Stand-alone true pitch shifting vibrato for guitar

[Willabe]

Thanks Ed.

If I keep at it, maybe I'll get it done by June?     


          Brad    

[sluckey]

I don't have a 500K for the mix pot on hand. I can use a 1M with a 1MR across the o/x ends of the pot until I get 1, right?

You can use that 1M without a resistor. And probably forever. I chose 500K for no particular reason other than because I had one.

[Willabe]

Got a question about the phase of the SR coils.

Looking at the Hammond AO-47 chassis I have and the Hammond drawings some things not right.

Red and black wires are flip/flopped from start to finish on opposite sides end to end, pins 1/7. Hammond schematic drawing doesn't have the SR coil wire colors, but their layout drawing does show the SR coils wired pairs colors. If you look at the schemo, SR 103 coil goes to the 3rd stage with C106 plate coupling cap and it's bias coils are fed from the LFO drivers K.

In the Hammond chassis I have, SR103 is the 3rd stage coil and is the blue/green pair. But on the SRA coils the black ground wire, pin 7 is across from the blue/green pair, pins 8/9, not the red LFO driver bias feed.

And you have pin 1 going to ground with pin 7 feeding the bias coils with pins 13/12 going to stage 1.

Or doesn't it matter which end of the bias coils you bias up or ground, as long as you don't flip the phase coil wires?

It's easer to see it in the drawing below than to write it.


            
                  Brad      
          

[Willabe]

You can use that 1M without a resistor. And probably forever. I chose 500K for no particular reason other than because I had one.

OK, sounds good to me, thanks.


                 Brad     

[sluckey]

Or doesn't it matter which end of the bias coils you bias up or ground, as long as you don't flip the phase coil wires?

Quick answer, it does not matter.

Remember, I used an AO-41 chassis, not an AO-47 chassis for my warbler. In the 41, the SR was plate driven, ie, one end of the primaries was connected to the plate of a tube and the other end was connected to B+. In the 47, The SR was cathode driven, ie, one end of the primaries was connected to the cathode and the other end was connected to ground. There's a phase reversal right there.

My 41 SR assembly had no markings on it whatsoever. I arbitrarily assigned those numbers to the SR terminals so I could connect it exactly the same as it was connected on the original. The main focus was on the secondary windings. I filed a notch in the top right corner of my SR while it was still mounted in the AO-41 chassis and called the top/right terminal pin 1, just like a 14 pin DIP chip. Then I counted clockwise until I ended up at pin 14. That seemed logical to me. There are many other ways the terminals could have been labeled, but using a familiar DIP chip pin assignment was easier for me.

Bottom line, keep the secondary wiring exactly as shown. And primaries, pin 1 and 7 can be swapped at will and you'll never be able to tell the difference.

[Willabe]

Quick answer, it does not matter.

Bottom line, keep the secondary wiring exactly as shown. And primaries, pin 1 and 7 can be swapped at will and you'll never be able to tell the difference.

Ok then. Will do. Putting in the board and SRA now. I do have my SRA numbered the same as yours, as in my drawing. I agree it makes sense the way you numbered it.


             Thank you,     Brad     

[Willabe]

Ok, good news and a little bad news.

I have every thing wired up except for the front panel controls, the components that hang from them, LED and the eyelet/turret board tag leads. Tubes heaters light up. Tested for 12.6vac on the tubes, I'm getting 13.4vac with a ~125vac wall voltage. A little high but within 10% +, 12.6 + 1.26 = 13.86. B+ no-load is ~350 vdc at 1st filter cap node.

Went to put the pots in and the CTS pots I have the bushing is too short to get the nut on.        

My chassis is .090" (~3/32"), face plate is 1/16", so very close to 5/32".

CTS with plastic shaft > bushing = 1/4", shaft = 3/8", marked > CTS 3MEG 0831 on sliver colored back cover shield. (I'm pretty sure I bought it from Doug.)

