Varistor for magnatone vibrato?

[six_eight]

Does anyone know what the part# for a VDR suitable for use in the Magnatone vibrato circuit?  Or what the specs are?  How many mA @ what voltage?

[sluckey]

Try to contact dinkotom.

[HotBluePlates]

Yep, he knows.

Are you building a Maggie?

Do you have to use varistors? Cause there are other variable-impedance elements you could use that aren't un-obtainium, and will work the same. However, there will be some circuit changes needed.

[six_eight]

Try to contact dinkotom.

Thanks.  I found a place that lists the Zenith 63-5053 which are .05mA@80V which is supposed to be the magic number, as being a part they stock.  But it's one of those places that doesn't have real time inventory, so I'm waiting to hear back.  If they don't have them in stock, I'll try contacting dinkotom.

[six_eight]

Yep, he knows.

Are you building a Maggie?

Do you have to use varistors? Cause there are other variable-impedance elements you could use that aren't un-obtainium, and will work the same. However, there will be some circuit changes needed.

I was thinking about building a revibe, but replacing the 6G12 part with the Maggie part.  And also adding a switch to kill the phase that doesn't get cancelled for a tremolo effect.

Other parts that will do the same thing, you say?  I'm listening.

[HotBluePlates]

Well, the original patent by the guy that invented the Magnatone Vibrato shows a bridge circuit where the arms are a cap and a "variable impedance element". When that variable impedance changes and the cap value stays the same, the phase angle for a given frequency changes. A changing phase mixed with a constant-phase (dry) signal gives a varying pitch, akin to Doppler effect.

As the Magnatone incorporates the invention, that variable impedance is a varistor, which alters its apparent resistance in response to a changing applied voltage. That "changing applied voltage" is the signal created by the oscillator, just like a trem circuit. The difference is the application of the oscillator signal varies signal amplitude in a trem, while it changes phase, and thereby pitch, in a vibrato circuit.

It's worth noting the Univibe uses LDR optoisolators as its variable impedance element. I've been thinking we should be able to use Vactrol optos as the variable impedance (there's a whole range of these devices; Doug sells at least one type).

The catch is the control signal has to be applied slightly differently, because it won't be applied directly to the controlled element, as in the Maggie vibrato. Also, the size of the control signal may need tweaking and/or cap values in the bridge circuit may need to be adjusted.

It's something that's worth experimenting with, but it needs breadboarding to zero-in on good parts values and overall circuit implementation.

I've just seen the original varistors selling for something like $75/pair, and you need 4-8 of them depending on which specific Magnatone model you copy. To me, that seems unconscionable, and there's got to be a better way...

[kagliostro]

Some time ago I got an old italian amp a GEM Deluxe Reverb 50R

the schematic was not disposable and so I started to draw it by myself, so I discovered that also this circuit uses the same principle as Magnatone, but they use only a pair of varistors

I had a long research and was not able to find an alternative to the use of varistors

in this image you can see the difference between old style varistor and new varistors



In the australian forum www.guitargear.net.au there is a member (electric triode) who has build two amps with new varistors

I've built two Magnatone clones using current technology varistors http://www.guitargear.net.au/discussion/index.php?topic=29720.0, and it works fine.

an italian guy proposed to build a surrogate of varistor using a resistor in series with a diode and paralleled to a diode in series with a resistor (I mean something like upside down eachother - hope you can understand what I mean) but no try about this solution

Here you can download the original patent for the use of the varistors

http://www.mediafire.com/view/?7exvwm8lvcuufvm

K

[Geezer]

http://www.guitargear.net.au/discussion/index.php/topic,29720.15.html

Reply # 15 may be of interest....he lists the Farnell part # he uses and the voltage to the circuit.

G

[six_eight]

http://www.guitargear.net.au/discussion/index.php/topic,29720.15.html

Reply # 15 may be of interest....he lists the Farnell part # he uses and the voltage to the circuit.

G

Thanks!  68V@1mA is the closest I've seen in a new production MOV.  But then again, I really don't know if 80V@.05mA is the intended spec.  I have several vintage Magnatones, but I don't see any P#s on the varistors and I have no idea how to test them.  I'll order some of those and give them a try.  I've got a Twilighter 260.  I'm gonna remove the original varistors and install alligator clips to experiment with different parts, so if you've got any other part # suggestions, let me have 'em.

[six_eight]

Well, the original patent by the guy that invented the Magnatone Vibrato shows a bridge circuit where the arms are a cap and a "variable impedance element". When that variable impedance changes and the cap value stays the same, the phase angle for a given frequency changes. A changing phase mixed with a constant-phase (dry) signal gives a varying pitch, akin to Doppler effect.

