Reverb pans...WTF

[Leo_Gnardo]

IMO you can get pretty good reverb sounds with the Belton bricks for $18.50. While they are digital you can keep the dry sound in your amp 100% analog.

They may sound acceptable but have a reputation for failing fast both in OEM builds as well as replacement in ordinary amps.

About 25 years ago one of my eagle-eared clients asked me whether he could safely use a digital reverb in his Deluxe Reverb. I reasoned, why not? as long as the mix is dialed full wet (so that dry signal won't cancel the amp's dry signal if it happens to be reverse polarity.) So we plugged in a MicroVerb and voila' - excellent reverb plus a choice of reverb types hall, chamber, plate plus decay length choice etc. You could do this with most any digital reverb & I've done it with an LXP1 with outstanding results. DDL's can be used in this application as well as multi FX units.

Lots of old digital reverbs kicking around for a dime on the dollar what they originally cost. Might not be the solution for everybody but at least they don't go SPROINGGGG! when you rattle the amp.

[bob p]

Eagle ears? That must be the corollary to dog eyes.

I'd be interested in hearing opinions on how well the digital reverb units respond to being overdriven. I've never heard a digital reverb unit (box or pedal) that didn't sound really *NASTY* when it saw too much voltage on the input and started clipping. I've always had to be careful to limit the input signal amplitude to a digital effects box because things can get really ugly when you don't. I don't like digital FX in the signal path of a guitar/amp because they require you to be vigilant about limiting voltage in the signal chain, and that goes against a lot of the tone-shaping objectives for electric guitars/amps.

My friend who was working on the theatre organ asked me about the digital reverb unit and I advised him against it. He tried it but ended up having similar problems -- the organ put out a large signal that would overdrive the digital reverb unit. The only solution was to redesign the send/return by attenuating the input and boosting gain at the output. He ended up getting rid of the digital reverb unit and using a new pan.

I'm worried about using the digital boxes because driving the device with too much level could be a problem. It may or may not be a problem with guitars like it was with the organ, because the organ puts out a huge signal. Maybe they'll work OK with guitars, but I'm worried about the case where a guitarist overdrives the input stages in their amp, and whether that would cause problems like it does on an organ. Something to think about, anyway.

[Mark Hammer]

Well that's just it, isn't it? Guitar amplifiers' use of reverb pans is designed around the properties of those pans. Not just in terms of suitable input and output levels, but in terms of tone shaping as well.

That is not to say digital modules can NOT be inserted. Heck, lots of amps are making effective use of the Alesis/Wavefront chips or the Spin chips (FV-1), and heaven knows how many other chipsets. But they are inserted into the circuit in a manner that acknowledges their input level needs, the way that reverb pans have been used. Again, the amplifier's front end is designed around the properties of the chips.

Are digital reverb chips/modules suitable replacements for spring reverb pans? Yes. Are they complete replacements? No. Craig O'Donnell had a terrific article in Polyphony, 30 years ago, arguing that very point. I was sure I had scanned and posted it, but can't seem to find it, so I'll summarize it. O'Donnell's point was essentially that, as a mechanical system, reverb springs can be made to behave differently, depending on how you push them. Essentially, they can be dynamically controlled in a way that maybe some digital units can, but not during performance.

[Leo_Gnardo]

Eagle ears? That must be the corollary to dog eyes.

I mix my metaphors with a big rusty runcible spoon. If that's not handy a splintered canoe paddle will do.

The guy who tried the MicroVerb was so happy with it, he made a bracket & stuck it inside the back of his Deluxe where he could easily reach the controls. And left it there for many a year. His playing style is very dynamic, and he never complained about any digital overload racket.

Another old friend who once worked for Lexicon told me one of their "house secrets" was a limiter right at the input to prevent (as much as possible) digital overload. So . . . if you're tempted to try a digital reverb/delay in this application, Lexicon is a good bet. Any of 'em. But you might have a hard time squeezing a 224 into the back of your combo amp.

[Chuck H]

Greg Farres of UltraSound amps put together a reissue CD60 product for Dean Markley. Greg couldn't get the pans to sound and behave the way he wanted. So he used a Belton brick and made a few circuit mods. I was surprised that I didn't hate it. I thought something would be missing or notably "off" somehow. But it sounded fine.

[R.G.]

Another old friend who once worked for Lexicon told me one of their "house secrets" was a limiter right at the input to prevent (as much as possible) digital overload.

Quotation marks around "house secrets" is right!

Pre-limiting inputs is a good trick, and has been used forever. It was built into the USA Thomas Vox amps, for instance. I know of some older Boss pedals that do this before a delay chip. Even some "soft clipping" hifi/stereo amps do this.

It's not that tough to do. If the delay you're using has any kind of input maximum spec, you pick a pair of LEDs to use as clippers on the inputs so that the input simply can't go over the max input that would make a digital clip. The digital input never sees an out-of-bounds input, and is happy. Signals coming out are clipped, OK, but it's analog clipping, not digital.

