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Old 3rd September 2007, 11:48 PM   #11
lohk is offline lohk  Europe
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Here the schematic of the Velleman VM100 (copied from the UserManual, available on the Velleman site):
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File Type: gif vm100.gif (59.2 KB, 1861 views)
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Old 4th September 2007, 06:37 AM   #12
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janneman, yes, it's really bad! money "make the rocking world go round", it rules our lives and destinys
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Old 4th September 2007, 06:46 AM   #13
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Quote:
Originally posted by noah katz
"Blin, they want money for article, i'm very disappointment, damn!"

$1.60 for the article seems very reasonable to me.

Actually, it's free if you register.

Jan Didden
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Old 4th September 2007, 06:56 AM   #14
ssanmor is offline ssanmor  Spain
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Hello,
Some comments now that you have given some data about our Coldamp modules.

As you have pointed out, to be fair, all the measurements must be made with the modules as they are received, and all of them under the same measurement conditions.

Some hints...

The gain can be changed. We decided to use 45V/V gain (for each input, so 90V/V balanced) as this allows direct connection to typical unbalanced line sources, such as CD players. In a day or two we are about to open a new version of out www.coldamp.com website, where users can download more documentation. Casually, one of the application notes described how to easily change gain.

About the bandwidth, it fully covers the audio band. In fact, the 2dB drop at 20KHz (4ohm) is of little importance sonically. No customer has complained about that when they have heared the modules, as highs are perfectly balanced and clear. The -3dB point was set at 27KHz aprox as a compromise with ripple rejection, stability, etc. This can be easily increased if desired, too, so no problem. We see no use in setting the -3dB point at 50KHz, to be sincere, but that's a personal decision.

And about the rest of measurements, you know that getting accurate results while measuring Class-D is very difficult, and depend on the setup heavily. The IMD has appeared a bit high, although we have got much better measurements at our labs (below 1% in that conditions), as well as for the 1W THD (other measurements have shown below 0.2%). Proper wiring, power supply, etc. are the key to excellent figures.

In a nutshell, measurements have to be taken with great care, as they have a limited impact in sound quality and cannot be taken as a figure of merit alone. The proof for us is the satisfaction of our customers, some of them with very very critic ears as required by their jobs (studio recorders, etc).

We also take the opportunity to say that the Spanish edition of ELEKTOR has some errata, such as saying that our modules have pre-filter feedback. That's not true and was corrected, but they have inadvertently published the uncorrected version of the article. This edition also doesn't mention the fixed sw. frequency and output notch filter, as the rest of issues publish.

Sorry for the long reading...
Best regards,
Sergio
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Old 4th September 2007, 06:56 AM   #15
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Hmm, "it's free if you register" it doesn't work.
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Old 4th September 2007, 07:05 AM   #16
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"Actually, it's free if you register."

After registering it said 10 credits were needed to download.
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Old 4th September 2007, 07:18 AM   #17
IVX is offline IVX  Russian Federation
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Bender blin, come on, what you wanna find in the article exactly? About UcD you can find here everything, did you really wondered about Velleman?
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Old 4th September 2007, 07:33 AM   #18
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Quote:
Originally posted by noah katz
"Actually, it's free if you register."

After registering it said 10 credits were needed to download.

When you register you have 10 bonus credits (look at the left bottom side) which you can use to download the article. That's what happened to me at least.
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Old 4th September 2007, 08:23 AM   #19
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Quote:
Here the schematic of the Velleman VM100 (copied from the UserManual, available on the Velleman site):
How do you dare to post the schematic of such terrible and inefficient things on a CLASS-D forum ????????

Moderatoooooooooooooooors !!!!!!!!!!!!



Regards

Charles
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Old 4th September 2007, 12:12 PM   #20
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Default Re: ELEKTOR September article

IVX, ok, ok you are right
all i wanna know about Velleman, i found it in #11 .
phase_accurate, +1

janneman, i didn't complete regisrtation yesterday, but few minutes ago finished it, and now read article...thanks for hint !
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