As the Magnatone incorporates the invention, that variable impedance is a varistor, which alters its apparent resistance in response to a changing applied voltage. That "changing applied voltage" is the signal created by the oscillator, just like a trem circuit. The difference is the application of the oscillator signal varies signal amplitude in a trem, while it changes phase, and thereby pitch, in a vibrato circuit.

It's worth noting the Univibe uses LDR optoisolators as its variable impedance element. I've been thinking we should be able to use Vactrol optos as the variable impedance (there's a whole range of these devices; Doug sells at least one type).

The catch is the control signal has to be applied slightly differently, because it won't be applied directly to the controlled element, as in the Maggie vibrato. Also, the size of the control signal may need tweaking and/or cap values in the bridge circuit may need to be adjusted.

It's something that's worth experimenting with, but it needs breadboarding to zero-in on good parts values and overall circuit implementation.

I've just seen the original varistors selling for something like $75/pair, and you need 4-8 of them depending on which specific Magnatone model you copy. To me, that seems unconscionable, and there's got to be a better way...

I've done quite a bit of experimentation with translating the Magnatone vibrato circuit into solid state form.  As you've pointed out, the hardest part is matching the amplitude/voltage of the LFO to whatever variable impedance device you are using.  It gets even more complicated when you consider that you need two oscillator signals that are perfectly out of phase with one another. 

The Univibe and the Magnatone circuits are essentially the same.  The Magnatone just has two "arms", as you call it, on the changing phase side that work in a push-pull manner. 

Aside from some different component values, the LFOs in the AA763 and the Magnatone are very similar.  So I would assume the the shape of the wave generated by the AA763 is the same as the shape generated by the Magnatone (one of the things I found is that the shape of the wave plays a huge part in the actual sound produced), but it is of an amplitude and voltage that is ideal for driving an LED coupled with an LDR.  I think if one were to take the AA763 circuit and use a vactrol that had an LDR in it that was similar to the LDRs used in a univibe, this could be used in one half of the phase changing arm in the vibrato circuit.

The only tricky part would be getting a second LED to blink out of phase with the other LED.  Maybe it could be done similar to the way the LED is already configured, but inversely.  The LED is in series with a 100k resistor between the anode and +V.  Perhaps an LED in series with the 56k/25uF  between the cathode and ground would do the trick.

[Willabe]

Here's the 2 part # from vibro world;

FR1039   (disk shape)

FS308     (tubular/fuse shape)

These are supposed to be what Magnatone used.

He's been out of stock for a long time.

Someone still makes a version in Japen (?) that's supposed to be correct but (like HBP said) the guy that sells them want's like $75 (?) a pair for them.

There's a thread in this forum from a year or 2 ago on the Maggie virato that has info on them.
 

                 Brad     

[six_eight]

Here's the 2 part # from vibro world;

FR1039   (disk shape)

FS308     (tubular/fuse shape)

These are supposed to be what Magnatone used.

He's been out of stock for a long time.

Someone still makes a version in Japen (?) that's supposed to be correct but (like HBP said) the guy that sells them want's like $75 (?) a pair for them.

There's a thread in this forum from a year or 2 ago on the Maggie virato that has info on them.
 

                 Brad     

Thanks.  Still no definitive data sheets, but it looks like the general consensus on those part #s is that they should be somewhere between 68V - 110V @ .05mA - 1mA.  This gives me quite a few new production parts (at less than a dollar each) to test out in my 260.

[sluckey]

It gets even more complicated when you consider that you need two oscillator signals that are perfectly out of phase with one another.

Not complicated at all. Just run the oscillator signal thru a phase inverter just like Magnatone did.

The only tricky part would be getting a second LED to blink out of phase with the other LED.

Same as above.

[Willabe]

IIRC in the other thread on finding new production varistors is the new ones behave differently than the old types. PRR said they figured out how to fix what was considered a problem/flaw in the old design in the way it was made?

Look at the pic kaliostro posted, the sharp shoulder of the new types is shown. It might not sound as smooth as the old style with the softer shoulder. You'll have to A/B them side by side to see if you hear any difference.

OTOH, have you seen the thread on a build Sluckey did called the Warbler? A number of guys here have built one and love it. It does a great maggi sound and more. It's a true pitch/phase shift circuit and the variable element is much easier and cheaper to get a hold of.

Here's the link;        http://www.el34world.com/Forum/index.php?topic=10681.0  



                   Brad      

[PRR]

> I have no idea how to test them

B+ from any handy amp, resistor, voltmeter.

[SoundmasterG]

I've got 8 of the originals that I got from Zack at Vibroworld....in fact I have the last 8 that he had, and I got them probably 10 years ago. I let Ted Weber borrow a couple for awhile to test, and he sent them back and never said anything about what he found out. Of course we can't ask him now.

