Mini digital reverb?

[Steve Conner]

Hi all

Does anyone know of a very small and dinky digital reverb? I'm looking for something that I can build into the chassis or cabinet of an amp, and maybe even run off the heater supply with a rectifier and regulator. Basically like a sort of 21st century spring reverb tank, that doesn't need all those driver tube and transformer gubbins, and can offer other sounds too. (and doesn't go Sproinnngggggg if you bump the amp)

I started out with an old Digitech Studio Twin rackmount unit wired up to the effects loop. I think it sounds great, but it's never going to fit in the cabinet. It has loads of guts and uses a lot of power.

I checked out the Alesis Nanoverb and Picoverb, but they are a bit expensive and need 9V AC, and I don't really have room for another transformer.

I also saw the RA-FX3C module from Resolute, that is tiny, pretty cheap, and only needs 5v DC. But since it's only like $25, surely it's going to sound terrible :rolleyes:

Another option would be the digital FX chipset that Alesis sell. I think it's basically the guts of the Picoverb. It's not too expensive and they have a good reputation for sound quality, but it needs a PCB made :(

Has anyone experimented with stuff like this before? I'd be interested to hear your $.02.

[Ray Ivers]

Steve,

I haven't heard one, but the Danelectro DJ-4 reverb pedal is only $30USD; perhaps you can find one over there to try out.

Thanks for the info on the RA-FX3C; the datasheet looks impressive. I guess they also offer the RA-FX1V, a few more algorithms for 3GBP more. This PCB looks similar to one I pulled out of a 15W SS Crate amp, so maybe all the built-in-FX amps are using the same PCB.

The Nanoverb converts the 9VAC to +/-5VDC; don't know if that makes a difference for you or not. I really like the Nanoverb, it's what I'll be using in my amp (I hope it'll fit!).

Ray

[Mark Hammer]

Go over to the diystompbox forum, specifically the digital sub-forum, and check out the Fem-to-Verb project. This is based on the Alesis/Wavefront chipset, and produces 16 different digital effects. It is seemingly the basis for a LOT of built-in digi-FX in budget-conscious amps, but apparently delivers half-decent reverb. One does not have to use all 16 effects programs if one does not wish to.

A tested board layout is posted on the forum. Note that it assumes one has the chops to solder surface-mount chips. I made one, and it was relatively easy to "sweat" the chip into place, but unfortunately I put it together prior to when a few layout errors were noted by forum members. While those have since been corrected, I haven't got around to re-making it so I can't comment from first-hand experience.

I'm not sure if he carries them...yet...but folks have been pestering Steve Daniels at Small Bear Electronics to carry them.

[Steve Conner]

Hi guys,

Thanks for the info. Mark: I noticed that a local electronics supplier carries a ready-made board with the Alesis/Wavefront chipset and a couple of op-amps on it, for about $40. It has connections for power, audio, and the 4 digital lines for choosing what effect program you want.

I guess I'll be trying to order one of those.

[Gregg]

a ready-made board with the Alesis/Wavefront chipset and a couple of op-amps on it, for about $40

This is interesting and well worth the money saving the hassle of ordering from Wavefrontsemi and soldering SMDs. Can you post a link and keep is informed on that?
I've already built the Femtoverb using the layout from Aron's forum and I like it but next time I would prefer a presoldered board if possible.

[Mark Hammer]

I would also be interested in the supplier particulars. That's a decent price for the unit. Obviously, one can keep an eye open and find a Pico-Verb second hand for a decent price, but a populated board like that permits easy insertion of digi-FX into an amp.

[Steve Conner]

http://www.profusionplc.com/cgi-bin/gex/pcatdtl?ipartno=AL3201-RVB
:D

I don't know what size, shape etc. it is, but if you hang on I'll post pictures of mine when I get it, and document my install of it into an amp.

[Mark Hammer]

Thanks, mate.

[Steve Conner]

Another forum member just sent me a message telling me about this:
http://www.behringer.com/FEX800/index.cfm?lang=ENG

It's bigger and uglier than even the Nanoverb, but it seems to have great tweaking options including a tempo tap button for the delay. When I'm practising I sometimes like to hook up a 1/4 or 1/2 note delay, it's kind of like playing to a metronome but more fun :rolleyes:

If I'd wanted that on the Wavefront chipset, I'd have had to write my own delay patch and add a microcontroller to upload it. So I'm tempted to get the Behringer thing instead and steal its guts. (or cover it in tweed or something...)

