Powering a Distortion Device With Phantom Power

Help Support GroupDIY:

cpsmusic

Well-known member
Joined
Dec 3, 2013
Messages
237
Location
Melbourne, Australia
Hi All,

I'm interested in putting together a basic distortion device for use in my home studio. I'd like to use the DIYRE JFT Class-A Transistor Colour. Info about the device is here:

JFT Class-A Transistor Colour

I've also attached a schematic.

One of the things that put me off these is that they require a host (either 500-Series or standalone) which are quite expensive. So I was thinking that a cheaper option would be to build my own power supply and use it that way. Would it be possible to power one of these from the phantom power on my mic preamp (a Warm Audio WA273-EQ)? If so, is there a schematic available anywhere for doing this (i.e. 48V to ±16V).

Cheers,

Chris

 

Attachments

  • JFT_mkII_Schematic.pdf
    19.4 KB · Views: 31

mhelin

Well-known member
Joined
Mar 12, 2005
Messages
595
Location
Tampere, Finland
Probably not possible because of the maximum current the phantom supply can source (depends on Colour model but Class-A circuits likely consume current quite a lot).
 

NOON

Well-known member
Joined
Nov 26, 2014
Messages
218
Location
Melbourne, Australia
Easy enough to set up some voltage rails from the 48v feed but it's quite high impedance because of the 6k8 feed resistors so very limited current available and the voltage drops as the current goes up. You could make it work with the right circuit but not all of those colour modules will be able to drop in.
 

Bo Deadly

Well-known member
Joined
Dec 22, 2015
Messages
2,959
Location
New Jersey, USA
No. Phantom power is through two 6.8K resistors so the source impedance is 3.4K which limits the amount of current to at most 10mA or so and at 10mA the voltage would drop to 48 - 0.01*3400 = 14V. So 14V 10mA isn't going to be able to do much.

You can find +-15 V SMPS for less than 10 bucks for sure. But they will require extra circuitry to make them really quite which is especially important for some class A device like you're looking at because it has no supply rejection.

Another cheap possibility might be a eurorack synth supply. Don't know how much those run for but shouldn't be much.
 

ccaudle

Well-known member
Joined
Mar 18, 2010
Messages
348
Location
Houston
You could also modify the circuit to run on a single supply, e.g. 24V (just because 30V or 32V power supplies are not very common).
The circuit is already capacitor coupled on the input and output, so bipolar supply doesn't really provide a benefit in that circuit.
 

JohnRoberts

Well-known member
Staff member
GDIY Supporter
Moderator
Joined
Nov 30, 2006
Messages
23,283
Location
Hickory, MS
You might need to change a few values, have you tried?

Back in the 80s I designed a JFET input buffer that was phantom powered (it fit inside a 1/4" jack barrel), later at Peavey I designed a op amp direct box that could be phantom powered.

JR
 

cpsmusic

Well-known member
Joined
Dec 3, 2013
Messages
237
Location
Melbourne, Australia
You could also modify the circuit to run on a single supply, e.g. 24V (just because 30V or 32V power supplies are not very common).
The circuit is already capacitor coupled on the input and output, so bipolar supply doesn't really provide a benefit in that circuit.

Sounds like a good way to go but my electronics knowledge isn't advanced enough to do the mods - how would I do this?
 

JohnRoberts

Well-known member
Staff member
GDIY Supporter
Moderator
Joined
Nov 30, 2006
Messages
23,283
Location
Hickory, MS
It requires a rudimentary knowledge of discrete device design. Just because it is possible doesn't mean its and easy path for a beginner (sorry).

Perhaps consider adding a simple external power supply.

