The Multi Amp aka Dynalo Mk2

[Skooby]

Nice rework station!  The price is pretty reasonable too, should have known about it six months back (when i bought my rework station).  

Any recommendation on desolder gun?  Hakko fr300/301 any good?

[mypasswordis]

Maybe someone else can chime in. I try to stay as far away from through hole components as possible these days, partly from my horrible experiences with desoldering THT (of course never with anything as nice as the Hakko). Quick googling of the Hakko seems to be mixed, with some people constantly blowing out the motors but it's probably mostly just the fiddly nature of the beast. Maybe they fixed the problems since those reviews ¯\_(ツ)_/¯

[Pars]

After building the 3 minis, I’m not in any hurry to do any SMT anytime soon Though changing out the th caps on one board wasn’t any fun.

Just got a notice from Mouser that the MBTA06/56 used on the mini is EOL. Now they are discoing SMT parts, not just TO92s. Haven’t checked to see what good replacements might be.


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[mypasswordis]

You just need moar POWAH!! Just checked mouser and Diodes Inc seems to still be making them... 57000 MMBTA06 in stock and another 40000 on the way, much fewer MMBTA56 though.

[Pars]

Ooops, yes should have clarified that On Semi is EOLing them.


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[cspirou]

There seems to a similar part (MMBTA56LT) that isn't  EOL and seems like a direct substitute. Need to check the datasheet for compatibility though.

[sbelyo]

4 hours ago, Pars said:

After building the 3 minis, I’m not in any hurry to do any SMT anytime soon Though changing out the th caps on one board wasn’t any fun.

Just got a notice from Mouser that the MBTA06/56 used on the mini is EOL. Now they are discoing SMT parts, not just TO92s. Haven’t checked to see what good replacements might be.


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Did you happen to make a BOM for those builds?

[Pars]

Yes. I won't share that one however.

Let me clean something up and I'll send it to you.

 

EDIT: see attached. Allows color selection for jacks, THAT340 or JFET, onboard or Amb regs (including associated parts).

EDIT2: Replaced file; description wrong on 160K for Amb reg. Also note that the JFET selections chooses the TO71 package. The SOT223 package is a bit cheaper, so you would have to manually handle that. Also, many of these parts are small. You might want to order extra. Also, the Elna Silmics don't fit worth a crap, and didn't sound better (sounded worse to me). Not recommended.

 

 

ssdynalo-v1-4 cby.xlsx

Edited November 12, 2018 by Pars
BOM revised for correct power switch

[sbelyo]

thank you much sir

[JoaMat]

On ‎2018‎-‎03‎-‎29 at 10:32 AM, Skooby said:

Any recommendation on desolder gun?  Hakko fr300/301 any good?

I’ve been using Denon SC-7000Z for several years and I would say it’s a great tool. With 1.5 mm tip it’s easy to remove a 5 terminal block or a small teflon tube socket. It can also be used as an “hot air gun” and then it’s very practical for desoldering surface mounted components. If interested check Howard Electronic Instruments – I buy spare parts from them.

Edited March 30, 2018 by JoaMat

[navigator]

Hello, What are you guys using to feed it with assymetric input signal, to get output symmetric? I am searching for the most up to date schematic, but as I see from assimetric signal it will run only one half and assymetric output. There is no phase invert or such to feed the negative inputs.

Do you maybe has experience with this and some interstage transformers?

Thanks!

[Pars]

The supersymmetry input section does unbalanced to balanced conversion. You can use either single-ended or balanced sources with this. For single-ended source, the - inputs should be grounded.
You might try actually reading the thread...


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[navigator]

I'm reading backwards and from the 50 page I'm at page 30, not bad I think :-) , but I continue

I also admit I'm not very good in understanding transistor circuits, even I built a lot, but I thought grounding the negative input will virtually ground the negative output and that is not what I was looking for. If that is not the case, the positive signal is inverted and gets into the negative input, that is great. I see the feedback is crossed, so the positive output gets fed back to the negative input and same on the other side, but to fully understand how that works is above me.

The best schematic I found so far are the SSDynalo-v1-5-PS.jpg, SSDynalo-v1-5-Channel.jpg, SSDynalo-v1-5-Amp.jpg in pictures. Do you know a pdf version?

Thanks,

I started from the back because at the front the schematic links do not work. I know why, but I thought I should find in the recent posts.

In general I was familiar with the Dynalo, but now I read the beginning also and see posts saying it is symmetric or assymetric in and symmetric out. I guess than it means there is signal out on the negative output, not virtual ground.

Thanks,

[Pars]

The jpg are the only schematics that Kerry provided for the mini. I may draw a set up if I have time, as the legibility of these leaves something to be desired.
The ss Dynalo (and Dynahi) will handle any combination of input/output.
1) balanced in/balanced out
2) single ended in/balanced out
3) single ended in/single ended out
4) balanced in/single ended out
If you opt for only a balanced output jack(s) you won’t be able to provide single ended out without some pre-planning. The mini as Kerry has defined it provides both a 4-pin balanced XLR and a standard 1/4” stereo single ended output. Single ended input loses ~6dB compared to balanced in.


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[cspirou]

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.

[Pars]

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.

[jose]

Could I use those regulators as dc-dc converters?

Edit: I need a step down from 20 Vdc to 12Vdc

Edited April 11, 2018 by jose

[Pars]

You should be able to, just as you could if you were using something like a 7812/7912.


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[jose]

Thanks Pars. I bought both. 

[cspirou]

I was auditioning some low-z headphones the other day and noticed the left channel was starting to sound a bit distorted through my Dynalo Mini. After I powered down everything and turned it back on the obvious distortion seemed to disappear, but things just don't sound as 'good' as when I first built it. Did some voltage checks the power supply seems normal and DC offset is ~1-2mV on both channels. However I noticed that when I turn the volume pot that the DC offset jumps to 40mV and then gradually comes back down to 1mV after 5-10 seconds. For the balanced output this is +40mV/-40mV or 80mVp-p. This DC while turning the potentiometer seems to explain why I hear some scratchiness when turning the volume while there's no music playing.

Anyone else notice scratchiness while turning the volume? Is this sort of DC-offset normal as long as it drops after awhile? Would changing the THAT chips to JFETs do anything to resolve this?

Edited April 28, 2018 by cspirou

[kevin gilmore]

scratchy on the pot means there is some dc offset somewhere

[cspirou]

When I initially adjusted the offset I didn't short the inputs. I'll remove the zero ohm resistors and re-adjust with shorting jacks.

[Pars]

If you have the pot turned down all the way on a mini, it is equivalent to shorting the inputs. Not sure using shorting plug etc. would make any difference...

[Skooby]

A new DynaloMini for a friend:

 

 

[Pars]

Nice!

Std. board layout? Interesting SE headphone jack on the front, not sure I've seen one like that before. Care to share what it is?