ROC with metal shaft > bushing = 5/16", shaft = 3/8", marked > 0990926 1M A 9804 ROC on gold colored back cover shield.

PEC with metal shaft > bushing = 3/8" , shaft = 1/2", both of those measurements are from the center of the brass colored ring/washer in between the bushing and shaft.

ROC pots bushing is just long enough with the star washer in place to tighten down the nut with the top end of the bushing just barely coming out a .001" or so.

PEC pots shaft length will cause the knobs to be sitting up off the face plate, it will look funny to me. AES's spec sheet says the PEC 2w pot's shaft is 3/8". How'd I get a 1/2" shaft?        

Any body know where to get the ROC pots? And do they make a 3MRA? AES and mojo don't have them.

I could cut the shaft on the PEC pots with a dreamel but that's a pain.

I'm going to go ahead and wire up what I have and swap out different pots later.


 
              Brad        

[sluckey]

I could cut the shaft on the PEC pots with a dreamel but that's a pain.

Not as painful as where you are right now. I would not hesitate to cut them. But I'd use a hacksaw and a bench vise. Stick the end of the shaft in the vise and use the edge of the vise as a guide for your hacksaw. For example, say you want to cut odd 1/8". Then stick 1/8" of the shaft into the vise. Then just use the side of the vise jaws as a guide for the saw. Some of the PEC shafts are hard so use a new 32 TPI blade and go slow. Should take about a minute. Finish off with a little touchup filing and you should have a nice square cut.

I don't really have an answer to the pot that the bushing is not long enough for the faceplate. I used Doug's CTS pot for my speed pot and the bushing on it is just long enough to pass thru my .09" chassis and allow the nut to fully engage. There ain't no extra bushing length! I couldn't even use a star washer, but the thin flat washers that come with the Alpha pots will securely lock the pot in place.

[Willabe]

Good idea about the vice. I have a couple here that should work nicely.

Some of the PEC shafts are hard so use a new 32 TPI blade and go slow.

I think their stainless steel?



                  Thanks,   Brad     

[DummyLoad]

Good idea about the vice. I have a couple here that should work nicely.

Some of the PEC shafts are hard so use a new 32 TPI blade and go slow.

I think their stainless steel?



                  Thanks,   Brad     

yes, they're stainless steel... i use a dremel but have a wet washcloth handy to soak away heat. you don't want the shaft to get too hot when cutting with the dremel. otherwise slucky's hacksaw method won't heat things up too bad.

--pete

[Willabe]

Thanks DL, I seemed to remember they were stainless steel.

I just remembered what I did before on the 5G9 I built. It has the same LFO and driver and I used the 3MRA CTS pot I bought from Doug.

I used the thin star lock washer from the PEC pot and although the bushing doesn't clear the outside top face of pot nut it does grab the bushing threads about 1/2 to 2/3rds of them. I wouldn't fell comfortable selling or fixing an amp like this but for myself I can live with it.

Back to work.


            Brad    

[Ed_Chambley]

Check with Steve at apexjr.com
He has a lot of NOS pots.  His website does not have everything listed so you may need to call him.  I have had the same problem of the threads not reaching and or the shaft being too long.  Old radios present this problem often.  The reverse pot is probably your worst concern.

I use PEC mostly except for the RA pot.  Your knobs may have enough plastic in the inside to drill them a little deeper.  The cool thing about CTS pots is you can take them apart and replace the thread with a longer one.  A fastener company can supply hollow threaded rod.  If you can get the rod, you could use CTS all the way.  If not just simply get solid and get a local Machine Shop to put it into a lathe with a bit in the tailstock and drill your own.  Take the warbler with you as they will be fascinated with it and much more inclined to do it as a favor.  The only other option I can think of is to mount the pots without the faceplate.  Drill the faceplate larger to go over the nuts and attach the faceplate in a different way.  This is provided you have knobs with a large enough base to cover the nuts, which they should.

This is the problem you run into restoring old radios all the time and at one time or another I have done everything I have mentioned.

