Thanks for sharing.
To be explicit, please advise which trace (top/bottom) is associated with the comparative resistive loads.
I've seen a few posts inquireing about how the ACA sounds. I've been listening for about two weeks since I finished building it, so I thought I'd share my observations.
The ACA was swapped into a setup replacing a N.E.W. A-20 amplifier (Nirvana Eletronic Works). This amp was apparently copied from the Aleph amplifier design. The rest of the system (very old) consists of a carver CT-seven Preamp/reciever, and Shahinian Obelisk speakers (89db sensitivity, 6 ohm impedance). The source is a very cheap CD player. I've been swapping the amps back and forth so I could compare.
The ACA sounds good. My first impression was that it was quite similar except it could be driven to distortion much more easily. As expected, it's not better than the A-20, though it has it's own strengths. The ACA has a slightly punchier sound for drums and bass, a bit richer bass and a touch more presence on very high frequencies, especially cymbals, snare drum and vocal sybillants. It's best with music from smaller ensembles, acoustic instruments . Some loud rock, and some other very saturated music don't bring out its' best qualities, perhaps, not enough power to avoid distortion, especially in the midrange. It has a very good soundstage, the speakers disappear just as they do with the A-20, though the soundstage has less depth, but greater width.
Overall it's very enjoyable to listen to, and compares favorably to a very highly regarded amplifier. It was really fun building something and having it work - well. Thanks to Nelson Pass for designing such a simple but great sounding amp, and the DIY Audio crew for making something like this easy to build with a great build guide.
Jim
The ACA was swapped into a setup replacing a N.E.W. A-20 amplifier (Nirvana Eletronic Works). This amp was apparently copied from the Aleph amplifier design. The rest of the system (very old) consists of a carver CT-seven Preamp/reciever, and Shahinian Obelisk speakers (89db sensitivity, 6 ohm impedance). The source is a very cheap CD player. I've been swapping the amps back and forth so I could compare.
The ACA sounds good. My first impression was that it was quite similar except it could be driven to distortion much more easily. As expected, it's not better than the A-20, though it has it's own strengths. The ACA has a slightly punchier sound for drums and bass, a bit richer bass and a touch more presence on very high frequencies, especially cymbals, snare drum and vocal sybillants. It's best with music from smaller ensembles, acoustic instruments . Some loud rock, and some other very saturated music don't bring out its' best qualities, perhaps, not enough power to avoid distortion, especially in the midrange. It has a very good soundstage, the speakers disappear just as they do with the A-20, though the soundstage has less depth, but greater width.
Overall it's very enjoyable to listen to, and compares favorably to a very highly regarded amplifier. It was really fun building something and having it work - well. Thanks to Nelson Pass for designing such a simple but great sounding amp, and the DIY Audio crew for making something like this easy to build with a great build guide.
Jim
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Thanks for sharing that Hook, just wondering, what gain if any the preamp has?
I ask this as I've gleaned from here that a 6db gain improves output sufficiently to make it better with slightly less sensitive speakers.
Unless I've misunderstood the posts here, that is!
Semmyroundel,
I looked at the manual for the CT-7 on the internet, among other information, it provides the following:
Tone boost/cut: 8dB treble/bass; 6dB midrange
Signal to noise ratio: 98dB
Maximum output level 8v
Not sure if they are referring to gain here.
Hope that answers your question.
I looked at the manual for the CT-7 on the internet, among other information, it provides the following:
Tone boost/cut: 8dB treble/bass; 6dB midrange
Signal to noise ratio: 98dB
Maximum output level 8v
Not sure if they are referring to gain here.
Hope that answers your question.
Yeah... it should all be taken with regard to what other amplifiers provide.
ACA is a single-input, no volume control, no protection(s), no thumps' mutes, a very short signal path amplifier with only 10dB of gain... so, as long as we know what we are talking about here...
I compared it sound-wise-only, to a "proper" amplifier with:
- relay input selection, right next to the RCA inputs
- delayed turn-on/volume control going to minimum setting automatically
- TKD motorized volume control
- short circuit protection (two separate relays for each channel, i.e. two sets of contacts working in parallel, per each stereo channel)
- full IR control (input selection, mute, motorized volume control)
- just enough gain (around 20dB) to drive the speakers to good levels with all sources
- no global feedback
.... the ACA sounds "better", but only because of all of its other shortcomings, that the other amp has!
ACA is indeed just an introduction to a two-gain-stages, pure class A, short signal path amplification, which does indeed sound really great!!!
But.... what about the other items from my list, that are required to make a "complete" amplification unit???
ACA is a single-input, no volume control, no protection(s), no thumps' mutes, a very short signal path amplifier with only 10dB of gain... so, as long as we know what we are talking about here...
I compared it sound-wise-only, to a "proper" amplifier with:
- relay input selection, right next to the RCA inputs
- delayed turn-on/volume control going to minimum setting automatically
- TKD motorized volume control
- short circuit protection (two separate relays for each channel, i.e. two sets of contacts working in parallel, per each stereo channel)
- full IR control (input selection, mute, motorized volume control)
- just enough gain (around 20dB) to drive the speakers to good levels with all sources
- no global feedback
.... the ACA sounds "better", but only because of all of its other shortcomings, that the other amp has!
