Would be tough to choose which to build. Haven't seen the BOMs for both but looking at the parts on the PCBs, I suspect the Dynafet would be a little more expensive.

I don't know if it's appropriate but do you think adding a protection circuit, something like Ti's E12, makes any difference? There are quite a lot of space at the bottom of both boards.

The E12 integrated in the MiniMax is pretty tiny too.

Edited April 4, 201115 yr by Lil Knight

Ti wanted me to add a common mode servo. Which i did to the board.

Will test circuit later. I don't think its necesary, but what the

hell do i know. Have the design for the power supply.

The main difference between the dynahi and dynafet is whether

you like the sound of bipolar as outputs vs fets as outputs.

And a slight difference in the cost of all the additional parts.

The safety circuit really is a great idea, but no easy way to

get the output wires to a corner of the board. Will look at that

later.

Edited April 4, 201115 yr by kevin gilmore

Well after working on this for a bit, and Ti can certainly prove that i'm wrong...

The opamp servo is in fact a common mode servo. The differential stuff comes from

the susy. So i think that the balanced dynahi and balanced dynafet are correct as is.

But i ran into something last night i have to warn everyone about.

I got to playing with one of these new all discrete I/V converters. The thing

has 100mv of DC output.

Why is that a bad thing, for a differential amplifier like these two, with a

voltage gain of 10 (differential voltage gain of 20) that 100mv of dc turns

into up to +1 volt of output at one of the terminals and -1 volt of output

at the other terminal. So 2 volts DC across the headphones. While no big

deal for electrostatics, and this is something the stax mafia have known for

years, this is REAL BAD.

Think AMB's protection circuit will protect you. Think again.

His circuit adds +L and -L and +R and -R together.

In this case it would be +1 volt plus -1 volt. Result is zero,

so the protection circuit is happy. But there is still 2 volts of

DC on the output ready to destroy your headphones.

Gets even worse if you are making an amplifier with a voltage gain of 40.

Think about it for a minute, what the gain has to be to be able to

do 160 volts peak to peak on the output.

power supply board in progress

http://gilmore.chem.northwestern.edu/dynahips.jpg

edit: i finally see what Ti was talking about.

So i added a single 1M resistor.

Edited April 5, 201115 yr by kevin gilmore

power supply board in progress

http://gilmore.chem....du/dynahips.jpg

edit: i finally see what Ti was talking about.

So i added a single 1M resistor.

It's always so reassuring to see all those HV parts in a LV circuit.

Those parts are CHEAP.

Besides which, it makes it easier for me, less parts

to keep in stock

The most expensive part is the transformer.

It's always so reassuring to see all those HV parts in a LV circuit.

With SumR labeling your transformer, you might need it

Now now...

Now I just need to find a 6800uf/450V cap just to be sure...

Now I just need to find a 6800uf/450V cap just to be sure...

I assume that capacitor would be larger than Andre the Giant's fist.

Remember the pictures of some of mikhail's disasters with the juice can caps..

Those were 4700uf/450v.

Kevin, what's the cost of building one of these, roughly. I'm thinking of getting in on this.

Next you gonna ask for a BOM with the mouser parts labeled

I have absolutely no clue. The originals were done before i ever did a bom.

Likely similar to a 4 channel B22.

here is the dynahi balanced parts list for one channel not including power supply