Not to worry, the solution will come.

T

[DummyLoad]

Thanks DL, I seemed to remember they were stainless steel.

I just remembered what I did before on the 5G9 I built. It has the same LFO and driver and I used the 3MRA CTS pot I bought from Doug.

I used the thin star lock washer from the PEC pot and although the bushing doesn't clear the outside top face of pot nut it does grab the bushing threads about 1/2 to 2/3rds of them. I wouldn't fell comfortable selling or fixing an amp like this but for myself I can live with it.

Back to work.


            Brad    

mojotone sells custom mfg. CTS pots with the .4" long bushing including the 3MRA trem pot. they're the pots that you need for fender amps that have the brass backing plate and you wish to use the star-tooth washer. cost is steep - about 3.60 for most values, and the 3MRA is 5 bux. they used to sell these pots with a nylon shafts like the original 60's fender units had, but now all that they carry are made with a brass shaft.

http://www.mojotone.com/amp-parts/potentiometers-CTS

all other CTS and alpha brand pots i've bought from CE/AES have the standard .375" long 3/8-32 bushing unless you're buying a "genuine fender" replacement part.

--pete

[Willabe]

Thanks Ed and DL.

It was a little heart breaking at first after I had measured and re-measured everything for my layout drawing only to have forgotten the pot bushings.          

I'm going to order some from mojo or AES soon, but I'll finish wiring it up with what I have on hand.


               Brad     

 

[Willabe]

All right, I've got the tube sockets wired up and am working on the LFO parts that go on the panel controls.

On an LED the flat spot (and is the shorter leg) on the housing lens is the cathode, right? And the cathode goes to ground in this circuit, right?

I think I'll get it finished today. I have to finish the LFO controls then all that's left are the input/output jacks, bypass switch, 4 pots, the drive, tone, volume and mix.


            Brad      

 

[Willabe]

LFO is wired up. Fired it up, LED comes on and is blinking. Turning the speed pot slows down and speeds up the LED. Flip the speed switch and turn the speed pot, slows down and speeds up.  

There is a noticeable difference of range in the LED blinking, from fast to slow, when I flip the speed switch and rotate the speed pot.

Tested with a 12AX7 in, seems to be working fine.       

Now for the input/output jacks, bypass switch, 4 pots, the drive, tone, volume and mix. Should be down hill from here.




              Brad      

[Willabe]

It's working.       Everything is wired up except the panel bypass switch, it was getting late and I was getting tired, will add that in later.

I played it for a little while with a couple of 12AU7's in the 1st >2 positions, 12AX7 in the 3rd for LFO and driver. I need to put the knobs on so I can see where my settings are. I left the drive and volume full up while I played and quickly found I needed to turn the tone control up full. I was playing a rosewood fret board strat on the neck pup, volume/tone both full up, through my (stock) 5E3 clone on ~3, ~4, no verb.

It seems to be, the little I played through it, 15 minutes or so, that moving the mix and depth even a little really changed the effects sound a lot. I don't think the circuit is overly sensitive or finicky, that it's wired wrong or any of my parts are bad, I think it's just a powerful effect with a wide range available between the depth and mix. It's not like a boost/distortion or delay where you add more or less with a single knobs setting, in their most basic forms anyway. It's more involved with this effect and it's settings.

I didn't like it at 1st, but after a few minutes of playing with the knobs I found a few settings I really liked. My wife liked the sound of it right away and her ear is pretty good.      

It can go really deep into a chorus type swirl with the depth set past 6/7 and the mix set (I think, I had the chassis upside down with no knobs on) past 5 going towards more dry signal. Gonna take some time to fool with the settings to learn what it can do.

The tone control might be in the wrong place in the signal chain? Steve, you might have had the ticket when you put it on the input. It's only cutting the high end where it's at right now and with the effects thickening of the sound, I can't think of a reason why it would be needed, at least the way it's wired and functioning right now. Maybe if I played the lead pup or with a tele or other bright guitar, but I live on the neck pup for lead and the middle pup (neck/bridge with a pair of bucks) for rhythm.    