If you have a 'scope and a signal generator, you can roll your own quite successfully by watching input and output with a sine wave and turning up the signal till the output shows digital clipping. Pick a resistor (4.7K - 10K is usually good) and a pair of LEDs to clip below the level of digital clipping.

[olddawg]

Quotation marks around "house secrets" is right!

Pre-limiting inputs is a good trick, and has been used forever. It was built into the USA Thomas Vox amps, for instance. I know of some older Boss pedals that do this before a delay chip. Even some "soft clipping" hifi/stereo amps do this.

It's not that tough to do. If the delay you're using has any kind of input maximum spec, you pick a pair of LEDs to use as clippers on the inputs so that the input simply can't go over the max input that would make a digital clip. The digital input never sees an out-of-bounds input, and is happy. Signals coming out are clipped, OK, but it's analog clipping, not digital.

If you have a 'scope and a signal generator, you can roll your own quite successfully by watching input and output with a sine wave and turning up the signal till the output shows digital clipping. Pick a resistor (4.7K - 10K is usually good) and a pair of LEDs to clip below the level of digital clipping.

Back in the 1970s when PA equipment was relatively expensive, I was always cobbling together large PAs out of available broken amps and such that I bought and repaired. I built several electronic crossovers for bi-amping systems. For input limiting I would use 4 diodes back to back across the input. It would clip any input signal at about 1.2v. It helped a lot when some if those old boards would put out a 10v max signal.

[Leo_Gnardo]

Quotation marks around "house secrets" is right! Pre-limiting inputs is a good trick, and has been used forever.

I don't know how sophisticated a limiter Lexicon used, I expect something a little nicer than back to back LED's but who knows. Their products always had a smooth sound, and when other brands were making aardvark noises, Lexicon's weren't. And Lex never let on about it in their product descriptions, didn't tout it in their ads. I think they let people listen and make their own decisions based on what they heard. How quaint & old fashioned. I can say I've definitely heard digital barking from the much more expensive Eventide and even AMS gear. Whoa, slap another 160, 1176 or LA4 or whatever you got on that input!

[Tom Phillips]

... I think they let people listen and make their own decisions based on what they heard. How quaint & old fashioned. ...

Right on! That's the way it should be. Customers come in because they hear good things about my work and like the sound of an amp that I refurbished for one of their buddies. That's cool. However, there are a few who start asking questions based on internet lore. "Are you going to use NOS Carbon comp resistors?" "Will you replace all the caps with Sprague orange drops?" Do you use cotton covered wire?" Etc, Etc. My answer is always the same. Listen to the amp...Close your eyes and set the controls where they sound good to you. Don't worry if your friend's Deluxe Reverb is louder on "2" than yours is on "3." Etc, etc, etc.
Cheers,
Tom

[Leo_Gnardo]

"Are you going to use NOS Carbon comp resistors?" "Will you replace all the caps with Sprague orange drops?" Do you use cotton covered wire?" Etc, Etc.

Good stuff Tom & I'm sure many others on MEF do similarly. I use NNS carbon comps as well as NOS, depending on the function. Also resistors made every other way again, depending. I wear cotton underwear while wiring up the amp, and keep a candy dish with orange drops for customers to chew on whilst they wait...'' but seriously now I generally keep OD's out of audio circuits, they sound "clacky" to me. Although they are very reliable, can't say I've ever seen one damaged. Been enjoying Mallory 150 after I found them, and before that Xicon metallized polypropylene. Xicon seems to be gone now, at least they're not in the Mouser catalog anymore. Before them I got good tone & reliability with Siemens film caps from Active/Future Electronics.

[Chuck H]

I used a butt load of Xicon stuff when I was starting out (cheaper!!!) and I never had any trouble with it. I do think Mouser still sells plenty of Xicon product. At least they did the last time I checked. I stopped using CC resistors because I can't hear any difference other than hissssss! I did use orange drop caps, until they started charging a premium for them! Five bones for a coupling cap?!? C'mon. I used the OD polypropylene 715's. I liked them because they're more temp stable. My amps sounded the same whether they were worked hard or just played a short time at bedroom level. Kind of a big deal with me. If your tone inspires you, you don't want to find yourself dealing with a different sound in the middle of the second set and have it affect your playing! But the nerve of doubling the price over the last few years is offensive. I've switched to Panasonic polyester caps. But I liked the Mallory 150's A LOT when I used them on a couple of builds.

Same story with the Atom caps from the same maker as OD's. The price went up as the performance went down. Now using Nichicon PW's for filtering. I had to adjust my build MO to suit the radial leads but that was really NBD.

EDIT: Hey... Just checked Mouser and it seems that Xicon is still making CC resistors, film caps and aluminum electrolytics that mouser distributes. BUT... More significant is that all the OD caps (715 polypropylene and 225 polyester) are either obsolete or marked to end as such. OD caps are history it seems. Sort of a big deal I think. Glad I was off the boat before it sank.

