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Old 7th June 2008, 10:33 PM   #11
mobyd is offline mobyd  New Zealand
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I notice that when you click the "buy" button on Monolithicpower's website, you get routed to Avnet USA as the vendor, and as a non US person (New Zealand) I'm very wary of playing the "Shipping will be calculated on despatch, just give us your credit card number" game of Russian roulette. Has anyone bought these (or indeed any other chips) from Avnet this way, shipping to a non US address, and how were the shipping charges. FFS Microchip Direct can work it out, why can't these guys.
Cheers
M
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Old 8th June 2008, 02:11 PM   #12
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Quote:
I notice that when you click the "buy" button on Monolithicpower's website, you get routed to Avnet USA as the vendor, and as a non US person (New Zealand) I'm very wary of playing the "Shipping will be calculated on despatch, just give us your credit card number" game of Russian roulette. Has anyone bought these (or indeed any other chips) from Avnet this way, shipping to a non US address, and how were the shipping charges. FFS Microchip Direct can work it out, why can't these guys.
Once I buy this chip from AVNET, shipped to Indonesia. The chips cost me about US$75, but the shipment billing about US$125. I know the cost of the chips, but the shipment cost is not known until it appears in your credit card's billing.
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Old 17th June 2008, 02:18 AM   #13
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Hi,

I just received 2 board from Sure Elec.

I have also noticed a cap discharge sound when turned off...Kind of Ray Gun like.

The Av gain is set too low so when you crank up the amp it creates some weird distorsion artifact. Based on the schematics I received from them (and the actual components on the PCB) the gain is set to 8.2 which is quite low compared to the T-Amp by sonic impact set at 21.6 or the one from Sure Elec. (TA-2024) set to 12.

f3 (input) is set at 16Hz and f3 (output) is set at 42Hz via the 470uF driving an 8 ohm load.

The sound is quite good and will be even better when I increase the gain to about 16-18 to avoid these nasty artifact spike.

It's too late now to give it a try but if anyone is interested I will report back. By the way the IC is surface mount type and not DIP8.

Regards,
Eric
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Old 17th June 2008, 11:14 AM   #14
mobyd is offline mobyd  New Zealand
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Quote:
Originally posted by e_fortier
Hi,

I just received 2 board from Sure Elec.

I have also noticed a cap discharge sound when turned off...Kind of Ray Gun like.

The Av gain is set too low so when you crank up the amp it creates some weird distorsion artifact. Based on the schematics I received from them (and the actual components on the PCB) the gain is set to 8.2 which is quite low compared to the T-Amp by sonic impact set at 21.6 or the one from Sure Elec. (TA-2024) set to 12.

f3 (input) is set at 16Hz and f3 (output) is set at 42Hz via the 470uF driving an 8 ohm load.

The sound is quite good and will be even better when I increase the gain to about 16-18 to avoid these nasty artifact spike.

It's too late now to give it a try but if anyone is interested I will report back. By the way the IC is surface mount type and not DIP8.

Regards,
Eric
I have not had good results with these Sure Elec amps
This is what I got with a 24 volt supply and an 8 ohm load
Click the image to open in full size.
The thing LOOKS competently laid out and they are claimed to
be tested.
M
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Old 17th June 2008, 09:42 PM   #15
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Was your power supply regulated, it looks like at least 26Vpk to peak which could explain your problem.

Is this the glitch that we hear ?

Regards,
Eric
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Old 18th June 2008, 03:14 AM   #16
BWRX is offline BWRX  United States
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Quote:
Originally posted by mobyd
I have not had good results with these Sure Elec amps
This is what I got with a 24 volt supply and an 8 ohm load
The amps I made with the MP7720 used split supplies (+/-12V rails) and I never saw what your picture shows as the amp output. I tested them hard too, clipping into 8 ohm and 4 ohm loads and the chip got so hot I couldn't even touch it but the output was just a clipped sine wave. That could be the result of a problem with a component in the boost cap circuit.
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Old 21st June 2008, 03:42 AM   #17
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Hi,

I have just finished to modify a Sure Electronics PCB that comes with 2 x MP7720 (7 USD + 5 shipping Intl) it is cheap fun for $12 USD

From a +18Vdc, 5A power supply I get 20W rms into 7.5 ohm just before any sign of clipping on the scope.

Modifying the unit is quite simple, a few component to remove, bypass the output cap and 2 x 2pF cap to add in the pre-filter feedback loop. I had the schematics for the PCB and thanks to BWRX I was able to synchronize both amp by looking at MP7731 IC, Thanks !

I'm missing the cap connected to the load, how do you calculate that one...

Regards,
Eric
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Old 21st June 2008, 02:48 PM   #18
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I forgot to mention that now instead of 2 SE amp I have bridge both amp for a single channel.
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Old 21st June 2008, 09:31 PM   #19
mobyd is offline mobyd  New Zealand
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Quote:
Originally posted by e_fortier
I forgot to mention that now instead of 2 SE amp I have bridge both amp for a single channel.
Would you mind posting a schematic for the modded unit.
cheers
M
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Old 22nd June 2008, 01:57 AM   #20
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Default Required mods to get bridge amp from MP7720 of Sure Elec.

Hi,

While I do a nicer copy and scan the document, here are the required modifs.;

Remove the following components;
1. R2
2. R4
3. C5
4. R10
5. C14
6. C19
7. R7 and R13 (Zobel)

Bypass the following components;
8. C8 and C21 (output cap)

Add the following;

9. 0.68uF in parallel to the load (8 ohm min.)
10. 2pF film cap. from pin 7 (output) of U1 to pin2 of U2
11. 2pF film cap. from pin 7 (output) of U2 to pin2 of U1
12. small wire from pin 1 of U1 to pin 2 of U2
13. small wire from pin 2 of U1 to pin 1 of U2

That 's it, now Left input is the + audio signal and Right input is the
- audio signal (gnd)

Connect the loudspeaker between both speaker + terminals.

Enjoy

Regards,
Eric
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