Checked the datasheets for the Mean Well RS150-24 and the Mean Well GST120A-24 (the GST is included in the kit). The RS150 has a higher current rating of 6.5 A, a lower max ripple, and better voltage tolerance, line regulation, and load regulation specs than the GST. It also should run cooler because the enclosure is perforated metal, not a solid wall enclosure like the GST's. That said, the RS150-24 presents multiple installation options while the GST is a simple one output package which should be easier to handle for builders with little experience. Both PSUs appear very good. If the current provided by the PSU is not a major problem with ACA 1.6, there are 48v models available for both the GST and the RS150 Mean Well PSU lines for possible upgrades. Extreme Boky please let us know if or when you decide to up power your build just to see what happens. I would be interested in knowing is this is feasible.
Well, 24V x 2 (one per per channel) still results in 24V delivered to the ACA. A 48V would require some modifications... assuming the JFEts can even take that voltage, would JFEts and MOSFETs still be in their 'good region' when the circuit is BIASSED at 24V? (If not biased at half voltage there is asymmetry on the output, I think).
That is assuming you have enough heat dissipation to actually work without starting a fire!
I believe an experiment like this would have to be done by someone that really knows about circuits and stuff. I would not recommend a newby trying to double the voltage and expect more power! Please be careful!
Rafa.
That is assuming you have enough heat dissipation to actually work without starting a fire!
I believe an experiment like this would have to be done by someone that really knows about circuits and stuff. I would not recommend a newby trying to double the voltage and expect more power! Please be careful!
Rafa.
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Hi all, I'm still confused despite Rafa's excellent answer about doubling the power.
Let's see if I've got this right, my goal is to get 15wpc with a stereo output.
On the build guide, at step 55 it mentions a Y lead and a photograph that needs to be loaded up, is this the configuration to get 15wpc with stereo RCA inputs?
All this talk about monoblock and XLR's is confusing, I just want more power to drive my average sensitivity speakers (86db) a little louder through a regular stereo input.
There is another problem, I don't use a pre amp, on other builds, i've simply added a selector switch to distinguish between inputs, and an Alps pot for volume, worked just fine for me, however they were single stereo amps, if I bridge 2 ACA's where would I install the potentiometer to control volume?
Let's see if I've got this right, my goal is to get 15wpc with a stereo output.
On the build guide, at step 55 it mentions a Y lead and a photograph that needs to be loaded up, is this the configuration to get 15wpc with stereo RCA inputs?
All this talk about monoblock and XLR's is confusing, I just want more power to drive my average sensitivity speakers (86db) a little louder through a regular stereo input.
There is another problem, I don't use a pre amp, on other builds, i've simply added a selector switch to distinguish between inputs, and an Alps pot for volume, worked just fine for me, however they were single stereo amps, if I bridge 2 ACA's where would I install the potentiometer to control volume?
Not possible from one amplifier.
You need two amps and wire them for bridged operation.
Thanks 6L6, I did understand that I'd have to wire them for bridged operation, but how to, the photos on the build guide don't appear to show the configuration that I want. There's still the issue about volume control.
On another note, one of the two sets of speakers I'd earmarked to be used with this amp is rated from 15-100 wpc.
Does this mean that if I opt just to build the regular stereo configuration at 8w that I might do damage to the speaker?
Hi semmyroundel,
If you made two amps, with the front switch and the back switch and the XLR input, and wired them according to the pictures in the 1.6 build guide, then they will be wired correctly for bridged operation through both the RCA and XLR input. If this is the case, then you use the left channel RCA input, set the back switch to the up position, and wire the speakers into the outer speaker terminals on each side (positive speaker terminal goes on the side where the right channel RCA input is located.
If you don't have both switches, follow the wiring guide at the end of the ACA 1.5 build guide starting at step 46 ( Amp Camp Amp V1.5 Build Guide - diyAudio Guides )
Not so fast. If you were to add a preamp so that the signal fed into the ACA becomes stronger, the gain of the ACA will remain the same but what is fed to the speakers may increase. Before you abandon the project or rewire the Amp plus adding another amp to your setup, I would try to add a preamp to add gain to the signal chain. I currently use a preamp and do volume control with an ALPS pot like you do (this is my current pre ACA system which I like a lot). The way I would handle this is by getting a preamp that produces gain. This configuration uses only one ACA amp and, I believe, will result in higher power supplied to the speakers.
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What configuration are you wanting? Monoblock bridged, using RCAs as input?
Not at all. Recommended power ratings on speakers are not really useful numbers. More of a marketing thing.
Not so fast. If you were to add a preamp so that the signal fed into the ACA becomes stronger, the gain of the ACA will remain the same but what is fed to the speakers may increase. Before you abandon the project or rewire the Amp plus adding another amp, I would try to add a preamp to the signal chain. I currently use a preamp and do volume control with an ALPS pot like you do (this is my current pre ACA system which I like a lot). The way I would handle this is by getting yourself a preamp that produces gain and continue controlling the volume with your ALPS pot.
semmyroundel,
Sorry if this is a longer-than-needed answer, English not being my native language, it takes a bit longer to explain things. I apologize.
