if new roms do get burned, keep in mind that it is trivial to add
multiple roms to the 707. i have chips for both the 707 and 727 in
mine right now. all you have to do is solder all the pins of the chips
together, except the one labeled CE on the schematic, then wire those
CE pins to a switch that goes to the original connection for the pin.
you have to cut the original trace as well. oh and you have to add a
pull up resistor to the pin when its not in use. if anyone wants, i'll
post the details.

you could have multiple sets of new sounds with switches to choose
between banks. since there are only 2 chips for the main sounds and
one each for the cymbals, each switch swaps 5 or 6 sounds at a time.
you would be limited by the space between the circuit boards, if you
use sockets you can't fit as many. i think without sockets you can fit
maybe 3 roms in a stack.

i rather like the original sounds in the 707, by the way. they are
very punchy and in your face compared to a lot of digital drum
machines. of course, my music is housey and the sounds are perfect for
that.

--- In tr-707@yahoogroups.com , "acousmatique" <acousmatique@y...> wrote:
>
> The 707/727 must be the worst machine in this regard! It honestly
must be easier to burn
> new sounds for practically *anything* else.
>
> Going over the improved schematics which were posted a while back,
it is finally possible
> to see the pin numbers on the ICs. This means that the "scrambling"
is basically explained.
> With some kind and helpful explanation from Colin Fraser, I have
learned how to verify
> that these are as they appear, which I will do this weekend. If this
was the only issue to
> consider in making new sounds, it'd be really easy.
>
> The sounds used are of varying quality. For example, the crash and
ride cymbals each fill a
> whole SRAM chip. They are each 32kB, which is decent. Since they are
each on their own
> chip, with their own clocks and addres counters - making new chips
for these is fairly
> simple! One could replace these two cymbals with their own samples.
Just look at the
> schematic and see IC19 (crash), and IC22 (ride) - note the pin
numbers listed for A0-15,
> and D7-D2. Once I socket my chips, I will try this. (after I get
like three other big projects
> off of my bench, which I've had little time for this summer)
>
> What I would really rather do is replace other sounds, such as the
kicks, snares, hats, etc.
> The toms and hats are all 8kB samples. All of the remaining sounds
are only 4kB. This is
> pretty lo-fi. As each sound is decoded, a special envelope signal is
matched up with it.
> Also, lots of the remaining sounds are paired together: bass1+bass2,
snare1+snare2,
> rim+cow, clap+tambourine. So each pair is 8k, with the even
addresses being one sound,
> and the odd the other. And if this wasn't all difficult enough, new
samples in these places
> would still get the same pre-programmed (analog) envelope contour
applied to them,
> which may or
> not sound any good. I bought better quality scans of the service
manual from Mark
> Glinsky, so I can read the timing chart from "707svc-07.tif". Now
that I am beginning to
> understand all of this, I am less inclined to want to drop new ROMs
in. I will probably try it
> eventually anyway. Meanwhile, I certainly will try new sounds in
place of the cymbal ROMs,
> since they are relatively easy.
>
> What I am more inclined to do is do away with the Gate Array and DAC
entirely. I love the
> 707 interface, but this is a lot of work to get lo-fi samples.
Roland did this because it was
> cost-effective for them, but so what. Another consideration is that
some of us have
> already put tunable sample clocks in these machines - yet another
thing we no longer
> need the gate array for. Easier to just get a more EPROM-friendly
machine like a Linn,
> Drumtraks, DMX, etc, but of course this loses us the best X0X
interface in the world! I'd
> rather "maximize the potential" of the 707. Since I already fit my
707 for a board of clock
> circuits, I am going to try to make a better board with improved
clocks, along with voice
> EPROMs and DACs. A full 8-bit sample for each sound, put through the
707 audio board.
> The tricks in interfacing to the original 707 voicing circuits are
sending gates to sound the
> samples at the correct time, and applying the articulation. The
former I think is easy, but
> the latter I haven't tried yet. In the 707, the envelopes for the
sounds (except cymbals) are
> timed to change the DACs +reference. It should be possible to use
them from IC38 and
> IC39 without multiplexing them first.
>
> OTOH, maybe new SRAM samples are enough The grunge isn't horrible,
but new samples
> would need to be specially compressed and treated for the analog
envelopes. The
> envelopes themselves could be redone, but this means either
replacing parts each time the
> samples are swapped out, or adding yet more controls to my already
knob and switch
> covered 707. I think that reproducing the address circuitry around
the ride and crash
> cymbals is a little easier and will probably sound better. Once I
socket my machine and rip
> the ROMs though, I guess I'll try to make new sample sets.
>
> CJ - trying to decide!
>