First, thanks for making this kit available, providing a nice looking chassis, and rounding up all the parts and organizing them so well. I’ve finished the PCBs, attached them to the heat sinks and assembled the back plate hardware, but not sure if there is a final wiring diagram or photo. I’ve seen the photos on the No. 5075 post on the ACA build thread and really can’t tell exactly how the power terminal is wired. And is there a recommended use of the heavier gauge red and black wires vs. the smaller gauge red and black wires? I ordered the version with the front power switch and plan to use the RCA jacks in a stereo setup.
Jim
Jim
Thank you very kindly for those words Jim.
At this stage, what you have available is:
* The beautiful V1.5 Build Guide
* This gallery of V1.6 Build Guide photos (under construction, but I post the link just to give you some ideas)
The V1.5 build guide contains 95% of what you need to know. The only significant differences are the power switch wiring in V1.6. It's a new PCB, but all the parts are otherwise the same.
The V1.6 build guide isn't finished yet, because (1) the final V1.6 kit and chassis are hot of the presses with new parts, some only designed or decided in the last month or two, (2) we wanted the V1.6 build guide to have every step and photo exactly the same as the V1.6 kits and chassis so there could be no confusion, and (3) we rely on the grace of great builder-photographers like Jim who do have a life outside of DIY, to make these beautiful guides. It'll be ready in a couple of days and an email will be sent to all kit purchasers the minute it's ready.
So, this is the result of our iterative improvement process. It means that things are always changing for the better, but it means we have a lot of work to do each release to keep the build guides up to date. Pretty much every single photos from the V1.5 build guide has needed to be re-shot, and there's over 100 of them in that guide. I hope that explains the delay.
At this stage, what you have available is:
* The beautiful V1.5 Build Guide
* This gallery of V1.6 Build Guide photos (under construction, but I post the link just to give you some ideas)
The V1.5 build guide contains 95% of what you need to know. The only significant differences are the power switch wiring in V1.6. It's a new PCB, but all the parts are otherwise the same.
The V1.6 build guide isn't finished yet, because (1) the final V1.6 kit and chassis are hot of the presses with new parts, some only designed or decided in the last month or two, (2) we wanted the V1.6 build guide to have every step and photo exactly the same as the V1.6 kits and chassis so there could be no confusion, and (3) we rely on the grace of great builder-photographers like Jim who do have a life outside of DIY, to make these beautiful guides. It'll be ready in a couple of days and an email will be sent to all kit purchasers the minute it's ready.
So, this is the result of our iterative improvement process. It means that things are always changing for the better, but it means we have a lot of work to do each release to keep the build guides up to date. Pretty much every single photos from the V1.5 build guide has needed to be re-shot, and there's over 100 of them in that guide. I hope that explains the delay.
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I ship containers from Europe to North America on a regular basis. You are looking at a minimum of 45 days, dock to dock. Often containers arrive and sit for weeks before inspection and trucking. It often takes two months before I see my shipment arrive. Then there is the matter of filling a container......Have you thought how many ACA's would fit into a container? Yes, hundreds of thousands. Perhaps millions. The demand is not of the size that a container is cost effective. At. All.
A note to the DIY team. Stay with the tried and proven delivery systems. And don't play fast and loose with any countries' import laws (I am telling you what you already know). The issue here is NOT the cost of your kits. The issue is with the country of receipt and their massive and punitive import duties. This is NOT a DIY Audio problem guys!
For all you folks in Europe and GB who wish to circumvent the rules. Do not ask the vendor to risk their livelihood to save you money.
I'm waiting for the new build guide before I start because: 1) I am a complete newbie and want to leave very little to chance. And 2) I don't really have time to dig into the project for at least another couple of weeks.
BUT .... I do have a question! And while this question has been addressed in other threads that I have gone back and read, I'm still uncertain what the answer is for me. The question concerns PREAMPS!
I already have an Emotiva BasX PT 100 preamp which lists a maximum analog output of 4 VRMS. Is this too high for the ACA? Or can I use this preamp with some restraint while I find another option, like build a B1?
BUT .... I do have a question! And while this question has been addressed in other threads that I have gone back and read, I'm still uncertain what the answer is for me. The question concerns PREAMPS!
I already have an Emotiva BasX PT 100 preamp which lists a maximum analog output of 4 VRMS. Is this too high for the ACA? Or can I use this preamp with some restraint while I find another option, like build a B1?
rekterx,
You should hopefully be fine. But there are some details you need to consider.