[Mark Hammer]

You might want to take a look at this chip as well from Spin Semiconductor.
http://www.spinsemi.com/get_datasheet.php?prodnum=SPN1001&pdf=FV-1.pdf

It costs $10@ in small quantities, but then you only need one chip instead of the 3 required by Wavefront, and it has 3 parameters to control for each program. Looks promising.

[Gregg]

http://www.profusionplc.com/cgi-bin/...tno=AL3201-RVB

29.00 GBP or 55.1392 USD for shipping outside UK something that costs the half??? Now that's a perfect way to do business!
Thank you very much! I'll skip.

[Steve Conner]

Update: I just bought a RA-FX3C from Profusion. (The shipping is a lot more reasonable if you live in the UK.) It was cheaper and smaller than the board I originally posted, and though I thought it was a different chip, it's actually based on the AL3201, with a Cirrus Logic 24-bit codec, and a micro of some sort that loads in 16 new effects programs- including a spring reverb yay!- in place of the Alesis originals. Also it runs off a single 5V rail, the other one needed split rails, so it's all good! :D I've already hooked up a voltage tripler arrangement to run my 12v channel switching relays off the heater winding, so I can regulate that down to 5V easy.

I still need to get a binary code switch to select the program, and figure out how to mount it neatly in the amp, and then I'm good to go. I guess I can hack it to let me choose between the Alesis programs and the new ones, too.

[Gregg]

Good to hear more digital reverb alternatives are becoming available.

[audiomaster]

Update: I just bought a RA-FX3C from Profusion. (The shipping is a lot more reasonable if you live in the UK.) It was cheaper and smaller than the board I originally posted, and though I thought it was a different chip, it's actually based on the AL3201, with a Cirrus Logic 24-bit codec, and a micro of some sort that loads in 16 new effects programs- including a spring reverb yay!- in place of the Alesis originals. Also it runs off a single 5V rail, the other one needed split rails, so it's all good! :D I've already hooked up a voltage tripler arrangement to run my 12v channel switching relays off the heater winding, so I can regulate that down to 5V easy.

I still need to get a binary code switch to select the program, and figure out how to mount it neatly in the amp, and then I'm good to go. I guess I can hack it to let me choose between the Alesis programs and the new ones, too.
r u complete the project? How it works? i'm using al3201.

[audiomaster]

Hi all

Does anyone know of a very small and dinky digital reverb? I'm looking for something that I can build into the chassis or cabinet of an amp, and maybe even run off the heater supply with a rectifier and regulator. Basically like a sort of 21st century spring reverb tank, that doesn't need all those driver tube and transformer gubbins, and can offer other sounds too. (and doesn't go Sproinnngggggg if you bump the amp)

I started out with an old Digitech Studio Twin rackmount unit wired up to the effects loop. I think it sounds great, but it's never going to fit in the cabinet. It has loads of guts and uses a lot of power.

I checked out the Alesis Nanoverb and Picoverb, but they are a bit expensive and need 9V AC, and I don't really have room for another transformer.

I also saw the RA-FX3C module from Resolute, that is tiny, pretty cheap, and only needs 5v DC. But since it's only like $25, surely it's going to sound terrible :rolleyes:

Another option would be the digital FX chipset that Alesis sell. I think it's basically the guts of the Picoverb. It's not too expensive and they have a good reputation for sound quality, but it needs a PCB made :(

Has anyone experimented with stuff like this before? I'd be interested to hear your $.02.
do u have electronic background? can try bd3201 with suitable adc/dac.

[audiomaster]

can any one sugest me the equv./replacement for AL1101(adc)& AL1201(DAC)
THNKS

[puretube]

http://www.diystompboxes.com/smfforum/index.php?topic=49130.0

[Steve Conner]

Yes, I have an electronic background. I'm actually an EE and currently designing computer-controlled lab instruments for a living. I have built and programmed DSP systems from scratch, and could make a digital reverb entirely out of Game Boy guts if I wanted to. But what's the point when I can buy a ready-made circuit board for a good price.

FWIW, the board I bought uses some Crystal Semi codec chip in place of the AL1101 and AL2101, I forgot the part number.

I haven't installed it yet as I was too busy partying over Christmas and New Year and the amp is now on loan to a friend who's using it for tracking in the studio.

[puretube]

AL3201 & CS4271... driven by a 8.192 quartz
plus: 2115 & a tiny ball-grid-array chippy I can`t decipher... (eprom?/µP?).

