Hi all,
I have been re-visting Reverb circuits so I thought I'd share my findings.
I scoured an old bit of junk a Ross 5 channel powered mixer. A rather poor performer for audio but did have a 3 spring 9 inch rev tank. The tank has high Z transducers at both ends. bum. :grr
My Maxiverb circuit will only drive the lower Z units so I came up with a plan and it certainly works way better than I expected. <3)
My original Maxiverb needed two supply voltages and had a rather oddball output but
This circuit only needs split 15 volt rails and lower parts count so it would be much easier to build.
So if you have one of those high Z reverb tanks this might just be the ticket for a very good Reverb unit that won't break the budget.
The small Output/Line Transformers should be easy enough to find and likely dirt cheap.
The DC reading is around 190 Ohms / 330 Ohms. The Resistance can give a clue as to the Z.
My guess is this one I've got is 600 Ohm / 1k Ohm Z.
I've spent a few days A/B testing between the original *MaxiVerb* and This one and although it does not have quite the big slap there is little between the two circuits.
The short tank does sound a tad different but on stage you would not be able to tell.
If you specifically need the country slap-back effect then you will likely need a long tank for that.
With short springs the slap delay is way too short to get that particular effect.
Just like the Maxiverb this one is bright and airy due to plenty of bass roll off which allows a higher output of reverb before it all turns into undefined mud.
With the Dwell full up this is dripping wet reverb reminiscent of the old surf sound which is what the Maxiverb does so well. Not quite the big tank slap of the Maxiverb but I hardly ever use that anyway.
As The Maxiverb (long tank) takes up more space the short tank might be well suited to a smaller chassis and I might even be able to implement it as a floor unit.
Time will tell, still a long way from a working unit but no point in rushing it.
I have no doubt that other chips will work just as well maybe even the tiny LM386 but it's single supply and may not have enough drive and you would likely need an 8 ohm/ 1k Ohm transformer.
I'm Not sure about the NE5532 as they have compensation pins I'm assuming they are not needed here but if anyone knows more about those fine details feel free to comment. :tu:
Anyone have a background on the 3 spring tank?
OC Electronics, Milton Wi and 2 long patent numbers, on the side reads 756
I assume Wi means Wisconsin?
Phil.
Cool !! 8)
Eager to listen to some MP3 !!! :dbtu: :dbtu: :dbtu:
You know, right as I posted that I somehow knew it would be You that would want to hear it working.
In time, in time. :-*
Sadly it's all under the bench for a few days until I redesign that Performer 1,000 I fixed a while back.
The owner now wants me to get rid of the massive bass response,, Wish me luck.
Meantime I'm going to try and find some other drive transformers for the reverb testing.
I might even go crazy and drive an 8 Ohm / 1k Ohm tranny with a LM1875. :duh
Heck why not? I hear it is BBQ season. ;)
Phil.
Well, you are known to often drive a puny tiny reverb coil from +/-35V rails. :o
If *that*'s not a BBQ, what is? 8|
Is the Performer a single 12"?
If so, it probably has a big heavy 2" VC , thick cone and heavy magnet.
If it's anything like the heavy speaker fit to Stage 100/160 combos or in pairs to Super Twins, it is a "bassy woofy" speaker and not getting any sparkle out of it is not your fault.
Kind of Physics getting in the way.
But cutting some bass at the first or second Preamp stages will help you .
At least Distortions (and "Clean") will be "cleaner", as in "less muddy".
Just for sake of comparison, try that amp with another more "normal" speaker(s).
@Phatt - I consider the NE5532 to be a bit of serious overkill for most situations.
My personal fave is the LM833 which is cheap, easy, and as close to a perfect amplifier as most of us will ever need. I changed the preamps in my Twin-50 from BC109C's to LM833's and now you literally can't even tell it's switched on with everything flat tack. And talk about bandwidth - the first incarnation took off at 455kHz(!) and I had to deliberately roll it off around 35kHz.
Thanks Roly,
well I don't think my springs will ever reproduce signal at 455kHz :lmao:
The NE5532 was sitting in my pile of trashed bits and I just wanted to see if my plan would fly.
Most of the reverb circuits found in gear I've seen/heard is not all that good and getting the drive end to move the darn magnet is the tricky bit.
While clearing out the bins of trash I found a few small line trannies I'd forgotten about and got a brain wave. I still have not cleaned out the bin, much to my wife's disgust. lol
Spurring this on also, a local player has heard my way out maxiverb and wishes to buy/swap for it.
Being it was one of my first success stories with Audio stuff it kinda erks me to sell it,,, but hey I can't keep stuff forever :(
So the challenge is to see if I can find a simpler way to get big drive energy to the driver transducer.
So while the original is still here I'm A/B testing some ideas.
I'm working on the idea that if I can get an output transformer to swing a big enough voltage then it may work.
@ JMF,
Thanks for the tips on the Performer 1000. I might start another thread on that soon as I'm interested in your observations about speakers and such.
BTW, I did get a 10 watt power chip to drive an OT for reverb drive (Z= 8/1k) and it ran stone cold.