With the ACA 1.6 version overall gain is 10dB. Which means for 7-8 watts max RMS, you will need about 2.53V RMS (the input sensitivity) to reach that power output. You have 4V RMS and a variable volume control (since the Emotiva unit you mentioned is a combo preamp/dac/etc...). This is good.
What is important to find out is the sensitivity of your speakers since 8 watts may or may not be enough depending on your listening habits, listening distance/size of listening room etc...if that is the case, an option is to build 2 ACA’s and use them as monoblocks for 15 watts/8 ohms. The overall gain is still the same in this build, ie 10dB.
Building the B1 pre to go with the ACA wouldn’t be something I would recommend to everyone since it has no gain whatsoever. It might work with a system using very efficient speakers in a small room (ie > 95 dB). And of course your listening habits play a part too. If you have a reasonably efficient speaker but you turn up the volume all the way and it is still quiet sounding then you need more gain. A preamp of about 6-15 dB would work well with the ACA since the overall gain of the “system” is then about 15-26 dB which most audiophiles are used to.
Understanding the differences between gain and power output vexes many audiophiles for some reason but when you break it down into applications of Ohm’s law and the power equation, it is actually straight forward.
Best,
Anand.
You should hopefully be fine. But there are some details you need to consider.
With the ACA 1.6 version overall gain is 10dB. Which means for 7-8 watts max RMS, you will need about 2.53V RMS (the input sensitivity) to reach that power output. You have 4V RMS and a variable volume control (since the Emotiva unit you mentioned is a combo preamp/dac/etc...). This is good.
What is important to find out is the sensitivity of your speakers since 8 watts may or may not be enough depending on your listening habits, listening distance/size of listening room etc...if that is the case, an option is to build 2 ACA’s and use them as monoblocks for 15 watts/8 ohms. The overall gain is still the same in this build, ie 10dB.
Building the B1 pre to go with the ACA wouldn’t be something I would recommend to everyone since it has no gain whatsoever. It might work with a system using very efficient speakers in a small room (ie > 95 dB). And of course your listening habits play a part too. If you have a reasonably efficient speaker but you turn up the volume all the way and it is still quiet sounding then you need more gain. A preamp of about 6-15 dB would work well with the ACA since the overall gain of the “system” is then about 15-26 dB which most audiophiles are used to.
Understanding the differences between gain and power output vexes many audiophiles for some reason but when you break it down into applications of Ohm’s law and the power equation, it is actually straight forward.
Best,
Anand.
Great post, thanks Anand.
In that front, I own a NuPrime DAC-10 which can configure it unbalanced RCA outputs to put either 2V (the default, called Low) or 4V (called 2X). Would it be worth it to feed the ACA with the 2X setting rather than the normal 2V? Would that have some negative effect on the sound? (My simulator starts clipping after about 2V, no idea if that is true in the 'real amp').
Thanks in advance,
Rafa.
In that front, I own a NuPrime DAC-10 which can configure it unbalanced RCA outputs to put either 2V (the default, called Low) or 4V (called 2X). Would it be worth it to feed the ACA with the 2X setting rather than the normal 2V? Would that have some negative effect on the sound? (My simulator starts clipping after about 2V, no idea if that is true in the 'real amp').
Thanks in advance,
Rafa.
Rafa,
Do you have a preamp in between or does the dac have a variable volume control?
With the 4V RMS output you’ll have some “play” since invariably there will be some recordings that are “quieter”, ie, not at 0dbFs.
I don’t see a problem with the 4V RMS output as long as you are able to adjust volume. And the output impedance is plenty low at < 100 ohms which is great as well.
Best,
Anand.
Do you have a preamp in between or does the dac have a variable volume control?
With the 4V RMS output you’ll have some “play” since invariably there will be some recordings that are “quieter”, ie, not at 0dbFs.
I don’t see a problem with the 4V RMS output as long as you are able to adjust volume. And the output impedance is plenty low at < 100 ohms which is great as well.
Best,
Anand.
Anand,
Thank you for taking the time to write such a thorough response. The speakers I will be using with the ACA have an SPL of 92.4db (Wild Burro Betsys). I feel confident now that I should be in pretty good shape with the PT 100 and the way you explained things will allow me to dig in a little deeper and "gain" a bit of understanding.
Just finished the ACA 1.6 kit using the schematic and new photos. A very quick and easy build. I'm testing with my basement workroom speakers - some old Mirage 85db floor standers. Using one of my Aikido tube pre-amps with 6CG7 tubes to drive it. The ACA is biased at 10 volts now but I just saw somewhere in a thread that with the 24 volt power supply it should be biased at 12 volts. I'll re-bias before testing with my B&W 803s. The sound is liquid and detailed. Low end is tight and detailed - a bass guitar sounds like one rather than a thump thump of some amps. Very engaging to listen to no matter what type of music I tried with it. At higher volumes it distorts but that won't be a problem on my 95 db Omega 3U speakers. Loving the sound on this amp and so easy to build compared to some of my scratch built tube amps.