I plan to use four in a combo amp that is as yet undetermined, and will be the Magnatone 260 vibrato circuit....and the other four I plan to use in a Torevibe with the Magnatone 260 vibrato added in to the stock Torevibe circuit. Obviously I would need a longer chassis to do this. If I knew how to test them I would get specs, but I have no idea. I can do some checking around though with some engineer friends I know locally and see if there is an easy way to test them.

At $75 a pair maybe I should sell them....that's highway robbery!

Greg

[SoundmasterG]

By the way, I've attached some pics of the originals, and a a word doc file with the specs for them. They are the two highlighted.

Greg

[plexi50]

six_eight have you had time to try the LITTELFUSE - V68ZA2P - VARISTOR, 3.0J, 40VAC ?

Data:
VARISTOR, 3.0J, 40VAC
Series: ZA
Varistor Type: Metal Oxide Varistor (MOV)
Peak Surge Current @ 8/20µs: 250A
Varistor Case: Disc 7mm
Clamping Voltage Vc Max: 135V
Peak Energy (10/1000uS): 3J
Voltage Rating V DC: 56V
Voltage Rating V AC: 40V
Operating Temperature Range: -55°C to +85°C
Body Diameter: 7mm
Capacitance: 600pF
Clamping Voltage: 135V
Clamping Voltage @ 8/20µs Max: 135V
Device Marking: 68Z2
External Width: 5.6mm
Lead Diameter: 0.68mm
Lead Length: 25.4mm
Operating Temperature Max: 85°C
Operating Temperature Min: -55°C
Package / Case: Radial
Peak Pulse Current IPP @ 8/20µs: 250A
Suppressor Type: Varistor
Surge Current: 250A
Temperature Coeff. +: 0.05ppm/°C
Test Voltage: 2500V
Transient Energy: 3.0J
Varistor Voltage: 68V
Varistor Voltage @ 1mA: 68V
Varistor Voltage @ 1mA: 61V
Varistor Voltage @ 1mA Max: 75V

I bought 100 of them just in case they turn out to dissapear as well. It wil be about 30 days before i can start building.
Leg OP,Dentures,PITA. Jee isnt getting old fun???

[Willabe]

Now wait a minute Plexi, when did you get those?

Did I miss school that day?


             Brad     

[plexi50]

Now wait a minute Plexi, when did you get those?

Did I miss school that day?


             Brad     

I went to that link you steered me to and took a look at what he was doing. I dont know what his results were just yet as im waiting to hear back from him. Need to check my mail/ http://www.guitargear.net.au/discussion/index.php/topic,29720.15.html

[Willabe]

Ok, I rember looking at that link a while ago.

But did you buy a 100 of those or did he?


            Brad     

[plexi50]

I bought 100 of them this afternoon from element 14 which is also newark. It will be an interesting project

[plexi50]

Got an email from Andrew at http://www.amplifiers.com.au/  He says the LITTELFUSE - V68ZA2P - VARISTOR, 3.0J, 40VAC works wonders in his amp vibrato builds. I have 100 of them on the way to me so if they dissapear i will have a varistor good enough to do the job

[Willabe]

I looked them up by part # at Mouser and Digikey and they both have them in stock. Mousers price was 0.17 @ 100. Digikey had only price for 1, it was 0.47 ?

Both had stock in the 1000's. Digikey also had a few more that were 40v raitings too.


             Brad     
 

[jazbo8]

Got an email from Andrew at http://www.amplifiers.com.au/  He says the LITTELFUSE - V68ZA2P - VARISTOR, 3.0J, 40VAC works wonders in his amp vibrato builds. I have 100 of them on the way to me so if they dissapear i will have a varistor good enough to do the job

Thanks for the tip, so it's an exact sub? Any component change for the build?

[plexi50]

He sent me gut shots of his amp with vibrato but no other details. I will email him and ask him if he can tell me what resistors he used in the 2 stages plate and cathode. That would be asking for the secret sauce though and i dont think i will get that info but all i can do is ask.

[jazbo8]

Just read on ampgarage that Magnatone is back in business. May be varistor won't be in shortage anymore?!

Jaz

[jojokeo]

Just read on ampgarage that Magnatone is back in business. May be varistor won't be in shortage anymore?!

I was told by a guy in the Maggie booth at NAMM Friday that they are back to making the original Vibrato in their amps just like the old days and using the same parts. I even made clear that are the varistors being remanufactured and he said yes. However, the man to actaully talk to was busy at the moment so I couldn't get a confirmation on this from him but it appears promissing.

[jazbo8]

Cool, so you were at NAMM! Please keep us posted if you learn something new, I'm not sure if they would go through the trouble & expense of getting the exact same varistor made, although it is a possibility, it's more likely that the circuit is tweaked by the engineers to work with what's available the market now, either way, it would be interesting to see if they can get the company back in business and sustain it - looks like they were trying to get distributors/dealers and some order commitments at NAMM before formally re-launching the brand...

