Stand-alone true pitch shifting vibrato for guitar

[sluckey]

Vibrato junkie!

And I remember when everything you touched became a plexi. You've come a long way!    

[plexi50]

Boy your right about that. It has been a wild journey. I could have had my own cereal brand / plexi O's

I paralleled a .022 cap across the exhisting .022 rate cap but that was too slow. I tacked a .0047 across the .022 and nice

I paralleled the .01 cap and got the same results with the speed rate but just used the .022 as it was more convenient

I think though that the .01 to the rate pot is where i should have put it

Something in the rate cap change itself has made the vibrato blossum a bit more even when compensating for the slower rate by CW pot

I see what i did. I changed the plate coupling value of V4B. It did something nice. I wouldnt think it would have slowed down the rate though
 

[Willabe]

Something in the rate cap change itself has made the vibrato blossum a bit more even when compensating for the slower rate by CW pot
 

Ahh,                Very interesting.


              Brad             

[plexi50]

See what i typed above. Not looking at the Layout at the time, i changed the V4B plate coupling cap value. But the rate slowed down so thats where i put it. umm!  

As well maybe changing the .01 cap going to the 2.2Meg resistor would also change the tone of the depth and buffer the pumping action a bit. My 500KL pot in the rate position is down to 248KL using a 470K resistor across the wiper and outer pot terminals

All said this thing is fun tweaking. Im looking for and getting a more active so to speak (EQ) and so far the little changes are producing  that for me

[sluckey]

My 500KL pot in the rate position

Huh? I used a 3meg pot for my rate (speed). Put the right pot in and you'll probably be happy with the slower speed. Bigger value equals slower speed.

[plexi50]

Im sorry i did it again*

My 500KL pot in the Depth position is down to 248KL using a 470K resistor across the wiper and outer pot terminals

I am using a 3Meg RA for the Rate pot

On the board is where i made the parallel cap addition of .0047 to the .022

Im keep getting the rate and depth pot mixed up

 

[bobmegantz]

Just wanted to report that I finished this delightful project today.  I used the board and some of the circuitry from the original Hammond box, then added the LFO and input amp using terminal strips and empty parts of the board.  It fired up nicely and works fine.  The only problem I encountered was with the tube sockets I bought from Antique Electronics - two of them had jammed holes, which I didn't notice until the whole thing was wired.  I'm not sure if they were defective as delivered or if solder wicked up in the holes during construction.

The sound is better than I expected - very useful for modern jazz (a la Scofield or Metheny) or as a sub for chorus or tremolo in rock tunes.  I'm going to ask my bass player to try it next.

I did find the mix and depth controls to be somewhat duplicative sonically, even though they perform different functions.

Anyway, tnx for the nice idea.

Bob

[Dave]

Well, I'm glad it wasn't me who bumped this thread into existence again. Not that I don't like the thread, I do, but oh well get ready for prices to skyrocket again.
Now that the cat is out of the bag again, here is what I have to add.

I have built it too and I have these observations.........

PRR speculated that it could be built using only 3 tubes. Eliminating the final stage (which functions as an output boost) and reconfiguring it as an input boost. He couldn't have been more right. Eliminating the last stage, from my tests, had no noticeable effect. Reconfigure........ I left it as is and ran the input signal straight into it as is. The output then became my clean signal and it worked perfectly both as a guitar input and running with an effects loop.

On mine, there was some disparity between the extremes of the mixer pot because there is some loss thru the circuit. I found that this was easily compensated for by using a 25/25 bypass cap on the first (original) stage. I thought at first that it might cause problems because the cathode had series resistors tapped in the middle for some grid feedback and one of the SR leads attached there, but no, the only effect was a positive one.

The cap that Sluckey uses as a slowness boost for the LFO is interesting. I changed mine to .1uF. The frequencies still overlap, but I get some really slow oscillations with .1 and I thought why not have the range be as wide as possible.

Next, I did a lot of tweaking and fiddling, and the biggest thing that stood out to me was that this thing (with certain tweaks) makes a very convincing wah effect, but it oscillates by means of the LFO circuit. It would be very interesting if someone could come up with a dynamically responsive LFO circuit, we could have this thing double as an autowah. Just a thought.

Enjoy.

