MLA
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Posts posted by MLA
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Not my field of expertise, but I would i imagine the start sequence is designed to start from full power, so if it was me I'd rather just flick the switch and see what happens as I would be worried that gradually ramping up voltage might leave parameters out of spec at the wrong time... But that's mostly a guess :).
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That's the LT1085 regulator, right? Formula for setting voltage is on page 11 or 12 in the data sheet if I remember correctly.
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Another option is https://www.mueller-rondo.com/eng/ in Germany.
They build exactly to spec, sometimes cheaper than Toroidy, and turnaround has been about a month on previous orders.
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8 hours ago, bdinnev said:
I am reading -500mv on one board with the 10k pot trimmed to the max (or min depending on how you look at it) , the other board is reading around -2.5v! Any ideas where to look?
For what it's worth, my CFA3 bords fell 2,5V short in terms of offset when I built them. In my case, swapping all the red LEDs to a version with much less forward current than the ones I installed first (I'm now using LTL-4221, which has 2mA I believe) put all numbers back in the right places.
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For me they ship to Sweden without problem. Don't know what you need to do to make international delivery happen though...
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Interesting. I believe I followed the board and came up with about 60mV offset w/o servo.
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Toroidy will do whatever you need in my experience (including dual primary); anything T2 will be custom spec anyway.
Mueller-Rondo lets you specify the exact diameter when you place an order, so that's quite helpful.
The larger Mueller-Rondo (think 300VA) have a bit more mechnical hum than the corresponding Toroidy's (have built T2 psus with trafos from both). Not a dealbreaker if you're not sitting absolutely next to the psu box. Also, if you go with 3 trafos (I think that's what's in Kevin's original chassis?) I think if you spread the load none of them needs to be more than 150VA each, which should sort that problem.
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Good riddance
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10m90s in stock at Mouser; currently 2237 of them. Go get 'em while they last.
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On 7/6/2015 at 12:08 PM, kevin gilmore said:
for signal input, unbalanced you put hot to amplifier input +
you put ground to signal ground and input -
for output you wire hot to amplifier out +
and you wire ground to signal ground
anything else, and bad things happen
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They are probably genuine if it was long ago, but may not necessarily have been new/unused. Anyway, replacing those and seeing if you get a clean signal could be an easy first check.
Where do you connect to ground for the SE output? Needs to be from signal ground if I remember correctly; Kevin had some very clear instructions on that early in the thread.
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Since you're using a GRLV, dirty power would be unlikely I think.
I would replace those transistors for starters. Mpsa06/56 are in stock at least at Mouser.
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True. Will keep supply voltage low and bias reasonable.
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So, if all goes well, I'm picking up a pair of Quad 2805s next weekend, which means I have to build an appropriate amp for them
The Uberamp I have boards for and that's probably what I'll build, but I'm wondering if a cfp3Large (with the Sanken output boards) would be a good fit also? Or is that a less good match?
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If I read simmconn's post right, simmconn measured G to B- (over the 20K resistor) for those 20+ volts, not Vgs directly. So your 21.8V is that measurement and thus indicates all is well
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Haven't tested these particular boards but my CFA3 runs fine and fully adjustable from no to full volume with a 10K pot, so I would say something's off...
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I've sucessfully used stn0214 as replacement for ksc5026M as per JoaMat's recommendation in several other builds. Don't know the heat dissipation requirement for the position where they are used in KGSSHV, but someone more knowledgeable than me might chime in here.
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I think you've done all you can and done it well, so next step is examining the circuitry closer and possibly start replacing parts, or plug in a new left channel (which actually might be the faster and more straightforward option, but requires some soldering skills). Or sell, of course.
If sending to an expert, it's probably enough to send the circuitboard package rather than the whole amp; looks like you can take the whole thing out using a screwdriver if you loosen the headphone jack from the chassis; no need to desolder anything (unless I missed something in the pics).
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A question on the CFA3; I just built one using 50k feedback resistors for SS and 4.2k ZF resistors, also excluding the C9/C10 caps as per mirkos final edit earlier in this thread.
Builder error: was using the wrong LEDs (too much forward current I believe). Swapped those and now it's all well balanced with 10k at R1.
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You can do both but do it in two steps; first, swap the output wires from the volume control so L+ and L- go to R+ and R- on the circuit board (and vice versa). If static moves to the other channel, the pot is the culprit.
If no change, swap the XLR input wires on the pot so the one previously going to left channel now goes to right (and vice versa). If static moves to other channel, it's the XLR input wire or input jack causing trouble. Not likely, but worth ruling out.
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Great! Having some boards made; have some current drive friendly speakers as well a 3 way active system that both will be great matches I think. Thanks!!!
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On 1/11/2023 at 3:20 PM, kevin gilmore said:
So, the split cfp3 pre-board goes in front, right?
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Where are you located?
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You have to think Joachim style, i.e., smd-small and vertical
. I believe the board is stereo and it mounts flat (vertical if seen from above) to a 2U heatsink. In the pic four posts above you can see how the previous edition boards are mounted through the grille.
and now for something completely different part 3
in Do It Yourself
Posted · Edited by MLA
Very good suggestion; pentaconn is a good idea but the shorting risk sucks.