Spring Reverbs again

[Roly]

No, I've been a ferric-chloride man, but I've been thinking about giving this a go for my next etch (which now may not be too far away) since I haven't had any FeCl since my last big move, and I'll do a photo-essay when I do.

[joecool85]

No, I've been a ferric-chloride man, but I've been thinking about giving this a go for my next etch (which now may not be too far away) since I haven't had any FeCl since my last big move, and I'll do a photo-essay when I do.

Excellent, I look forward to it!   :tu:

[phatt]

I take the idiot prize this month.
I purchased an LM1875 power chip and promptly snapped a pin clean off while trying to slip a short length of insulation on one of the pins. :embarassed:

So No updates as yet but I did stumble across a rather good page that might be useful for those interested in the inner workings of tanks.
http://www.modkitsdiy.com/spring_reverb_tanks_explained_compared

I've finally relented and swapped my original Maxiverb to a lovely chap who just would not except my constant excuses for not wishing to let go of my Reverb unit.
But hey I've scoured some nice stuff in the deal,, so little time left to work on my Tverb idea.

Phil

[phatt]

Well bugga me a mobile phone with a Spring Reverb how interesting :lmao:
Phil.

[bobhill]

Yup, another spammer snuck in. :trouble

[phatt]

Update,
        Finally had time to experiment and this is working well and is actually half built.
This time I etched a board for the test so as not to chance breaking any pins on the power chip.

Those tiny line transformers do heat up but I did have a larger OT laying around which works fine.
I did try a small mains transformer (12V/240) which also works but not quite as good.

I was tempted to try an LM383 but they are only single supply and I already spent hours on dual supply.
The LM1875 runs direct from supply but the other chips are fed by a regulated 12-0-12VDC.

Another week and I may even have some pictures of the finished product for U, meantime here is the rough schematic of the unit I'm building.
Phil.

[J M Fahey]

Are you aware you are feeding some 300V RMS to that poor little spring tank?  :duh :loco
Do the math     8|
That said, it may be KILLER reverb 

[phatt]

Yes I know you chaps must think I'm crazy,,, but so far no smoke. <3)

Here is the case and some bits that will be going into it.
The case is a dead feedback buster by Alto,, comes with psu, switches, trick front panel and the small rev tank fits inside.

That covers most of my cost and speeds up the build process big time.

Interesting to note that Rod Elliot (ESP) also mentions the use of LM1875 if you need more grunt for drive.

After about 4 hours of playing this new circuit with the Drive flat out nothing is getting hot beyond what I would expect, including the driver transducer in the tank, which is stone cold.
Bare in mind that the 1n5 cap going to the LM1875 cuts massive bass response. Bypass that 1n5 Cap and it sounds like mud and is then rendered useless.

My best guess is that most of the SState rev circuits around make little effort to cut bass which means you can't implement much drive as those transducers seem to be incapable of producing clean bass response.
Hence you have little chance of developing much drive and all that is left is lotsa gain on the pickup end which usually results in noisy reverb.
Even the big name Valve Amps are now mostly SS reverb circuitry and they are also mostly dead pan boring and hardly worth having.
Phil.

[phatt]

Are you aware you are feeding some 300V RMS to that poor little spring tank?  :duh :loco
Do the math     8|
That said, it may be KILLER reverb 

Thanks for the warning Jaun, :tu:

You chaps know far more than I ever will but all I can say is that it works and it shows no sign of going up in smoke.
I doubt I will ever have the capacity to understand the complexities involved but as I'm sure you can understand if the maths says it's about to go poof but in reality it sounds as good as any Valve driven rig I've ever heard then I don't
care much for the maths.

Maths??? Well I've learned a little but those transformer thingoz bend my brain and it often gets the better of me.
It's a bit like someone (who can only count to ten) punching big numbers into a calculator,, you get an answer but you have no way of knowing if it's right. You need to have enough knowledge to know if the answer is in the ball park.

Often I wish I was gifted to make useful comment but on the other hand with no formal training it's a journey into the unknown which is a fascinating hobby,, So Maybe that is the magic for me,, but with enough sense not electrocute myself.
Cheers, Phil.

[phatt]

Well it's done and it works ok,,,,,,but in truth probably not worth the extra effort. xP

OK scrap the LM1875,,and the 300volt stuff, 

A New plan.

A simple 1k/8R transformer may well be better. (See Schematic and pic)

I've been messing with all kinds of thoughts on Voltage /Current transfer and I'm still lost.
I may as well be eating too many bananas and slipping all over the place in stuff that is beyond me. 

But not to give up,, with dogged persistence I've arrived at this one which gives me all the treble back and the drive is much cleaner running.

