Schematic help please

I can read a little in this language, but am confused on something.  Probably the dumbest inquiry of the day.

Am building a d.i. and am at the Pot section.

It seems to say to tie lug 2 to the housing of the Pot yet connect lug 3 and 2 together. Am I reading that correctly?

Thanks in advance.

ReRibbon said:

It seems to say to tie lug 2 to the housing of the Pot

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Does it? I don't think so. It says to connect pin 3 to the 1k resistor, which other end goes to ground.

yet connect lug 3 and 2 together. Am I reading that correctly?

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This is correct, but I think it's far from being the best. Pin 2 should go to pin 3 of the RH section of the dual switch.

This is correct, but I think it's far from being the best. Pin 2 should go to pin 3 of the RH section of the dual switch.
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Thanks for the reply and suggestion. What would the benefit be to that as opposed to following schematic?

RH? Forgive me not knowing abbreviations on this language.
This circiut is the old Motown d.i.

This is the Ed wolfram di box schematic. It is credited to Ed’s work as a Motown engineer an being in use at Motown.

Connecting it as shown in the schematic(tying pin 2 and 3 together) would make a variable resistor.

Wiring it as Abby suggested (without connecting pin 2 and 3 together) would have it as a variable voltage divider ultimately  making a volume pot.

abbey road d enfer said:

This is correct, but I think it's far from being the best. Pin 2 should go to pin 3 of the RH section of the dual switch.

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Not sure I agree with you there. That would change the gain structure. As-is switching in gives you -20dB right away and the 1K presents a fixed impedance to the transformer whereas if wired as a volume, the high position is 100K in parallel with the source which is ill-defined.

ReRibbon said:

I can read a little in this language, but am confused on something.  Probably the dumbest inquiry of the day.

Am building a d.i. and am at the Pot section.

It seems to say to tie lug 2 to the housing of the Pot yet connect lug 3 and 2 together. Am I reading that correctly?

Thanks in advance.

Click to expand...

2 and 3 are tied together making a rheostat (variable resistance). The housing of the pot would need to be indicated for a schematic by a 4th terminal, so leave it floating.


JR

squarewave said:

Not sure I agree with you there. That would change the gain structure. As-is switching in gives you -20dB right away and the 1K presents a fixed impedance to the transformer whereas if wired as a volume, the high position is 100K in parallel with the source which is ill-defined.

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Each solution has its pros and cons. The final evaluation would depend on application, workflow and taste. And anyway, that is relevant only for line levels.
Connecting a guitar to an input of which the impedance varies from about 100k to 10k is like the legendary "Suck" button.

abbey road d enfer said:

Each solution has its pros and cons. The final evaluation would depend on application, workflow and taste. And anyway, that is relevant only for line levels.
Connecting a guitar to an input of which the impedance varies from about 50k to 1k is like the legendary "Suck" button.

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If I'm understanding that A-11J transformer it's 60k:600 so with the DPDT out and a typical 10k load that gives the guitar a 1M load which is pretty much spot on I think.

But you'll never catch me spending $200 on a transformer to make a DI no matter how legendary it might be.

Well, maybe I've had made all of you proud. I am using a 12$ edcor and it is 10k:600ohm.

Using a 250k pot and adjusting resistors to 10% and 1% accordingly.

Maybe..... It might work?

squarewave said:

If I'm understanding that A-11J transformer it's 60k:600 so with the DPDT out and a typical 10k load that gives the guitar a 1M load which is pretty much spot on I think.

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his is correct when the attenuator is not in circuit. I was mentioning the input impedance with the attenuator on.

ReRibbon said:

Well, maybe I've had made all of you proud. I am using a 12$ edcor and it is 10k:600ohm.

Using a 250k pot and adjusting resistors to 10% and 1% accordingly.

Maybe..... It might work?

Click to expand...

With a typical 10k line input, that's 10k / 600 * 10k = 167k load which is a little low for a guitar. Not sure if you're going to capture the whole "wolfram" mojo with that.

There are lots of transformers on Ebay that are in the 60k / 600 range (50k / 600 is probably a little more common and would be ok) because that's about right for a tube line input or mic input. The cool looking triad ones are expensive but the boring looking ones can be just as good and much cheaper. Generally bigger is better but there are smaller ones that would work. The tiny Beyerdynamic ones are actually pretty good but you have to lookup the codes (you would need 60k/600 or maybe 20k/200 would be ok too). Just get one with a decent frequency range. There are lots that are only good from like 300Hz to 5kHz or so. You need something that is 50Hz to 15kHz or wider.