I need to check all the voltages and the current through the 1R that I put in series with the B+ FWB's ground. I'll post those when I get them. (I did check the voltages as I wired up different sections, B+ but unloaded, heaters and the dc standoff voltage and all were fine.)

My EH Wiggler which is a SS/tube pedal that has 4 basic mode settings on a 4 position rotary switch, plus a vibrato/trim switch. There labeled, Looz, Hamm, Acey and Wurl.  It responds the same as the warbler as far as the settings. Just a little bit of change can send you off to a sound that's not really very usable, to me any way. But the sounds that are usable sound really good to me.


             Brad          

[Willabe]

I do have 2 problems.

1. With the 12AX7 in the LFO/driver socket, turn up the intensity and it thumps, not ticks, but thumps real good.    

Here's the specs for the red LED I put in, 1.7v, 20mA, 3000mcd, 12 deg. viewing angle.

I'll try a 12AU7 and see if it helps.

2. The pilot light is acting up. Might just be the bulb. Turns on/off by the smallest touch to chassis when turning the knobs. Unscrew the jewel lens a turn or 2 and it lights back up. I did hit the bulbs base with some fine steel wool, but no go. It's a Fender clone pilot light, never used, a few years old.   

I'll post pics in a day or 2.


               Brad      

[tubeswell]

... seems to be, the little I played through it, 15 minutes or so, that moving the mix and depth even a little really changed the effects sound a lot.... it's just a powerful effect with a wide range available between the depth and mix... It can go really deep into a chorus type swirl with the depth set past 6/7 and the mix set (I think, I had the chassis upside down with no knobs on) past 5 going towards more dry signal. Gonna take some time to fool with the settings to learn what it can do.

Pretty much sums it up for me too. Its a lot more versatile than a straight trem. Have you got some sound-clips to post/link?

[Willabe]

Have you got some sound-clips to post/link?

No, not yet. I just finished wiring it up tonight. I'll try to post something in the next few days.

What do you think about the thumping?


              Brad      

[sluckey]

Thumping is because the LFO signal is so BIGGGGG, especially since the LED mod. Mine does it also if you turn the Depth up too much. You can increase that 2.2M to about 4.7M to knock the LFO signal down, or just don't turn the Depth up so much.

I find that I usually set the Mix to max. For slow speeds I like the Depth turned up a lot and for faster speeds I usually turn the Depth down some.

EDIT... More info. I had tried a 5751 and 12AX7 in the LFO circuit and they both seemed to work fine. But later I switched back to the 12DW7. I remember preferring the 12DW7 but I can't remember why. 

[Willabe]

Thumping is because the LFO signal is so BIGGGGG, especially since the LED mod. Mine does it also if you turn the Depth up too much. You can increase that 2.2M to about 4.7M to knock the LFO signal down, or just don't turn the Depth up so much.

I find that I usually set the Mix to max. For slow speeds I like the Depth turned up a lot and for faster speeds I usually turn the Depth down some.

OK, I'll try what you say and see how it goes for me. I still need to dig another 12AU7 and a 12DW7 outa my stock pile and try those.



                       Thanks,    Brad     

 

[Willabe]

I took some voltage readings, here's what I got;

Wall voltage was holding around ~121.7 or so while testing. 12AU7 in V1/2 and 12AX7 in V3.

B+ > 325.5vdc 1st node, 323vdc 2nd node.

264vdc K driver for LFO V3/pin 1 = 264vdc. 147vdc V2/pin 6, 145.3vdc V2/pin 1, 146.4vdc V1/pin 6, 251.5vdc V1/pin 1. V1A is biased with 47K plate R, 10K cathode R.

The 3 phase shift triodes are on the same B+ node, has a 10K dropping R. Input preamp is on it's own B+ node with a 10K dropping R. Do you think I should change values for either?

