I think I understand - the idea is that if the sampling rate is more than twice the frequency you can reconstruct the wave - at least from a mathematical perspective. On the practical level, a DAC can only output output fixed voltages at the chosen sample frequency. In this situation I would (I ...

I'm currently having a go at making a microcontroller-based VCO and consequently pondering issues around sample rates and wave reconstruction. As far as I understand the Nyquist sampling theorem, to reproduce a sine wave at a given frequency you need to sample the wave at least double the wave's ...

Just noticed a new 1.1.0 firmware update. Release notes here: http://downloads.music-group.com/software/ReleaseNotes/Model_D_firmware_update_v1.1.0.pdf" target="phpbbpopup I don't have Gordon Reid's review to hand but I think he mentioned a retriggering issue when playing fast lines which they ...

... a quick addendum should it be of use to anyone. I replaced the L7812 and all has been working well for a couple of weeks. Thanks again to all who offered assistance.

Understood and thanks again.

PS Yes, earthed.

Re your earlier questions the mains enters the case via a switched and fused IEC socket. I've put the transformer in a sealed box separate from the rest of the case. To clarify your first suggestion about putting 'two diodes reverse biased across the output' - are those the diodes marked D3 and D4 ...

I got and built the power supply circuit before I got the transformer - originally I was just going to use the suggested wall wart option. As I don't really know what I'm doing (you've probably gathered that by now) it looked like an easier option to just populate a ready-made circuit board than ...

The 12VAC transformer I am using is this one: https://uk.rs-online.com/web/p/chassis-mounting-transformers/0504672/ I decided to use this rather than the suggested wall wart as it has two secondary outputs allowing me to add an additional power supply in the future. If I understand the specs ...

Thanks for the suggestions. Looking around at various current limiting devices I have come across NTC thermistor inrush current limiters - from what I have read they appear to offer a higher level of resistance at power on which drops to a negligible level as the devices heat up. One of those in ...

It does seem to happen more with more modules attached - though intermittent so hard to be sure. A fair number of the modules do have capacitors on the power supply so that looks like a good suggestion. In any case I'll try replacing the regulator to see if that fixes it. If not is there a practical ...

I've just built a Eurorack Power supply ( http://www.frequencycentral.co.uk/?page_id=894 ) which is working well bar one intermittent oddity - every so often when I power it up I don't get any signal from the +12V rail. When it doesn't start up correctly I am seeing 16V DC after the rectifier and ...

I've recently got into the Eurorack thing and cost-wise a bit of DIY goes a long way. It's really easy to make the 16-16 or 16-10 power cables. You can buy the connectors on e-bay for next to nothing: search for 16 (or 10) pin IDC socket. You then get a reel of 16 way ribbon cable (which you can ...

I can't help you with the wheel, but during a recent restoration of a Sharma rotating speaker I had to make a number of drive belts that connected the motors to the rotating baffles. I bought some 4mm polyurethane belt, cut to length and 'butt-welded' the ends together (ie melted with a soldering ...

My previous cross over test was flawed in many embarrassing ways (incorrect impedance of inductor, test equipment incorrectly set up etc). I've (hopefully) sorted that all out and wound both inductors to match the Leslie specs. I have run a couple of tests - firstly the high and low pass filters in ...

As I've never attempted to make an inductor before I thought I'd try knocking up a test one to get an idea of how many turns it would take to get to the desired inductance for the passive crossover. I coiled around 4m of 1mm enamelled copper wire around a 10mm x 50mm ferrite rod and by some strange ...

In terms of motor switching I was considering using an RF remote - similar to the sort that are used for controlling lights with a remote control. I'm not sure if this is practical given the potential interference of the RF remote and also the power draw of the motors - these are mains powered and ...

It looks like I could get a mains switched relay as here http://uk.farnell.com/finder/55-33-8-230-0000/relay-3pdt-250vac-10a/dp/1169240?mckv=kmyXOTEc_dc|pcrid|78108381549|&gross_price=true&CATCI=aud-294759717834:pla-131290224789&CAAGID=15002612229&CMP=KNC-GUK-GEN-SHOPPING-FINDER&CAGPSPN=pla&gclid ...

Noted - relay it is.

I'm an idiot - I see exactly what you mean. I've had another go based on your suggestion but rather than trying to switch all the poles I wondered if it might be possible to do it with a 2PDT switch in combination with the input jack break switch on the common wire. The advantage of this would be ...

While I'm waiting for a few bits and pieces to finish of the amplifier I have started to give some thought to the passive crossover and associated switching. I would like to have the option to take a 16Ω Speaker output from a guitar amp and plug that into a passive crossover and on to the speakers, ...

Sorry - I see what you mean - there's a small bulge between the two connectors. I'll look at tracking down a replacement.

Much obliged for the info - hope the festival was good. I did notice the bulge on that green thing - however it should be a resistor rather than a capacitor, at least based on the markings(I haven't measured it). I don't know if resistors can fail like that, but I'll certainly replace the other ...

I've removed the old Op Amp and replaced it with a socket. I've installed a 741 Op Amp I had lying around and it seems to be working and has sorted the noise problem: http://godsholytrousers.co.uk/sharma/new_socket.jpg I'm honestly not sure whether it is a low current variant or not and a quick ...

I'm now pretty certain it is the Op Amp - I've disconnected capacitor C6 to remove the first part of the amplification circuit and there is virtually no noise at all. I'll try and replace it and report back.