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It's crazy, I suppose the chip design has been around so long, it's so well understood, the dies copied so many times, that even dodgy sounding brands can get it right. I still detect some noise, but only when I place my ear about 4cm from the tweeter. It's definitely fit for purpose.

So there I am with noise coming from my speakers. I did use those 1875's I had lying around. (a tube full I picked up for R20). How can you not take it? The brand, BoomTech, didn't sound promising. But at less than 50c a chip. Why not give it a go? Each channel's 2 way active crossovers with...

Ah. so now I know what that "spare part" in my bosh router is for. I was thinking of making a foot with a small radius protrusion just for that guide.

On the protector, C5 and 6 theoretically have no use. Theoretically because if the OP amp doesn't keep up they could help. But in practice they will probably not be inserted. Space on the PCB is left none the less. The Power supply boards have been re layed out to accommodate a star earth on...

Final revision, I hope on the speaker protection circuit. What has changed: Some input protection for the op amps. A processor with more analogues. Sens pins to monitor the amplifier power supply. A programming jumper. Idea: The protection system monitors the amplifier positive an negative...

So, as usual, start with innovative different, end with something a bit more conventional. 7812 regulator. Op amp integrators on the inputs. The op amps chosen is not a fet based input though, but rather the old LM358. This device has a pretty low offset and will run on the micros 3.3V...

TVS added. Also a pre voltage divider to help the 1117 cope with higher voltages. On the relay's side, the idea is to use a type of switch-mode converter. Were monitoring the supply voltage for the setting. We can use the drive transistor as the switch, the massive inductance of the relay as...

I'll add a TVS. The relays usually have a pretty wide range, and the sup_sens pin doesn't worry me at all. The micros have diode protection going high and low, and a 100k Input resistor is used to limit the input current in the eventuality of excessive voltages entering. The one part will...

Orcish75 Thanks I'll try it on a VM. For the protection I put a micro based system together. That will allow for a programmable initial switch on delay and a quick switch off if the supply is failing. A combined digital and analogue offset detection circuit allows for quick averaging of...

It does look like an amazingly comprehensive package.

Never heard of it. Thanks. Had a look, but looks like it's one that doesn't want to run with my penguin, and you know I won't have M$ in my house. Perhaps I'm missing a trick.

While confirming the compensation graphs, I found the slope was not sufficient The sealed enclosure has a 12dB roll off, so i decided to try match it with a 12dB filter. The 5K6 resistors in series with the 330nF capacitors puts a lower limit to the falloff after the LF compensation boost...

Based on the success of the bass compensation circuit, and the 2/3 way modification,  I've decided to put it all on a PCB. The enclosure compensation RC components were left as through hole as although there are pots, some enclosure may not be accommodated by a one size fits all approach...

Well I finally got some nice Seas Drivers for a workshop active crossover build. The Drivers were originally from a pair of Musical fidelity MF40s. Thank you Facebook marketplace. If anyone is interested in a single MF40 case, let me know The midbass drivers are Seas P17RC4Y H 509...

I bought a set of transistors for a RS TA 90 from RSE back in the day. The ladies identified the purpose and went to ger 'special' transistors. Not sure if is was for matching the output stage or whether specific gains were required for correct opperation. Just something to look out for.

Silver corrodes, gold would be a better bet.

Boards are io tests look good, slightly off the scale on the PCB due to the calc error, but workable. It looks like one of you guys bought all the local 12nF, 5mm pitch, poly caps.  ;D . Ive had to order batch in from the US via Digikey. Should be in and then ready to ship in 7 to 10 days.

Quite right. I looked as the phases at cross point and they're both 60 degrees, so that would be the crossover. I had it at the -3db its at closer to the -2dB point. A few hertz off, probably less than capacitor tolerance. The initial design used the standard formula for calculating the filter's...

The new PCB.

Update. In verifying the design, an issue crept up. The traditional reference "crossover", is a problem with a differential crossover. Traditionally, the crossover frequency is just that, the point where the 2 levels cross over on a graph. With a differential crossover that is no the case. The...