Decent volume and sweet sound
Between the 1.5 build guide and the new photos of the 1.6 wiring I completed my ACA without incident. I then hooked it up to the preamp of my Marantz 2230 receiver (couldn’t fine any specs on the preamp) and a pair of Boston Acoustics HD 5 speakers, which are 8 ohms nominally and 89 dB sensitivity, per the manufacturer. In a 20x20 room, a variety of classical and vocal performances really impressed me. The amp has a very natural sound, even with the Marantz’s volume cranked up. Not party loud, but at 12 o’clock it was certainly loud enough for normal listening levels. A really great learning experience and a quality product. Nice job, diyAudio.
Between the 1.5 build guide and the new photos of the 1.6 wiring I completed my ACA without incident. I then hooked it up to the preamp of my Marantz 2230 receiver (couldn’t fine any specs on the preamp) and a pair of Boston Acoustics HD 5 speakers, which are 8 ohms nominally and 89 dB sensitivity, per the manufacturer. In a 20x20 room, a variety of classical and vocal performances really impressed me. The amp has a very natural sound, even with the Marantz’s volume cranked up. Not party loud, but at 12 o’clock it was certainly loud enough for normal listening levels. A really great learning experience and a quality product. Nice job, diyAudio.
ACA V1.6 low gain
I've built the ACA V1.6 kit and adjusted the bias to 12 VDC. I can drive a pair of NHT speakers but the gain is lower than expected. I hooked it up to my scope with a 8 ohm pure resistive load and it showed a -8.5 dB gain with a phase shift of -1 degrees at 100 Hz, -9 dB and -9 degrees at 1 KHz and -8.5 dB and -3.6 degrees at 20 kHz. There is essentially the same performance from the right channel. I have images from the scope but it looks like they have to be on a server with an HTTP address to post them here.
This is my first experience with a Class A amp but I expected more gain (certainly not negative) and essentially no phase shift.
Is this normal? I have, of course, been over the boards many times and I am convinced I have placed the components according to the directions that were given for the V1.5 board and the schematic. Is that maybe wrong for the V1.6 board and I have done something wrong?
Thanks for advice and suggestions
I've built the ACA V1.6 kit and adjusted the bias to 12 VDC. I can drive a pair of NHT speakers but the gain is lower than expected. I hooked it up to my scope with a 8 ohm pure resistive load and it showed a -8.5 dB gain with a phase shift of -1 degrees at 100 Hz, -9 dB and -9 degrees at 1 KHz and -8.5 dB and -3.6 degrees at 20 kHz. There is essentially the same performance from the right channel. I have images from the scope but it looks like they have to be on a server with an HTTP address to post them here.
This is my first experience with a Class A amp but I expected more gain (certainly not negative) and essentially no phase shift.
Is this normal? I have, of course, been over the boards many times and I am convinced I have placed the components according to the directions that were given for the V1.5 board and the schematic. Is that maybe wrong for the V1.6 board and I have done something wrong?
Thanks for advice and suggestions
I don't know exactly what the gain should be. I wish there was a manual with all the technical specs of the ACA somewhere. That'd be cool.
But in other threads I've seen people asking about which preamp you're using with it. I believe the 2V from a CD or even less from a phone is not generally able to drive the ACA close to clipping.
But in other threads I've seen people asking about which preamp you're using with it. I believe the 2V from a CD or even less from a phone is not generally able to drive the ACA close to clipping.
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We do have some specifications on the schematic. These are the posted specs:
Gain: 10 dB
Frequency response: 10 to 100 kHz
Input impedance: 10 kOhm
Sensitivity: 1.72V = 4 W output
Damping factor: 10
Output: 4.5 W @ 1% distortion
Bias current 1.45 A
Noise: 15 microV from 20 to 20 kHz
This does not agree with my build so there must be something wrong with what I did. Beats me what it is though. I have put bunches of kits together but this amp only kinda sorta works.
Gain: 10 dB
Frequency response: 10 to 100 kHz
Input impedance: 10 kOhm
Sensitivity: 1.72V = 4 W output
Damping factor: 10
Output: 4.5 W @ 1% distortion
Bias current 1.45 A
Noise: 15 microV from 20 to 20 kHz
This does not agree with my build so there must be something wrong with what I did. Beats me what it is though. I have put bunches of kits together but this amp only kinda sorta works.