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Old 4th March 2012, 01:50 AM   #331
cwier60 is offline cwier60  United States
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Originally Posted by cwier60 View Post
Quote:
Originally Posted by Jolojl View Post
1) The IRAUDAMP7 data sheet (http://www.irf.com/technical-info/re...iraudamp7d.pdf) mentions various AMP7D implementations, including one AMP7D-55 running on 25V. Is this just a matter of supplied voltage (i.e. can one run any of the AMP7D kits available on for instance 30V) or does this require a specific implementation?
There's no problem running any of the higher power implementations at lower supply voltages and thus lower maximum output power, unless the undervoltage points have been set above this supply voltage. Sorry, but I haven't checked whether that is the case.
It looks like Z101 sets the minimum supply voltage (UVP), so you would need a lower voltage Zener to operate one of the higher power options at 30; 18V would be a good choice, but anything under 24V would probably do.
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Old 4th March 2012, 09:27 AM   #332
Jolojl is offline Jolojl  Sweden
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Originally Posted by cwier60 View Post
There's no problem running any of the higher power implementations at lower supply voltages and thus lower maximum output power, unless the undervoltage points have been set above this supply voltage. Sorry, but I haven't checked whether that is the case.Looks like it's 3.3K, which is pretty low. It's R2 + R7. This gives a high-pass DC block at 2.2 Hz with the 22uF CP1.
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Originally Posted by cwier60 View Post
It looks like Z101 sets the minimum supply voltage (UVP), so you would need a lower voltage Zener to operate one of the higher power options at 30; 18V would be a good choice, but anything under 24V would probably do.
Thanks a lot cwier60, great answers! Now I understand this probably isn't an amp for me at the moment. Johan
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Old 4th March 2012, 06:13 PM   #333
MrSlim is offline MrSlim  Canada
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Originally Posted by cwier60 View Post
It looks like Z101 sets the minimum supply voltage (UVP), so you would need a lower voltage Zener to operate one of the higher power options at 30; 18V would be a good choice, but anything under 24V would probably do.
ljm_ljm's L15D, L20D and L25D do not have the OVP/UVP circuitry in them (I already looked for it..), so you won't find Z101, etc from that circuit. It is a simpler design in that way.
The resistor changes that need to be made to adjust the design for various power supply voltages(and power outputs) are listed on page 37 here. Unfortunately, ljm_ljm hasn't provided a schematic, or part IDs for the design, so it would have to be reverse engineered to identify which parts need to be replaced. (something I may get to one of these days)
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Old 4th March 2012, 08:24 PM   #334
alkasar is offline alkasar  France
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Originally Posted by MrSlim View Post
Unfortunately, ljm_ljm hasn't provided a schematic, or part IDs for the design, so it would have to be reverse engineered to identify which parts need to be replaced. (something I may get to one of these days)
yes that's missing. I started the job. Did not yet identify them all.
The parts ref are those from the IRAUDAMP7S reference design, page 30. It's a L25D board picture.

Click the image to open in full size.
it's a preview of work in progress and there might be errors at this stage. I just found one

A question at this stage :
The reference design BOM recomends ultra-fast switching diodes for D3, D5, D6.
The kit comes with 1N4007 which are not known to be ultra-fast.
Is this something to worry about ?

Last edited by alkasar; 4th March 2012 at 08:34 PM.
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Old 4th March 2012, 08:51 PM   #335
cwier60 is offline cwier60  United States
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Originally Posted by alkasar View Post
The reference design BOM recomends ultra-fast switching diodes for D3, D5, D6.
The kit comes with 1N4007 which are not known to be ultra-fast.
Is this something to worry about ?
The IRAUDAMP7D BOM shows 1N4003 for D5-6 but MUR120 for D3. D5-6 are on the output, which should be limited to the audio band. If you plan to drive this at full power at 20 kHz, then the UF diodes may be necessary, but you're probably OK with the standard diodes.
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Old 4th March 2012, 09:54 PM   #336
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Originally Posted by MrSlim View Post
Unfortunately, ljm_ljm hasn't provided a schematic...
I thought it was followed the IR reference design, or maybe you mean the translation from schematic to board layout.
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Old 5th March 2012, 12:53 AM   #337
MrSlim is offline MrSlim  Canada
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Originally Posted by noah katz View Post
I thought it was followed the IR reference design, or maybe you mean the translation from schematic to board layout.
No, what I meant was that the IR reference design includes circuitry(OVP/UVP) that ljm_ljm left out of his design. Also, the board layout for the L15D (showing all the values) that are provided by the ebay resellers does not match the layout of the boards I purchased. The L20D layout is slightly different also, (various versions I suspect), so a reverse engineering of the boards may be required to get a true schematic.

Alkasar is doing the work of identifying the correct components for the L25D, which will help some of us, but it looks like the layout between the various boards is different enough that it may have to be done for all of them..
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Old 5th March 2012, 02:20 AM   #338
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For me, I easily identified what are to be replaced because those are unique values for resistors in the board...

Here are the values, same as page 37 of iraudamp7s datasheet
Quote:
Originally Posted by ljm_ljm View Post
+ -52V 4ohms。
I suggest you to change only 8 resistance.
130K 1/4W - 120K 1/4W
5K1 1W - 3K3 1W (2PCS)
2K2 1W - 1K 1W
20K 1/4W - 15K 1/4W
5K1 1/4W - 7K5 1/4W
8K2 1/4W - 9K1 1/4W
75K 1/4W - 47K 1/4W

Do not need to change the IRFI4020.
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Old 5th March 2012, 01:18 PM   #339
alkasar is offline alkasar  France
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I am done with the reverse engineering to cross-reference L25 board.

For memory, the original IRAUDAMP7S is here, page 30

http://www.inductor.com/irf/iraudamp7s.pdf

L25D cross reference

Click the image to open in full size.

The design follows almost exactly IRF reference design.

some comments:

- The components values on the board follow the reference design, except for those to adjust according to power (in red in the schematic)
R7, R8, R17, R18, R12, R114, R115, R117, CP7, CP8

- pot P1 is not there. Instead, R11 is adjusted to 300R (resistor already sold on board)

- The protection led signal is not implemented (R14, CSD1, FET2, R3, D1)

- There is an additional 15V Zener, not on the schematic. Z? on board, already soldered. It is between pins 13 and 15 of IS2092
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Old 5th March 2012, 01:48 PM   #340
alkasar is offline alkasar  France
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Originally Posted by cwier60 View Post
The IRAUDAMP7D BOM shows 1N4003 for D5-6 but MUR120 for D3. D5-6 are on the output, which should be limited to the audio band. If you plan to drive this at full power at 20 kHz, then the UF diodes may be necessary, but you're probably OK with the standard diodes.
Hi,
We dont read the same bom I read page 33 of IRF ref design. D3, D5, D6 are supposed to be mur120.
D5 and D6 are indeed clamping diodes at the output. A safety protection mecansim against overvoltage at the output. The zobel R30, C13 should limit bandwith to 150kHz. This is to filter out the modulator freq. Chances are if there is an overvoltage it could go up to high freq.
I agree, there is little risk.

Not shure what D3 is for....

edit: oops, I looked too fast to the kit ! The diodes in the kit are actually UF4004, not 1N4004. So ultra fast

Last edited by alkasar; 5th March 2012 at 02:18 PM.
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