diode bridge rectifier as a clipper?

HydrozeenElectronics · Post by **HydrozeenElectronics** » 16 Aug 2009, 00:19

anyone tried this? I read that marshall used this in their jcm 900's

Sounds like it might be a cool trick.

lolbou · Post by **lolbou** » 16 Aug 2009, 07:25

More info here viewtopic.php?f=7&t=4599&hilit=+bridge+rectifier

Do you mean signal diodes in bridge config, or a big black power diode bridge as found in the power supply?

HydrozeenElectronics · Post by **HydrozeenElectronics** » 16 Aug 2009, 11:10

lolbou wrote:More info here viewtopic.php?f=7&t=4599&hilit=+bridge+rectifier

Do you mean signal diodes in bridge config, or a big black power diode bridge as found in the power supply?

From what I understand they article was saying the 900 used a bridge rectifier package and not discrete parts.

That thread is what I was talking about thanks.

I wonder how using a rectifier bridge like that vs regular diodes in series changes things?

Here is the original thread I was reading and one guy mentioned that this was better for uper end harmonics

http://music-electronics-forum.com/t5984/

here is what he said:

"The bridge rectifer is wired so that the signal & ground are going into the bridge rectifier just like you would wire in a transformer in a powr supply. The extra diode has its anode connected to the + terminal on the bridge & its cathode to the - terminal on the bridge. This diode creates a path for both the negative going & positive going AC waveforms to pass from the top of the bridge (signal) to the bottom (ground). Draw it out & you'll see waht I mean. The path for each half of the waveform is 3 diodes (about 1.8V). The cool thing about this setup is that both the positive-going & negative going signals pass through the "extra dioide" in the middle going in opposite directions. This set-up is very similar to a frequency double circuit...and that is essentially what it sounds like as a clipper, it sounds like a frequency doubler. Everything that gets clipped basically has its harmonics pushed up by an octave (double the frequency) and it ends up sounding very smooth and sweet. Try this setup vs. 3 series diodes in the normal configuration (just side by side strings) & you'll see what I mean. The harmonic content is at a higher frequency."

RnFR · Post by **RnFR** » 16 Aug 2009, 11:43

doubling circuits usually have diode clamps that are out of phase with each other. this might be similar, but i think it is still a bit different, because the diodes are set up as clippers going to ground instead of clamps in series. that's not to say that there may still be some sort of frequency cancelling going on though.

for the record i have tried some of what i believe were bridge rectifiers for clipping before. they were motorola components that looked like a normal to-18 metal can tranny except they only had 2 leads. they were really great sounding, too! i have never been able to find a similar component since i bought the last few from the shop.

they were single diode packages though, and i think you might mean the little boxes with multiple diodes in them?

Emanuele · Post by **Emanuele** » 16 Aug 2009, 13:00

in my borther's JCM900 MkIII the bridge is the same used on the power supply..I know it's not the same of a pedal but the overall disortion is very rich..definetely a LOT of harmonics..

HydrozeenElectronics · Post by **HydrozeenElectronics** » 16 Aug 2009, 22:30

Emanuele wrote:in my borther's JCM900 MkIII the bridge is the same used on the power supply..I know it's not the same of a pedal but the overall disortion is very rich..definetely a LOT of harmonics..

Can you spot a part number on there anywhere on the bridge? Also what is the part number on the 5th diode wired up to the bridge?

Thanks

Naz Nomad · Post by **Naz Nomad** » 16 Aug 2009, 22:38

In the JCM 900 ...

Bridge Rectifier is W005F

Additional diode is 1N4007

SCHEMATIC

HydrozeenElectronics · Post by **HydrozeenElectronics** » 17 Aug 2009, 08:02

Naz Nomad wrote:In the JCM 900 ...

Bridge Rectifier is W005F

Additional diode is 1N4007

SCHEMATIC

Thanks, that's what I needed.

chicago_mike · Post by **chicago_mike** » 17 Aug 2009, 17:20

Maestro brass master also uses a bridge rectifier for od.

marshmellow · Post by **marshmellow** » 17 Aug 2009, 18:13

In 99,9% of the cases, a silicon (rectifier) diode is just a diode is a diode is a..., they only differ in maximum voltage and current, but that makes no difference for this application. The important parameter is the forward voltage drop, but that is (almost) always the same 0,7V. And a bridge rectifier is just four ordinary diodes in one package, instead of four single ones, nothing else.

The JCM900 setup makes no sense, at least to me. The bridge rectifier is just there instead of two diodes. But maybe one BR is two cents cheaper than two diodes, who knows. If you compare the datasheets of the 1N4001 and the W005F, you will see that the W005F is more or less four 1N4001 integrated. And what you get in the end is the same old two diodes parallel to one = standard asymmetric clipping.

5thumbs · Post by **5thumbs** » 17 Aug 2009, 20:00

marshmellow wrote: The JCM900 setup makes no sense, at least to me. The bridge rectifier is just there instead of two diodes. But maybe one BR is two cents cheaper than two diodes, who knows. If you compare the datasheets of the 1N4001 and the W005F, you will see that the W005F is more or less four 1N4001 integrated. And what you get in the end is the same old two diodes parallel to one = standard asymmetric clipping.