ACA is indeed just an introduction to a two-gain-stages, pure class A, short signal path amplification, which does indeed sound really great!!!
But.... what about the other items from my list, that are required to make a "complete" amplification unit???
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nope, sorry: you compared a power amplifier to an integrated amplifier (and one with many extras) which is never fair (... to the latter
)
Well, if you:
- design and AMP with those characteristics that is just as good sounding as the ACA
- make the circuit 'open source' and share it with everyone
- create a stunning ´how to build it´, and
- provide ready-made kits with all the required components sourcing out from different places and making a very comfortable one-stop purchase possible...
I'm sure everyone will probably buy yours instead of this one... or perhaps most people will be like me and still believe that Papa Nelson's designs is where we want to put our faith in and our time into.
You are free to try. What I think is rude is to demand all that and just expect people here to 'give you the answer'.
By the way, a 'proper AMP' usually has no volume controls, input selectors or remote controls. Those tasks are usually given to the pre-amplifier, of which one is also rumored to be coming the way of DIY by Mr. Nelson. But we can't 'demand' that he produces it within our (your) time frame.
If you are pressed for all you 'demand' to get a 'complete amplification unit', I'm sure you will be really happy with a Pass Labs XA25 + Pass Labs XP-10, or one of their integrated Amplifiers (which is what you are describing, and not a 'proper amp') like the Pass Labs INT-60.
Those will surely fit your needs nicely!
Rafa.
Edit: plsvn beat me to explaining the difference between a power and an integrated amplifier while I was researching the options to suggest you go look into.
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Now, THAT would be something truly special, wouldn't it... the ACA / Alep J are already there for the masses, to serve as the reference point - sound-wise... I mean, not everyone can afford SIT-3, right?
But.... even if we consider the above, even the mighty SIT-3 that I would love to hear (supposedly a single-ended triode sound, sans the output transformers), we are still short on.... those goodies that I listed (itemized) above...
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Sure, but at what cost???? LOL
We are Greedy Boyz bunch, remember?
The amp/pre-amp combo you mentioned is the absolute top end for people who have money to spend and status to achieve...
I am taking a tiniest nuances' preservation, that is really, only possible by few gain stages, of which the last one must be a single valve/transistor, working in pure (deep) class A; but - it must allow me to select inputs and change volume...
The best I heard was a 2A3 single ended pure class A amp of whopping 1.8W of power... but the cost was 50K - it was homemade, the output transformers were made with silver wires.
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My two cents worth to this discussion are these:
1. Extreme simplicity and signal path purity are desirable features which can be had with the ACA.
2. Features like volume control and proper signal strength have to come from somewhere else, ACA is limited in this regard. Please keep in mind that volume is an important feature in obtaining enjoyment from music and that different types of music require different volume levels.
3. For most human beings that like and enjoy music, the price you pay to obtain it is a major issue. If you are in the net worth percentile that can have an unlimited budget for pure music, simplicity and purity of signal plus having all the other desirable features in a system, then good for you, you can do it. Those that do not have unlimited funds have to compromise to some degree or the other.
4. It is my belief, which you may disagree with, that by planning carefully for what you want or need to get out of a system, you can get your personal system to perform in a way that satisfies your needs and desires.
For those who have no idea how to get there, one answer is substitution. For example the issue of internal wiring. It is true that silver, and gold wires will improve sound. If you cannot, as most people can't, buy the real thing you can find more affordable silver plated copper wiring. The goal is is to improve the sound, not to spend money and impress people, no one knows what kind of wiring you have unless you show them. Silver plated wiring will impress no one but it will or may sound better to your ears at a reasonable price.
Another way to get there is by focusing purchases, whenever possible, around professional music sites that cater to the music and entertainment business. These people NEED wires that do their job and provide good sound. Buy leftovers whenever possible, you do not need 300 ft of wire for your rig. For example I just bought wire and connectors to build my XLR connects. The actual connectors are Neutrix XX series, black, with gold plated terminals and I got them for about around $3.30 each. The wire is Canare quad core L4E6S which is what the pros use in recording studios, their price is $0.50 per foot. You can also buy Mogami W2820 at $0.82 per foot. The prices given are the regular prices at REDCO, the leftovers are less. Compare your cost with the price you pay for the factory made XLR cables.
It is all like this, if you want to keep the price low and the quality high you just must have to do your homework and buy what you want, where the professionals buy them and pay what the professionals pay. Remember, recording studios have no need to impress anyone with anything but the quality of the finished product.
There are ways to get good quality sound and save money at the same time.
1. Extreme simplicity and signal path purity are desirable features which can be had with the ACA.
2. Features like volume control and proper signal strength have to come from somewhere else, ACA is limited in this regard. Please keep in mind that volume is an important feature in obtaining enjoyment from music and that different types of music require different volume levels.
3. For most human beings that like and enjoy music, the price you pay to obtain it is a major issue. If you are in the net worth percentile that can have an unlimited budget for pure music, simplicity and purity of signal plus having all the other desirable features in a system, then good for you, you can do it. Those that do not have unlimited funds have to compromise to some degree or the other.
