observations
There is a sonic difference in the stereo and mono-block configuration to consider. The two side by side driven with the same source driving level matched Air Motion Transformer's of various manufactures sound completely different balanced and unbalanced. Balanced is greatly attenuated to the point of not existing harmonic energy. Unbalanced is full of really nice sounding harmonic stuff. (Alvin!)
(2) ACAs drive AMT's in the balanced mode.
(1) ACA in the unbalanced mode to drives a set of Polk in wall.
We like both of them together. Very "rich"
There is a sonic difference in the stereo and mono-block configuration to consider. The two side by side driven with the same source driving level matched Air Motion Transformer's of various manufactures sound completely different balanced and unbalanced. Balanced is greatly attenuated to the point of not existing harmonic energy. Unbalanced is full of really nice sounding harmonic stuff. (Alvin!)
(2) ACAs drive AMT's in the balanced mode.
(1) ACA in the unbalanced mode to drives a set of Polk in wall.
We like both of them together. Very "rich"
TJw59. Let me get this straight, you have two sets of stereo equipment (1. 2 ACA monoblocks in balanced input mode, driving two speakers, and 2. a single ACA in stereo mode driving two separate speakers) all driven by the same music source. You really like the music resulting from this combination.
Question do you have a single preamp capable of simultaneous single end RCA outputs and balanced outputs (what gain?) processing the music being fed to the amps simultaneously or two separate preamps doing the processing? If using two preamps are they the same kind of preamps or are they different (as the speakers which are also different)?
Final question, just wonder what would happen if you combined the balanced mono outputs with the unbalanced stereo outputs and used it to feed a single pair of speakers? Does this make them sound better or not?
As I said, this is very intriguing information.
Question do you have a single preamp capable of simultaneous single end RCA outputs and balanced outputs (what gain?) processing the music being fed to the amps simultaneously or two separate preamps doing the processing? If using two preamps are they the same kind of preamps or are they different (as the speakers which are also different)?
Final question, just wonder what would happen if you combined the balanced mono outputs with the unbalanced stereo outputs and used it to feed a single pair of speakers? Does this make them sound better or not?
As I said, this is very intriguing information.
Just remember that when talking about how the ACA sounds subjectively in all its configurations it is massively influenced by the real world speaker loading you hang on the end.
Post #5988 didn't draw any comment at the time:
Amp Camp Amp - ACA
but it shows how much the output voltage varies with a reactive load. At 1.8kHz in this example the driving voltage available to the speaker is nearly 5db less than in the lower bass. A parallel pair will improve that significantly, a bridged pair in antiphase will accentuate that effect even more.
So its no wonder there are such huge variations in what you all hear.
Post #5988 didn't draw any comment at the time:
Amp Camp Amp - ACA
but it shows how much the output voltage varies with a reactive load. At 1.8kHz in this example the driving voltage available to the speaker is nearly 5db less than in the lower bass. A parallel pair will improve that significantly, a bridged pair in antiphase will accentuate that effect even more.
So its no wonder there are such huge variations in what you all hear.
I cannot think of any way that what you suggest is actually possible unless you use a specially designed o/p transformer with dual primaries.
Answer is: Not sure. And.
Yes have two independent systems. Driven by one source.
One bi-amped with an active crossover. I use the ACA as balanced mono-blocks and drive Great Heil AMT's with that.
Use an A/B amp to drive the two 12 inch woofers.
They are all balanced i/o and the Emotiva Stealth DAC has both balanced and unbalanced outputs - and both are active.
Then use polk audio RC85i in wall speakers. They get their audio from a stereo ACA.
To set the levels I start with the system that can make the least noise. That is the in wall speakers. Use pink noise and a microphone with a real time analyzer. Get a reference level.
Using that reference sound pressure level. Use a big set of wire wound attenuators to slow the woofers down to the in wall speakers level. And get it precise with the level controls on active crossover.
And then drive each speaker and adjust each one: one at a time to match the reference level of the in wall speakers.
behringer ultra curve pro and a mic has a pretty nice real time analyzer section on it for level setting.
behringer makes a couple of pretty nice speaker management devices for crossovers with balanced i/o. I chose the super x pro.