Jaz

[Willabe]

I even made clear that are the varistors being remanufactured and he said yes. However, the man to actually talk to was busy at the moment so I couldn't get a confirmation on this from him but it appears promissing.

JoJo! What the....   You where there????

 And you didn't wait to talk to the boss man????        

You should have talked to him and if he said they where not going to sell the varisor's to the public for a reasonable price, then you should have grabed him by the kah@$&% ...... and told him..... Hey listen bud, look here......         .........      and then if he didn't listen, tell him, this is what's gonna happen to you if you don't ......

          

Please would you start a new thread on anything you saw that we would find interesting?????


            Brad      

[plexi50]

I would like to believe that the manfacturing process,chemicals,mineral grade,and good old caustic agents that were used in the 1950's to make products could be duplicated. It may be a close clone but it will never be the real thing. Just like Coke! Coca Cola. Remember those little tiny bottles? There was something in that Coca Cola that was magical. Same with the magnatone varistor. All kidding aside it could be done but i hardly think it would ever happen. Bring back pee wee's,rootbeer fizzies and Lafayette and i will believe

[jojokeo]

JoJo! What the....   You where there????
And you didn't wait to talk to the boss man????         

Yes *see new avatar
I couldn't wait, was with fellow friends/band members

It may be a close clone but it will never be the real thing. Just like Coke! Coca Cola. Remember those little tiny bottles? There was something in that Coca Cola that was magical.

It was called coca aka cocaine

[Willabe]

Yes *see new avatar

So that's you with the 2 girls?


            Brad     

[jojokeo]

Yep getting goosed from behind by the little she-devil that she is.

Here's the Maggie Vibrato info from one of their brochures...again I was unable to confirm for myself but the brochure states the varistor info on it.

[lego4040]

I'm researching for my next project and the Magnatone 410 was very interesting but I've been informed by Sluckey that those varistors are not easy to find and substitute. I looked at the link here for the varistors in mouser and they are available still. I was wondering if this is what my only choice is or has new information come about since last post in this thread. If the little fuse is the best and what needs to be done to use them.
Cheers

[kagliostro]

Reading this tread

http://ampgarage.com/forum/viewtopic.php?t=23839

you'll find a solution for substitutes to the varistors in a Magnatone circuit

this one



a lot of researc was done to catch the solution

my council, however, is that you read all the tread, because you can find very interesting info


K

[lego4040]

I started reading that thread, so this diagram would be a substitute for one varistor. needing two in the amp you would have to do this for each varistor in the circuit

[lego4040]

Ok, who bought em up! They're gone from ebay

[lego4040]

  I contacted the seller who has three pair and he relisted them. So I bought a pair of the real McCoy's

[Willabe]

Where on e-bay? I can't find them there.


                  Brad   

[lego4040]

http://m.ebay.com/sch/i.html?_nkw=Magnatone+varistors+&sqp=&trksid=

[Willabe]

Thanks, but that link just goes to e-bay.

I'll search Magnatone, varistors.


         Thanks,   Brad   

Edit; Found them.   

[lego4040]

That's how I found them, using Magnatone varistors. You going to build Maggie to or use in a different vibrato circuit

[Willabe]

I didn't buy them.

I was just curious.



                        Brad     

[kagliostro]

http://www.ebay.com/itm/Pair-of-Magnatone-Estey-VERY-RARE-NOS-VARISTORS-Price-Cut-Closeout-Sale-/171670071549?pt=LH_DefaultDomain_0&hash=item27f85568fd




here an auction for a 431
http://www.ebay.com/itm/Magnatone-Starlite-431-Tube-Amp-Vintage-1965-Tone-Monster-RARE-NO-RESERV-/131420470679?pt=LH_DefaultDomain_0&hash=item1e99453d97


Franco

[lego4040]

Those are the the pair I ordered. As for a PT I have two choice which will give me a close B+ Using the current calculator. My extra Hammond 290cax will work

[sluckey]

That's about half the price he was getting for those varistors a couple years ago. I think that means that a suitable, cheap alternative has been found. BTW, that guy makes some nice amps.

[lego4040]

I wrote over at amp garage thread if there was any new insight on them. I have to look at thread again, I don't know if I had a reply. I'm still trying to layout a board from the 410 schematic  I must have rearranged the caps and resistors 10x already just for v1 & v2

[sluckey]

I don't see your post over at TAG.

[lego4040]

? I guess thats why I haven't heard anything  I've been having internet problems so I guess my post is in Internet matrix world somewhere. I'll have to repost, on that note did you get a pm from me yesterday? I had sent one to you