Dave

[plexi50]

Can you show your changes in circuit and possable part changes? I know it is quit a detailed layout Steve made. For a guy that works 9-5 he sure puts a lot of THINKING which i lack sometimes into his layouts and schematics. I would not be where i am at today without his and many others teachings. I may be having a little trouble with mine between the mixer and depth pots. I have a cutoff point before full CW on either pot. Like grid cutoff. The only part that i used that differs (1K) is a 1.2K resistor on V4A cathode

I have not had the tme to tinker with it latley. But over all it does a nice job once i can set the mixer and depth pots
The mixer and depth pots though are very sensitive and quick to go into cutoff or should i say a dry signal not leaving much pot functionality

Im sure i need to go over it again with a fine tooth comb

[Dave]

These are the changes (the ones I can think of off the top of my head) in a very rudimentary mutilation of Sluckey's schematic.
I am not able to look at it right now, but I will see if I can get a peek at anything else when I can.

I will say that I messed around with the voltages a little bit, and fenagled voltages that mimicked both the original hammond circuit and the fender LFO circuit.

Dave

[sluckey]

Glad to see y'all still have interest in this project. Keep the tweaks coming. I'm taking note.   

[Dave]

I just remembered something else I did.....
The .47 coupling caps have DC on both ends whether they are leaking or not. I suspected mine were leaky, but I wasn't sure so I changed them out.
I didn't have any .47 caps with a voltage rating high enough, and in an attempt not to have to buy any, I changed them for what I had on hand.
I didn't want to go with 1/10th the capacitance, so I went with more capacitance.
Mine are now 1.2uF film caps.

No perceivable difference in tone.

Dave

[flocentblack]

Found one of these on a shelf in the basement while doing some pre-move sorting...

Don't know if its an AO 41 or AO 47...

If any one is interested, i', not looking to get some exorbitant price...




flocentblack   aaaaattttttt   yahoo dot  com 

[DummyLoad]

Found one of these on a shelf in the basement while doing some pre-move sorting...

Don't know if its an AO 41 or AO 47...

If any one is interested, i', not looking to get some exorbitant price...

flocentblack   aaaaattttttt   yahoo dot  com 

it is the AO-47.   this is good. 

[Willabe]

Well I just came back from Lenco Transformer Co. Talked with a salesman and after he looked at it for a while, he said off the top of his head he thought for a run of 25, maybe $40 a - single - inductor, each unit has 3, so $120         , and thats if they can even wind them. He said they sometimes used a very fine wire, smaller than what is used on guitar pups, on the coil windings. Not the center coil but the 2 end coils. He also said he thought the lams. were nic. and not steel which cost's more. He did find a company that still makes them.

I left it there so one of their techs can look at it and do some tests to figure out for sure what it is and if they can make it. He said that they wont damage it.  

I'll know more late next week.  


               Brad              

[PRR]

> The .47 coupling caps have DC on both ends

One end is at plate voltage. One end is at cathode voltage. Why a problem?

> now 1.2uF

Feeding 15K, we want 0.6uFd for 20Hz response. Hammond knew 20Hz was not needed, used half uFd. Guitar is shorter bass than organ, 0.2uFd would be fine. You "spent too much" for 1.2uFd, can pass 5 times deeper bass than guitar needs. Like I put a 9x3 wood block where 2x4 would have carried the toilet-load... it's what I had handy, cheaper than going out for 3 feet of smaller lumber.

[Dave]

1. Why a problem?

2. Feeding 15K, we want 0.6uFd for 20Hz response. Hammond knew 20Hz was not needed, used half uFd. Guitar is shorter bass than organ, 0.2uFd would be fine. You "spent too much" for 1.2uFd, can pass 5 times deeper bass than guitar needs. Like I put a 9x3 wood block where 2x4 would have carried the toilet-load... it's what I had handy, cheaper than going out for 3 feet of smaller lumber.

1. I didn't say it was a problem. Just that it its akward to check for leakage.

2. I didn't spend too much. I had those caps laying around. I wasn't going to use them for anything else, so I really saved money.

Dave

[Willabe]

sluckey,

Do you think we could put in a passive FX loop with a couple of volume pots, from the output of the 3'rd stage shifter and back into the 1'st stage input? Then insert a delay pedal and send just the wet signal back to the input, kind of like the regeneration control on a flanger?

Might be very interesting to play around with. Maybe with a short delay of say 10 to 40 ms it would make it even more lush?  

OTOH, maybe it'll just feedback/freake out and make noise, but it's worth asking.


