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Old 30th January 2009, 02:34 AM   #1
Thzar is offline Thzar  Sweden
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Default NCD1 problems: No blue led blinking at startup

Hey.

I just assembly my NCD modules today, it have been collecting dust in the closet for a while.

Netfilter
NewclassD Softstart DC filter
Homemade PSU supply. 2x24v 300VA
2 Rectifiers
4pcs 10.000uF Nichicon KG caps 63V
->Correct Connected. Triple checked the connections.
Starup and nothing happens. No blinking blue leds.

Measure 13.8 Volt DC offset at both channel spk terminals with no speaker attached.
No inputs.

(0.8mV with spk attached. )

I attach a simple MSpaintpicture of my layout.
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Old 30th January 2009, 02:57 PM   #2
Thzar is offline Thzar  Sweden
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Join Date: Jun 2008
Yo.

I got contact with Lars at Newclassd, (quick answered) he said I forgot the Gate Drive transformator 15Vac / 20Vdc.

Well I didnt find any information in the ncd cookbook that I need a gate drive supply to make NCD modules work.
Only that it lower the power idle, and could wrk without them.

Must get a 15Vac transformator then, or will a 12 Vac do the job?
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Old 9th February 2009, 11:39 PM   #3
Thzar is offline Thzar  Sweden
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Lars C. recommend between 15-21 Volt for the Gate Drive.

I fixed a Gatedrive PSU.
[12 VAC trafo 35VA: 1x12VAC]
[4pcs 1N5401 diods]
[2 pcs Rubycon YXF 1000uF 50V]

-> Unload 16.5 volt with load 14.5-15.5 Volt.

The NCD1 modules works now with some minor/major issues.

- With turn on clicks in the spks.
- Shutdown procedure create a shutdown noise, sounds like
#caps venting#. Measured 12 vdc on the spks output so I
guess the sound come from the treble.
#Lars C. recommend two power off switches.
1. Turn off the gate Drive supply
2. The rest of the system.


That worked and resulted in a silent shutdown.
But turn on clicks still exist.
I will need to do a new layout for the new objects thats have been added, now the just float around in the chassi

*Without any source connected its "silent"
The ear have to be extremly close to the spks to hear a weak noise. No hum at all.

But I got a huge signal ground loop when I use computer soundcard as sourse. I even hear when I move the mouse around on the screen in the spks + high level of noise and humm.

Found something in other NewclassD topic about adding 10k resistor in serie with the "hot" input.
I did that and it lower the noise.
Lower the gain?!
But its still useless with the soundcard.

The sound I got from the NCD1 except the high noise is a flat and no dynamics and hard sound.
mismatched inimpendance?

I had some test with inimpendance of my gainclones and with higher inimpendance (20k +) more dynamics, softer and more detailed sound I got, with lower inimpedance (10k and lower) the opposite. flat, hard, no bass etc.
My gainclones LM3886, deadsilent with same setup and play with high details and dynamics + wonderful bass.

more to come.
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Old 13th March 2009, 05:36 PM   #4
cdl is offline cdl  Denmark
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Location: Copenhagen
Nice work, your amp has more stuff (but less mess) inside than my NCD does ;-) I have the turn-on clicks too - have had the amp for a year or two now, they are always there and seem to be harmless.

I also have small shutdown noises, but as long as there is no signal on the amp, they really are nothing much. The shutdown noise could be caused by a small amount of DC on the input?

Quote:
Originally posted by Thzar
But I got a huge signal ground loop when I use computer soundcard as sourse. I even hear when I move the mouse around on the screen in the spks + high level of noise and humm.

.... adding 10k resistor in serie with the "hot" input.
I did that and it lower the noise.
Lower the gain?!
But its still useless with the soundcard.

The sound I got from the NCD1 except the high noise is a flat and no dynamics and hard sound.
mismatched inimpendance?

