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Post by feijai on Feb 17, 2024 21:11:10 GMT
I picked up a MultiFX and am wondering about some things. There are two basic Reverbs (Reverb 1 and Reverb 2), and their parameters are each reverb time, high filter, and low filter. This is unfortunate because there doesn't appear to be a parameter for predelay prior to early reflections: both reverbs have LONG initial delays, so neither of them sound like a room or even a chamber: they both sound like rock arenas. :-(
I would sacrifice Parameter 2 (High Filter) in a heartbeat in order to shorten the initial delay time. As it stands I don't think MultiFX has any reverbs suitable for "typical" reverb.
What is confusing to me about this is that on the Wiki it describes the Par 1 knob in general as "Pre delay / room size". But I don't think any of the effects have Par 1 as a pre delay. Did something change?
Also unfortunate is that there are both wet and dry knobs, rather than a simple wet/dry knob. One wonders if a new firmware revision could allocate one of those knobs to a Parameter 4 (for, for example, early reflections).
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Post by astroman on Sept 18, 2024 13:30:47 GMT
There are only 3 knobs to assign parameters, so a 4th one would be unobtainium  One could (kind of) extend parameter count by defining pot ranges, though. But then then parameters would be exclusive: one or the other. The pot range of the MultiFX is 0 to +3.5V, while the Z-DSP is zero in center position and -/+ 2.5V at the ends. (according to documentation) That doesn‘t mean they use more parameters, but pot response is different, which is my subjective impression when running a Z-DSP card in the MultiFX. Imho the 2 reverbs on MultiFX aren‘t intended to compete with high quality studio devices. Not necessary anyway as Reverb always depends on context. Something working great on drums may suck on synths... or fail on guitar. In particular the latter is often a surprise. Many „trash“ reverbs simply rule on 6 strings, while high quality can even be annoying. YMMV. Of course an eeprom update at some point in time is possible, but I‘d rather expect a dedicated module then, not a „Multi“. |
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Post by leethargo on Sept 21, 2024 9:31:33 GMT
when running a Z-DSP card in the MultiFX. Does that mean you replaced the chip on your module? Are they for sale somewhere? |
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Post by astroman on Sept 21, 2024 13:30:05 GMT
Yes, I took the basics from this thread (2021) forum.aemodular.com/thread/1630/tiptop-audio-dsp-card-multifxZ-DSP cards are available from multiple sources, mine (ZVRB70,80,90) were from Schneiders Laden in Berlin. I considered this as a 2 part evaluation for the AE environment and the Z-DSP reverb quality. (but admittedly should have done some more investigation before diving in...) I‘m not unhappy with the MultiFX at all, powered by USB 5V from a MacMini M1, audio in/out by iConnectAudio4+. Noise floor on wet signal is in the range from -57 to -60dB, quite solid for a single unshielded module. Of course „budget“ strikes at AE. I fully get the idea of the concept and even found myself searching for improvements, but that‘s really a tough one. Bottomline (in my case) Z-DSP would have been the better choice, even at 4 times the price tag. It has full 2 path audio io, 2 path feedback with patch inserts, variable clocking, better control design and display. (for obscure reasons I only found a picture of the Z-DSP circuit board too late) Problems when running a Z-DSP card on the MultiFX: the program selector hides the first 2 algorithms of a Z-DSP card because it switches to the 2 internal programs. I would have expected them at a different location, but failed. Long story short: to get access to the FV1, I had to remove the program selector/display, added a 3 part binary switch and pulled up line 13 on the FV1 to get access to the external eeprom. Remove means it had to be unsoldered. Program selection works, but parameters often seem off, in particular the 1st is frequently not active at all. As mentioned there may be range differences due to the -2.5V zero +2.5V reading of the pots on Z-DSP.(I still had great fun with the ZVERBS card set and reverb quality indeed fulfilled expectations) My main point (to check these reverbs) was the variable clock feature of the FV-1. MultiFX has a fixed clock at full and half frequency, which is ok in most cases, just not in this very specific one. I have a ton of reverbs, some high quality, but all of them are (of course) fixed at the audio sample rate. The feature is similar to old samplers like the Akai S900 where variable bandwidth (sample clock) leads to different results in audio processing. |
