LM833 project

[Kipper4]

I've got some spare chips going begging and i'm looking for a project to suit.
I found this MI Audio Crunchbox
and thought it looked ripe for clipping diode mods.
I thought maybe try some assymetic arrangements and differant diodes too (eg;Germanium)
maybe include a diode switch option (rotary switch)
heres the layout.

http://www.aronnelson.com/gallery/main.php/v/diyuser/MI+Audio+Crunch+Box.gif.html?g2_imageViewsIndex=1

let me know what you think and include possible diode options you like that might work well in this circuit
thanks
Rich

[hex_void]

Looked up the datasheet for the LM833... good noise figures but I'm not sure about the input resistances.
I'd say it's best suited in high gain circuits (distortion/overdrive/compressor). It's even quieter than the NE5532.
Layout doesn't help much though, a schematic would be more useful (way too lazy to reverse engineer it).
As far as diode clipping circuits go, try them all. You can never know which one will sound better and as far as I know about overdrive/distortion circuits changing the power supply voltage makes a huge difference (depending on the gain of course - at high gain and lower supply voltages the opamp will clip to the supply rails sooner and there's going to be a noticeable difference in sound, usually it gets dirty).

[J0K3RX]

I love the LM833!

You might want to consider the layout with the presence pot... makes a huge difference!
http://www.diystompboxes.com/smfforum/index.php?topic=85104.0

You also might want to check out the Tone Freak Severe... I like it better!
http://rapidriotboxes.blogspot.com/2011/01/tonefreak-severe-distortion.html

[Kipper4]

Thanks Jim.
It looks like those schematic have a few problems so i'll look up some more.
And i just love the LM833 too.
I put them in my YJM 308 (dod 250) they sound spot on.
i liked the tone freak samples on youtube

[J0K3RX]

Thanks Jim.
It looks like those schematic have a few problems so i'll look up some more.
And i just love the LM833 too.
I put them in my YJM 308 (dod 250) they sound spot on.
i liked the tone freak samples on youtube

I built a few of the rapidriot version of the Severe... Works perfectly and sounds killer. About the same as the Crunch box but the clipping circuit is in the feedback loop of the frist opamp.. You can't go wrong with either of these pedals, they both sound fantastic!!

rotary switch is a good idea!

[Kipper4]

sounds very viable Jim.
I'll give it a shot in the morning.
thanks for the tip off.

[Kipper4]

I made the crunchbox today and its a stunner. Plenty of dirt (gain).
I ended up building it turretboard style.
From an old layout at turretboard.org (part of the other forum now)
its a really neat layout style.
I think im going to try some of the other distortions they have in turretboard style.
I'll have a play with it later.
i've left a little bit of spare board so i can make some other diode arrangements but im unsure how to do it so if anyone fancies giving me a few tips pm me and i'll pm you back with the layout so you can point me in the right direction for adding other diode options.
And maybe some tips on which may be suitable
Heres a pic
https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#f:crunchbox.jpg
thanks

Rich

[J0K3RX]

looks good man! For the clipping options maybe just try different combinations of LED's and diodes and even mosfet maybe in sockets on a piece of perf board...?

[Rock_on]

Is there a good substitute for LM833??

It is not available here, how about TL072??

[Kipper4]

I guess you could sub the TL072. Its the same pinout. I'd double check the spec sheets first.

[Rock_on]

Im asking about the performance not if they are same pinout (no offense)

How about these??

Source : http://www.electro-tech-online.com/datasheets-manuals-parts/25596-ic-equivalent-lm833-ne5532.html
NTE891M

Source : http://www.diyaudio.com/forums/solid-state/892-lm833-op-amp.html
LF353 and NE5532 (is it true it has better midbass response?)

[merlinb]

Is there a good substitute for LM833??

I was under the impression the LM833 was identical to the NE5532, but now I'm not so sure. Wonder where I got that idea...

[gritz]

Is there a good substitute for LM833??

I was under the impression the LM833 was identical to the NE5532, but now I'm not so sure. Wonder where I got that idea...

Yeah, the LM833's differential input pair are PNP and the 5532's are NPN. On a wider note, there may even be more subtle differences between identical opamp types from different manufacturers. S.T. Micro, Texas and National Semi all make versions of the LM833. National and T.I. quote (if I remember correctly) minimum supply voltage of ±5V, while ST quote ±2V5. Schematics on datasheets from different manufacturers may be misleading as the don't tell the whole story - they might not show protection or biassing circuitry, darlingtons may be notated as single trannies, etc.

Does it matter? Can a normal human being hear a difference? A smart designer will design an application such that it doesn't push component parameters to the edge, but guitar electronics often isn't very smart. Still, I've heard some pretty dramatic claims from users who have reported a night-and-day difference between opamps in rather undemanding applications and I've generally failed to detect these "significant" differences with either listening tests or some pretty deep signal analysis (not simulation!). On the other hand it's a piece of cake to identify large performance differences between opamps in more demanding applications, like precision rectifiers, but no-one cares about those. I was recently testing an envelope follower and I found a 10dB increase in useable dynamic range with an OP275 when compared to a TL072, but do these opamps sound (or measure) night and day different in a typical audio application? Not here - not so far, anyway. Getting all the other stuff right - layout, decoupling, due regard to impedances and whatnot - has far more affect on performance imo.

Finally, any listening test that isn't at least single-blind should be taken with a huge pinch of salt imo - a flawed testing process can easily mislead.

[Rock_on]

Is there a good substitute for LM833??

I was under the impression the LM833 was identical to the NE5532, but now I'm not so sure. Wonder where I got that idea...

I listened to the demo of crunchbox in youtube

And i loved it!! But sadly there's no LM833 here, i'll just NE5532

[J0K3RX]

You can use a variety of different opamps all with varying results... TL072 will work fine but most people prefer the sound of the LM833 myself included. Experiment!

[Kipper4]

I think the LM833 is part of the crunchboxs mojo.

[J0K3RX]

I think the LM833 is part of the crunchboxs mojo.

The LM833 does sound the best so far that I have tried in the crunchbox circuit... kinda like the Wampler 4580 mojo. same goes for the suhr Riot and the 4580...

The Tone Freak Severe also uses the LM833 also and is a close cousin to the crunchbox but with the clipping in the feedback loop of the frist opamp which I like better... personal preference.

[jymaze]

It works very well with the good old 4558 or a 4580.

To elaborate on gritz's comment, I can really hear a difference between a LM833 and a RC4558 for example. It is subtle, but there. The thing is that an opamp is pretty much like any opamp in normal operation, but in distortion circuits they are usually pushed in heavy clipping where things are totally unpredictable and don't appear on the datasheet. It is not that guitar circuit designers are not smart to push opamps to the edge (actually well beyond the edge), it is just that huge gain is needed so it has to clip, period. I even had some opamps refusing to work in some pedals for some reason. I just had to switch to a 4558 and it worked and sounded beautifully. Still wondering why to this day...

There can be different ways of recovery from clipping, more or less smooth, more or less quick, more or less natural (some opamps have ugly phase reversal). So it matter in clipping applications in my opinion. For more mundane linear operation (which is actually pretty rare in guitar electronics, besides a simple buffer) any opamp will do.