Actually, in the bridge rectifer configuration in the Tonebone/Marshall JCM-1 info linked by lolbou, you end up with three diodes in series in each direction, not two. I used this bridge rectifier arrangement in my last DS-1 mod, the Huevos Grandes mod. It sounds really good, but my gut feeling is that two sets of 3 identical diodes in series clipping both halves of the waveform would sound extremely similar. (I haven't A/B'd the two arrangements, mostly because I'm prejudiced in favor of the aforementioned theory being true, but also I'm too busy to mess with it now.)

I'm sure I've grossly oversimplified bridge rectifiers in my usage, but to me, using a bridge rectifier as a clipper in a distortion circuit means I can get the sound of two sets of three diodes in series (6 diodes total) by only using 5 actual diodes. That doesn't sound like much, but when you're planning large production runs like Marshall, Radial Engineering, etc, saving the expense of that one diode can add up to substantial $$$. (I don't benefit from economies of scale like that...I initially tried it just to see what a bridge rectifier clipper sounded like in a modded DS-1.

)

bajaman · Post by **bajaman** » 17 Aug 2009, 20:43

I wonder what a similar configuration of LEDs would sound like

bajaman

RnFR · Post by **RnFR** » 17 Aug 2009, 20:59

reminds me of this soft clipping circuit. minus one diode of course.

http://sound.westhost.com/articles/soft-clip.htm

marshmellow · Post by **marshmellow** » 18 Aug 2009, 08:41

5thumbs wrote:Actually, in the bridge rectifer configuration in the Tonebone/Marshall JCM-1 info linked by lolbou, you end up with three diodes in series in each direction, not two.

Yes, you're right, I didn't look at that schematic until now. But in the JCM900 the OP referred to, it is the way I explained above (1 diode || 2 diodes). But really my point was, a bridge rectifier is nothing else but four diodes, so it's nothing to get too excited about.

mictester · Post by **mictester** » 18 Aug 2009, 14:55

Naz Nomad wrote:In the JCM 900 ...

Bridge Rectifier is W005F

Additional diode is 1N4007

SCHEMATIC

'
A quick look at the circuit suggests that the valves (tubes U.S.) are going to be responsible for the nice harmonics. The bridge rectifier (and additional diode) is just a (slightly) asymmetrical clipper, and isn't worth getting excited about. Marshall just used the W005F bridge rectifier because they've got thousands of them in stock, and it's a cheap source of diodes! There's no significant mojo here!

5thumbs · Post by **5thumbs** » 18 Aug 2009, 17:29

marshmellow wrote: Yes, you're right, I didn't look at that schematic until now. But in the JCM900 the OP referred to, it is the way I explained above (1 diode || 2 diodes). But really my point was, a bridge rectifier is nothing else but four diodes, so it's nothing to get too excited about.

You are correct. Marshall used a bridge rectifier in a more classic sense in the JCM900 than they did in the JCM-1 rack preamp. (Classic sense in that they have a transformer/differential power load between two points of the bridge rectifier, as opposed to the JCM-1/Tonebone, where they put a 5th diode in place of the transformer/battery.)

HydrozeenElectronics · Post by **HydrozeenElectronics** » 16 Nov 2010, 21:50

Update. I just built a rectifier circuit based on the one in the marshall schematic out of Germanium Diodes. It sounds pretty damn good. I a/b'ed with a simple germanium diode clipping pair shunted to ground and the rectifier type has more harmonics and is louder. The other is a little more bass heavy and fuzzy sounding though but the rectifier seems like it could do some really good things.

I'm going to try schottky diodes next because Normal SI's have to high of a voltage drop and you don't get much clipping and the GE takes a while to get warmed up before it sounds right.

I'll keep you posted.

Cheers

DrNomis · Post by **DrNomis** » 16 Nov 2010, 21:59

bajaman wrote:I wonder what a similar configuration of LEDs would sound like
bajaman

Since Leds have a slow turn-on characteristic,like Ge diodes,I'd imagine that the clipping would be soft,if you want,i could do a quick breadboard of it,run a signal through it,and post a screenshot of the clipping,actually I might just do that,but after I get home from work....

HydrozeenElectronics · Post by **HydrozeenElectronics** » 17 Nov 2010, 00:13

I had an idea to make the GE diodes stable I was thinking of placing a small flashlight size bulb next to them to act as a heater. I would have to have external power but I was thinking if I got the temp up to like 99 degrees then in anything but a smoldering heat wave I should get reliable consistency out of them. Does anyone see any pitfalls to that? would that shorten the life of the diodes?

Thanks

DrNomis · Post by **DrNomis** » 17 Nov 2010, 00:21

HydrozeenElectronics wrote:I had an idea to make the GE diodes stable I was thinking of placing a small flashlight size bulb next to them to act as a heater. I would have to have external power but I was thinking if I got the temp up to like 99 degrees then in anything but a smoldering heat wave I should get reliable consistency out of them. Does anyone see any pitfalls to that? would that shorten the life of the diodes?

Thanks

I've actually had no temperature instability problems with Ge diodes at all,they have all worked fine for me,I think the only way to shorten the life/destroy a Ge diode,is to exceede their power rating,or their PIV (Peak Inverse Voltage)....