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Post by astroman on Sept 28, 2024 21:17:04 GMT
Sorry for spreading nonsense: while the Z-DSP‘s doc mentions a Pot CV range of -2.5 to +2.5V it does NOT say this is passed on to the FV1. FV1 specs clearly state 0 to 3.5V as Pot input voltage, so a fundamental difference of handling Pots in code is unlikely. (I‘d better checked the spec sheet more thoroughly)  Noise floor after some signal tweaking stays below -60dB and it‘s plain white noise, with no buzz or hum. Good. It‘s worth to balance input and dry/wet according to momentary signal level. Feels a bit unusual initially, but it‘s surprisingly quick once familiar with the dials reaction. I also liked the clock/2 mode. It colors significantly and stretches (of course) time scale. Not as crazy as continuous clock, but a welcome addition.  |
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Post by feijai on Sept 29, 2024 5:23:55 GMT
So a little more on the MultiFX. This unit uses the FV-1 IC as we know. The FV-1 has 16 slots for effects patches. 8 slots are hard-coded in ROM and 8 are programmable. These correspond exactly to the patches on the MultiFX: the first 8 are the FV-1's hard-coded patches.
In my opinion many of the FV-1's 8 hard-coded examples are bad. Reverb 1 and 2 don't have an initial delay time among their 3 parameters, which is just an amazing omission. And the Shimmerverb is really poor, bright and weird. However TW's own 8 offerings in the programmable section are pretty fun. But there are MANY open source FV-1 programs available, including lots of reverbs much better than the ROM defaults. It'd have been good for the MultiFX to have offered some path to program the 8 programmable slots so we could add some better reverbs, short of hacking the board as you are!
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Post by astroman on Oct 1, 2024 15:13:05 GMT
But there are MANY open source FV-1 programs available, including lots of reverbs much better than the ROM defaults. It'd have been good for the MultiFX to have offered some path to program the 8 programmable slots so we could add some better reverbs Yes, some expansion path would be well worth the basic quality of the FV-1 capabilities. I was quite surprised when running (as an example) ZVERB‘s 70s Hall in A/B mode with Relab‘s QuantX. Of course both are different, but feature a similar character and both could have made it into a final mix. Which is almost bizarre comparing the amount of programming/processing that went into each of them. FV-1 is a few kilo bytes, QuantX some hundreds of mega bytes. (if one only cares about sound, it doesn‘t matter that QuantX emulates a vintage unit as close as possible) So there is quite some potential in the MultiFX. I’d rather sacrifice the internal ROM for 2 eeprom sockets with selection 0-7, 8-15. (afaik it‘s not too difficult/expensive to write an eeprom outside of the module, only to be safe) Also the 2nd audio path would be worth activating, because it offers more than just stereo capability. F.e 2 different fx on 1 input or serial processing, possibly including a feedback path. (atm it seems input is buffered by 1 section of the MCP604 opamp while the other 3 are engaged elsewhere) Anyway... I don‘t want to come over as complaining about my 1st module. In fact it serves me well and I‘ve already learned a lot by it. |
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Post by rockysmalls on Oct 1, 2024 21:54:55 GMT
So a little more on the MultiFX. This unit uses the FV-1 IC as we know. The FV-1 has 16 slots for effects patches. 8 slots are hard-coded in ROM and 8 are programmable. These correspond exactly to the patches on the MultiFX: the first 8 are the FV-1's hard-coded patches.