                  Thanks,      Brad                  

[sluckey]

Do you think we could put in a passive FX loop with a couple of volume pots, from the output of the 3'rd stage shifter and back into the 1'st stage input? Then insert a delay pedal and send just the wet signal back to the input, kind of like the regeneration control on a flanger?

Absolutely! Sounds like a good experiment for you to try. I don't have a clue what might happen or what sound you may be chasing. Could be a real tone generator. Let us know what happens.
 

[ThermionicEngine]

This thing is really cool.  Never owned or serviced a Magnatone.  Looks like a great project.  I also liked the looks of the finished product.

[Willabe]

Hi ThermionicEngine,

 Did you hear the sound bits sluckey posted? They sound great! Much thicker and more fluide than a Maggie, IMHO.

Look back thru the post and you'll find them.

Yeah, hats off to sluckey, not only is his work very, very nice, but he posted the schem and layout for the chassis and eyelet/tag board!

Absolutely! Sounds like a good experiment for you to try. I don't have a clue what might happen or what sound you may be chasing. Could be a real tone generator. Let us know what happens.

I was thinking maybe if you send the output signal back in, slightly delayed, it would re-phaseshift the signal again --but-- now the sine waves of the 2 signals would line up at a different time. The peaks would be at a different point time wise and this would cause the signal to thicken. Maybe even act/sound somewhat like a 6 stage phaseshifter with out doubling the whole thing.    

I'll let you know when I get to it what it sounds like or if it even works.


                  Thanks,     Brad              
                
{EDIT-- untangled quote -- PRR}

[Willabe]

Thanks,  PRR.


           Brad      

[DummyLoad]

i was going to base my LFO on a Exar XR2206 or the Maxim MAX038 function generator IC. alas though i've been thwarted again and no good intention goes unpunished. BOTH devices are obsolete and out of production. NTE still lists a replacement for the Exar 2206 and my local fry's still has a few in stock, but i'm NOT playing at 30bux a pop.

why the sand state? thought it might make some cool noise with a triangle, sine and square wave LF source. looks like i'm gonna have to roll up my sleeves and roll_my_own with op-amps.

oh well...  

[sluckey]

thought it might make some cool noise with a triangle, sine and square wave LF source.

I played around with that idea too, but just never did it. I was gonna use my HP 3310B function generator for an external modulation input. It would only require an input jack and maybe a resistor. I may do that yet. Thanks for the reminder.

Are you gonna build this? Got a saturable reactor?

[DummyLoad]

Are you gonna build this? Got a saturable reactor?

yes, and yes. i have two. a forum member made me deal on a AO-47 i couldn't refuse.

if i $crew one up, i have a backup.   

[DummyLoad]

It would only require an input jack and maybe a resistor. I may do that yet. Thanks for the reminder.

you should - if'n yer a-waitin' on me...    ...you may be waiting a while.  i have nearly 3million bux worth of routers and fiber optic transport equipment to install all over the state within the next year. it is likely that very soon i will be scarce here and my thermionic experimenting slowed considerably.

http://www.utexas.edu/news/2010/12/16/regents_support/

 

[sluckey]

Sounds like a nice contract. Do you do fiber work too (I mean connectorizing)?

[Willabe]

Well you cant count your chickens before they hatch, but I just talked to a guy who might have the spec/order sheet for the SR --and-- might have a small number of SR's layin around.        

Have to wait and see.              He said he had to look up the part # to find the part and any info he would have on it. I gave him the # off the Hammond schem. of SR 1,2 and 3, but that might not be it. I have mine at a transformer company right now getting checked out, so I could'nt look at it to see if there's a part # on it. Which still might not be Hammonds . I don't recall seeing one on it. Do any of you'rs have a part # on it that you recall?    


             Brad          

[DummyLoad]

Sounds like a nice contract. Do you do fiber work too (I mean connectorizing)?

we do some but usually only in emergency situations. we have an old fusion splicer that's a chore to use. nowadays we mostly contract our FOC work.




   

[DummyLoad]

don't recall seeing one on it. Do any of you'rs have a part # on it that you recall?    


i have one AO-47 unit that looks like it's brand new... i'll check it tonight when i get home. honestly, i think that all you're going to get off the hammond part is an OEM number.

--pete

[Willabe]

Thanks Dummy Load, and I think you'r right about it only being an OEM #. If he's got the part and/or some info on it, he'll find it.

Oh well, have to wait and see. How long it'll take for him to just to get to it and look around for it, who knows.     


               Brad       

[mresistor]

What is Sluckey's homepage?