Using the ACA amps in both modes: with speakers that compliment each other. Sounds really nice.
@tjw59. Wow! you use no preamps at all just the Emotiva Stealth DAC with its simultaneously active single ended and balanced outputs going directly to the ACAs. The rest is a matter of complimentary speakers adjusted to the level coming from your baseline reference speakers. You make extensive use of measuring and analyzing devices as well as attenuators and active cross overs with balanced I/O. This is a professional sound engineering project you have done. Congratulations, truly a fantastic job.
No reason not to call the Emotiva a preamp. Obviously the analog stages of the Emotiva Stealth DAC produce really high quality balanced output, and no doubt they provide some degree of gain as well. I am having trouble finding the Stealth DC1 DAC specs but it was sold through the Emotiva Professional product line and launched 2015. No idea about the price but below $2000 at the time of launch.
Yes, the analog stages of the Emotiva DC1 can be called a preamp stage, even though the output gain may be limited. Again I have not found the DC1 specs.
Yes, the analog stages of the Emotiva DC1 can be called a preamp stage, even though the output gain may be limited. Again I have not found the DC1 specs.
I have a DC1 that I bought used and have it as a spare dac. It is like a Swiss Army knife and is a very versatile compact product. I think it was meant to offer a lower cost version of the Benchmark dacs. I think US retail cost was 500$. I have thought of selling mine a few times but always back out when I look at how much the little dac can do. I used it in my system as a preamp with the balanced outputs feeding a pair of F5V3 monos and the rcas feeding a subwoofer crossover. A lot of dac for the $.
Searched for the specs can be found here. When I bought mine they were around 450.00. I am on the list for when they release the next version with balanced outputs.
https://www.concertoaudio.com/images/productos/6024_Emotiva_Stealth_DC-1_manual_ingles.pdf
https://www.concertoaudio.com/images/productos/6024_Emotiva_Stealth_DC-1_manual_ingles.pdf
I'm sure it's been asked a dozen times but searching thru 654 odd posts is not easy and the search function ... meh.
Why are there (6) 10k resistors in the ACA kit? Only 2 are required on the board that I can see at R7.
And while we are at it I guess: I have a fairly mediocre Mastercraft Autoranging multi-meter (052-0052-2). What kind of tolerances should I be okay with when measuring the caps and resistors, or am I pretty much just making sure it's close?
Edit: My bad for not seeing that R7 is just the spot and that there are other 10k slots. still would like to know about the tolerances though please.
Thx
Tris
Why are there (6) 10k resistors in the ACA kit? Only 2 are required on the board that I can see at R7.
And while we are at it I guess: I have a fairly mediocre Mastercraft Autoranging multi-meter (052-0052-2). What kind of tolerances should I be okay with when measuring the caps and resistors, or am I pretty much just making sure it's close?
Edit: My bad for not seeing that R7 is just the spot and that there are other 10k slots. still would like to know about the tolerances though please.
Thx
Tris
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@Trismos, if you think your multimeter is too mediocre for this job I suggest you visit Tequipment.net and check their clearance multimeters. They currently have 31 units listed in clearance. I am fairly sure you can get something that will do the job for a very reasonable price. Please compare the specs of your current multimeter with the ones they have for clearance. Make sure you download and print the schematic for the ACA 1.6. Thsese are just suggestions.
Frequency Response:
20 Hz to 20 kHz + / - 0.1 dB @ 44.1k sample rate. 20 Hz to 40 kHz + / - 0.1 dB @ 96k sample rate. 20 Hz to 70 kHz + / - 0.1 dB @ 192k sample rate.
THD+N:
0.00033% or less @ all sample rates.
IMD (SMPTE):
0.0025% typical.
S/N Ratio:
> 95 dB @ all sample rates; 16 bit word length. > 115 dB @ all sample rates; 24 bit word length.
Input Connectors:
One pair unbalanced analog audio (consumer level); gold plated solid machined RCA. One AES/EBU digital audio (XLR).
Three S/PDIF digital audio (1 x RCA, 1 x BNC, 1 x Toslink optical).
One USB digital audio input (“type B” USB connector; UAC2).
