Missing resistors and led..

[mikechw]

I have bought 2 AMP1B kits..

From the BOM, I see 49.9k should be placed at R2,R10,R12,R14,R15, but I couldn't find it in the pack.
Is it possible that the BOM is wrong ?
Does the kit include the led ?
:(

I am stuck without those 49.9k SMD, does anyone's AMP1B kit also misses those parts ?

For C46 and C47, I couldn't ditinguish the caps, anyone can help ?
330pf and 390pf is too small for my meter to measure..

Thanks...

[krilli]

I got 47K resistors instead of 56K resistors in my Amp11, and had to count everything to make sure that there was a swap. Are there any extra similar-value resistors? What are those positions in the Amp1B?

And - Are C46 and C47 the same voltage spec? You may be able to tell the difference in size and color. (In my Amp11, 390pF was darker than 1000pF, of same voltage spec.) You could also measure them with your sound card by playing white noise through a loopback rig, if done carefully you should be able to tell a difference. Were they in the same bag?

[mikechw]

For the cap, one should be 330pf and the other is 390pf.
They comes in different bags, but there are no labels.
So darker color means lower capacitance.. I will try my luck.

In the pack there are 2 47.9k resistor left, after I solder everything else to the board.
But even I solder these 2 to the board, I still need 3 more.
Even I used these from my other AMP1B kit, I still need one more..
These resistors goes to the area below the 2 op-amps, so I assume its value is critical.

[krilli]

Can you find the maximum voltage spec. for the 330 / 390 pF caps? That will serve as a hint ...

[V-bro]

This may be a good thing for you to buy:
http://www.conrad.nl/goto.php?artikel=122211
http://media.conrad.com/xl/1000_1999/1200/1220/1222/122211_BB_00_FB.EPS.jpg

As for the resistors, this is something Jan should know so he can stick a bag with these resistors with the other kits he has in stock...I'll mail him...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[Scratchy]

I have built one of 2 AMP1-B kits so far and all the bags are labeled and complete.
The 330pF cap is in bag 4 along with 3Kohm, 100Kohm and 1.2Kohm resistors.
The 390pF cap is in bag 3 with 300ohm, 1Kohm, .1uF 50V x10 and .1uF 100V x2.
I received 5 49.9Kohm in bag 9 along with one 200Kohm SMD resistor.
I also received the LED in the anti-static bag along with all the other semi-conductors.

If you are missing pieces, then you must contact Jan for the remaining pieces.

***If it was easy, everyone would be doing it***

[Jan]

Hi,

Odd resistor values have in some cases been replaced by closest E12 series resistor values when possible. So 20K have in some cases been repalced by 22K and 49.9K by 47K. The difference in gain is hardly audible, and both input resistors and feedback resistors are exchangeable depending on your sound source signal level. With all kits except AMP9, therer are a few alternative resistor values included withthe kits, so you can select input sensitivity (the chip used for AMP9 has internally fixed sensitivity). Sorry if this has not been clear in the documentation. I know it can be confusing when you get components that are not exactly what you expect. There is a section in the documentation describing how to set the input sensitivity/gain.

Surface mount caps generally have no marking. Therefore they are packed in different bags / quantities so they can be kept apart. The 330pF / 390pF positions can be swapped on the board and still be OK. These caps are tehre to ensure the idle frequency is a little bit different between the two channels. Otherwise, you could get an audible interference when there is no signal input. If you have a frequency meter, the idle signals (residual on speaker outputs) should be around 600kHz, and preferable around 40kHz apart. Under power the switching frequency with the Tripath chip is changing all the time, and can vary between 200kHz and 1.5MHz.

[mikechw]

Thanks,

Actually I went out to buy a LCR meter... :)
And got some SMD resistor myself.
The shop don't have 49.9K so I bought some 51K resistors.

I am using these 2 amp1b to drive my KEF speakers.
One amp for one speaker. Left channel driving HF and Right channel driving LF.

Hopefully I can post some photos after I finish the whole thing :)

[mikechw]

Since I bought a LCR meter, I have a chance of measuring the inductance of the toroid that I wind.
It measured 19 uH.
From the instructions, it told us to wind 44 turns and it suppose to have an inductance of 11 uH.

Should I unwind it until I get a measurement of 11 uH ?
Whats the influence for the inductance to be greater than 11 uH ?
Is the inductor suppose to filter out some ultra high frequency ?

Thanks..

[thomaseliot]

First measure the inductance of a short stright wire and see if it is zero. :)

Higher inductance will filter more switching residuals, maybe around 90khz instead of the standard 107khz, that is a good thing.

[V-bro]

What frequency does the meter measure inductance with? This can make a difference...especially at such low inductance measurements, you need a really precise meter to get reliable readings....

------X-max. can be several meters on any driver, too bad it can be done only once...------

[mikechw]

After I read the instructions for my LCR meter..
I measured 7 uH just with a straight wire.

So 19 uH - 7 uH = 12 uH... So 44 turns is correct :)