I always wanted to build a stereo chimp amp combined with one of the those ubiquitous Toslink/SPdif DACs in the same smallish box. Hopefully as nice looking as yours turned out, maybe with a volume control and input selector.
You'd leave the crossovers in place but separate the treble (high pass) and bass sections ( low pass) and wire the treble part of them to a new set of terminals. This wouldn't be hard at all, but I think you are on the right track to go for the B-1. The ACA isn't really that important at this time, better for the future. I'd get your new DAC going as the next step. Since your amp works fine I'd declare it Done, and move on. .
Last edited:
Will get the new DAC going Friday, same with the B1 Buffer (getting the parts tomorrow).. exciting stuff! I also bought the amp camp boards just now lol. And looking into making some LM-1 speakers as well -- but the speakers and ACA will come later.. but soon 🙂
Gonna go with a dual secondary antek power supply and feed both amp camp boards in a linear fashion in the same case, hope this okay (or will there be a lot of negative impact on sound since it isn't dual mono?). Any recommendations for a dc supply board to feed both of the amp camp boards?
I want to use my other spare aluminum bar faceplate (identical dimensions as the LM3886 amp I just built) for the ACA amp. I'll build the frame out of MDF and line with aluminum tape if I have to hah.. would like them to match on the front. Or maybe I'll buy the frame from par-metal instead of MDF.
Last edited:
The single PSU is fine. Not sure what you mean by linear, but feeding them in parallel is just fine.
HOWEVER, I would recommend that instead of the standard 19v, running them with 24-25v . which would be about an 18v transformer. Many of those have dual secondary outputs so each amp would get its own secondaries off the transformer which is kind of half way between separate PSUs and a single PSU.....nice...
The ACA is single ended so doesn't use a +/- PSU, just + and ground, so that's why you can run each of the ACA's off of a secondary of the transformer...
I'm sure people here will explain any confusion.
HOWEVER, I would recommend that instead of the standard 19v, running them with 24-25v . which would be about an 18v transformer. Many of those have dual secondary outputs so each amp would get its own secondaries off the transformer which is kind of half way between separate PSUs and a single PSU.....nice...
The ACA is single ended so doesn't use a +/- PSU, just + and ground, so that's why you can run each of the ACA's off of a secondary of the transformer...
I'm sure people here will explain any confusion.
Sorry what I meant with "in a linear fashion" was it was a linear power supply not switching (e.g. laptop power bricks).
Is it possible to run those amp boards at 35V (i.e. using caps that are higher rated than the 35v that comes with the kit/schematic)? I have a 25V toroidal and unregulated dc supply board in my existing amp case already. I could temporarily bypass the LM3886 amp boards fairly easily to try out the amp camp boards 🙂 I could just use the positive 35V rail of the snubberized chipamp unregulated dc supply board I already have in the amp.
I could easily build my own dc supply boards for the 18v transformer, using perf board, but I'd probably not make the best design. If anyone has a good schematic for this situation I'd appreciate it. I'd like to make two separate dc supply boards, one for each secondary / ACA amp board.
Transformer output voltage = Vinput/Vrated * Voutput * (1+transformer regulation)
eg.
115:25Vac 8% regulation on a 126Vac supply gives an output of:
126/115 * 25 * (1+0.08) = 29.08Vac
The peak voltage could be 41.1Vpk
Subtract two diode drops (Vf) for the bridge rectifier and you can have 40Vdc across the smoothing capacitor, when the load current is very low, or disconnected.
It's even worse for a dual polarity supply from a Centre Tapped transformer.
eg.
115:25Vac 8% regulation on a 126Vac supply gives an output of:
126/115 * 25 * (1+0.08) = 29.08Vac
The peak voltage could be 41.1Vpk
Subtract two diode drops (Vf) for the bridge rectifier and you can have 40Vdc across the smoothing capacitor, when the load current is very low, or disconnected.
It's even worse for a dual polarity supply from a Centre Tapped transformer.
You need to model your transformer and supply to predict what to expect.
Or just buy it and measure. Then buy again when it turns out to be higher than you were led to believe.
Or just buy it and measure. Then buy again when it turns out to be higher than you were led to believe.
So like Variac says, get the 18V transformer (I'll figure out the VA later).
Ideally I'd like to buy a couple dc supply boards that could go between this 18v transformer and the two amp camp boards I got. Regulated or not (whatever is appropriate).
Well I just multiply the output voltage of the transformer by 1.4 (minus diode loss) to get the expected dc output. That's how I understood it anyways. Earlier, I was just asking if the ACA circuit could handle the extra voltage (i.e. 35v). I guess it can't. (Reason I asked is because he already said I could up it from 19v to 24v.. wanted to know if I could push it further somehow).
The lower the VA the higher the transformer regulation.
In general EI have higher regulation than toroid.
115:18+18Vac 200VA 7% regulation on 126Vac will give 29.8+29.8Vpk
and subtracting two Vf gives ±29.2Vdc when current is very low.
In general EI have higher regulation than toroid.
115:18+18Vac 200VA 7% regulation on 126Vac will give 29.8+29.8Vpk
and subtracting two Vf gives ±29.2Vdc when current is very low.
Have you asked your supplier what range of voltage they are contracted to supply?
Here in the UK where we have a "harmonised" supply at a nominal 230Vac, they can supply anywhere from 216Vac to 253Vac.
The USA will be similar range but at half those voltage values.
Here in the UK where we have a "harmonised" supply at a nominal 230Vac, they can supply anywhere from 216Vac to 253Vac.
The USA will be similar range but at half those voltage values.
If I got the 15V transformer (200VA) that'd be 15V * 1.4 = 21V and a little more than that with your calculations considering peaks. So this might be the best way to go? It's better than the 19V at least.
Well the kit normally comes with a pair of 19V DC regulated laptop switching mode power supply bricks (for a 2 x mono block scenario). Variac was just suggesting running at 24-25V instead of 19V if I was going to build my own linear power supply.. I guess it improves the sound?
Generally the members who know the most, including Papa Pass recommend 24v. for the ACAs. You get more power and they should sound a bit better. We supply 19v because those are the most popular laptop power supplies, so are easily available and/or cost about a third of what 24v supplies cost.
Yes, Andrew is warning about higher than average voltage. He also wants to teach you stuff, but knows a lot so should be listened to. I haven't built them with a linear supply. Perhaps others will have input. .. I believe that JFETS are about at their limit at 25v so that shouldn't be exceeded.
He should keep in mind that most Pass amps use an unregulated pi power supply with resistors in the middle of the Pi so that should be taken into account.
At 19v the minimum required is 2A per channel but more is better..
Yes, Andrew is warning about higher than average voltage. He also wants to teach you stuff, but knows a lot so should be listened to. I haven't built them with a linear supply. Perhaps others will have input. .. I believe that JFETS are about at their limit at 25v so that shouldn't be exceeded.
He should keep in mind that most Pass amps use an unregulated pi power supply with resistors in the middle of the Pi so that should be taken into account.
At 19v the minimum required is 2A per channel but more is better..
Last edited:
- Status
- Not open for further replies.