Output Connectors:
One pair unbalanced analog audio (consumer level); gold plated solid machined RCA. One pair balanced analog audio (pro level; +6 dBV); XLR.
Two headhone connectors, front panel (2 x 1/8” stereo “mini”, individually amplified).
20 Hz to 20 kHz + / - 0.1 dB @ 44.1k sample rate. 20 Hz to 40 kHz + / - 0.1 dB @ 96k sample rate. 20 Hz to 70 kHz + / - 0.1 dB @ 192k sample rate.
THD+N:
0.00033% or less @ all sample rates.
IMD (SMPTE):
0.0025% typical.
S/N Ratio:
> 95 dB @ all sample rates; 16 bit word length. > 115 dB @ all sample rates; 24 bit word length.
Input Connectors:
One pair unbalanced analog audio (consumer level); gold plated solid machined RCA. One AES/EBU digital audio (XLR).
Three S/PDIF digital audio (1 x RCA, 1 x BNC, 1 x Toslink optical).
One USB digital audio input (“type B” USB connector; UAC2).
Output Connectors:
One pair unbalanced analog audio (consumer level); gold plated solid machined RCA. One pair balanced analog audio (pro level; +6 dBV); XLR.
Two headhone connectors, front panel (2 x 1/8” stereo “mini”, individually amplified).
The output of the DC1 are what you would expect from a DAC with a decent analog stage but nothing too fancy. As it has been shown they are adequate for the ACA. The real question that remains (and please remember that very few people can do the type of sound analysis and adjustment that tjw59 did) is could the music coming from the ACA be improved by a greater gain from the source. This means a preamp. I would say this is possible.
The only reason to measure the resistors is to avoid mixing them up. The components them selves are OK. Just difficult to read the values. Therefor you have to measure the values. Any multimeter will do.
Hi Tris
That multimeter will work just fine for what you need here. It is unltimately not as accurate or precise as a higher end meter, but for the purpose of building and testing an ACA it will get the job done. I don’t know why they would include extra parts. As long as you have the correct schematic and the parts needed to build it, you are good. As far as tolerances go the ACA BOM or parts listing should indicate the tolerance of the parts. Your meter will probably have no problems with 1% parts. In many cases the resistors could even be specified as 5% tolerance, so that is what you would be looking for. Same thing for capacitors, they are usually labelled with a tolerance which can be as high as 20% for an electrolytic type.
I am not familiar with the ACAparts kit, having built mine from parts I had in stock.
Check out the build guide for the ACA. It is written by a member here who takes great care to produce a guide which is thorough and easy to follow.
I have driven the amp with everything from a cell phone to said DAC with pretty favorable results. All of the sound I need happens way below a watt out of the ACA's.
You sound like your frustration is you cannot get good level from your speakers.
One thing to remember if your speakers are mega high efficiency is the tweeter and midrange probably are. The woofer probably is not by comparison.
So a 100dB tweeter sitting atop a 92 db efficient woofer creates an issue of we have to match these two speakers in level. Can't turn the woofer up. So let's pad the tweeter.
Now you have an 8 dB pad that your amp has to overcome. Along with the reflections of a passive LC network.
Some manufacturers put on a minimum amplifier rating to drive their speakers. That is why. Because you have to overcome the losses of the crossover network. Could be a simple matter of the ACA, even running as hard as it possibly could does not have enough steam to overcome the losses. And a watt in either direction won't make a bit of difference.
tjw59 I am not frustrated with my ACA, I am still planning the build which now includes a balanced DAC and a balanced preamp. I am just saying what I have gathered from the information available in the various blogs about ACA, my chosen preamp, and my chosen DAC. You have done an excellent job that needs to be acknowledged by the community as I have done. Other than that I think everyone is free to experiment with their builds, if there is success we should share it. If I wind up burning the ACA by giving it a stronger signal, or if it clips like crazy, I am the only loser. I will wind up buying a new set of boards if that is the case.
Again, I am not trying to minimize your achievement in any way shape or manner and believe me, I am having a ton of fun just planning the stuff, as I will when I build it.
Again, I am not trying to minimize your achievement in any way shape or manner and believe me, I am having a ton of fun just planning the stuff, as I will when I build it.
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