The Multi Amp aka Dynalo Mk2

[joehpj]

Hi, KG

Do you have schematic for this?

Thanks!

[ang728]

31 minutes ago, joehpj said:

Hi, KG

Do you have schematic for this?

Thanks!

THIS

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

 

Original Post at here:

 

Edited March 25, 2016 by ang728

[mtoc]

On ‎2015‎年‎6‎月‎13‎日 at 3:10 AM, kevin gilmore said:

http://gilmore.chem.northwestern.edu/dsc_0658.jpg

why are there two labels ac25v, confused..

[kevin gilmore]

don't see any ac25 in that picture

depending on which supply, some are dual 25v windings, some are 25v center tapped

 

[mwl168]

Just started testing a second SS Dynalo I am building for a friend. 

This one is also powered by a GoldenReference PS running 20VDC rails. 255 ohm bias resistors (R38/R39) resulting in 300mV voltage drop over the 20 ohm emitter resistors so about 15mA per MPSWx6 devices.

Bolted the pass transistors of the GoldenReference to the chassis. After 3 hours running, the temp of the pass transistors is about 35C and 64C for the MPSWx6 devices. 

For whatever reason, this one seems to sound quite a bit better than my first one. It may be due to better soldering job, the fact I tuned the offset correctly (thanks to information from Kevin and Pars) or better combination of supply voltage and output current.  

EDIT: forgot to mention, I also cleaned the flux residue on this build which I did not do for my first one (did not start following this practice till I built my first high voltage Stax amp ). Maybe this also contributes to the better outcome. Needless to say, I went back to clean the flux on my first SS Dynalo 

 

Edited April 26, 2016 by mwl168

[kevin gilmore]

power supply makes a big difference

 

[mypasswordis]

Is that GRLV PCB the one from the most recent group buy? About to build mine out and just want to make sure everything works before I start blindly parts stuffing. Odd indeed that they sound different, let us know if you find out why.

[sorenb]

7 minutes ago, mypasswordis said:

Is that GRLV PCB the one from the most recent group buy? About to build mine out and just want to make sure everything works before I start blindly parts stuffing. Odd indeed that they sound different, let us know if you find out why.

looks like the previous one.
But no problems with that - so far I've built six. AFAIK the only change is an added option for using CT transfomer, so the latest is the most versatile

[mwl168]

2 hours ago, mypasswordis said:

Is that GRLV PCB the one from the most recent group buy? About to build mine out and just want to make sure everything works before I start blindly parts stuffing. Odd indeed that they sound different, let us know if you find out why.

The GRLV PCB is from the GB I ran in 2015. As Sorenb pointed out, this version does not accept CT transformer. There is a BOM in the GB thread which is what I used to source the parts for this most recent build. Do remember to make adjustment needed for your targeted output voltage.

IT's a cracking PS. I've built 3 so far. Having a hard time keeping pace with Sorenb.

As to why it sounds different; there may be a few factors. In addition to the ones I already mentioned, I did also use different filter and bypass capacitors both on the PS and on the amp. Of course it could always be the wiring between my ears   

Will report back if I can confirm my findings so far and figure out what contributes to the difference. 

Edited April 24, 2016 by mwl168

[mypasswordis]

Thanks to both of you! That's a lot of GRLVS.

[mypasswordis]

After a few hours of head scratching and retouching solder joints I tested the LM4040s out of circuit (too much work to make a separate order of LT1021s from digikey) and found out the datasheet lists the pins wrong. A new GRLV is born. +18.00V, -18.02V without any parts matching.

Happy birthday to Kevin Gilmore, who made this all possible!

[sorenb]

2 hours ago, mypasswordis said:

After a few hours of head scratching and retouching solder joints I tested the LM4040s out of circuit (too much work to make a separate order of LT1021s from digikey) and found out the datasheet lists the pins wrong. A new GRLV is born. +18.00V, -18.02V without any parts matching.

Happy birthday to Kevin Gilmore, who made this all possible!

Con grat 

What's the right pin order then?

[mypasswordis]

I don't have it handy to check but from memory I'm pretty sure it's mirrored from the datasheet, so the NC and - terminals are swapped. 

