my orban 642b eq hisses too much, fixable?

[earworm]

well half a year ago i bought an orban 642b parametric eq,
i like the way it works but it just hisses too much, and its not just high frequencies, highcuts don't solve the problem, seems like its in the entire audio spectrum.

its an old unit of course so maybe some components on the inside had their time. Any idea what parts might be damaged, and is this something that can be fixed? I'm not planning to open it up myself, but there might be people out there that fix audio equipment.

all info is welcome!

cheers

[dementedchord]

orban was always a top notch co... found them alot in the install and radio markets... can't offer any specifics on this problem other that to start with rebuilding powere supply and perhaps replacing some electrolytic caps... would be worth it to me...

[Massive Master]

Ahhh... The 642B... It should be relatively quiet - If it's the black-faced model, it should be crazy-quiet. It's also relatively "tech friendly" to the average electronics service technician (from what I'm told from the guy who used to clean my gear - including my old 642B black-face).

[rsolinski]

Sounds like capacitors that have aged out of spec..posting a sound sample would help..it may be in the power supply or the filter section..or both..

Cheers,
Ray

[earworm]

its the black face, this weekend (i i wont forget) i'll record and upload some sound samples, what would be the best,
just recording the hiss, unplugging a cable to compare the hiss witht the silence of my soundcard..

last weekend i recorded vocals and the noise is just terrible, you can hear it in the mix and i didn't use high volumes and only tiny boosts

then comes the next question, any idea where i can find a decent technician in europe to fix it?

(and to keep on asking questions, i also have an Ashley sc66 (http://www.ashly.com/images/relics/lres/sc-66-ad.jpg) once again its got some basic hiss, not too much but i notice it clearly, anyone got the same unit and also hiss?

[brendandwyer]

Originally Posted by earworm

well half a year ago i bought an orban 642b parametric eq,
i like the way it works but it just hisses too much, and its not just high frequencies, highcuts don't solve the problem, seems like its in the entire audio spectrum.

its an old unit of course so maybe some components on the inside had their time. Any idea what parts might be damaged, and is this something that can be fixed? I'm not planning to open it up myself, but there might be people out there that fix audio equipment.

all info is welcome!

cheers

hmm, that's odd. mine is excellent. granted i had it wired wrong for 6 months, but now it's wired correctly and i love it.

Are you sure you have it correctly wired?

[formerlyfzfile]

I have a blueface model and it was completely recapped by the studio I bought it from..... but mine is DEAD quiet.

If you're hearing the hiss across the board you might look at the output wiring at the "block". Make sure the the output wiring isnt cracking or broken where it screws or is soldered into the unit. I am not sure if the black units are the same but mine has a "screw block" that the inputs and outputs attach to and the wiring is slightly exposed aat the block. If you've moved the units recently that could be an issue.

Bad (old) caps sounds more probable. The studio tech I taked to that I bought the unit from said it was fairly easy to recapp. Of couse easy is a realative term.




-mike

[brendandwyer]

Originally Posted by formerlyfzfile

I have a blueface model and it was completely recapped by the studio I bought it from..... but mine is DEAD quiet.

If you're hearing the hiss across the board you might look at the output wiring at the "block". Make sure the the output wiring isnt cracking or broken where it screws or is soldered into the unit. I am not sure if the black units are the same but mine has a "screw block" that the inputs and outputs attach to and the wiring is slightly exposed aat the block. If you've moved the units recently that could be an issue.

Bad (old) caps sounds more probable. The studio tech I taked to that I bought the unit from said it was fairly easy to recapp. Of couse easy is a realative term.




-mike

mine is the single channel and i've replaced the opamps. i will probably recap it soon. but the opamps made a pleasant and noticeable difference

[dementedchord]

Originally Posted by earworm

and its not just high frequencies, highcuts don't solve the problem, seems like its in the entire audio spectrum. cheers

and there's your best indicator that it's a general systemic type problem like power supply filters and'or decoupling caps... anyhow gives ya chance to swap some op-amps while your in there...