EDIT2: It looks like the blue ATOM caps are going away too! I'll guess the price increase over the last couple of years was an attempt to make some $$$ off the mojo rep of OD and ATOM caps. I feel like a shower!!!

[Leo_Gnardo]

Same story with the Atom caps from the same maker as OD's. The price went up as the performance went down. Now using Nichicon PW's for filtering. I had to adjust my build MO to suit the radial leads but that was really NBD.

Roger THAT. I'm using filter caps I get from Magic Parts (Ruby Tubes) that have worked well & cost reasonable, even cheap in quantity.

A couple weeks ago I posted a link to our friends at The Amp Garage who dissected & photo'd some caps. Atoms are loaded with a smaller (regular size) cap plus stuffing. Some caps found on ebay are obvious pulls, radial caps loaded into axial shells, even underspec voltage caps stuffed into bigger shells. A year or more back Audio Asylum had a similar expose' and found hi voltage 600-800V caps that were series connected & loaded into familiar "dynamite stick" configuration such as we find in old B-15's. No balancing resistors here. Also just out & out counterfeits. If Mesa can blue-coat Illinois & other caps to look just like Atoms, no reason anyone else can't. I expect now that Atoms are going out of production, fakers will start showing up on the market. Same for OD's. Just keep a bucket of orange paint around & you can turn any cap into an OD. There's already some folks who have "personal label" OD's, Torres for instance. Where does he have 'em made?

So, stick with well known distributors who vet their stock & all should be OK.

Try this link for photos & discussion of capacitor bogosity:

The Amp Garage :: View topic - Inexpensive Electrolytic Capacitors

Well we've wandered well off topic but I think we kicked the heck out of the reverb pans too. Can't ya hear 'em - ka-KLANG-ang-ang....

[Steve A.]

But I liked the Mallory 150's A LOT when I used them on a couple of builds.

I like the Mallory 150's- to my ears they similar to the 418P polyester Orange Drops and fit much better on circuit board. I just looked on the Torres site and he is selling his "special secret formula" 418P's for $5 to $8.50- or you can get a matched pair of 0.1uF caps for $28! He buys them in bags of 1000 I think so he'll probably have them around quite awhile at those prices. The only thing I really like about the big OD's is that they are great for intentional parasitics! I think that might be the reason they work really well as the tone caps in the BF/SF amps- those caps are right next to each other, chattering away in their own cosmic language. Orientation of the outer foil side is very critical for parasitics (whether you want them or don't want them.) I just ran across one of the OD caps that I had wrapped with wire to induce parasitics- I need to take a picture of that and post it.

I have only heard the Belton brick in a foot pedal- the Malekko Spring Chicken which was discontinued a few years ago and sounds better than the spring reverb in many amps. I think that you would want a more sophisticated limiting circuit than diode clippers- maybe go back to the Craig Anderton opto-isolator circuits in his books and start from there. I guess people are making their own opto-isolators these days...

Steve Ahola

[Chuck H]

Well we've wandered well off topic but I think we kicked the heck out of the reverb pans too. Can't ya hear 'em - ka-KLANG-ang-ang....

I looked into the MOD tanks and it seems that the standard long decay vintage "Fender" type tank is sold everywhere. But IMHE when you order a long decay tank you always get a tank that's closer to the long end of long decay. And for modern guitar that's too long. So I'm looking for a medium decay tank. I'll probably have to get the three transducer tank since it's the only MOD distributed tank I can find. MOD does make a medium decay two transducer tank with the vintage impedances, but I can't find a vendor!?! So there you go. I've read good things about the MOD three transducer tanks anyway. So it's all good. I'll report back when I've heard it. Could be awhile.

I didn't know that Mesa was using other cap brands and coloring them blue! That's interesting. But I haven't had a Mesa amp on my bench in a decade. I don't do repair for a living. I think it says volumes about a company that will cosmetically mask their attempt to find cheaper, or even more suitable parts when they choose to hide it from their customers. Never been a Mesa fan anyway.

[Leo_Gnardo]

Don't neglect the short tanks - I recently had a nice old Jim Kelley amp in for servicing. Amongst other things the tank was shot (and nearly impossible to remove). I tried all my long tanks & none of 'em were getting along. So I started auditioning the shorties I had in the tank box and one of them sounded really sweet. I think it was a MOD. So in it went. With a lot less fuss than removing the old one.

Chuck I'm not sure you'll like the 3-spring tanks. I've avoided them entirely. Every one I've heard has an RT60 (decay time) of 15 seconds or more. Arena reverb, just ridiculous.

And Mesa's filter caps, at least they don't print ATOMS on them. The manuf. is represented on the blue wrap but I think the blue cylinders are a way to fool those who don't look closely enough and assume they're ATOMS.

You can always talk to or email the folks at CE, find out if they can source any of the "special" MOD tanks. Worst that can happen is "no", right. Sometimes I've been disappointed that something in the catalog is unobtainium, not only at CE but lots of other places (Chicago Transformer for instance.)