In my opinion many of the FV-1's 8 hard-coded examples are bad. Reverb 1 and 2 don't have an initial delay time among their 3 parameters, which is just an amazing omission. And the Shimmerverb is really poor, bright and weird. However TW's own 8 offerings in the programmable section are pretty fun. But there are MANY open source FV-1 programs available, including lots of reverbs much better than the ROM defaults. It'd have been good for the MultiFX to have offered some path to program the 8 programmable slots so we could add some better reverbs, short of hacking the board as you are!
yes indeed, i’ve been hoping ( and i’m sure many others too ) for some revamp on this sometime ... wish i had the skill set to do something , but there are plenty of super-clever peoples on here that probably could ;-) |
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Post by astroman on Oct 26, 2024 0:19:58 GMT
Almost 1 month later... tweaking the MultiFX on literally hundreds of DX7 presets, with (sorry) the alien ZVERBZ. Audio quality is really nice, but seriously: that fixed clock is such a missed opportunity. MultiFX switches the clock via 2 resistors of 10k each for the high/low setting. After replacing the resistors by a 50k pot dialing from the (lowest) most grainy sound to the highest (and stall the osc) was possible. (attn: ear piercing, don‘t try with speakers connected)  A 2.5k trim pot (adjusted to prevent the stall) combined with a 10k pot gave the full range of sound, but avoided the radio like low end. 25k for the action pot probably would get into that territory, too, but wasn‘t available. Anyway, the most significant experience was how useful this variable clock was. I expected hickups, but could move the dial quite fast, even over the full range. (it‘s a rather simple mod with almost no circuit redesign) Btw I used an ALPS pot which is way better than the no names on MultiFX. Imho the 1.2€ (single qty) are well worth the improvement. |
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pol
Wiki Editors
Posts: 1,349
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Post by pol on Oct 27, 2024 15:36:39 GMT
Almost 1 month later... tweaking the MultiFX on literally hundreds of DX7 presets, with (sorry) the alien ZVERBZ. Audio quality is really nice, but seriously: that fixed clock is such a missed opportunity. MultiFX switches the clock via 2 resistors of 10k each for the high/low setting. After replacing the resistors by a 50k pot dialing from the (lowest) most grainy sound to the highest (and stall the osc) was possible. (attn: ear piercing, don‘t try with speakers connected) A 2.5k trim pot (adjusted to prevent the stall) combined with a 3.3k pot gave the full range of sound, but avoided the radio like low end. 10k for the action pot probably would get into that territory, too, but wasn‘t available. Anyway, the most significant experience was how useful this variable clock was. I expected hickups, but could move the dial quite fast, even over the full range. (it‘s a rather simple mod with almost no circuit redesign) Btw I used an ALPS pot which is way better than the no names on MultiFX. Imho the 1.2€ (single qty) are well worth the improvement. Could you take photos of what you actually did? Not being that confident with my electronic skills, not sure I fancy tackling this blind!
Ta.
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Post by astroman on Oct 27, 2024 20:42:08 GMT
The oscillator is a CD40106, together with C33 and R50, 51 on the right bottom of circuit, above the power connector. It‘s hidden below the display but the cap and the 2 resistors are the rightmost parts in that area. I didn‘t trace the high/low switch logic, but audio suggests 5k for high (parallel), low 10k. In my case the MultiFX was considered „experimental“ anyway, but I wouldn‘t suggest mechanical force or excessive heat to get the resistors off.    (the „insert point“ for the trimmer/pot series would be the outmost pads of the previous resistors) It‘s the most simple oscillator, see www.fluxmonkey.com/electronoize/40106Oscillator.htm for reference. On their Oscillator 1 example replace 1,2 by 5,6 and that‘s what is on the MultiFX. Nevertheless it‘s a surprisingly solid solution, as mentioned it scales really well. Sorry for the „not so gentle“ treatment of the module...   |
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Post by astroman on Oct 30, 2024 22:54:41 GMT
A short sound snippet while turning the clock pot. 1 note at 90 bpm, sound from chip synth OPS7, the patch is called ARP2600. It's program 4 "Tape -> Plate" from the ZVRB70 card.  |
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