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The Multi Amp aka Dynalo Mk2

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Pars, the plus is Rean NYS221.  That extra front recess is for a guitar strap.  I think NYS2203 looks nicer.  Mouser got 'em all. 

Yes, standard SMD board.  I moved everything off-board except for the XLR inputs in the back.

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^ Yeah I like that one (NYS221). Will have to remember it. The other is a cable connector, not front panel. Thanks!

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On 4/10/2018 at 12:30 PM, cspirou said:

i just came across these regulators on eBay

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F322870941945

much cheaper then the other supplier and I believe comes with a heatsink. If it's pin compatible with the Dynalo Mini then It seems like a great option to the AMB modules.

 

On 4/10/2018 at 10:05 PM, Pars said:

Those don't look too bad and are a bit cheaper. Not sure about the pot for voltage adjustment; might be better to replace it with fixed resistors if doable.

Here's the negative:

https://www.ebay.com/itm/TPS7A3301-Ultralow-noise-LDO-Regulator-3V-33V-Max-1A-Replace-LM337-7905-7912-/322538830904

They do appear to be pin compatible with the mini.

 

On 4/11/2018 at 11:07 AM, jose said:

Thanks Pars. I bought both. 

What do you think of these Jose? Had you ever used Amb's?

Thanks!

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I only have ebay regulators. They look good and with 20Vdc AND WITHOUT LOAD they worked correctly (as any LM3X7 would do) but I have not yet tested them in any project.

I had thought to use them in a phono preamp (the VSPS) but finally they didn´t work because the size of the preamp's pcb is very small. :wacko:

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On 3/25/2016 at 10:35 AM, joehpj said:

Hi, KG

Do you have schematic for this?

Thanks!

12899550_1146955785349906_1191324136_o.jpg

Dredging a little in an old thread, sorry. Has anyone successfully built the bal/unbal converter on the eBay-pcbs shown here? I found pair in a box a few weeks ago and put them together, but they are behaving strangely. I have only done basic troubleshooting for now, but I just want to know if the boards are confirmed OK before I start spending more time on them :)

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yes they definitely work. where the schematic is, not sure at the moment.  if there are troubles its usually the that340 chip.

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Thanks Kevin, I think I have the schematic (at least the one that was linked to the post I quoted). I'll go over the boards in more detail and post again if I can't figure out what's wrong.

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at one point there was an error on that board, Kevin fixed it

problems were, both outputs stuck on -3V, adjusts only .1v, OP07 servos do nothing, lower LED not lit,

I abandoned it and moved on to a newer version after finding this:

1542932.png

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Not 100% sure I see what the problem is (and I am not near the board right now), but that is exactly what I am getting?

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for the CCS       power should go through the LED to the base and also to 10k string to other side

not emitter  to resistor string

cut trace at E and connect to base

IF same as your board

make like schematic.......?

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Thanks Congo, I think that did the trick. Not sure how long it would have taken me to work out on my own what the problem was, so really appreciate the help ?

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2 hours ago, Skooby said:

How do you manage the heat?  Is it getting too hot (> 50C)?

The prototype got pretty hot. This case I haven't tried nearly as long but i did go brute force and had a bunch of holes on the top and bottom plate. I don't know how much more can be done except to drill the sides.

I'll report back on temps

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I ran it for about an hour last night listening. The case got warm/hottish but nothing I couldn’t hold my hand on for as long as I cared to. I didn’t shoot it with an IR gun to measure where the sinks were at though.

 

 

Sent from my iPhone using Tapatalk

 

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On 8/20/2018 at 8:40 AM, Pars said:

Another one lives... thanks to cspirou and his case GB!

 

 

IMG_1061.jpg

IMG_1063.jpg

Planning to sell this some time in the near future? ?

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That one was built for another member. I will have one for sale in the somewhat near future however. Looks just like it :)

PM me for details.

  • Haha 1

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If I were to replace input BJTs with JFETs(toshiba or linear), what IDSS range should I aim for?

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On the mini SS Dynalo, to increase the gain a bit, would I want to raise the 25K some or lower the 5K? I would assume raise the 25K but just checking.

From what I recall, the stock gain is 6 ((R feed / R in) + 1)? Going to an R feed of 39.2K would give 8.8 gain; 42.4K would give 9.4. Not sure I want to go up to 11 using 50K (49.9K).

Also, would the compensation cap need to be changed? Is there a formula for calculating what that should be?

Thanks!

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Except from K170 and J74, what else could be used as front end? K170 and J74 are long obsoleted and prices are high now. Any easier sourcing / cheaper substitution? 

I know linear system has some but the prices are high too....

Edited by joehpj

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LSK489 and LSJ689.  If those are too expensive then you are just shit out of luck

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I'll make a few boards, I've heard the GSX Mk2 before, I'm praying the dynalo answers my prayers for a fast amp that is not overpowered. My current SS amp has a bit of top end rolloff, which is unfortunate

It will have a sigma22 to power 2 boards so I have a balanced dynalo. How do I connect it for SE on the output? (I'm also using the epsilon 12 i have lying around)

Just to be sure, at 200mA that's 400mA for the whole amp right? Trying to calculate how much heatsinking I need for the sigma22

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6 hours ago, DaveLTX said:

I'll make a few boards, I've heard the GSX Mk2 before, I'm praying the dynalo answers my prayers for a fast amp that is not overpowered. My current SS amp has a bit of top end rolloff, which is unfortunate

It will have a sigma22 to power 2 boards so I have a balanced dynalo. How do I connect it for SE on the output? (I'm also using the epsilon 12 i have lying around)

Just to be sure, at 200mA that's 400mA for the whole amp right? Trying to calculate how much heatsinking I need for the sigma22

As for an SE out, L+, R+ and gnd straight back to the power supply (not to the amp boards). Either use 2 conductors for the gnd, or a heavier wire (usually 24ga for signal, so maybe 20ga for the gnd).

I wouldn't use an epsilon 12 with this, as it won't properly handle balanced signals. I'd use one of Kevin's balanced protection boards instead.

400mA sounds about right (don't recall exact figures, but it's probably here in the thread somewhere).

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