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Chip Amps Amplifiers based on integrated circuits

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Old 26th October 2012, 12:57 PM   #571
kroyin is offline kroyin  India
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I had the same issue with myref d...lm318 was getting 24V in between pin 4&7.
Nothing across relay diode..relay led switches on & off & then stays off.
Linuxguru told me that this was a problem with the compensation circuit.
If you have 1 working channel debugging would be easier (as for me I had missed a jumper :-D)
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Old 26th October 2012, 01:06 PM   #572
bcmbob is offline bcmbob  United States
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"Jumper" - are you referring to a solder bridge where it shouldn't be, causing a short or current interruption?
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Old 26th October 2012, 01:12 PM   #573
kroyin is offline kroyin  India
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Not actually ...rev c & rev d differs with cap value changes & a resistor omission (that has to be jumpered).

In any case if one has a working channel one can always compare values (voltage) across important points like pin 1&4 (3886) c4 r2 etc etc (I am receding to the rev c circuit fremen might be different)
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Old 26th October 2012, 01:49 PM   #574
bcmbob is offline bcmbob  United States
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O.K. Thanks.
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Old 26th October 2012, 08:05 PM   #575
Marra is offline Marra  United Kingdom
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I have one working board;I say working it has'nt actually played music but all voltages appear correct and the relay clicks on ;led lights up and there is low offset.I'll do a voltage check between pcb's this weekend.Thanks
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Old 27th October 2012, 05:15 PM   #576
bcmbob is offline bcmbob  United States
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Just a quick note on the Audyn Plus caps. They are a great bargain in my opinion. At installation they sounded fairly bright and forward in one rotation and comparatively subdued but wider stage in the other. I chose the second position for the Isotek process thinking (as Dario has suggested) that what initially grabs you might eventually produce more ear/listening fatigue.

The result is a very clean and transparent sound with excellent front to back imaging. One of the pieces I used has a lot of that bronze shimmer in the cymbals Tom talked about earlier. After the burn-in it is still there, still warm but better balanced. Vocals are distinct and realistic without any fuzz on the sssses. So far I would call them just a bit light in the cello/trombone registers but that is truly personal and not necessarily a fault.

Nothing is lacking in stage width and ambiance projection into the room. Right now I using the MTMs at only five feet across a twelve foot wall. At a sweet spot of ~ fourteen feet instruments and percussion appear clear and well beyond the spread.

Have a lot more listening to do and I haven't yet matched them with the Sunflower speakers. I will be able to describe the low end better when I do that, but with these speakers, the balance and response is dead on. I did run them against the Sonicap 1.5s and these caps retained the majority of the musicality but with a clear improvement in refinement. Another way to say that is it appears both Audyn caps I've tried produce a great blend between the warmth of the Sonicaps and the resolution of the Mundorf ZN caps. I'll report on them again later, but I would recommend the Plus series without hesitation. They belong in the excellent category at a fantastic price.

P.S. I got a big lesson on the power of the FE amps. My SPL comfort zone with the Sunflowers requires a eighty to ninety percent spot on the JRiver volume bar. That level appears around thirty percent with the MTMs and it feels like the FEs are two and a half times more powerful. There is all the headroom I could want and a SPL that could drive me out of the room. I hadn't hooked up these speakers since the V1.2 - V1.3 days so this was quite a pleasant surprise.
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Old 27th October 2012, 08:30 PM   #577
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Thanks for the kind words, Bob and Andrew.

One more note on striving for clarity: I have been running my amps "topless" because I've been fiddling with them and the active xovers that are both in the same chassis. I think I'm done with that, so I put the tops on the chassis and it resulted in what I perceive to be a significant improvement in clarity and depth. I guess these amps are susceptible to air borne vibration. I don't think I have a problem with RFI, but perhaps the covers also helped isolate the circuitry from any minor amounts and that contributed, as well. My chassis are nothing special--just thin aluminum. I used some damping material around the PCB mountings on the bottom of the chassis, but nothing special to damp the tops. Just putting them on made the difference.

All you builders with "bare" amps, try closing up your chassis and listen if it makes any improvement in the sound.

I intend to experiment further with isolation from structural vibration, as my amps sit directly on the floor (well, with elastomeric feet on the bottom) near the speakers, and I can detect slight vibration of the floorboards when bass is playing. I was always a skeptic about the need for amp stands, but these little amps might benefit from a combination of isolation and mass loading underneath them.

Peace,
Tom E
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Old 27th October 2012, 09:56 PM   #578
bcmbob is offline bcmbob  United States
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lehmanhill and I believe one other builder are doing a speaker mounted placement. It will be interesting to hear what vibration does in that situation.

The integrated build suffers no such problem as it was built with two 3" X 3" X 1/4" aluminum channels and a 1.5" center brace. Not necessarily intended for dampening - just what I had in the shed at the time. The transformer cover is 16 ga. and chassis covers is 20 ga. steel. The whole mess comes in at just over 38 pound.

All my auditioning has also been with the amps on the floor between the speakers, but in my case resting on thick carpet and pad. If I ever get it on a shelf I plan to use speaker spikes and pads for an experiment. I'll do some cover on/cover off tests and post the findings.

If you havn't seen it, Mick Feuerbacher has an interesting approach for the PS CD player in this area.
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Old 27th October 2012, 11:16 PM   #579
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I can't imagine a worse place to mount any amplifier than on a speaker, inside or out. Every part of a speaker enclosure vibrates almost continuously. What is to be gained? The pros do it only to simplify an active system. I'm sure they use extraordinary means to damp the amp, and it would probably still benefit from being mounted apart.

Seems to me a seriously misguided design decision with zero benefit.

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Tom E
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Old 28th October 2012, 06:52 PM   #580
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Quote:
Originally Posted by Marra View Post
I have one working board;I say working it has'nt actually played music but all voltages appear correct and the relay clicks on ;led lights up and there is low offset.I'll do a voltage check between pcb's this weekend.Thanks
Marra,

One possibility comes to mind. The 24V relay has a range of closing voltage possible. On the board where the relay switches on, then off, could it be related to the relay? The Omron suggested in the Mouser BOM could be as high as 18 volts before closing. My relays are working fine, but I measured the voltage at the inboard (away from the edge of the board) of R14 at 15 volts DC (the schematic suggests 24V). I could see where that could be marginal to close the relay and keep it closed. Perhaps Dario or others could suggest how to test this safely.

Actually, I'm somewhat confused by this anyway. Using a 22 V transformer, my simulation of the relay system suggests that voltage at the relay should be about 30 volts, the same as V+. Yet the schematic says 24V and I'm measuring only 15V.

Good luck, Marra.
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