Dave

http://home.comcast.net/~seluckey/amps/index.htm

[Willabe]

Well my guy came thru.        He's putting 8 SR's in the mail to me. He said there brand new and have never been installed. He also said he thinks the last time he saw the price list for them they were $55, and has only sold maybe 4 of them in the last 30/40 years, all of which were international sales.

He still has'nt had a chance to look for any paper work he might have on them. If he has any it's in another warehouse and will get back to me after the next time he goes over there.


           Brad            

[Willabe]

Well I got them the other day and they all test good for coil resistance. Look to be the same as the 1'st one I got a hold of.     

I've been thinking about if you could use the unused 12AU7  triode as a 4'th stage of phase shift, but wiggle the cathode with a light bulb and LDR like in a Uni-vibe.

Could I drive the bulb with/off the LFO driver, maybe pin 2, of VA4 would keep the two in phase, but still isolated? Or do they even need to be isolated from each other? Would they be/work at the same speed? The light bulb is susposed to give a slighty different shape to the signal wave form because the fillament heats up/cools off at a slightly different speed.

Since there's an unused triode left over, I'd like to try to put it in as the 1'st phase shift stage to feed the next 3 stages the slightly differently shaped signal wave to work with and see/hear what it sounds like. Do you think this can be done?

Also, how much current are the 12AU7's biased for? RCA book says they can eat up as much as 11.8mA per triode from the high voltage supply.

       
              Thanks,     Brad          

[sluckey]

I think you can probably do it. Just jump in with both feet. I don't really have any specific ideas.

Could you take a pic of your SR? I'd like to see what it looks like. Is it 3 SRs on a common form like the Hammond?

[Willabe]

Could you take a pic of your SR? I'd like to see what it looks like. Is it 3 SRs on a common form like the Hammond?

Yes, it's about time I learn how to do that. I'll talk to my neighbor tonight and see if he will show me.

I was able to get 8 SR's and there all the same. Exactly like the 1'st one I bought and I belive, from the pics in this thread, are the same as all the pics. Yes, there 3 SR's on a common form. They are Hammonds. The guy I bought them from was the head tech at Hammond for many years. When Hammond was going to sell to Susukie music, they offered him the option to buy all of there parts stock, and he took it. These were spare parts and he does'nt belive he has any more, but who knows? I belive he's still got a big storage building full of parts, so he might run across a few more. I told him that I was hoping he had a big box full of them, like 50, 100, maybe 250 of them. He laughed a little and said he does'nt think he ever had more than dozen. He's still looking if he might have any info from Hammond on them, like maybe even the order/spec sheets and who Hammond had make them. Have to wait and see.        He sold them to me for $15 each, which I thought was nice of him. He could have asked for more, he did say he seemed to remember the last time he looked at the book price list they were $55.

Now that I have a few to play with, I think I'll try a 6 stage shifter and see what happens.       I can make a few for friends and keep a couple for myself.

How much plate current do you think the Warbler wants to draw the way you have it biased up?


             Thanks,     Brad       
               

     

[Willabe]

Here's the coil resistance readings I took on the new RS's I got.

       Brad

[sluckey]

How much plate current do you think the Warbler wants to draw the way you have it biased up?

The easiest thing to do would be just stick a 1Ω resistor in the PT center tap and just read the actual B+ current. However, it would be a week or so before I could do that.

Another way would be to calculate the plate current for each tube and then just add them all up. For example, V1A has a 100K plate resistor, 155v on the plate and node E is 312. So, that 100K has 312v-155v=166v across it. So, plate current must be 166v/100kΩ=1.66ma.

V4A is a little trickier. You have 4.4v across a 1K in series with the 260Ω resistance of the SR (just ignore the 10K resistor. So, 4.4v/1260Ω=3.49ma.

That's two tubes. You do the rest and just add them up for the total B+ current.

If you're wondering about PT or choke sizes, my PT is a Hammond 269JX rated for 500vCT @ 69ma dc. And the choke is a Hammond 155H rated for 5H @ 50ma dc.

[Willabe]

Thanks sluckey.

         Brad     

[sluckey]

Here's a LED/LDR version of a vibrato circuit. Might be adaptable to your favorite 12A_7 tube.

http://www.freestompboxes.org/viewtopic.php?f=13&t=4861&hilit=tube+vibrato

[Willabe]

Thanks sluckey, the link was very helpfull. I found a page while reading in there from R.G.Keen on phase shifters and flangers that is very interesting.

