October 28, 201510 yr I'll be running it uncased for awhile, so need something until I case it. Bottom panel sounds like an idea then though
October 28, 201510 yr From the blackhole thread (interesting amp, I musta missed that one), it appears that you went with the Ohmite heatsinks but didn't document which one...Maybe a 588-C247-025-1AE ? You had an Aavid clip part number listed; it looks like the Ohmite sinks come with clips?
October 28, 201510 yr From the blackhole thread (interesting amp, I musta missed that one), it appears that you went with the Ohmite heatsinks but didn't document which one...Maybe a 588-C247-025-1AE ? You had an Aavid clip part number listed; it looks like the Ohmite sinks come with clips? I'll post a pic when I get home to show the heatsinks I am using - they are quite big but still not up to snuff. If you are running the multiamp around the same current setting I am, I suggest you consider larger heatsink than the one you mentioned in your post Another problem with large heatsink for the GR LV is that they may interfere with the terminal block for the AC wires. When I come to case the amp, I very likely will go with Kevin's suggestion and mount the transistors on the chassis. Edited October 28, 201510 yr by mwl168
October 28, 201510 yr Here is a pic of my GoldenReference LV PS. The heatsinks in the front are what I originally put on it. As I said, even these large heatsinks get hot - I can only put my fingers on them for a few seconds. I am using a toroid with 22v secondaries regulated to +/- 18VDC. My rough estimate for the current draw by the Susy Dynalo is 190mA per rail. Edited October 28, 201510 yr by mwl168
October 29, 201510 yr Based on your description of how hot the transistors run, I wonder how toasty the chassis will get if you use it as a heatsink.
October 29, 201510 yr I wired up a 25VA toroid with 18v secondaries to the GoldenReference (set up for +/- 18VDC) tonight and as can be expected the heatsink temperature dropped significantly powering the same Susy Dynalo amp. They still run warm but no longer hot to the touch. I guess the take away lesson for me is to allow sufficient headroom choosing the transformer but not to get too overboard. Spent a couple of hours dialing in the offset of the Susy Dynalo, finally sitting down to listen to some music. Happy to report everything appears to be in good working order. I settled on 18VDC rails and 312 ohm for R38/R39 which, after warm-up, results in about 19mA per output device (380mV voltage drop on the 20 ohm emitter resistors). The MPSWx6 output devices run very warm but not hot to the touch.
January 21, 201610 yr Author As I've been promising to do for months I'm finally working on some dynamic amps. Here is something new, a Susy Dynalo with switchers... Running at +/-18V there.
January 24, 201610 yr Seeing your picture Spritzer reminded me: I just bought a 100 ohm 0.005% .2ppm/C tempco resistor to see what my Keithley DMM reads. Has anyone tried to calibrate one of these, or verify its spec?
January 24, 201610 yr Does your Keithley work on 4 wire mode? Recommended for all resistances up to 10kilOhms. That's the most accurate method of measuring resistance as it compensates for the lead and contact resistances. You also should clean the multimeter lead sockets and lead connections with isopropyl alcohol and then use Deoxit on the connections. If the meter has a null function on the resistance ranges, you short the leads out and null the reading. That takes care of the lead resistance. Then you measure the resistor. Make sure the meter is on the right resistance range. I know that sounds silly, but it is an easy mistake to make, especially if your meter auto-ranges. Set the range manually. For further reading:- http://www.tek.com/sites/tek.com/files/media/media/resources/2w_4w_ohms.pdf http://www.edn.com/design/test-and-measurement/4411117/2/Two-wire-vs--four-wire-resistance-measurements http://www.pages.drexel.edu/~hj56/manual%20files/CircuitsBasic.pdf
January 24, 201610 yr On 10/28/2015 at 6:28 PM, mwl168 said: Here is a pic of my GoldenReference LV PS. The heatsinks in the front are what I originally put on it. As I said, even these large heatsinks get hot - I can only put my fingers on them for a few seconds. I am using a toroid with 22v secondaries regulated to +/- 18VDC. My rough estimate for the current draw by the Susy Dynalo is 190mA per rail. Which heatsinks are those that you are using? I had been toying with using something like these: http://www.mouser.com/ProductDetail/Ohmite/R2A-CT4-38E/?qs=%2fha2pyFadugu%2fkSjFHjoOqIUacMQSR81IknUuMHd2REdwNmhs01RGA%3d%3d Edited January 24, 201610 yr by Pars
January 25, 201610 yr 8 hours ago, spritzer said: Nope, my own version of the BH circuit. Looks quite a bit smaller than the original BH IIRC. A mini-BH?
January 25, 201610 yr 8 hours ago, Pars said: Which heatsinks are those that you are using? I had been toying with using something like these: http://www.mouser.com/ProductDetail/Ohmite/R2A-CT4-38E/?qs=%2fha2pyFadugu%2fkSjFHjoOqIUacMQSR81IknUuMHd2REdwNmhs01RGA%3d%3d Sorry Pars, I don't have the part number handy. I just grabbed them from my parts bin. I'll need to look up my past Mouser orders and see if I can find it. There is also the possibility they came wih kits I bought in the past. I do remember the heatsinks were for TO220 package but happen to work in this case. ( I was not able to save edit to my last response so have to submit a separate response.)
January 25, 201610 yr I am more interested in the R-core transformer. Where did you get that? Is that good?
January 25, 201610 yr 17 hours ago, Pars said: Which heatsinks are those that you are using? That heatsink looks a lot like the Aavid 531302B02500G (Mouser part 532-531302B25).
January 25, 201610 yr Author 8 hours ago, joehpj said: I am more interested in the R-core transformer. Where did you get that? Is that good? It's from China and some are ok, others cause a lot of issues.
January 26, 201610 yr Could you post the picture of the ok ones? I am recently interested and thinking to try one. Thanks!
January 26, 201610 yr 13 hours ago, gepardcv said: That heatsink looks a lot like the Aavid 531302B02500G (Mouser part 532-531302B25). Yes, that's it.
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