Actually the ones currently in the store were tested by me.
yup, I'be read that somewhere
What speakers are you running the Freya and ACA amp with ? I ask because I have the same set up and driving Tyler Acoustics PD15s I heard lots of distortion in the bass region. Have got two of them and same result when they are run as monoblocks. Thinking there may be a synergy issue between the ACA amps and the Tylers even though they are rated 8 ohm speakers.
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Johnah5. Please do let me know how you get on I’ve got ACA monoblocks with ultra linear power supplies and Korg Nutube pre amp all of which makes for deep wide tall soundstage with amazing texture and clarity but my music streamer is bricked so I’m looking at replacing the pre-amp streamer and Cambridge DAC magic with the Atom Headphone amp. Pre-Amp section of the headphone amp is upgraded from regular Atom. Have XLR cables on order that I can try direct from the DAC. Would really appreciate your impressions as Naim dealer network has been thrown into disarray in NZ and hard to get my hands on an Atom to try out in my system.
when paralleling ACA's would it be beneficial to match the gain mosfets for transconductance at 12 volts?
ACA Stereo Voltage 11vDC -> 50% of supply
Hi All,
I finished my ACA 1.8 build last week, have been enjoying the hell out of it, probably a good 50 hours up on it now.
Upon finishing the build, as we've Summer coming on down here in Oz I decided to set the MOSFET voltages at 11.0vDC, supply rail voltage from the SMS is 23.7vDC.
Earlier this week I ordered some test resistors (100w), they turned up today so decided to run some tests on this ACA.
I think some will no doubt understand my findings, some will be curious and some will no doubt comment - hence why I'm posting this so please add your thoughts... ideally with explanations please!
With the MOSFETs set at 11vDC, I noticed the harmonics were there, probably a little too much though for my liking.
I've always had SS Class A amps so my ears are well accustomed to the sound (ex Krell 300cx driven by Pass X1 fella here). I did a power check using a scope into the non-inductive resistors, below are my findings;
MOSFETs set at 11vDC
3.1vDC @ 500KHz Sinewave input (just below clipping)
Power into 8 ohm = 5.6W
Power into 4 ohm = 5.6W
FFT showed distinct 2nd, 3rd and 4th harmonics
I read where its suggested to run the MOSFETs at 50% of rail voltage, so I upped them to 11.83vDC, below are my findings
MOSFETs set at 11.83vDC
again 3.1vDC @ 500KHz Sinewave input (just below clipping)
Power into 8 ohm = 5.8W
Power into 4 ohm = 5.8W
FFT showed distinct 2nd, but 3rd and 4th harmonics had nearly disappeared!
So onto the listening test I went. WoW, what a difference. The bass had gone from being a little on the woolly side and tightened right up, it now has distinct bass texture.. more overtones in bass notes.
The mids are now so much more yummy, particularly on acoustic guitars, I play guitar, I luv this amp now.
The soundstage depth may have dropped in depth just a little, I need to do more listening to be absolutely sure of this though.
No measurable change in temps (hands on over 10 secs).. not even going to bother measuring with temp gauge.
This ACA is a beast, I love it. Its running a pair of ProAc Studio 125's via a Krell pre. I got all bar the tansfo on hand now for a F5, man I cant wait!
Thanks Mr Pass, I luv U
Hi All,
I finished my ACA 1.8 build last week, have been enjoying the hell out of it, probably a good 50 hours up on it now.
Upon finishing the build, as we've Summer coming on down here in Oz I decided to set the MOSFET voltages at 11.0vDC, supply rail voltage from the SMS is 23.7vDC.
Earlier this week I ordered some test resistors (100w), they turned up today so decided to run some tests on this ACA.
I think some will no doubt understand my findings, some will be curious and some will no doubt comment - hence why I'm posting this so please add your thoughts... ideally with explanations please!
With the MOSFETs set at 11vDC, I noticed the harmonics were there, probably a little too much though for my liking.
I've always had SS Class A amps so my ears are well accustomed to the sound (ex Krell 300cx driven by Pass X1 fella here). I did a power check using a scope into the non-inductive resistors, below are my findings;
MOSFETs set at 11vDC
3.1vDC @ 500KHz Sinewave input (just below clipping)
Power into 8 ohm = 5.6W
Power into 4 ohm = 5.6W
FFT showed distinct 2nd, 3rd and 4th harmonics
I read where its suggested to run the MOSFETs at 50% of rail voltage, so I upped them to 11.83vDC, below are my findings
MOSFETs set at 11.83vDC
again 3.1vDC @ 500KHz Sinewave input (just below clipping)
Power into 8 ohm = 5.8W
Power into 4 ohm = 5.8W
FFT showed distinct 2nd, but 3rd and 4th harmonics had nearly disappeared!
So onto the listening test I went. WoW, what a difference. The bass had gone from being a little on the woolly side and tightened right up, it now has distinct bass texture.. more overtones in bass notes.
The mids are now so much more yummy, particularly on acoustic guitars, I play guitar, I luv this amp now.
The soundstage depth may have dropped in depth just a little, I need to do more listening to be absolutely sure of this though.
No measurable change in temps (hands on over 10 secs).. not even going to bother measuring with temp gauge.
This ACA is a beast, I love it. Its running a pair of ProAc Studio 125's via a Krell pre. I got all bar the tansfo on hand now for a F5, man I cant wait!
Thanks Mr Pass, I luv U
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Well Naim Uniti Atom Pre-amp/streamer/headphone amp ordered and uniti core CD ripper. XLR from the Naim into the ACA should be good, built in streamer and DAC should be better than Cambridge DAC Magic and Apple TV box i'm having to use at the moment. Keeping fingers crossed that the built in Pre-amp comes close to the Nutube which it would replace in the system. Big gamble but with Tidal subscription and pretty tiny record/cd/tape collection it makes sense.
-+++++
Is it important to have those screws and washers on the PCB? It holds well with the end screws and the solder.
Thanks
jh
Atom HE edition it different it has multiple headphone sockets and a pair of XLR output sockets. It's a dedicated Headphone Amp that can be used as a Pre-Amp. It runs class A as a Pre-Amp. The Pre-Amp circuitry I supposed to be a step up from the standard Atom set up too. It's said to be just slightly on the warm side of being neutral.
My Speakers are Carfae Horn Replicas good for 106db/per watt and with seperate 100watt plate amps built in to drive subwoofers. Crossover set on the plate amp. The back loaded horn Creates a mechanical baffle step so there's nothing between the driver and the amps. So the little ACA's don't see much load at all. Bass with Korg Nutube as pre-amp is very sharp and defined with huge high wide sound stage with lots of depth.
Using the ACA in balanced mode should kill any distortion according to the operating modes information. So the big question is if The Atom HE driving the ACA in balanced mode will sound as good as Nutube driving in unbalanced.
Amp has to go from Austalian importer and distributor to NZ and through Auckland which is under total lockdown. Fengers crossed for a deliver that's not too delayed.
Hi, Thanks for the reply. I found two mistakes. I had 3300uf capacitor backwards and I had the ZTX450 and LSK 170 mixed up.
I successfully switched the orientation of the capacitor. Is it possible I damaged that component/ should i replace it?
I couldn't remove the transistor/jfets without breaking them so I'll need to get replacement parts. Does anyone have advice on getting replacement parts cheaply? I think i found them on digikey ZTX LSK170 Not sure if that is the correct LSK170 and it also cost $40(min order 10)