A dual opamp doubler and the 1k/8R transformer is giving me what I'm after. <3)
(I think this just doubles the current?)

Interesting point here for me at least,, The Laney Amp Reverb already has the stacked opamp driver for reverb so I may just need to add the transformer and tweak a few values.

The Laney Reverb has way too much low freq on the driver end and you can't get decent drive without distortion due to too much low freq content and now that I've had time to reflect on these recent tests it seems I can improve that circuit without much effort.

The Laney is my main Amp and although basic and a little under powered it suits the smaller gigs I play so I don't want to have it all in bits for weeks on end trying to improve it. But now I think I understand what needs to be done to improve it. Lets hope it works.

This Reverb circuit should not be too hard to build and the addition of one cheap Transformer which I think are a common device that most will be able to source without much hassle. You just need a 1k/8 Ohm 350mA line transformer which are cheap as chips.
And again the whole thing can run from a single supply of 12-0-12 VDC.
With some alterations you may even get away with a single 18VDC supply but I doubt it will go well on 9Volts.
Hope you have fun with it.

The Laney mod will have to wait now as I've spent many hours and meanwhile the grass needs mowing and the house needs maintenance, you know all the boring stuff.
I must be improving as no devices lost their magic smoke during the tests, winky.

I'll update this when I get time to build the new circuit. 
Phil.
Edit; Fixed, Transformer drawn wrong way round

[phatt]

Busy at the mo,,, but I did finally get this built. See pic.

Very happy with the result.. :tu: :dbtu: 8|
This is as close to the original Maxiverb build I can get with a short tank. I will hopefully get some sound clips done soon so you can all hear why I get so excited about such a simple effect.
That tiny transformer makes a world of difference. :dbtu: :dbtu:
Cheers all,, Phil.

[phatt]

In between dogs barking and phone ring interruptions and the birds singing in the background  :grr
I did get a quick and dirty recording done.

Guit> Reverb> PhAbb Preamp> Laney> Mic off axis.
Recorded flat via a cheap Mixer into Lappy > Normalized and ripped into mp3.

Reverb is muted for the first few notes.
Phil.

[Roly]

Reverb sounds nice Phil.   :dbtu:

{The recording has a lot of "overs"; you need a compressor/limiter like...

}

[Roly]

Okay, this contains a lot of guesswork and assumptions, but it should give you a bit of an idea what is going on around your reverb line driver (and it looks pretty believable to me).


Parallel op-amp drivers->8r:1k transformer->springline driver 160r (160mH)

1000/8=125^0.5=11.1803398 turns ratio

[phatt]

Thanks for the input Roly.

Yep it's got plenty of top end and easy to get the spring excited. call me crazy :duh
With heavy Odrive you have to back it off a fair bit.
The recoding was done with the Dwell on 2, Depth at 4.

The curve shown does line up with my Circuitmaker sims even without the OT.

Oh dear Compressors,, I never liked them but if you reckon it will help maybe I'll give it another try.

I did breadboard a few Comp ideas some time back with the help of *mictester* from FSB, He seems to have an infinite working knowledge of those circuits. After many breadboard tests,, I gave up in disgust.

In my experience they are highly noise prone and no matter what design I used they NuffeN All my sounds. :grr

By the time you back off the dials to not sound like a comp you may as well not bother.
Dial them up for more sustain (which most players use them for) and the Noise then renders it all useless. I'm aware that studio stuff is obviously better designed but most pedal units are shocking.

Anyway,, back on track after my rant. 

When you say *Overs* do you mean the whole signal or just the reverb?

Maybe I could handle a comp on the reverb signal path But I'd bork at Comp on the Dry signal path.

I'm aware that the driver has big output and after a short gig at the local pub today it may need to be backed off a tad.

That chap Roy Mallory mentioned reso problems with the tanks and explained that Current FB circuits give better (flatter) results. I could not get his ideas to work but maybe I needed to spend more time with it.

Whether this flat response be a good or bad thing I have found that the Tanks themselves can differ quite dramatically and no amount of good circuit design maybe able to fix it. I have one tank here from a cheap Jade mixer and it reverberates for well over 5 seconds and has a shocking self resonance. The reverb also squealed like a pig at high volumes.

I assumed the driver circuit was the problem until it finally dawned on me that the tube end supports in the tank had No rubber grommets which are needed to stop this exact problem.
The whole build screamed of cheapness and short cuts so to be expected I guess.

So it seems that depending how much damping is done at that point in those support tubes greatly effects the Time result and sensitivity of the tank. I can only speculate and assume this may also help to balance out any self reso problems that maybe present.

Final Q.
Does the circuit you give do a a good job of *Limiting*?
That idea I've found much more useful for guitar than Compressors.
Cheers,, Phil.