Went fine for about 4 hours but I must have bumped something when the phone rang and my dodgy old BBoard must have popped a wire which melted the chip including the OT.
upon return I burnt me finger on the heat sink trying to establish why it no longer worked. :'(
While working it was very close to the same energy as the Maxiverb,, so maybe the idea has merit.
I'll have to wait for another power chip.
Phil.
Ugh !!
I don't trust push-in breadboards for anything carrying more than a few mA.
Not their fault, really, they just weren't meant to do that. :(
For power amp prototyping and such I *still* use the nails_into_some_wood type (usually chipboard leftovers).
They look like baby Alien nests but, who cares?
Quote from: J M Fahey on November 27, 2012, 01:48:46 PM
Ugh !!
I don't trust push-in breadboards for anything carrying more than a few mA.
Not their fault, really, they just weren't meant to do that. :(
For power amp prototyping and such I *still* use the nails_into_some_wood type (usually chipboard leftovers).
They look like baby Alien nests but, who cares?
You don't happen to have a picture of this, do you? I've never heard of doing this but it sounds like an interesting idea.
In my (pre)teens "breadboarding" was still literal, a lump of timber, some wood screws, and something like cup washers.
(http://www.prostitch.com.au/images/products/IMG_3470l.jpg)
(http://upload.wikimedia.org/wikipedia/commons/1/12/1920s_TRF_radio_manufactured_by_Signal.jpg)
My experiences of the modern plastic ones have been second-hand, but unfortunate, so I have no time for them - I just lash stuff up, Veroboard or "aero-board" (aka "birdsnest").
Wow!! That one predates me . my grandfather !!! ;)
Ok joecool, I'll take and post some pictures.
You will see the light ;)
I love it! Especially the "insulation is for whussies" approach to wiring. What is it? Regenerative receiver?
Quote from: JHow on November 30, 2012, 10:01:27 PM
I love it! Especially the "insulation is for whussies" approach to wiring. What is it? Regenerative receiver?
It came from Wikipedia under "breadboard".
It's apparently a TRF - Tuned Radio Frequency receiver. These predated super-regenerative and super-hetrodyne receivers in that they don't self-oscillate or have a down-conversion oscillator. The TRF generally consists of a tuned amplifier on the signal frequency which feeds a detector then into the audio amplification.
They have rather limited sensitivity, but normally more than enough for receiving local AM broadcast stations, and not having an oscillator are very clean and free of annoying hetrodyne whistles. They are also therefore well suited to clandestine operation where local oscillator radiation could be a fatal giveaway. At one time I worked for a radio manufacturer and one of our models was a cheap TRF 'rockerbox' that had surprisingly good performance.
Oh TRF. The cub scouts and I put together some ZN414/MK484 TRF receivers a couple of years ago. Yer basic cub scout radio. We etched small circuit boards using enamel paint as the resist and just painted simple pads for dead bug style circuit. Fun stuff.
Yep, that's a way to go; no-drill dead-bug style works fine, as do a lot of other things for etch resist, nail polish, roofing paint, waterproof marking pen, ... you could quite reasonably do a whole amp like this, say stage by stage modular style. A cub-safe etchant is vinegar, some salt, and some hydrogen-peroxide.
Quote from: Roly on December 02, 2012, 06:26:43 AM
A cub-safe etchant is vinegar, some salt, and some hydrogen-peroxide.
Any experience with this? If so, I'd love for you to do a thread about it!
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.
Quote from: Roly on December 04, 2012, 02:17:21 AM
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:
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
Well bugga me a mobile phone with a Spring Reverb how interesting :lmao:
Phil.
Yup, another spammer snuck in. :trouble
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.
Are you aware you are feeding some 300V RMS to that poor little spring tank? :duh :loco
Do the math :o 8|
That said, it may be KILLER reverb ::)
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.
Quote from: J M Fahey on December 29, 2012, 01:15:57 AM
Are you aware you are feeding some 300V RMS to that poor little spring tank? :duh :loco
Do the math :o 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.
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, :P
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. :-X
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 :-[
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.
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.
Reverb sounds nice Phil. :dbtu:
{The recording has a lot of "overs"; you need a compressor/limiter like...
(http://www.ozvalveamps.org/playmaster/compressor.jpg)
}
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).
(http://i1341.photobucket.com/albums/o743/Roly49/Solid%20State%20Guitar%20Amps/Phabbspringlinedriver130106-LTspice_zps835489c0.gif)
Parallel op-amp drivers->8r:1k transformer->springline driver 160r (160mH)
1000/8=125^0.5=11.1803398 turns ratio
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.
I only meant a compressor/limiter in the path to your recorder, just to contain the dynamics on the recording, not as a normal part of the guitar path, coz you've got some really hard headroom limiting on some of the louder parts. With a tape recorder the rule is "lickin' the red" but with digital recordings anything higher than -3dB starts to cause problems. Post compressing won't help, the level has to be contained before it is digitised, so it has to be analogue in the front-end to the recorder.
The EA cct allows adjustment from no action at all to hard brick-wall limiting.
The rising characteristic looks similar to current drive. If we conceptually transfer the two parallel 47 ohm resistors into the tranny to the secondary they would appear as a very much larger resistor (~3k) between tranny and line driver, and combined with the voltage transformation would give you effectively current drive.