The Multi Amp aka Dynalo Mk2

[Helium]

Ordered off board version of golden reference boards from seeedstudio 1.6mm 2oz copper

Will have some extras for grab when my order gets here.

Kevin, are Golden reference boards finalized? You mentioned that there is oscillation unless some parts are not omitted...

[kevin gilmore]

the oscillation was in the ltspice simulation.

 

board run now, will know for sure once i build it.

 

possibility of z-foil .15 spacing resistors, going to screw up

the ground plane on the back

 

will try later

 

no 20 ohm z-foil resistors that i can find...

Edited June 24, 2015 by kevin gilmore

[G600]

Texas components make them to order with no additional cost.

[G600]

Texas components make them to order with no additional cost.

[kevin gilmore]

it fits just barely

 

http://gilmore.chem.northwestern.edu/dynahibal17.jpg

[G600]

It looks good all SMT.

And quite straightforward.

I have just finished Sjostrom's Qrv-08 today, which is trickier with it's massive PS.

[b0bb]

it fits just barely

 

http://gilmore.chem.northwestern.edu/dynahibal17.jpg

Very cool, much appreciated.

 

Thanks!

[nopants]

one of my boards can't be adjusted below 1.3v/-.4v, can/should I change r26 to get the values closer to 0?

 

Also getting like 3V input DC, is this normal? Right now I'm floating everything and tying IEC ground to earth, amp boards are taking com from the power one supply (equivalent)

Edited July 18, 2015 by nopants

[kevin gilmore]

those are bipolar inputs, with a bit of offset current, so you really need a 10k input pot, or 10k

resistors to ground. other than that I listened to my latest set of boards on the new power supply,

and there is definitely a noticeable difference in noise with iem's.

[nopants]

I'll throw in a tkd then, you think that will help both input and output dc? does the input dc even need to be zeroed?

[kevin gilmore]

can't really zero the input dc. some of the that340 are better than others.

 

if you can get the lsk170/lsj79 parts, those sub directly. and have

much lower offset currents.

 

on the 8 boards I have done, all adjust to less than 1mv.

[mdr30]

Anyone tried a mini xlr as headphone out?

 

[spritzer]

The conductors are too small to let the bass molecules though... 

[JimL]

Back when Monster cable was first selling their cables with 3 sizes of wire (fat for the bass and thin for the treble), Frank van Alstine offered to wire the thin ones to an AC plug and plug it in while a Monster salesperson held on to one wire in each hand.  For some unfathomable reason, the salesperson declined.

[mdr30]

Thinking wear and tear.

Don't want these pairs of 3pin xlr anchors hanging down my neck.

[mvwvm]

What's the intended current through Q6 and Q9? Simulated THD seems to be minimal (0.021%) at ~4mA. Still getting high 3rd harmonic (-64.5dB, the 2nd is -77.8dB).

[kevin gilmore]

balanced in, balanced out, 7vrms out into 50 ohms 1khz

goldenreference power supply at +20.0000, -20.0000

(hand trimmed resistors)

thd is .011% which is actually the base line of this particular meter

typically .003% on the quantasylum400

and less on the audio precision

Edited August 22, 2015 by kevin gilmore

[mvwvm]

    typically .003% on the quantasylum400

and less on the audio precision

Neat. Still curious about the currents through Q9 and Q6. Could someone measure voltage drop across R3 and R15? Thanks.

[kevin gilmore]

1.25 volts

160 ma current draw on each rail at 20v

 

[MLA]

I happened to order 3 extra amp board sets when building this amp and I won't be using them.

Anybody needs a set, send me a PM and I'll ship them your way for cost of postage. These are rev 9, with smd ptza06/56 and the rest through hole. 

UPDATE: all board sets spoken for.

Edited September 4, 2015 by MLA
all boards gone

[mwl168]

1.25 volts

160 ma current draw on each rail at 20v

 

Hi Kevin:

How hot do the heatsinks on your GoldenReference PS get at this condition?

I just tried running my SUSY Dynalo with the GR PS running on 18V rails and about 18mA per output mpswx6 devices (360mV voltage drop on the 20 ohm emitter resistors). I was using the same heatsinks as shown on your pic but they got too hot to the touch and I had to put much larger heatsinks on. I am a bit surprised. 

Edited October 28, 2015 by mwl168

[kevin gilmore]

i had a variac on the power transformer and lowered the voltage to about 3 volts above the regulation minimum.So it really depends on how much voltage is on those transistors. With a total of about .5 amp, they can get warm.

[mwl168]

Thanks Kevin. 

I did not think of the variac idea, I'll give that a try. My toroid has 22v secondaris so the voltage drop on the pass resistor is quite high. I did test the PS without load and the heatsinks didn't even get warm.  

 

[kevin gilmore]

one other thing, i went to bigger heatsinks since that picture when i'm driving both boards.

the heatsinks are the ones from the blackhole amp driver

[Pars]

Hmmmm... I was going to do about the same thing as Michael, though I was planning on 20V outputs with 22/23V toroid. Must look up this blackhole amp driver to see what heatsinks I will need to get.