[brendandwyer]

Originally Posted by dementedchord

and there's your best indicator that it's a general systemic type problem like power supply filters and'or decoupling caps... anyhow gives ya chance to swap some op-amps while your in there...

hey demented, when recapping, if i source the same capacitance and voltage, making sure the cap materials are the same, there's no other catch to sourcing parts is there? Just look for high quality caps?

i've never done it so my orban will be the test

[dementedchord]

yeah that's it for the most part... sometimes you'll see some recommended for higher temp situations... which aint a bad idea say something about stabitlty... as for materiels if your looking at a bunch of mica's or something like that i'ld use polyproplene instead... BTW did you try the output thing for that hammond???

[brendandwyer]

Originally Posted by dementedchord

yeah that's it for the most part... sometimes you'll see some recommended for higher temp situations... which aint a bad idea say something about stabitlty... as for materiels if your looking at a bunch of mica's or something like that i'ld use polyproplene instead... BTW did you try the output thing for that hammond???

actually, i hit a road block. i sent you a PM today regarding it.

I can't find the G-G terminals. I have a Hammond L100. spinet organ, not quite the same layout as the higher end models.

It has what i think are preamps for vibrato and one for percussion. These then proceed to the volume pedal, then to the amp on the lower section. The amp appears to hit the spring reverb in a loop, and then output to the speakers.

Not being able to identify which preamp to tap ( i assume it's the perc preamp as it's the second one in lline) when i open it up, i find two tag strips, neither have any marking on them.

i read that i could tap the signal from the speaker wires, providing a dead load, but now i can't find the schem for that configuration.

thanks in advance

[earworm]

what does a capacitor do?

and if the caps and opamps are replaced, will this change the sound of the unit? Are there standard brands that are good/or behringer-like? Can i just go buy me some caps and opamps and ask a guy who's good in soldering to replace them for me?

[brendandwyer]

Originally Posted by earworm

what does a capacitor do?

and if the caps and opamps are replaced, will this change the sound of the unit? Are there standard brands that are good/or behringer-like? Can i just go buy me some caps and opamps and ask a guy who's good in soldering to replace them for me?

capacitors store electrical charge.

you would need to carefully source the correct capacitance and voltage of each cap in the device and purchase high quality caps. Texas Intruments and Burr Brown opamps are pretty good. What you'll need to do is to open the unit, find the model number on each of the opamps and cross reference them with newer models with either equal or better specs.

Then you can either find someone to remove and replace those components, or do what i did, learn how to do it yourself and here's the cliche "if i can do it, anyone can!"

it's intimidating, but if you research the basics it will make sense in a short amount of time.



no to hijack, but has anyone done a 3630 modification? Prodigy Pro has a mod that seems good. I've got all the parts accept single row 8 pin sockets. I cannot find single row 8 pin DIP sockets, and that's dumb because their just sockets!

[earworm]

OK, i'll start with opening the box and taking a look at it,
if i'm correct i still have the manual (with schematics)

i might try to replace the caps myself then, exiting!
But do you know places where they sell them? Of course i'm going to google (grin) but a hint is welcome.

i've heard of bruwn burr opamps before, but now how do i know what a high quality capacitor is (just look at the price?)

[brendandwyer]

Originally Posted by earworm

OK, i'll start with opening the box and taking a look at it,
if i'm correct i still have the manual (with schematics)

i might try to replace the caps myself then, exiting!
But do you know places where they sell them? Of course i'm going to google (grin) but a hint is welcome.

i've heard of bruwn burr opamps before, but now how do i know what a high quality capacitor is (just look at the price?)

i get parts through mouser. they have this cool "project manager" thing that allows you to save parts lists based on a project name.

SO i have a bunch of project parts lists pending and i buy them when i start a new project.

mouser.com

[MCI2424]

Originally Posted by earworm

what does a capacitor do?

and if the caps and opamps are replaced, will this change the sound of the unit? Are there standard brands that are good/or behringer-like? Can i just go buy me some caps and opamps and ask a guy who's good in soldering to replace them for me?

Capacitors store electrical charge and in audio circuits are used to block DC current (hum) and bypass unwanted frequencies (like hiss, which is high freq white noise). If your bypass caps have dried up, they essentially either short or open. Bypass caps are designed so that at a certain frequency they start to lower impedance and flow the unwanted AC frequency to ground. If the bypass cap opens, the unwanted noise is simply passed through with the wanted signal. This is a waaaay watered down explanation BTW. Caps also are not capable of passing DC current and can only pass a *changing* current (like AC signals). Power supply bypass caps are usually responsable when you astart to get hum and low freq noise (usually line 50-60Hz).