JR
 

ccaudle

Well-known member
Joined
Mar 18, 2010
Messages
348
Location
Houston
how would I do this?
In concept the positive supply pins would still go to the most positive supply, which would now be something like +24V or +30V, the negative supply pins would still go to the most negative supply, which you would probably call 0V or "gnd," and the pins that are labeled with the ground symbol on the circuit would have to go to a low impedance mid-point between the positive and negative supply. The "low impedance" part is relative, nothing connected to the gnd symbol on that schematic is drawing much current. The 100k on the output is not actually part of the circuit, it is just keeping the output side of the capacitor from floating, so it would still connect to chassis ground. As far as circuit gnd connections, one connection is through 1M biasing a JFET gate, so that is essentially no current, and one connection is the base of T2, which should be small fractions of a mA. A resistor divider between positive and negative supply using a pair of 50k Ohm resistors with a capacitor bypass of the mid-point will get the reference voltage you need. The gnd side of R2 and the base of T2 would connect to that node, and everything else should just work the same. If the total supply voltage changes from 32V to something like 24V you would need to re-check the bias points, since the bias is all set with resistor dividers and not using anything that is supply independent like diode chains it might shift slightly.
 

MidnightArrakis

Well-known member
Joined
Sep 25, 2015
Messages
198
Hi All,

I'm interested in putting together a basic distortion device for use in my home studio. I'd like to use the DIYRE JFT Class-A Transistor Colour. Info about the device is here:

JFT Class-A Transistor Colour

I've also attached a schematic.

One of the things that put me off these is that they require a host (either 500-Series or standalone) which are quite expensive. So I was thinking that a cheaper option would be to build my own power supply and use it that way. Would it be possible to power one of these from the phantom power on my mic preamp (a Warm Audio WA273-EQ)? If so, is there a schematic available anywhere for doing this (i.e. 48V to ±16V).

Cheers,

Chris

The "DIYRE" website states that the transistors used for this device are:
  • NOS 2SK170 transistor for musical, tube-like harmonics
yet, the schematic you have included shows the circuit using both BC327 and BC337 transistors. I do not know if these different types of transistors are compatible and/or similar or not. I am merely pointing out that there is a difference in information.

As far as your power-supply goes.....there is this possibility that is rather inexpensive:

1653339250709.png
Depending upon the model, you can an output of either +15VDC @ 42mA or +15VDC @ 342mA. Of course, it will require 2 units in order to obtain a +/- 15VDC power-supply. The 1W unit costs about $5.56 each and the 5W unit costs $11.00 each. I have also attached a PDF file of its datasheet for you.

Now.....here is the -- scary part, for me!!!.....I would offer to assist you in coming up with some "whatever" custom-design of combining the "Colour" schematic and these little power-supplies together in some type of a little box for you, >> BUT!!! <<..... if I did that, some other member of this thread or on this forum will report me to a "Moderator" complaining that I am either some kind of a "BOT" or a complete and total "SPAMMER".....only because I am offering you some assistance in helping you get together some little custom project for yourself. This was just done to me the other day ago when I offered some other member to correct a PCB-layout design he had that was full of layout errors. So, because of my offering to help this guy out, someone then reported me to the forum Moderator that I am either a "BOT" or a "SPAMMER" which then caused me to get a reprimand from the GroupDIY "Moderator" because of someone reporting on me!!! So.....I would help you design some little gadget that you could use in your studio, but if I did so, someone on this thread or forum will probably report me again as being a "BOT"!!! YAY!!!

GOOD LUCK!!!

/
 

Attachments

  • CUI -- PBO-1-B.pdf
    3.1 MB · Views: 14

cpsmusic

Well-known member
Joined
Dec 3, 2013
Messages
237
Location
Melbourne, Australia
The "DIYRE" website states that the transistors used for this device are:
  • NOS 2SK170 transistor for musical, tube-like harmonics
yet, the schematic you have included shows the circuit using both BC327 and BC337 transistors. I do not know if these different types of transistors are compatible and/or similar or not. I am merely pointing out that there is a difference in information.

As far as your power-supply goes.....there is this possibility that is rather inexpensive:

View attachment 94378
Depending upon the model, you can an output of either +15VDC @ 42mA or +15VDC @ 342mA. Of course, it will require 2 units in order to obtain a +/- 15VDC power-supply. The 1W unit costs about $5.56 each and the 5W unit costs $11.00 each. I have also attached a PDF file of its datasheet for you.

