goldenreference low voltage power supply

[Tinkerer]

On 4/1/2017 at 6:25 AM, Tinkerer said:

Thought I would build my spare GRLV board and transformer into a 12VDC PSU for the little STAX amp. What value do I need for the R8/R9?

So to reiterate on this. I should just need a lower voltage reference (7V) and 300? ohm resistors in place of the top 1.5K in each pair for 12VDC operation? Just want to make sure I have the resistor value right since I gotta make a part order soon for some other stuff and I'd like to get it all together.

Also, is there any particular reason the STAX people put the positive on the barrel sleeve of the plug for the small amps? If not, it seems smarter to just swap the socket wires around so it can use any old common 12VDC wall wart.

[gepardcv]

On 4/8/2017 at 7:36 AM, congo5 said:

when using single bridge it seems like a good idea to solder a wire in that one hole

rather than rely on the through hole plating

Yes, this was the problem. I drilled out the middle bridge holes to make the part fit and must have damaged the through-hole plating.  A wire reinforcing the via fixed it, and all three power supplies work beautifully now. Thanks, guys!

[mypasswordis]

3 hours ago, Tinkerer said:

So to reiterate on this. I should just need a lower voltage reference (7V) and 300? ohm resistors in place of the top 1.5K in each pair for 12VDC operation? Just want to make sure I have the resistor value right since I gotta make a part order soon for some other stuff and I'd like to get it all together.

Also, is there any particular reason the STAX people put the positive on the barrel sleeve of the plug for the small amps? If not, it seems smarter to just swap the socket wires around so it can use any old common 12VDC wall wart.

300 ohm would be for the standard 10V references, you need to recalculate the voltage divider values for a 7V reference (the formula has been posted several times) 

[JoaMat]

Long time since I did this kind of calculations. Try this: (12V/7V * 1.5kOhm) – 1.5kOhm = 1.07kOhm. If I’m wrong you get something else.

[mwl168]

On 4/9/2017 at 10:51 AM, Tinkerer said:

So to reiterate on this. I should just need a lower voltage reference (7V) and 300? ohm resistors in place of the top 1.5K in each pair for 12VDC operation? Just want to make sure I have the resistor value right since I gotta make a part order soon for some other stuff and I'd like to get it all together.

Also, is there any particular reason the STAX people put the positive on the barrel sleeve of the plug for the small amps? If not, it seems smarter to just swap the socket wires around so it can use any old common 12VDC wall wart.

The regulated output voltage is:

for V+: ((R8 + R7) / R7) x 10 (reference voltage of D5 - LT1021-10)

for V-: ((R9 + R10) / R10) x 10 (reference voltage of D7 - LT1021-10)

On the goldenreference4 board silkscreen, R7, R8, R9 R10 are all 1.5K. R7 and R8 are connected and R9 and R10 are connected. R8 and R9 are the 1.5K resistors closer to the DN2540 on each side of the board.   

[spritzer]

On 9.4.2017 at 3:51 PM, Tinkerer said:

Also, is there any particular reason the STAX people put the positive on the barrel sleeve of the plug for the small amps? If not, it seems smarter to just swap the socket wires around so it can use any old common 12VDC wall wart.

It's the Japanese norm.  Ditto for the reversed XLR wiring the use. 

[UFN]

FWIW I just made an adapter cable (polarity-reverser) with a male and a female DC jack + 4" of wire for my SRM-252. Everything can remain stock in that case and I can switch PSUs between different products without problems (as long as I read the labels )

 

//UFN

[mypasswordis]

@Tinkerer 's power supply plan inspired me to swap out the onboard stepup switcher to a real regulated supply (modified ksa5 supply) and crank the bias. So far only got to the taking out the power supply part because I'm waiting on parts. Any advice on how to mount the output transistors to a heatsink much appreciated. I have some ideas so far but none of them jump out as ideal.

[kevin gilmore]

huh?

where you getting the high voltage power supply?

 

[mypasswordis]

I was planning on using the above KSA5 dual stage zener capacitance multiplier, with ksa1156 and ksc5026 as pass devices. First zener stage set to 300V, second to 280V. Any reason why that wouldn't work? I know the pass devices would have to be mounted backwards because the pinout is opposite of the mjf.

edit: given the thread it would definitely be more appropriate to use a GRHV but I had this board laying around for a long time whereas I'm hoping mwl168's group buy will pull through for GRHV boards  

Edited April 26, 2017 by mypasswordis

[kevin gilmore]

i suppose that should work. as long as all the parts are rated for the voltages you want to use

[Kerry]

Here's a new layout I'm working on.  It's a GR HV/LV, Bias and Delay circuit (with LED flasher) all on one 4 layer board (3.5" x 5.5").  The pass devices can mount to the bottom plate or a heatsink.

Mostly SMD parts and uses the GR78/9xx modules.  Once tested I'll make this all available.

 

[cspirou]

No need for heat sinks for the mini GRLV boards?

[Kerry]

Not for most of Kevin's electrostatic amps.   

[sbelyo]

That's awesome

I've really got to get over my fear of SMD

[Whitigir]

Oh hell yes! WooooooTTTT

[JoaMat]

22 minutes ago, sbelyo said:

I've really got to get over my fear of SMD

Nothing to fear. With some practice everyone can do SMD soldering and it's fun.

[gepardcv]

Spectacular. Starting to think about how small a Carbon can be realistically made. It still needs a big ol' transformer.

[Pars]

Just tossed together a GRLV for my DynaFET and fired it up. Works fine (so far). +30.005/-30.014 Vdc on my HP.

I finally got around to measuring current draw on the DynaFET boards; around 415mA on startup, drops to ~375mA when warmed up mostly. This is at 2x pairs outputs biased at ~150mA each. Pretty close to my spice model (366mA). So the GRLV will be seeing around 750mA total.

I just realized that the MJW pass transistors have an exposed back (sitting at around 50V on these), so I am going to need some pads or insulators when I mount these to the heatsink (common).

What do you guys like for thermal pads for these? Didn't see any in the BOM I have. Also, is there a fully insulated version of the pass transistors? Might switch to those, but from what I read, the MJW is supposed to be the insulated version?

[Tinkerer]

I just used the same ones I use for all my TO-247 stuff. http://www.mouser.com/Search/ProductDetail.aspx?R=4180G

[Pars]

Thanks. Right after posting and going thru mouser, I had run across the 4180g which sounded quite familiar from all my reading of the electrostat amp threads. Duh
Are any insulating washers required or recommended for TO-247? Looks like a 6-32 screw fits quite well.


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[Tinkerer]

The nice thing about that case type if you look at the back is that it already has a few milimeters of isolation around the hole, unlike a TO-220. So the screw is all you need.

[Kerry]

1 hour ago, Pars said:

Thanks. Right after posting and going thru mouser, I had run across the 4180g which sounded quite familiar from all my reading of the electrostat amp threads. Duh
Are any insulating washers required or recommended for TO-247? Looks like a 6-32 screw fits quite well.


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I'm pretty sure you need 4-40.  I think a #6 bolt is to big.

[Whitigir]

On 4/27/2017 at 6:39 PM, gepardcv said:

Spectacular. Starting to think about how small a Carbon can be realistically made. It still needs a big ol' transformer.

And that heatsinks to properly venting those heat  sizes do matter hehehe

[Pars]

I'm pretty sure you need 4-40.  I think a #6 bolt is to big.

I checked it last night and a 6-32 fits perfectly, no drilling involved.


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