Thursday, February 11, 2010

Tiptop Audio Z-DSP

Tiptop Audio Z-DSP Review: Part I
by Steven Hayes

The Hardware:

The Z-DSP is 28HP wide, with a sandwich of PCB's stacked in plane with the front panel, so it's not very deep in the chassis. It looks fantastic. The display is bright and clear. The knobs are the same as what Elby ships (not yellow thank god). The knob spacing is about as tight as I'd like, but the knobs don't have any jacks above them, so nothing gets too obscured by your lovely spagetti.The jacks feel solid and tight as one plugs and unplugs. The build quality is better than average (average = Plan B headphone amp I once inspected).

The DSP software cards are actually PCBs with two SMDs covered in "stuff". The socket for the cards holds tightly, so you shouldn't expect anything to drop out mid-performance. It wouldn't matter - you can remove a card while the current program continues to run. Not sure it was such a good idea to colour the cards black though…

I've got the Z-DSP running on ±15V rails with no issues (I did check with Gur first ;) .

Ins & Outs:

The Z-DSP has two audio inputs (you can select between guitar and "synth" level inputs via jumpers), four outputs (two for feedback), plus the ability to insert other modules into the feedback chain via two extra inputs.

The Z-DSP has three CV inputs that are assigned to the current software program, as well as dedicated CV control for left and right channel feeback amounts. There's also CV control on wet/dry mix, program selection, program direction. Last, but not least, is the clock input, so you can control the speed that the program executes at.

In use:

I only been using the Z-DSP for a few hours, and have been concentrating on the "Dragonfly Delay". I am already amazed at some of the sounds and complex drones I've been able to get out of it with the CV control of feedback and DSP assigned controls.

It's pretty easy to let the sound run away when modulating the feedback via CV, which will result in clipping and a red LED doing a dance. Oddly enough, I actually like the way Z-DSP's clipping sounds…

There are two facets of the Z-DSP that I'm particularly enjoying at the moment:

1. CV control of feedback. This is so much fun! It is so easy to discover rythmic patterns by modulating the feedback to a delay program via CV, for example.

2. External clock input. It's impossible to describe the plethora of sounds that can be created when you plug a VCO into the Z-DSP's clock input, grab the VCO's tune knob and slowly sweep it. One second you're hearing raw FM, the next a massive bass note, the next is a high pitched squeal, and lots of amazing artifacts in between. It's completely unpredicatable in a wonderful way. The Z-DSP will function with a low frequecy input to the clock, but the lower the frequency the riskier things become, and it may crash. Having said that, I understand that there is a clock multiplier in the clock input circuit. Right this second I'm sending a 22Hz signal to the Z-DSP's clock input - and it hasn't crashed - and it's making an interesting sound - cool.

Bat Filter

I've finally been able to unplug the "Dragonfly Delay" card and put the
"Bat Filter" through it's paces. 8 different filter programs are available, and they're not simple filters. Often there are two (even three) filters implemented in a program, some organised in series, others in parallel. Many of the filters are 8-pole too.

The filters sound pretty good, but I can tell they are DSP-based. There's a hardness, or at higher frequencies, a glassiness to the sound, that says "digital" to me. I'm not complaining however - I've got plenty of warm analog filters. The Z-DSP is all about flexibility after all, and that's definitely what we've got here.

Like the "Dragonfly Delay", the "Bat Filter" really got interesting for
me when I started messing with the feedback facilities of the Z-DSP. For example, take a CV from a sequencer and feed it to both a VCO and the "feedback" parameter in one of the Z-DSP's filter programs. Feed the VCO into the inputs of the Z-DSP too. The resulting distortion can sound really musical and really add character to the sound if you don't over do it. I like it!


I'm really impressed by the Z-DSP. It's a great concept, very well implemented. While it is easy to "get lost" with the Z-DSP, espcially when your CV usage is excessive, I've found that it can be incredibily musical when you don't ask it to do too much at once. I'm particularly fond of the "Dragonfly Delay" - It's just nuts! (in the best possible way)

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