Arrigotti

VU Meter bridge rectifier for 1176
« on: December 28, 2004, 12:54:20 PM »
The cheap Mouser VU meters I got for my 1176's came with a separate bridge rectifier.  

My question is:  Should I use this or does the 1176 already have circuitry to rectify the AC signal to DC?

This obviously shows my newbie ignorance because all VU's probably have a rectifier circuit in them, but I don't know that.

Thanks!


RemcoV

VU Meter bridge rectifier for 1176
« Reply #1 on: December 28, 2004, 01:01:29 PM »
hi Arrigotti,

Yes, you can do the 1176 meter in 2 ways:
1. use the sifam (or equifilent). those meters have the rectifier inside.
2. use another meter,  but then you need to build a rectifier in the chain, that's not included in the 1176 layout.
When making your own rectifier make shure you use germanium diode for this.. they have less voltage drop across them, so the readout will be more accurate..

hope it helps!

Remco

CJ

VU Meter bridge rectifier for 1176
« Reply #2 on: December 28, 2004, 08:40:47 PM »
Copper oxide if you can find one.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

SSLtech

VU Meter bridge rectifier for 1176
« Reply #3 on: December 28, 2004, 09:53:02 PM »
the seperate Bridge Rec that you mention will possibly also have teh 3k 6 resistor in it as well... the cheapo crappo modutecs also have this arrangement, covered in solidified goo...

Use the supplied rectifier. It should be copper oxide or germanium. Your 1176 does need a "real" VU meter, i.e. something rectified.

keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Sleeper

DC to VU meter rectifiers
« Reply #4 on: March 06, 2006, 09:14:35 PM »
I'm going  to add some rectifiers to a few dc meters here. I've used germaniums with pretty good result, but I'm out of those and have to place an order.

Can't find copper oxide anywhere

I thought I'd browse some datasheets to see if maybe there is something even better than germanium... I don't know much about diodes except for what works in a power supply and a distortion pedal so I figure at the very least I'll learn something.

 Is it the same "soft" quality that makes the germanium good for diode clipping what makes it good for this app?

Quote
When making your own rectifier make shure you use germanium diode for this.. they have less voltage drop across them, so the readout will be more accurate..


Can I get some help deciphering the datasheet, what's the relevant info here :?  reverse leakage current? reverse voltge? forward surge current?
I'm confused.

http://www.nteinc.com/specs/100to199/pdf/nte110mp.pdf

or here
 
http://www.fairchildsemi.com/ds/1N/1N4454.pdf

Thanks for any help
Kelly

CJ

VU Meter bridge rectifier for 1176
« Reply #5 on: March 06, 2006, 09:56:52 PM »
1n5818/19
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

VU Meter bridge rectifier for 1176
« Reply #6 on: March 06, 2006, 10:27:35 PM »
Circuit Specialists still has a good supply of germanium 1N34A's.

Remember when you could walk into any Rat Shack and get them?

Cheers,

elco

Sleeper

VU Meter bridge rectifier for 1176
« Reply #7 on: March 06, 2006, 10:35:25 PM »
thanks CJ

so that one has a  
Reverse Current @ rated V
T= 25°C
0.5 mA

so reverse current is effectively the same as voltage drop/
that seems to make sense.
helluvalot faster. and much much lowerrev volts than than the 1n4007 silicon and the germanium...
i'll try em.
1176s crawling forward.
km

NewYorkDave

VU Meter bridge rectifier for 1176
« Reply #8 on: March 06, 2006, 10:39:05 PM »
1N34A is the germanium diode.

Are they becoming hard to find or somethin'? They were still cheap and readily available last time I checked.

CJ

VU Meter bridge rectifier for 1176
« Reply #9 on: March 06, 2006, 11:51:31 PM »
It could be that what they hang on the shelf as a Germanium diode these days has transpired itself onto a whole differnt plane of composite existance.
I do not think a 1n34 from 1870 would look like a mouser p/n these days underneath a mormon brothers spectrometer.

I am, as usual, only spectatulaiting. But ther might be at least an atom of truth to that.

I see all these freaks at Aron's going, "Dude, I just scored a selenium rectifier out of an old zenith and it totally kicks ass in my fuzz phace! iafter some heavy fumigation with the sticky icky, and a couple of shots of jack, i was in the groove, man. the next door neighbor called the cops right in the middle of the Hand of Doom solo, man, which really bummed me out, but that rectifier is kickin like the General's Fried Chicken!"(but I had to spray it with c67.")
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


hagtech

VU Meter bridge rectifier for 1176
« Reply #10 on: March 07, 2006, 12:37:54 AM »
Another approach is to use an active FW rectifier (opamp circuit), and then drive with a series resistor to match level.  You can tweak ballistics with a cap across the meter.  I'll be doing this in my soon-to-be compressor/pre.  It fixes the low end (-20dB) of the scale.

jh
Jim Hagerman
Hagerman Technology LLC - making audio fun again

Arrigotti

VU Meter bridge rectifier for 1176
« Reply #11 on: March 07, 2006, 01:30:10 AM »
I still have those cheap ass "VU Meters" if anyone wants them for cheap.  I ended up finding some used "real" ones on eBay and they worked like a charm.

VU Meter bridge rectifier for 1176
« Reply #12 on: March 07, 2006, 02:06:27 AM »
Quote from: "NewYorkDave"
1N34A is the germanium diode.

Are they becoming hard to find or somethin'? They were still cheap and readily available last time I checked.


They will be. They have lead and are not RoHS compliant. Mouser only carries the over priced NTE 1N34A equivalent junk.

It seems like every day some every day common audio part disappears from Mouser and Digykey stock. I suppose I can chalk it up to being lazy, but I like to get as many parts as I can from one supplier. I love those automatic BOM tools.

If we do a little leg work I'm sure we can still find parts discontinued because of lead, RoHS or proliferation of SMD.

Except for those cheap large value Toko 10RBH inductors. I sure wish I could have stocked up. I can't find them anywhere. :cry:

Cheers,

elco

Sleeper

VU Meter bridge rectifier for 1176
« Reply #13 on: March 07, 2006, 04:38:49 AM »
sorry to cause/spread confusion.  there's no problem to get the germaniums at all, they are all over ebay. newark has them too.  nte was the first datasheet i found.

I just thought that maybe there might be some new part that would do a better job of making these poor little akai tape deck meters get under control for my stereo 1176's.

I have digital meters on my DAW, where the accuracy really counts, so these are just for looks (and size in this case) and some visual indicator. since these are for personal use, and the metalwork is done and I put the money into transformers there's no turning back... sometimes you have to do the best you can with what you got

note to self: objects in meters are larger than they look.
 I'll be sure to listen to whats happenning :grin:

i think I'll skip the active circuitry, so a trimpot and some kind of rectifier should be adequate. the motor is very small though and when I tested them they are a tad skippy, more or less what I expected...

JH, what are you thinking with the cap across the meter? will this damp the movement a bit? polarized or bipolar?  what kind of values are you thinking?

kelly


 

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