous amp -- an early 80s vintage Harman Kardon. I don't have another pair of speakers to test with. Was planning on building some Markaudio 12P Pensils to go with the amp. But might see if I can borrow some speakers from a friend to test before I do.
Compared to a class AB amp like a Rega Brio, the ACA sounds much brighter to me, and with certain DAC inputs, annoyingly bright. I fixed that to my listening satisfaction with a B1 Korg NuTube preamp between the DAC and the ACA. Of note, I don't like having the B1K between the phono stage of my Rega TT and the ACA- it makes the music sound way more 'record-y' which I would describe as rolling off both the high and low end. FWIW.
Couldn’t find a measured impedance curve*, but if anything like any other factory XO typically has really bad imedance response, enuff so to be an issue with a stereo ACA, certainly enuff to screw u a bridged pair.
<rant>*(i did find a review with lots of measures, including measured distortion [which Geddes work has shown is a mostly useless metric for speaker distortion), but not the critical impedance)</rant>
dave
Neither of those 2 speakers will care much whether you use 1 or 2 ACA. A standard vented box for a monoBlok pair could be a bit larger, a good basic size is 9 litres. Most bass extracted by FHXL (i am ignoring Brodgar here) then Pensil and the other ML-TLs.
dave
Thanks for looking. I tried looking myself at some point and came up flat too. I'm mostly curious about the phasing now.
ACAs have a similar affect on Klipsch Heresy IIs, for another point of reference. Granted I've only heard it in stereo, not bridged. Klipsches are a whole different animal with a bit more horsepower behind them, regardless of their efficiency. The M2X was exquisite on mine. I imagine a bridged ACA would sound really nice on them in comparison to a stereo version. Still might need to tame the high mids a little. Mine have a bright spot in the 6-8K range when playing loud. Not sure if the RPs have a similar hot spot.
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Really curious about getting a pair of ACA's for my den/home office system.
It's a small room, and I don't listen super loud. Currently I have Harbeth P3ESR's playing through an Audiolab 8000A integrated (60WPC).
The P3ESR's are fairly inefficient (83.5 db sensitivity), so probably not a great match for the ACA, but again, I don't listen at really loud levels in this space, and I sit fairly close. I'd use the ACA's in balanced (XLR) monoblock operation, so I'd be setting them up for max power.
Reason for this experiment is that I happened upon a Schiit Freya+ preamp for a really good price, and I bought it on a whim. So I need to find a use for it!
Also looking at a pair of Schiit Aegir's, which have a similar form factor, but more power. But I love the idea of building a pair of ACA's.
I did a search for Harbeth within this thread, but didn't find much. Are they too inefficient to even consider?
Nominal impedance: 6 ohms ("easy to drive").
Sensitivity: 83.5dB/2.83V/m.
Recommended amplification: >15W.
It's a small room, and I don't listen super loud. Currently I have Harbeth P3ESR's playing through an Audiolab 8000A integrated (60WPC).
The P3ESR's are fairly inefficient (83.5 db sensitivity), so probably not a great match for the ACA, but again, I don't listen at really loud levels in this space, and I sit fairly close. I'd use the ACA's in balanced (XLR) monoblock operation, so I'd be setting them up for max power.
Reason for this experiment is that I happened upon a Schiit Freya+ preamp for a really good price, and I bought it on a whim. So I need to find a use for it!
Also looking at a pair of Schiit Aegir's, which have a similar form factor, but more power. But I love the idea of building a pair of ACA's.
I did a search for Harbeth within this thread, but didn't find much. Are they too inefficient to even consider?
Nominal impedance: 6 ohms ("easy to drive").
Sensitivity: 83.5dB/2.83V/m.
Recommended amplification: >15W.
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