The best caps to replace would be Panasonic 105C rated caps and the best place to get them is :http://www.digikey.com/

You can order off the site and they will fill any order from 1 part to 1000s.

Good Luck

[dementedchord]

Originally Posted by brendandwyer

I've got all the parts accept single row 8 pin sockets. I cannot find single row 8 pin DIP sockets, and that's dumb because their just sockets!

those would be SIP sockets... single inline ... which actually you dont want to use sockets for sips in particular... they tend not to hold tight... FWIW... other than durring experimental stages i dont use sockets at all... there's a thing called parasitic capacitence that can effect freq responce....

also when you upgade opamps sometimes you run into problems with the new stuff oscillating and such... the fix is to ad a cap between the power supply pins...(4-8)

[brendandwyer]

Originally Posted by dementedchord

those would be SIP sockets... single inline ... which actually you dont want to use sockets for sips in particular... they tend not to hold tight... FWIW... other than durring experimental stages i dont use sockets at all... there's a thing called parasitic capacitence that can effect freq responce....

also when you upgade opamps sometimes you run into problems with the new stuff oscillating and such... the fix is to ad a cap between the power supply pins...(4-8)

i was wondering why the article called for sockets for the vca's. I didn't think vca's were something i'd be changing out all the time.

That's good. i'll just solder them directly.

Any luck with my hammond fiasco?

[dementedchord]

Originally Posted by brendandwyer

.

Any luck with my hammond fiasco?

went by the old shop and looked at the schemo... this one is'nt like i remember but it's still doable... trying to get someone to scan the schemo for me so i can send to you... there's a wire coming out of the expression pedal that should work fine... it's the white one...(assumming it's not been rewired)

[brendandwyer]

Originally Posted by dementedchord

went by the old shop and looked at the schemo... this one is'nt like i remember but it's still doable... trying to get someone to scan the schemo for me so i can send to you... there's a wire coming out of the expression pedal that should work fine... it's the white one...(assumming it's not been rewired)

excellent! we're getting close. It has not been rewired as the original RCA type connectors are intact (and cracking a little bit).

Thanks

[dgatwood]

Originally Posted by earworm

what does a capacitor do?

Capacitor... it's like a balloon. No, hear me out. Imagine you have a pipe. That's a wire. You put an air-filled balloon in the middle of it. That's a capacitor.

Notice that no water can flow past the balloon. In much the same way, a capacitor blocks DC voltage.

Now imagine that the top of that pipe (above the balloon) is open. It is capped in such a way that the balloon can't jump out, but otherwise is open on top. That's like a ground. If the balloon weren't there, water would pour out on the ground.

So what happens when someone flushes a toilet near this balloon? The pressure in the pipe suddenly drops and the balloon expands a little to make up the difference, thus pushing the pressure back up a little bit. When the toilet stops, the pressure increases and the balloon contracts, absorbing some of the pressure. A capacitor between an AC source and ground tends to smooth out the AC signal in much the same way.

Finally, if you fasten the balloon over the top of the pipe so that the water fills it up, assuming the balloon is stiff enough to handle the pressure without exploding, it will build up to a point where the pressure in the balloon matches the pressure in the pipe and will stop expanding. What if this pipe can provide only a trickle of water, but at a high pressure? Say the balloon has two tubes in its mouth: a tiny tube connected to your water line and a large tube connected to the toilet.

The balloon will take a while to fill up, but will eventually be able to provide a large amount of water at the same pressure as the small tube is providing. If the toilet was designed to only handle that trickle of water provided by the small tube, when you flushed it, the toilet would likely explode.

That is like a capacitor between a power source and ground with no place for the power to go. The capacitor will charge up to the source voltage, but will be capable of dumping a large amount of current as soon as the stored power has a place to go. This is, if I understand correctly, roughly how camera flashes work, for example. A battery drives an inverter circuit to generate a high voltage at a relatively low current. The capacitor then stores this energy, eventually dumping it all at once, resulting in a high voltage with high current.

It's a slightly crude analogy, I know, but I think it illustrates the more important points of what a capacitor does.

[MOFO Pro]

Originally Posted by dgatwood

Capacitor... it's like a balloon.

Wow... A flash picture of an exploding toilet... Cool

[dementedchord]

this is the police.... put down the bong and step away.....

[earworm]

thanks for the explanation,
couldn't be better!