The first two (XLR and RCA Mono) allow for 15Wpc into 8 ohms, but keep the 5Wpc into 4 ohms.
The third option (which is still not finished in the build guide as of this writing) gives you 15Wpc at 4 Ohms while keeping the 8W into 8 Ohms and above.
So, for you to get the 15Wpc you expect, you would need to know which speaker impedance you are working with.
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So, with all the above, I believe that first you should try one Stereo ACA with
your setup as is and see what type of volume / body you get.
If you feel the sound a bit thin and with lower volume than expected (this happened to me when the ACA was fed by a 2v line-level source), you have two routes:
- try a PRE that has gain (this is crucial!... if you opt for a unity-gain Pre, it will probably not help much).
- try the Mono RCA ACA version (back switch up and connection done with RCA into the left channel, speaker terminals connected to both black binding posts, red speaker to the right channel). It seems that this give you about 6dB of extra gain (perhaps jury is still out on this one as there are conflicting reports here from very clever and knowledgeable people) as long as your speakers are 8 ohms or better.
As I said, in my case, the pre with x2 output gain (4V max via RCA) made all the difference in the world! Does your source have balanced outputs that you would be able to take advantage of?
Best regards,
Rafa.
Sorry if this is a longer-than-needed answer, English not being my native language, it takes a bit longer to explain things. I apologize.
As 6L6 mentions it, this is not possible from a single ACA Amp, you would require two, but you may not need to! Please keep on reading.
I agree it can get a bit confusing, but it is so because you have 3 different mono options, and all of them give you slightly different results. All of them are able to output 15W, but in different scenarios.
The first two (XLR and RCA Mono) allow for 15Wpc into 8 ohms, but keep the 5Wpc into 4 ohms.
The third option (which is still not finished in the build guide as of this writing) gives you 15Wpc at 4 Ohms while keeping the 8W into 8 Ohms and above.
So, for you to get the 15Wpc you expect, you would need to know which speaker impedance you are working with.
It would ideally go into the Pre. Otherwise you would need to add one Pot per channel and track them manually or by some other very complex scenario. Not sure how much a pot would affect in the middle of the input signal, I would leave that to the experts here... that is way beyond my knowledge.
I am driving 87db 4 ohm speakers with a 19V ACA which does not output 8W but 5Wpc! I get all the volume I need. The catch is that I have a Pre that adds an extra 6db of gain to the mix. The part where you could damage your speakers with an underpowered AMP is if you are pushing the amp into clipping and distortion. As mentioned here several dozen pages ago, the nice thing about the ACA is that it 'clips' really nicely. The clipping of the signal is very smooth and I have not heard distortion that could damage my speakers.
------------------------
So, with all the above, I believe that first you should try one Stereo ACA with
your setup as is and see what type of volume / body you get.
If you feel the sound a bit thin and with lower volume than expected (this happened to me when the ACA was fed by a 2v line-level source), you have two routes:
- try a PRE that has gain (this is crucial!... if you opt for a unity-gain Pre, it will probably not help much).
- try the Mono RCA ACA version (back switch up and connection done with RCA into the left channel, speaker terminals connected to both black binding posts, red speaker to the right channel). It seems that this give you about 6dB of extra gain (perhaps jury is still out on this one as there are conflicting reports here from very clever and knowledgeable people) as long as your speakers are 8 ohms or better.
As I said, in my case, the pre with x2 output gain (4V max via RCA) made all the difference in the world! Does your source have balanced outputs that you would be able to take advantage of?
Best regards,
Rafa.
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It can be difficult to predict with a real speaker as the impedance is complex and when it clips will also depend on the frequency. It is more predictable when using a standard test load (e.g. 8 ohm resistor). But using a real speaker the amp will probably clip with less input caused by the complex impedance (e.g if the speaker drops to 2 ohm at 50 Hz....something like this can be the case even they call it a 8 ohm speaker).
To test clipping using a real speaker requires ear protection and maybe a new tweeter unit
….a dome tweeter is easy to burn if amp outputs square wave at full output swing.
To test clipping using a real speaker requires ear protection and maybe a new tweeter unit
….a dome tweeter is easy to burn if amp outputs square wave at full output swing.
It can be difficult to predict with a real speaker as the impedance is complex and when it clips will also depend on the frequency. It is more predictable when using a standard test load (e.g. 8 ohm resistor). But using a real speaker the amp will probably clip with less input caused by the complex impedance (e.g if the speaker drops to 2 ohm at 50 Hz....something like this can be the case even they call it a 8 ohm speaker).
To test clipping using a real speaker requires ear protection and maybe a new tweeter unit
The tweeter crossover capacitor would conduct during transitional changes only.... wouldn't conduct when the delta voltage change is 0...