Here's a schem I drew up, what do you think? Might be a lot of work for not any or little difference in sound. But a real Leslie does have a hi/low combo. output ---plus--- the sound sources are spinning ---and--- in a cabinet with louver baffels that all add up to a lot of reflections and cancellations and who knows what else is shaping the sound.

The phase shift coupling cap values could be changed to different values in each of the hi/low shift stages. The univibe uses 4 different value phase shift/coupling caps. Maybe use 1 set of values for the low and the univibe set of 4 in the high shifter. That's if I go to a 4 stage shifter.

I'd like to see if the 2 different schems to control/wiggle the cathodes is enough to make a big enough difference to hear. Maybe not.    

I still think adding a feedback loop and inserting a 4ms to 20ms? delay, now maybe on just the hi or low signal would thicken things up a bit more. Keen says you just have to be carefull to only use a very small amount or it will oscillate, but done right "you can feed back enough to cause frequency peaks at places where the signals reinforce, and keep the cancellation notches"

Or maybe just string the 2,  -3 stage shifters together to get a 6 stage shifter?

I'm gonna play around with this and see what happens.        


             Thanks,    Brad            

[tubeswell]

@ Willabe, if you are thinking of selling some of those SRs you got, let me know. TIA Pete

[tubeswell]

Yay! 2 SR's arrived in the mail today. Big thanks to Willabe  . Now I can finally get on this bandwagon.

[plexi50]

Willabe what is the LDR you are trying out in this new idea?

[Willabe]

tubeswell, just glad they got to you safely. It's a Looooong way from Chgo. to NZ.     

Keep us updated on your build.

plexi, I'd have to find my notes but I did a search and found some guys who were very happy with the LDR's that they used in uni-vibe clones they had built.

When I find them again I'll post the numbers.


        Thanks,      Brad         

[tubeswell]

I am contemplating using one of my SR units (that I got from Willabe) using Steve's unit design, but taking on PRR's comments about the bypass stage and the gain on the driver stage for geetar use (and seeing as how Steve's unit had a spare triode). So I'm looking for some feedback on this schematic please.

1) will the driver stage (with a gain of about 5 - I think?) work okay this way (with the 1M level pot parallel with the 1M bootstrapped grid load for the 1st 12AU7 stage)? Or is it 'better' to put a level pot before the 'driver' stage (as Steve did in his original design)?

2) do the CF bypass stage's values look okay? (just borrowing it from a 6G15 CF bypass). I'm wondering if this will help better with the output impedance of the unit overall? (i.e.: does putting the CF bypass output 'in parallel' with the last 12AU7 stage's output (via the mixing pot) lower the output impedance overall?

3) any other things anyone can see that I might've missed. (should I be starting this in a new topic? seems a shame not to keep this intriguing discussion going)

I also have another variation in mind utilising an additional triode in the LFO driving stage (like the brown harmonic vibrato a.k.a. 6G4/6G5 etc) but I will post that schematic when I've finished doing it.

TIA Cheers

Pete

Edit (realised I did a blooper on the 12AU7 power supply decoupling - corrected version attached - sorry)

[tubeswell]

And this one is based on the "Liquidator" (more knobs) but has the CF bypass (instead of the 'recovery' inverting stage).

Qn1: will the feedback control serve as a 'level' control somewhat?

Qn 2: Or would it be 'better' using the spare triode as a recovery stage (as per the Liquidator) i.e.: instead of having the CF bypass?

(Edit: same 12AU7 power supply blooper fixed in this version)

[tubeswell]

And this is the above concept with a brown trem:

1) Is this too fanciful/waste of tubes? (i.e.: will the effect of the brown trem be noticeable?)

2) Is the red line the best place to take the trem input from?

3) Any additional comments?

TIA

[tubeswell]

The same as above but with switchable brown trem/vibrato effect (either mixable to buffered dry signal)

Is there any issue with leaving the SR connection floating/unconnected to the oscillator when switched into Brown trem mode?

[sluckey]

Look at page 9 of my scrapbook for an explanation of that brown trem circuit. (I know it's a slightly different circuit from yours, but the circuit operation is the same.)

You're trying to drive the SRs with the guitar signal, not the trem oscillator signal. The SRs are current devices and will want a lo z driver such as a cathode follower. You could pick up the trem signal at the wiper of the Depth pot, run it thru a CF then apply to the SRs. No need to actually switch off the SR drive. Just switch the guitar output signals.