4. It is my belief, which you may disagree with, that by planning carefully for what you want or need to get out of a system, you can get your personal system to perform in a way that satisfies your needs and desires.
For those who have no idea how to get there, one answer is substitution. For example the issue of internal wiring. It is true that silver, and gold wires will improve sound. If you cannot, as most people can't, buy the real thing you can find more affordable silver plated copper wiring. The goal is is to improve the sound, not to spend money and impress people, no one knows what kind of wiring you have unless you show them. Silver plated wiring will impress no one but it will or may sound better to your ears at a reasonable price.
Another way to get there is by focusing purchases, whenever possible, around professional music sites that cater to the music and entertainment business. These people NEED wires that do their job and provide good sound. Buy leftovers whenever possible, you do not need 300 ft of wire for your rig. For example I just bought wire and connectors to build my XLR connects. The actual connectors are Neutrix XX series, black, with gold plated terminals and I got them for about around $3.30 each. The wire is Canare quad core L4E6S which is what the pros use in recording studios, their price is $0.50 per foot. You can also buy Mogami W2820 at $0.82 per foot. The prices given are the regular prices at REDCO, the leftovers are less. Compare your cost with the price you pay for the factory made XLR cables.
It is all like this, if you want to keep the price low and the quality high you just must have to do your homework and buy what you want, where the professionals buy them and pay what the professionals pay. Remember, recording studios have no need to impress anyone with anything but the quality of the finished product.
There are ways to get good quality sound and save money at the same time.
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I wonder how it would work if ACA was designed with built-in gain control by selecting the amount of NFB desired to give the wanted listening level so you just connected line signal to ACA? …..the first ACA had a lot more gain because of less NFB......but still sounded good. So it could be possible to a certain "degree"?
Then there were no added components to implement a vol. control?
It could probably give some "pops" when switching NFB resistors using a selector…..it had to be a version with some "overlap" between two positions.
I guess there are reasons why such amp designs are not common...…..
Then there were no added components to implement a vol. control?
It could probably give some "pops" when switching NFB resistors using a selector…..it had to be a version with some "overlap" between two positions.
I guess there are reasons why such amp designs are not common...…..
Still waiting for my ACA kit. It's really frustrating if it takes the package 5 days to travel from the US to Austria and then spends more than 3 weeks in customs warehouse waiting to be released
in the meantime i'm thinking whether or not it would make sense to sand the enclosure to make sure there's continuity between all parts to make for better shielding. any thoughts on that?
in the meantime i'm thinking whether or not it would make sense to sand the enclosure to make sure there's continuity between all parts to make for better shielding. any thoughts on that?
MEPER - If you vary the gain resistor you will also vary the operating points of the devices downstream, and you'd have to re-set the DC operating point (the 'bias') at any given gain/volume.
It's one of those ideas where it seems like it would work, believe me, I've asked the same question!!
The right answer is a preamp. Wayne Colburn presented a perfect solution at BAF on Sunday.
It's one of those ideas where it seems like it would work, believe me, I've asked the same question!!
The right answer is a preamp. Wayne Colburn presented a perfect solution at BAF on Sunday.
Hello,
RE: " i'm thinking whether or not it would make sense to sand the enclosure to make sure there's continuity between all parts to make for better shielding. any thoughts on that?"
As nobody has reported so far any problems at all with RF or noise interference and unless you live next to a high power transmitter, pretty unlikely to need to go that far. Cost nothing but not likely needed.
Regards,
Greg
RE: " i'm thinking whether or not it would make sense to sand the enclosure to make sure there's continuity between all parts to make for better shielding. any thoughts on that?"
As nobody has reported so far any problems at all with RF or noise interference and unless you live next to a high power transmitter, pretty unlikely to need to go that far. Cost nothing but not likely needed.
Regards,
Greg
This is just a cruel post for those of us waiting!
I did see the schematic and the lovely boards powered by the WHAMMY board. Obviously, for someone like me, it may as well been written in Sanskrit... I have no idea what it does, how it works or how good it sounds... but by now I know that putting the hope on this giants is not a gamble at all! Really looking forward to it.
Rafa.
MEPER - If you vary the gain resistor you will also vary the operating points of the devices downstream, and you'd have to re-set the DC operating point (the 'bias') at any given gain/volume.
It's one of those ideas where it seems like it would work, believe me, I've asked the same question!!
The right answer is a preamp. Wayne Colburn presented a perfect solution at BAF on Sunday.
agree for preamp , but ......... both NFB resistors in ACA are DC isolated from rest of the circuit - with output and input caps
varying them (too much) is not good idea from other reasons , not related to DC conditions of circuit
This is just a cruel post for those of us waiting!
For what it's worth, I'm waiting as well.. I haven't gotten the final schematic from Wayne and won't for a few days, and there needs to be some more revisions to the PCB, because firstly, you may notice looking at the little purple boards, they have no mounting holes in them!! The prototypes were secured to the chassis with a blob of silicone adhesive.