These edcors are 20hz-20k frequency response. They are coming in the mail today. Is to be used for a bass signal. It might not have the same "mojo" electrically as an old Triad, but good luck finding one. Besides, tone comes from the hands.

ReRibbon said:

RH? Forgive me not knowing abbreviations on this language.

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RH= Right Hand.
Your schematic shows two different switches (pins should be numbered 1 to 6). Since there was no mention such as Sw1A or Sw1B, I could only differentiate them by geographical (I could have writ East or West).

This circiut is the old Motown d.i.

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I believe there is more than one Motown DI. I have seen one in film that has three guitar players on the same 3-input DI.

Sorry, late to the party on this thread. I've built two of these boxes, one just recently. The schematic has an error around the pot. As it's drawn, it does not work properly.

The fix looks like the attached, This works perfectly. Good luck and enjoy! These are great-sounding DI boxes

soapfoot said:

Sorry, late to the party on this thread. I've built two of these boxes, one just recently. The schematic has an error around the pot. As it's drawn, it does not work properly.

The fix looks like the attached, This works perfectly.

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It looks strangely similar to my recommandation in reply #6...

abbey road d enfer said:

It looks strangely similar to my recommandation in reply #6...

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Apologies, I must've missed it!

Once I read the OP I admit to skimming the rest...

We coincidentally had this exact discussion only last week on the PRW forum

abbey road d enfer said:

RH= Right Hand.
Your schematic shows two different switches (pins should be numbered 1 to 6). Since there was no mention such as Sw1A or Sw1B, I could only differentiate them by geographical (I could have writ East or West).
I believe there is more than one Motown DI. I have seen one in film that has three guitar players on the same 3-input DI.

Click to expand...

Correct. There was the famous 5 channel direct box. I have info here. 

Ok, so I built 1 of each versions of the schematic and also the ammended schematic as posted as well.

So channel 1, I built the original diagram as was posted in the OP.
It sounds great on the DI section, and when switched to the attenuate setting, loses about 17 db, the tone gets fatter, but there is a high end his to it .... sort of like a tape his.

Channel 2, I built the ammended diagram. The difference is lug 2 and 3 are not connected as the are in Ch. 1. Everything else is the exact same.The DI sounds great, the attenuated section doesn't lose nearly any volume in comparison, but sounds thinner. I've checked for phase, and all is correct. It doesn't have the roundness that CH. 1 has while enabled.

I've posted a YouTube link of a 1 minute audio sample of this. What are your thoughts and or suggestions please?

First on the audio is Ch. 2 DI, then switches to the attenuated section.
Then Ch. 1 DI, then switches to the attenuated section. The volume drop can be heard very clearly.

https://youtu.be/tOfqghT2CrI

ReRibbon said:

Channel 2, I built the ammended diagram. The difference is lug 2 and 3 are not connected as the are in Ch. 1. Everything else is the exact same.The DI sounds great, the attenuated section doesn't lose nearly any volume in comparison, but sounds thinner.

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Just to clarify how it should be connected:

• SW1B goes to the wiper (lug 2) of the pot only.
• Lug 1 of the pot connects to 10k resistor only
• Lug 3 of the pot connects to 1k resistor only

Is that how you have it wired?

The thin timbre you're experience is not normal in that case. Both of mine are wired as-above and both behave well with the attenuator switched in.

ReRibbon said:

Ok, so I built 1 of each versions of the schematic and also the ammended schematic as posted as well.

So channel 1, I built the original diagram as was posted in the OP.
It sounds great on the DI section, and when switched to the attenuate setting, loses about 17 db,

Click to expand...

That's the idea. The attenuated position is for line level.

the tone gets fatter,

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That's the effect of loading the pick-ups.

Anyway, no matter what, don't expect good results in the attenuated position with a passive gtr or bass.

Channel 2, I built the ammended diagram. The difference is lug 2 and 3 are not connected as the are in Ch. 1. Everything else is the exact same.The DI sounds great, the attenuated section doesn't lose nearly any volume in comparison, but sounds thinner. I've checked for phase, and all is correct. It doesn't have the roundness that CH. 1 has while enabled.

Click to expand...

That's the sign of too low a primary inductance. Are you using the Triad A11?