QTY PART-REFS VALUE

--- --------- -----

Resistors

---------

2 R1,R4 500

2 R2,R3 30k

4 R5,R15,R53,R57 10k

6 R6-R8,R13,R14,R16 5k

6 R9-R12,R23,R34 100

8 R17-R20,R32,R33, 300

R45,R46

4 R21,R22,R35,R36 3300

16 R24-R31,R37-R44 10

2 R47,R48 1M

1 R49 5000

2 R52,R56 200k

Capacitors

----------

2 C1,C3 1pf

1 C2 .47uf

Integrated Circuits

-------------------

1 U1 OPAMP

Transistors

-----------

5 Q1,Q11,Q12,Q23,Q24 2sa1145

5 Q2,Q13,Q14,Q25,Q26 2sc2705

2 Q3,Q4 2sc3381

2 Q5,Q6 lsj109 one of these, or 2 singles

2 Q7,Q8 2sk389 one of these or 2 singles

2 Q9,Q10 2sa1349

8 Q15-Q18,Q27-Q30 2sc3421

8 Q19-Q22,Q31-Q34 2sa1358

Diodes

------

2 D1,D2 LED

Edited April 6, 201115 yr by kevin gilmore

I suppose we need 2x PSU for a balanced build? Also, will the Dynahi and Dynafet use the same PSU?

2 Q7' date='Q8 2sk389 one of these or 2 singles [/quote']

Did you mean lsk389?

1 x lsk389 or 2 x 2sk179

1 x lsj109 or 2 x 2sj74

same power supply for both

one power supply should be enough.

but 2 power supplies moar better.

Oh god, I remember the man hours that went into my first dynahi build! Might as well go for the gusto and build a balanced rev 2. I'm up for four amp boards and two psu's

Why do I do this to myself?

This is very nice. Thanks for the efforts KG.

I am in.

Damn, I might be tempted to build this one. I'm tired of B22s, I need something else to build

I'm up for a set of boards as well, as I'll have space to build stuff shortly.

Looks like a great project, what's the timeline on first batch of boards?

Also, how is the availability on the LSK/LSJ parts? I haven't seen then outside of a group-buy from Linear.

dynahi power supply board that fits on the side of a pesante case.

redesign similar to sigma22 by Ti kan. current limiters, precision

regulators, fixed 30 volt design, single center tapped transformer...

http://gilmore.chem.northwestern.edu/dynahipowerschem.pdf

http://gilmore.chem.northwestern.edu/dynapower2.jpg

http://gilmore.chem.northwestern.edu/dynahipower2.zip

Edited May 7, 201115 yr by kevin gilmore

Next you gonna ask for a BOM with the mouser parts labeled

I have absolutely no clue. The originals were done before i ever did a bom.

Likely similar to a 4 channel B22.

here is the dynahi balanced parts list for one channel not including power supply

QTY PART-REFS VALUE

--- --------- -----

Resistors

---------

2 R1,R4 500

2 R2,R3 30k

4 R5,R15,R53,R57 10k

6 R6-R8,R13,R14,R16 5k

6 R9-R12,R23,R34 100

8 R17-R20,R32,R33, 300

R45,R46

4 R21,R22,R35,R36 3300

16 R24-R31,R37-R44 10

2 R47,R48 1M

1 R49 5000

2 R52,R56 200k

Capacitors

----------

2 C1,C3 1pf

1 C2 .47uf

Integrated Circuits

-------------------

1 U1 OPAMP

Transistors

-----------

5 Q1,Q11,Q12,Q23,Q24 2sa1145

5 Q2,Q13,Q14,Q25,Q26 2sc2705

2 Q3,Q4 2sc3381

2 Q5,Q6 lsj109 one of these, or 2 singles

2 Q7,Q8 2sk389 one of these or 2 singles

2 Q9,Q10 2sa1349

8 Q15-Q18,Q27-Q30 2sc3421

8 Q19-Q22,Q31-Q34 2sa1358

Diodes

------

2 D1,D2 LED

looks like I missed R47,R48 1M and C2 0.47uf when ordering my parts. But when looking at my boards I noticed a pair of capacitors that seem to connnect to the power legs of the servo opamps. the board says 0.1uf What type should they be? Also I'm going to assume the polypropelene is ok foor C2?

50v ceramic is what is on the old bom

50v ceramic is what is on the old bom

for the 0.1 uf ? is polypropelene ok for C2?

I'd like to buy 2 sets, may be an extra power supply when they become available. Thanks.