[audiomaster]

Sorry sir i dont want to heart you, I am new to DSP and want to develop programs. I have 3201 and like to complete. I dont have alesis made adc/dac. I understand that they are left justified. I'm searching substitutes. Can you help me any way?

Regarding DSP programing, is there any scope for designing DSP modelling
amplifier? any readymade board available?
regds.

[audiomaster]

AL3201 & CS4271... driven by a 8.192 quartz
plus: 2115 & a tiny ball-grid-array chippy I can`t decipher... (eprom?/µP?).

CS4220 WILL DO THE SAME THING?

[Steve Conner]

I think the tiny chippy is a uC that replaces the Alesis factory programs with 16 new ones, and maybe programs the config registers on the codec chip too.

Audiomaster, the problem with finding substitutes for those converter chips is that they only have wordclock inputs, and use an onboard PLL to regenerate the master clock that all sigma-delta converters need. If you make up your own master clock divider, or choose an ADC that has one, you can probably use just about any converter chips. Or 50% of them... I believe they fall into two categories, I2S and JIS, aka left and right justified, but there are other differences in the clock signals too.

Again though, that's another reason why I bought a ready made board! The last time I did this (at work) it took me a good few weeks of 9 till 5 work and >20 pages of lab notes to choose suitable ADCs and DACs, read all the datasheets together, figure out how to interface them to my DSP, and get all the config registers programmed, everything debugged and working, and the analog side free of noise. If you managed to get a 3201, can't you get the matching converters from the same place? It would make your life a lot easier.

For a DSP modelling amplifier, probably the best thing would be one of the Analog Devices SHARC evaluation boards. But the software that comes with them is crippled to 30 days, and then costs about $10k to buy. And you wonder why there aren't any hobbyist DSP modelling amps. :(

[audiomaster]

[QUOTE=Steve Conner;10802]I think the tiny chippy is a uC that replaces the Alesis factory programs with 16 new ones, and maybe programs the config registers on the codec chip too.

Audiomaster, the problem with finding substitutes for those converter chips is that they only have wordclock inputs, and use an onboard PLL to regenerate the master clock that all sigma-delta converters need. If you make up your own master clock divider, or choose an ADC that has one, you can probably use just about any converter chips. Or 50% of them... I believe they fall into two categories, I2S and JIS, aka left and right justified, but there are other differences in the clock signals too.

Again though, that's another reason why I bought a ready made board! The last time I did this (at work) it took me a good few weeks of 9 till 5 work and >20 pages of lab notes to choose suitable ADCs and DACs, read all the datasheets together, figure out how to interface them to my DSP, and get all the config registers programmed, everything debugged and working, and the analog side free of noise. If you managed to get a 3201, can't you get the matching converters from the same place? It would make your life a lot easier.

For a DSP modelling amplifier, probably the best thing would be one of the Analog Devices SHARC evaluation boards. But the software that comes with them is crippled to 30 days, and then costs about $10k to buy. And you wonder why there aren't any hobbyist DSP modelling amps. :

QUOTE: I'VE MANAGED TO GETA FEW 3201 FROM 'BDNC' BD3201 (NOT ALESIS MADE) AND THEY DO NOT PRODUCE ADC & DAC. THEY RECOMEND ME USE CS4345 & CS5344 (24BIT LEFT JUSTIFIED) BUT THRY ARE NOT AVAILANLE LOCALY.

FOR MODELING AMPLIFIER 'FENDER' IS USING TMS320VC5402 (FIXED PT. DSP) WITH CODEC TLC320AD77C. BOTH ARE TEXUS MADE. RIGHT NOW THESE ARE BYOND OF MY KNOWLEDGE.

ANOTHER THING, I WAN TO USE AN ENCODER (QUADRATURE OR A/B CODE) TO SELECT 16 PROGRAMS (WHAT 3201 OFFERS), WITH A PAIR OF 7 SEGMENT DISPLAY INDICATION. THE PROBLEM IS TO ENTERFACING WITH A 8051 CORE uP. DO YOU HAVE A IDEA HOW TO INTEFACE AVOIDING BOUNCING & CHATTERING.

[puretube]

4220? does it for B********

[Steve Conner]

Wow, I didn't realise the Chinese had managed to rip off the AL3201 :eek: Whereabouts are you? It can be pretty hard to get hold of specialised ICs in some countries, sure enough.

Yes, I do know how to do that thing with the quadrature encoder. There are lots of ways to do it, but a simple state machine with a 16-entry lookup table always worked for me. Debouncing is just a case of waiting for things to settle before checking them. The best way to do it often depends on the particular uC you're using, and I don't use the 8051, so I'll keep quiet.