Now I messed up on the heater transformer.          It's a Hammond 229A12 semi torrid/low profile, 115vac primary, when wired for 12.6vac secondary it's rated @ 450mA.  I thought the No. 47 pilot light bulbs were 40mA, turns out their 150mA.

I don't know if they pull only 1/2 the current when feed twice the voltage? But....

With the bulb in 11.16vac on heaters, with the bulb out, 12.85vac.DC standoff dcv was 66.8dcv. Wall acv was around 121.7 at time of readings.

Going to put the knobs on so I can turn them easily and see the settings to get my bearings while I give it another try. Also going to put a 12AU7 and 12DW7 in for V3.


             Brad      

[sluckey]

I don't know if they pull only 1/2 the current when feed twice the voltage? But....

No. If you run a 6 volt bulb at 12 volts it will burn much brighter and draw twice the current. A #1849 runs at 12v and will fit that bayonet socket.

[Willabe]

No. If you run a 6 volt bulb at 12 volts it will burn much brighter and draw twice the current. A #1849 runs at 12v and will fit that bayonet socket.

Oops.       So 3x12_ _ 7@12.6vac=450mA + 1x6.3, 150mA bulb run@12.6= 300mA= 750mA from a PT rated for 450mA. I'll get a few of those bulbs.


              Thanks,   Brad        

[Willabe]

Tried a 12AU7, 12AY7 and 12AT7 in V3. None of them thumped even with the intensity set to full. But these 3 all would stop oscillating if I turned the intensity and or speed down to far, like ~3 or less. Then it was a little hard to get it going again. 12AT7 worked the best but still stopped. I have a few 5751's laying around in a box, need to find them and give them a try. If they don't work I'll try upping the 2.2M and see if that will get the balance of not thumping but not turning off the LFO.

Also the lower gain tubes let the LFO go slower than the 12AX7. I thought at 1st with the 12AX7 in I was going to have to change out 1 of the .01 LFO caps for a .02, now until I find a tube that works in V3 I'll have to wait and see.

The other thing is it seems to be over driving the 5E3 clone with its volume only on 3 when the Warblers drive and volume are full up. Turn them down to get the amp to stop over driving and it sounds very thin and sterile. Some things not quite right with that.

Maybe I'll try by passing the volume and tone at the output with a alligator jumper and see if that helps? I wonder if it's an impedance load thing?

I'll also try inserting an A/B box between the guitar and Warbler to the amp and see if that gives me a better idea in my ears of how much it's driving/changing the tone of the amp.

            
                                  Brad      

[Willabe]

Hummm....        

Thinking about this more, I think it might be best if I disconnect and not just by pass the 1M drive pot and the 2@1M output volume and tone pots.

Strip it down to the bare bones circuit to eliminate any impedance/load issues?


                    Brad      

[Willabe]

I forgot to add that across the 1 ohm R in the tail of the FWB ground I'm getting a reading of 17mA on dcv setting. And the on/off jack is working.


            Brad      

[sluckey]

I don't seem to be able to find any 1849 lamps. I may have remembered that number wrong. Here are some current production bulbs that would be suitable. I like the 756 best because of cost, long life, and low current.

I can't comment on the 'thin' sound other than to say that on my first version there were some positions on the mix pot that would produce a thin, almost nasal tone. I chalked it up as a phasing issue. There were still some good full bodied sounds, but the mix never behaved as I imagined it should. That issue was totally resolved in the revised circuit.

[Willabe]

Thanks Steve, that bulb at only 80mA looks good. Long life and price are good too, I'll buy 10.


            Brad        

[PRR]

Are you looking for 12V pilot lamps?

If just to say "ON", an LED (with resistor) will last forever.

If power is unlimited, car lamps work. However the common stoplamp (try 1156) takes a large fraction of an Amp, is large, and more of a work-light than an indicator. There's teeny 1W lamps in my 2002 Honda for Cruise indicator and clock backlight, but the socket is way-odd and the life has been short (may be time to re-rig the clock with a white LED?).

