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FYI: the E-Mu signal path is as follows:

G chip --> H chip --> G05 chip --> outputs

The G chip, of which there is 1 per 64 channels, is the sound generation chip. It reads directly from sample ROM/RAM, and does 7-point Gossett-Smith pitch shifting with fully ramped pitch per output sample.

The H chip, of which there is 1 per 32 channels, is the filtering chip. It can process a 6-pole filter per channel, or can steal a voice and cascade two sets for 12-pole filters. It has a morphing buffer which can interpolate between two complete sets of coefficients automatically per output sample. I believe gain is also done here.

The G05 chip, while also containing 64 channels of pitch shifting and 64 channels of 2-pole filters, is used only for the DSP section that creates the two master effects. It also handles routing of signals.

Post H chip, the arrows go through an FPGA for signal routing and interleaving. Furthermore, all the ASICs are controlled by a ColdFire CPU which handles envelopes, LFOs, control signals, note queueing, UI, etc.

-Aaron

PS. the Emulator series adds an option to use the R chip, a DSP behemoth that did 16 simultaneous stereo high-quality FX.

From: Jack Pratt
To: xl7@yahoogroups.com
Sent: Wed, March 17, 2010 1:51:19 PM
Subject: Re: [xl7] Re: HELP: FX RAM failed error

Just incidentally, the same basic circuit is used for the sound generation in all P2K series units and command stations [The command stations have a different micro & the FLASH/SDRAM chips (it has an SDRAM chip instead of a DRAM SIMM) are different] So if you have a P2K module that's dead it could be the source of spare parts. I noticed that on a P2K the FX RAM is right next to the micro [U29] with 'IC405' beside it.

The FX RAM will only have an interface to the FX chip ['IC405'] next to it, so only the DRAM, that chip and the nearby passives are going to be contributing to a FX RAM error.

I'd look at it for you, but I doubt that its worth the trip to Australia...

From: steve_the_composer
To: xl7@yahoogroups.com
Sent: Wed, March 17, 2010 8:15:11 PM
Subject: [xl7] Re: HELP: FX RAM failed error

Thanks for the details, Jack. Such repairs are definitely beyond my skill set. I might be able to find someone else who can do it. I will look at the motherboard for the chips to see what I can find.

--Steve

--- In xl7@yahoogroups. com, Jack Pratt wrote:
>
> Hey steve.
>
> If the P2500 mother board is identical to an XL7 motherboard (I suspect so, but...)Â FX RAM is the SOJ28 (the one with missing central pins)Â package to the front left of the motherboard - U35; right next to the ROM slots. This is not memory used by the microcontroller (which is towards the right and back on the motherboard in a TSOP 54 package).
>
> The FX RAM (81C4256 = 256kBit) is used to produce a pipeline by the large IC next to it "IC405" (U34) for sound effects (not the FX bus) so that you'll probably find that any sound that has any effect (eg chorus) will be bad.
>
> It is unusual that a DRAM would fail, but if you have access to a hot air solder rework station you could try reworking the solder joints (which may have become dry). You also need to consider the bypass capacitors next to it and solder joints on U34 (with which it communicates) . If the DRAM has not failed (and its not just a dry joint or two) then U34 could be failing which means that you're unlikely to ever get good sound out of the thing wihtout stipping all effects [making the sound output very bland].
>
> If you are not competent to do the rework yourself, then you probably need to find someone who is to avoid damage to your unit [not something you should attack if the soldering iron is not your friend].
>
> Unfortuantely 81C256's are not common at all these days, and the package makes removal a challenge without a solder rework station [and then its trivial]. So if you wanted to try replacing it...
>
>
> Â
>
>
>
> ____________ _________ _________ __
> From: steve_the_composer
> To: xl7@yahoogroups. com
> Sent: Tue, March 16, 2010 7:31:21 PM
> Subject: [xl7] Re: HELP: FX RAM failed error
>
> Â
> Footnotes:
>
> (1) Since only the main outs are connected to the FX system, I suppose I could always use it was a non-FX E-Mu/sequencer/ controller using the sub outs. Still, it would be nice to have the FX working.
>
> (2) Putting FX into bypass mode does not get rid of the noise.
> --- In xl7@yahoogroups. com, "steve_the_composer " wrote:
> >
> > Does anyone have a solution for an FX RAM failed error?
> >
> > I have a backup P2500 that hasn't been used in several years. It used to work flawlessley. However, when I went to test it, there was an awful noise coming through the headphones. Everything testable in diagnostics passes, except FX RAM. I cannot imagine it would would have failed from lack of being used, but who knows. Any thoughts, suggestions? Is it possible to replace the FX RAM? If so, how? Thanks.
> >
> > --Steve
> >
>

Emu XL-7 & MP-7 User's Group

Re: [xl7] Re: HELP: FX RAM failed error

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