[audiomaster]

[QUOTE=Steve Conner;10816]Wow, I didn't realise the Chinese had managed to rip off the AL3201 :eek: Whereabouts are you? It can be pretty hard to get hold of specialised ICs in some countries, sure enough.

Yes, I do know how to do that thing with the quadrature encoder. There are lots of ways to do it, but a simple state machine with a 16-entry lookup table always worked for me. Debouncing is just a case of waiting for things to settle before checking them. The best way to do it often depends on the particular uC you're using, and I don't use the 8051, so I'll keep quiet.

pl. visit www.bdnc.com for rip of al3201.

for encoder please explain a little bit.

[audiomaster]

[quote=Steve Conner;10816]Wow, I didn't realise the Chinese had managed to rip off the AL3201 Whereabouts are you? It can be pretty hard to get hold of specialised ICs in some countries, sure enough.

Yes, I do know how to do that thing with the quadrature encoder. There are lots of ways to do it, but a simple state machine with a 16-entry lookup table always worked for me. Debouncing is just a case of waiting for things to settle before checking them. The best way to do it often depends on the particular uC you're using, and I don't use the 8051, so I'll keep quiet.

pl. visit www.bdnc.com for rip of al3201.

for encoder please explain a little bit.

[Steve Conner]

Well, I finally got this thing working, for a while at least! I got a nominal 12V (actually nearer 10-11V) from the heater winding using a full-wave doubler circuit. Since the winding was centre tapped to ground, I ended up using a strange doubler circuit with 3 capacitors and 4 diodes. I also use the 12V rail to power the channel switching relays and some LEDs.

I soldered a small daughterboard to the RA-FX3C that held a 5V regulator, some coupling and bypassing caps, and some jumpers to select the effect. I couldn't find a convenient place on the amp chassis for a rotary switch, so I figured I would just find my favourite one and leave it there.

The RA-FX3C datasheet shows the input being driven by an op-amp: I used a 12AX7 cathode follower instead, since I had already wired that up. I basically spliced the board into the existing parallel FX loop that I had put in the amp a while back.

All of this worked great on the bench. I wedged it on the "Spring Reverb" patch and it sounded pretty decent. But when I put the amp back in its cabinet and tried it again this morning, no reverb :( I'm hoping it's just a loose connection, and not the tubes rejecting the solid-state transplant ;)

[Steve Conner]

It was just a loose connection, all working now :D

[audiomaster]

Hi Steve, nice work. But do you tried for the PGM-5 (one variable parameter)?
What codec they use with the 3201 core DSP? What are the part no U4 & U5?

[Steve Conner]

I never figured out what PGM5 did, and I forgot to note the chip numbers. I have some photos of the board though, I can get the numbers that way.

I did some more experimentation, and found that when I dimed the channel volumes, the ADC would clip horribly and make the reverb break up with a disgusting noise. I changed the gain structure to cure this (5x attenuation before the reverb, 5x more recovery gain) but now I get a lot of hum and hiss with the reverb control up full. Also the reverb sounds rough at low volumes. No amount of messing with grounding fixed the hum completely. I'll try an isolated supply instead of the present one derived from the heater winding, to see if that helps.

The amp is a channel switching non-master-volume design, with the reverb after the channel volume controls, so I guess it demands a lot of dynamic range from the reverb if it's to be usable at quiet levels as well as dimed. Adding a reverb send level control as well as the existing one (which is on the return side) would help with this, but spring reverb amps seem to get by fine with just one control.

Maybe spring reverb just has more usable dynamic range than digital reverb? Any thoughts on this? Maybe I could use some zeners or MOSFETs or something, to compress the reverb send signal at high volume. Or maybe the structure could be rearranged to put the reverb before the channel volumes somehow, but I can't picture how to do that. I think I have it wired similar to the reverb channel on the Deluxe just now, except the last stage before the PI is an anode follower that mixes the wet and dry signals, with a gain of 5 for the dry and 25 for the wet.

I have an old London Reverb lying around, and I'm thinking maybe I should just lose the DSP and steal the reverb pan out of that. Now I think about it, I could even gut it, build my tube project into the chassis and cabinet, and pretend I have a BFDR :D

[Steve Conner]

I tried powering the reverb board off a 9v battery instead of the rectified heater supply. The hum was gone completely and the noise and roughness seemed better too. So I guess I'll try fitting an extra transformer into the chassis to make an isolated supply just for the reverb.