[FallenAngel]

The wiring input RCA and XLR wiring I've seen seems to put XLR - and RCA Ground switched and wired through the pot, while connecting XLR + and RCA signal together. Is this really a good way of doing this?

Should the RCA ground be sent through the pot for - input?

Is there any problem with connecting the outputs of two DACs together like this?

[kevin gilmore]

so I wire mine for balanced input only, all 4 wires go to the pot, and then when I need unbalanced I use unbalanced to balanced adapters which short rca ground to ground and xlr -

 

[mwl168]

On 4/26/2016 at 1:26 PM, mypasswordis said:

After a few hours of head scratching and retouching solder joints I tested the LM4040s out of circuit (too much work to make a separate order of LT1021s from digikey) and found out the datasheet lists the pins wrong. A new GRLV is born. +18.00V, -18.02V without any parts matching.

Happy birthday to Kevin Gilmore, who made this all possible!

What are the pro and con using LM4040 vs LT1021 for voltage reference?

[gepardcv]

3 hours ago, kevin gilmore said:

so I wire mine for balanced input only, all 4 wires go to the pot, and then when I need unbalanced I use unbalanced to balanced adapters which short rca ground to ground and xlr -

By far the easiest approach. I use Neutrik XLR-to-RCA adapters and they work well.

[Kerry]

3 hours ago, mwl168 said:

What are the pro and con using LM4040 vs LT1021 for voltage reference?

For the grhv it is critical to use the 1021 reference since it has alot less noise. On the LV version it is a bit less critical because of the lower multipliers, but still a good idea.

[mwl168]

Thanks Kerry!

LT1021 it is.

By the way, apologize for cross-posting but I tested my GRLV tonight and for regulated +/-20 VDC output, the drop out voltage is about 3 VDC (slightly lower actually).

Edited April 28, 2016 by mwl168

[mtoc]

On 2016/4/24 at 9:08 PM, kevin gilmore said:

don't see any ac25 in that picture

depending on which supply, some are dual 25v windings, some are 25v center tapped

 

sorry, i mean this pic. i made a mistake.

btw, is balancedoutputcast2.zip a must-need part of the preamp? i gonna use the attenuator board (plus the control board, led board etc) to wire these things to be a whole big integrate amp, well, here's my plan:

unbalanced/ balanced /cast to balanced board (uber3 is its another name) --->  attenuator board (contains control baord etc)---> uber1 ---> uber2 

of course numberless power supplies need to be involved

Edited May 14, 2016 by mtoc

[mwl168]

Another SS Dynalo lives. 20 VDC rails 255 235 ohm bias resistors. (see EDIT)

Running single ended input and balanced output which, using the same Buffalo II/Ivy DAC, does give up something to running fully balanced.

 

EDIT: With 255 ohm bias resistor on 20 VDC rails, the temperature on the output devices reached 95C after 90 minutes running with the chassis cover on. At that temperature the MPSWx6 max dissipation is derated to about 440mW. Even though they may be still running at the edge of their operating range, the amp sounded lean and harsh. Had to lower the bias resistor to 235 ohm which, upon fully warmed up, yields about 14mA current and the BJT case temperature is at a more reasonable 75C.  

 

Edited May 21, 2016 by mwl168

[Kerry]

Nicely done!

[johnwmclean]

Looking good!

[HemiSam]

Very tidy....nice!

My GS-1 Dynalo+ has brought me back around to my shelved HD650's.  Great pairing IMO.

HS

[mwl168]

Thanks guys! John's and Kerry's builds put mine to shame. But putting an amp in a real chassis once in a while does give one a sense of accomplishment 

 

On 5/20/2016 at 8:15 PM, HemiSam said:

Very tidy....nice!

My GS-1 Dynalo+ has brought me back around to my shelved HD650's.  Great pairing IMO.

HS

Similar experience here. I have a new found respect for my HD650 after listening to it through the SS Dynalo. I built this one for a friend to drive his HD650. After listening to the combination, he told me he is now saving to buy a HD800 to make the best use of the amp.   

Edited May 21, 2016 by mwl168