I had some test with inimpendance of my gainclones and with higher inimpendance (20k +) more dynamics, softer and more detailed sound I got, with lower inimpedance (10k and lower) the opposite. flat, hard, no bass etc.
Computers are difficult sound-wise because they are connected to ADSLs and other stuff, so hum from connecting computers to hifi is pretty common in my experience. Especially if you have the computer connected to the telephone net (one ground potential) and the hifi to a tuner or TV with an antenne (where ground can be very different from telephone ground!). Also, lots of computers can put out some DC on their line out connectors - if there's any DC you will have to get rid of it for the NCD to work.

I have never used my NCD directly connected to the computer, but I regularly listen to the computer via my DIY preamp (with DC servo), and it works fine. My guess on your hum problem is that the ground potentials of computer and amp are different... have you checked that? I use three-prong mains cords for computer and hifi so that everything is "in phase" and with a common ground (I know this is less important w. some devices that have double insulated power supplies). Also try connecting computer and amp to the same outlet.

If you already have them on common ground (or if grounding them together doesn't help), double check internal grounding of the amp - there should be about 12 ohm resistance from amplifier ground to chassis. If it's OK, you can try to connect a ground lead between computer case and amplifer case (measure the voltage first to make sure it's not too crazy...). If that helps you know where the problem is. You may need to build in a ground loop breaker... but really, it shouldn't be necessary.

The sound of the amp does change a bit after playing for a while. But it should sound pretty good from the beginning, mine did.

When reading your experience with impedance on your gainclones, I get the impression that your soundcard may be a bit picky about impedance. I believe NCD has an impedance of 20k which should be OK. But maybe in combination with the high gain (=> you have to turn the sound card volume way down) it might be a problem. Can you test running through a preamp? Maybe just a potmeter (passive preamp) so you can crank the soundcard up to full, and reduce volume with the pot. You may want to try playing with impedance and gain. Also, grounding issues / DC could be causing the bad sound quality, so make sure that's sorted out first.

Hope this helps and you manage to solve the problems!!! and that you become as happy with your amp as I am.

/cdl
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Old 13th March 2009, 08:34 PM   #5
Thzar is offline Thzar  Sweden
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Hey.
Thanks.

Some NCD1 updates:
I changed to a 15Vac trafo.
With the change I got some shutdown noise again. A quick answer from Lars C. told me to have the V.gate PSU power off switch after the caps on the V.gate PSU "module" and that wotks. Now silent.

No groundbreaker. I dont think the NCD have any contact with the chassi, floating ground!?

No grounded wall outlets.

No DC output from soundcard, it go dcblocking caps (10uF rubycon yxf)

NCD itīs completly useless together with the sources I gotīfor now. I even tried it with a CD player and played a piece of intro fron a CD. Strange digital noise, hear it searching and alot more. But with my gainclone its "deadsilent"

I think itīs all about the gain issue, too much gain its not good.
The input impedance of NCD is 5k
Gain 45db ?

I have started building a preamp, the NCD micro preamp described in the cookbook, if itīs not going to bee any improvments. I think I get rid of it.

So long...
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Old 13th March 2009, 11:00 PM   #6
cdl is offline cdl  Denmark
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Location: Copenhagen
Quote:
Originally posted by Thzar
Some NCD1 updates:
I changed to a 15Vac trafo. ... shutdown noise again... V.gate PSU power off switch after caps on the V.gate PSU "module" ... Now silent.
Really? Completely silent? Maybe I should think of a way to shut off V.gate before the rest...

Quote:
No groundbreaker. I dont think the NCD have any contact with the chassi, floating ground!?
Mine does have contact with chassis - there should be 12 ohm from signal ground to the aluminum plate. If not there's something wrong... whoops! I have the NCD psu - the ground resistor might be on there... if yoy have no measurable contact between chassis and GND, then connect power GND to chassis with a 10 ohm resistor (―W or larger). Make sure the aluminum plate under the modules has electrical contact with your chassis ;-)

Quote:
No grounded wall outlets.
OK, not to worry. But I'm pretty sure grounding is part of your problem... so try this: 1) Get a big power strip (multistik / fordelserstik på dansk), make sure it is one of the kind that has a ground rail in it (some of them here have holes for the ground pin, but no conductor inside!). Then get three prong connectors for computer, NCD etc. Plug everything into the power strip.
Now there should be direct contact between computer chassis and NCD chassis, and some 10 or 12 ohm between computer chassis and signal ground (NCD). I am pretty sure that will help!