Now.....here is the -- scary part, for me!!!.....I would offer to assist you in coming up with some "whatever" custom-design of combining the "Colour" schematic and these little power-supplies together in some type of a little box for you, >> BUT!!! <<..... if I did that, some other member of this thread or on this forum will report me to a "Moderator" complaining that I am either some kind of a "BOT" or a complete and total "SPAMMER".....only because I am offering you some assistance in helping you get together some little custom project for yourself. This was just done to me the other day ago when I offered some other member to correct a PCB-layout design he had that was full of layout errors. So, because of my offering to help this guy out, someone then reported me to the forum Moderator that I am either a "BOT" or a "SPAMMER" which then caused me to get a reprimand from the GroupDIY "Moderator" because of someone reporting on me!!! So.....I would help you design some little gadget that you could use in your studio, but if I did so, someone on this thread or forum will probably report me again as being a "BOT"!!! YAY!!!

GOOD LUCK!!!

/

The 2SK170 is on the left of the schematic between R1 and R3. I'm interested in any help I can get so just send me a PM.

Cheers!
 

ccaudle

Well-known member
Joined
Mar 18, 2010
Messages
348
Location
Houston
Would is be possible for someone to have a quick look at the PSUs I linked to at #5 and #6 and let me know whether or not they'd be ok for this project.

Cheers!

The supply in #5 would, but it requires a center-tapped AC input. What did you have in mind to supply the input power?
Also pretty oversized if you are only running the JFT Colour, it could supply up to 1A, and that circuit should only be using around 0.010 to 0.015A at most, from a quick estimate.

#6 could as well, but again capable of 100mA, so almost 10x what you need, and needs a 36V DC input.
That circuit in #6 is basically the same thing I suggested, but rather than just using the resistor divider to provide the mid-point voltage, it buffers it with $20 high speed buffer amp that can source or sink 250mA. As I pointed out previously all you need to drive is the gate of a JFET through a 1MOhm resistor (effectively 0 current), and the base of a transistor (assuming a beta of close to 100 the base current would be around 0.005mA).

Seems like a lot of money to avoid connecting up two resistors and a capacitor.
 

cpsmusic

Well-known member
Joined
Dec 3, 2013
Messages
237
Location
Melbourne, Australia
The supply in #5 would, but it requires a center-tapped AC input. What did you have in mind to supply the input power?
Also pretty oversized if you are only running the JFT Colour, it could supply up to 1A, and that circuit should only be using around 0.010 to 0.015A at most, from a quick estimate.

#6 could as well, but again capable of 100mA, so almost 10x what you need, and needs a 36V DC input.
That circuit in #6 is basically the same thing I suggested, but rather than just using the resistor divider to provide the mid-point voltage, it buffers it with $20 high speed buffer amp that can source or sink 250mA. As I pointed out previously all you need to drive is the gate of a JFET through a 1MOhm resistor (effectively 0 current), and the base of a transistor (assuming a beta of close to 100 the base current would be around 0.005mA).

Seems like a lot of money to avoid connecting up two resistors and a capacitor.

At this stage I'm not sure how I'm going to power the unit! Ideally I'd like it not to have mains, so a wall wart of some description is what I'd prefer.

If you could suggest something suitable it would be a big help.

Also, any chance you could draw what you suggest above.

Cheers!
 

ccaudle

Well-known member
Joined
Mar 18, 2010
Messages
348
Location
Houston

cpsmusic

Well-known member
Joined
Dec 3, 2013
Messages
237
Location
Melbourne, Australia
I guess this means I have two options PSU-wise:

1. Use the Silicon Chip I/O and the modified power version of the Colour Module which means I could use something like a +15V DC wall wart.
or
2. Use the SparkFun I/O and the standard power version of the Colour Module which means I would need to to use a ±15V supply.

Is there any difference between 1 and 2?

Cheers!
 

Latest posts

Top