A 6V can be run with a resistor on 12V. This will also increase life (reduced cold surge). For the once-common #47, 6.3V 0.15A, use 40 (39) ohms 2 Watt in series.

Two 6V lamps in series is 12V at the same current. (Lower reliability cuz when either breaks, both go dark.)

[Willabe]

Are you looking for 12V pilot lamps?

Yes.

Chassis is already drilled with face plate for a Fender clone pilot light. PT is Hammond 229A12 semi torrid/low profile, 115vac primary, when wired for 12.6vac secondary it's rated @ 450mA.  I thought the No. 47 pilot light bulbs were 40mA, turns out their 150mA.

The 756 bulb Sluckey suggested looks like will work. It's only 80mA so, 3x12_ _7, 12vac@150mA= 450mA+80mA= 530mA, looks like my best option so far.

No. If you run a 6 volt bulb at 12 volts it will burn much brighter and draw twice the current. A #1849 runs at 12v and will fit that bayonet socket.

Oops.       So 3x12_ _ 7@12.6vac=450mA + 1x6.3, 150mA bulb run@12.6= 300mA= 750mA from a PT rated for 450mA. I'll get a few of those bulbs.

With the (#47) bulb in 11.16vac on heaters, with the bulb out, 12.85vac.DC standoff dcv was 66.8dcv. Wall acv was around 121.7 at time of readings.

                   Thanks,    Brad      

[sluckey]

Any progress?

[tubeswell]

Tried a 12AU7, 12AY7 and 12AT7 in V3. None of them thumped even with the intensity set to full. But these 3 all would stop oscillating if I turned the intensity and or speed down to far, like ~3 or less. Then it was a little hard to get it going again. 12AT7 worked the best but still stopped. I have a few 5751's laying around in a box, need to find them and give them a try. If they don't work I'll try upping the 2.2M and see if that will get the balance of not thumping but not turning off the LFO.

Also the lower gain tubes let the LFO go slower than the 12AX7. I thought at 1st with the 12AX7 in I was going to have to change out 1 of the .01 LFO caps for a .02, now until I find a tube that works in V3 I'll have to wait and see.

The other thing is it seems to be over driving the 5E3 clone with its volume only on 3 when the Warblers drive and volume are full up. Turn them down to get the amp to stop over driving and it sounds very thin and sterile. Some things not quite right with that.

Maybe I'll try by passing the volume and tone at the output with a alligator jumper and see if that helps? I wonder if it's an impedance load thing?

I'll also try inserting an A/B box between the guitar and Warbler to the amp and see if that gives me a better idea in my ears of how much it's driving/changing the tone of the amp.

            
                                  Brad      

A 12DW7 (or JJECC832) will be the best bet for that trem circuit I think. The LFO stage (V3a) is set up with a 470k plate load that is high - even for a 12AX7, but a 12AX7 can manage that. (This could account for the other tubes' intensity cutting out sooner). Whereas the CF stage has a load of 11k, so that works best with a 12AU7.

However if it thumps with a 12AX7 triode in V3a, then you could try lowering the gain of that stage a bit by using either 390k, 330k, 270k or 220k plate load, and changing the bias point of the stage accordingly to maybe 3k3 or 2k7 or 2k2. You'd have to suck it and see.

[Willabe]

No progress, my wife's parents are coming into town for her sons HS graduation. Working on cleaning up the house and doing yard work. She deserves it and I do like her parents. They live in up state NY, so she doesn't get to see much.

Thanks Pete for the options to try to tame the thump, I'll try them when I get back to it.



               Brad     

[PRR]

> Chassis is already drilled with face plate for a Fender clone pilot light

I've put LEDs behind jewel-lamps. LED and resistor, little shrink-tube, hung on the solder-lugs and shining into the jewel. Looks a bit odd behind, but works forever.

[Willabe]

Ahh, thanks, that's a good option.


            Brad     

[Willabe]