Quote:
No DC output from soundcard, it go dcblocking caps (10uF rubycon yxf)
Try a 22k resistor in series as suggested by Lars in the cookbook (under use of tube amp). Careful with large (>1ĩF) blocking caps, in my experience they can need some "loading" - you may want to try 10k or 20k in parallel with the input (that is between + and GND).

Quote:
NCD itīs completly useless together with the sources I gotīfor now. I even tried it with a CD player and played a piece of intro fron a CD. Strange digital noise, hear it searching and alot more. But with my gainclone its "deadsilent"
Just to exclude more grounding issues, can you try it out using something battery-powered - MP3 player or the like - without connection elsewhere? Works fine with my NCD.
Hearing the CD search (in the speakers) is common in case of problems with grounding.

To me it sounds like either something is really wrong with the amps, or something is really wrong with the wiring. You sound like a bright guy but I don't know your level of electronics skill - so please forgive me for asking this: are you sure you have connected the inputs correct: Signal live to input+, ground to inputGND and short input- to inputGND? (page 13 /21). Just making sure that you didn't put signal GND into the - terminal ... sorry for asking if you're all in control, no PUN intended
Does the amp react to your touching signal ground (when on, no input connected)?

Quote:
I think itīs all about the gain issue, too much gain its not good.
The input impedance of NCD is 5k
Gain 45db ? ... I have started building a preamp, the NCD micro preamp described in the cookbook, if itīs not going to bee any improvments. I think I get rid of it.
Hmm, you're right about the input impedance... 5k is pretty low. Your soundcard may not like that. Should still play OK though.
Yes the gain is high - makes it possible to do without preamp. You can easily limit the gain using simple 2 resistors - better too much than too little.
Before you finish the preamp, I would do a quick test with a pot (wired up as suggested just above the preamp). If the gain is really a problem for your setup (possible), then once you find the optimal setting of the pot, you can just measure and buy 2 resistors to replace the pot.

Before you get rid of it, do ask Lars for help too - you might have to ship it to him, but he will get it running I'm sure.

/cdl
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Old 15th March 2009, 04:14 PM   #7
wtfaidh is offline wtfaidh  Netherlands
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Hmmm. Does not sound familiar. I've build mine using the PSU's from Lars.

First prototype on plywood (to prevent any groundloops), second one 100% by the cookbook.

Only thing is thad I did not use is a separate ground drain wire to the inputs (and both are floating vs case)

But because I'm using a dual-mono configuration I had to use a GND-Left GND-Right wire to prevent some residual hiss (interference)

No problems whatsoever besides some very, very, very small shutdown noise. No humm, no ground loops, just music...!!!

Currently attached to audiolab pré

Sound is great and realy addictive...

I would check, check and re-check all wires....
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Old 21st March 2009, 12:33 AM   #8
Thzar is offline Thzar  Sweden
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Join Date: Jun 2008
cdl:
Hey,


I tried the gnd drain wire as well, no change.

I borrowed a creative zen mp3 player and pushed play-
some serious sound issues. groundloops among others..

You said "short input- to inputGND?"
What?

What version of the ncdcookbook do you have? I got the 1.06 version. nothing about short inpu- to input gnd, or Im blind.

hmm.. I have tried every kind of combos connection with the inputs thats I can remember, same problem...
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Old 21st March 2009, 04:23 AM   #9
bro is offline bro  Singapore
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Quote:
Originally posted by Thzar
nothing about short inpu- to input gnd
Try page 10 for grounding input signals and page 19 for levelling ground between 2 monoblocks.
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Old 21st March 2009, 04:34 AM   #10
bro is offline bro  Singapore
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page 10
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