About to order parts for a Cmoy with modified ground + TREAD. Please check it

You won't need the rectifiers and associated caps if you are feeding it DC, and sorry no you loose some volts along the way so you'll be down a few volts

cheers

FRED

Yes, like Fred said, The rectifier is unneeded, the wall wort all read puts out DC.

LM317 needs a couple of volts to operate, I would only expect 22 volts out for

24 volts in. Using the OPA551 in the ground is an interesting idea. I'd like to

hear how it works out for you. My only worry would be that it might be too slow.

You might also want to use lower value resistor for R1/R2 in the virtual ground.

1% at 200k is a bigger voltage error than 1% at 20k. A TLE2426 will give you

the accuracy and low power consumption you might be looking for.

Good luck with it and let us know how it turns out!

You can do a star ground with OGND as the middle of your star,

just don't use VGND.

Yes, you can bypass the electrolytic caps with the left over SMD caps.

FYI: if you use a 24VAC walwart, you'll most definitely get more than 24VDC output - perhaps as much as 27VDC.  You'll need some filter caps after the rectifier string, though - a couple of 1000uf 50V would be best.  (I believe the original TREAD used a single 680uf, but IMHO, bigger is better if size is not an issue.)

EDIT: This schematic is used for both the Millett MiniMAX and MOSFET-MAX.  We always get 27VDC, unless there's a line voltage issue:


Performance is at or below 40uVAC ripple/noise.

The Vin question is a little harder to answer without drawing...but here it goes...

In the top schematic, remove the rectifier diodes and snubber caps.

Take the V+ in from the wall wart and connect it after the rectifier.

Take the V- in and draw a line across the bottom of the schematic

to the V- out. Connect all the down pointing arrows (Grounds) to this

line. Don't confuse ground in the power supply with ground in the amp.

I would not bypass signal input caps with ceramic caps.

Ceramic caps sound horrible. Good quality film

caps do not need to be bypassed.

The AC1 and AC3 inputs on TomB schematic are if you are using a fuse or not.

You should use AC2 and AC3 as your power inputs.

TomB has a point...you should just use a wall wort with AC output.

I use the type of wall wort that is meant to run security systems and

file alarms. They are rated for continuous duty and come in 24 volts AC.

There is a difference in "sound" among the various types and manufacturers.

Metal film type are better than carbon.

This series is considered to better sound quality.

These are what I use if I'm not concerned about the "best" sound quality.

I don't have a lot of experience with SMT resistors for audio, but these look like

they would be OK.

I try and keep all my resistor values as low as practical as well.

Higher resistor values generate more noise than lower values.

Quote:

Originally Posted by shake 

 

Quote:

Originally Posted by tomb 

FYI: if you use a 24VAC walwart, you'll most definitely get more than 24VDC output - perhaps as much as 27VDC.  You'll need some filter caps after the rectifier string, though - a couple of 1000uf 50V would be best.  (I believe the original TREAD used a single 680uf, but IMHO, bigger is better if size is not an issue.)

 

EDIT: This schematic is used for both the Millett MiniMAX and MOSFET-MAX.  We always get 27VDC, unless there's a line voltage issue:


Performance is at or below 40uVAC ripple/noise.

Is the the complete schematic? It looks like you might have chopped off some on the right side.  It looks very much like a TREAD but with AC inputs.  Would the AC-3 be the earth-ground pin?
 

 

No, this is the complete schematic ... there's nothing dropped off on the right side. If you do some research, you'll notice that this is an improvement with about 10uVAC better performance than the TREAD or STEPS. Avro_Arrow is correct - the AC-3 is simply an alternate connection with AC-1. One uses the fuse (AC-3), the other does not (AC-1).

BTW, the TREAD was originally designed for an AC input - that's why the rectifiers were there.

As for SMD parts, there is no benefit unless you're trying to corral all of this into a super-small layout and you need the small size.  However, with a linear-regulated power supply, the greatest thing you're trying to control is the 60Hz from the wall supply.  There is no inherent benefit in small SMD parts with frequencies that low.  Moreover, my guess is that the ripple removal is greater and the ESR lower from the large caps you can use with through-hole parts.  IOW, you won't be able to find large-enough capacitors in SMD with a voltage rating high enough to be of better benefit than through-hole caps.  So, there's not much point in building the rest of it that way.