LTC1799 on Alesis Hr-16

[heat00hunter]

Hi
I sell one of my Alesis Hr-16:

LINK REMOVED BY ADMIN

[Circuitbenders]

Links to ebay auctions or places where you are selling circuitbent machines are not allowed, sorry.

In the forum rules it says:

* Links to ebay auctions, ebay shops or other places where you have circuitbent machines for sale are not allowed and will be removed. Links to unbent machines people might be interested in buying are fine.

[heat00hunter]

Ok sorry guys.
Just unbent are authorize. 

[Circuitbenders]

 I thought i'd give this a go so i just installed an LTC1799 on one of my HR16's for the first time by cutting the clock connection going to pin 37 of the ASIC and replacing it with the LTC clock. Annoyingly it won't actually pitch very low before a high frequency whine starts creeping in that changes pitch as i pitch the LTC down.

Does this always happen on HR16's or have i done this wrong somehow?

[Gordonjcp]

How low do you get before it starts getting in?  Is it possibly the sample clock breaking through at audio frequencies?

[Circuitbenders]

if i'm reading my scope correctly the whine starts when the LTC1799 is running at about 2.5mhz and gets louder and pitches down as i slow down the LTC clock.

Might the whine be happening all the time but either my speakers can't reproduce it when the LTC is running faster than 2.5mhz, or my ears just can't hear that high?

[Z3R0]

Happens with just about all digital drum machines i'm afraid. Keyboards too. The lower you go the worse it gets until you can't really hear the sounds anymore. One of the few i've pitched is one of the newer dd's. I can't remember which model. They have glowing rings around the drum pads. DD30 maybe.... Anyway, they don't seem to suffer from it. The samples are probably a much higher resolution or maybe the clock runs much faster than in older machines. I can't remember which of the three speed configs i had the ltc set to in the newer machine.

The tr505 does it too.

[Circuitbenders]

hmmm, i've pitched a TR505 with an LTC before and didn't have any whine issues, but maybe i just didn't take it low enough. I've certainly never experienced noise as bad as on this Alesis.

[Z3R0]

It's possible. I think i had the ltc set to its lowest range when i did the 505. You could pitch the drums a bit higher and way lower.. I think.....

Since i tend to lean towards trying to make anything i mod as violently noisy as possible that probably is the case.

I think on all the DD vids i've done there's a lot of it. It was initially tempting to trim the pot but then i thought why bother. It's kind of defeating the object of it all. Why prevent it making a noise that it couldn't make in the first place...

[Circuitbenders]

If you want to avoid the whine on a HR16 i'd recommend using a 22k Linear pot and a 4k7 resistor as a limiter . This gives you the maximum range up and down without it cracking up at the top or starting to whine at the bottom.

Having said that, i found that the whine is completely masked by playing any kind of top end stuff like the hats and it is useful to be able to pitch that low as it sounds brutally nasty.
I think what i'll do is have two pots. The 22k for the normal 'safe' range and another 22k in series that will let me take it lower if i want but will otherwise act as a kind of limiter.

[Z3R0]

yeah. If i remember right i had two pots on the tr505's i did. A 100k for coarse tuning and a 10k for a signifigant sweep within whatever range it was set at.

I've got a couple more of them and a couple of 626's but have left them alone. When i do another one i want to be able to rom swap it. Which i think i could do now with the info out there but have yet to try.

Glad i bagged them when i did. Someone on ebay seems to be buying them all and putting them back up at £99.99 :/

[Gordonjcp]

Somewhere I've got the info on how the ROM is encoded - the address lines are scrambled up, which makes it easier to route the board but harder to brew custom ROMs ;-)

[Gordonjcp]

100 quid for a 626?  All the more reason to crack on with an alternative then!  I'm surprised at the lack of enthusiasm here for the AVR-based sample playback stuff I've been posting about ;-)

[Z3R0]

Somewhere I've got the info on how the ROM is encoded - the address lines are scrambled up, which makes it easier to route the board but harder to brew custom ROMs ;-)

I recently stumbled upon some good 505 Rom burning info. Making a loom to do it. I think the guy doing it couldn't get two of the samples to work though. He might have got around that by now.

As for the 626 for £100... It's actually the stash of £505's that are going for that. I've no idea what they're kicking the 626 out for and don't particularly care