The Multi Amp aka Dynalo Mk2

[DaveLTX]

18 hours ago, Pars said:

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).

Hmm yea, epsilon only switches half of the lines. In that case I'll probably just not use the epsilon lol but uh... it's claimed that it can handle balanced so i'll test it out 

[kevin gilmore]

switching half the lines is not the main problem. the main problem is that dc on the input with an unbalanced input will generate differential dc on the output which the epsilon 12 will not detect.

[DaveLTX]

On 9/8/2018 at 7:03 AM, kevin gilmore said:

switching half the lines is not the main problem. the main problem is that dc on the input with an unbalanced input will generate differential dc on the output which the epsilon 12 will not detect.

I see. thanks.

[cspirou]

What is the preferred potentiometer value if I go with 2sk170/2sj74 jfets instead of the THAT chips? Still 10k?

[lkong]

2 hours ago, cspirou said:

What is the preferred potentiometer value if I go with 2sk170/2sj74 jfets instead of the THAT chips? Still 10k?

I think somewhere in this thread said 100k

[penmarker]

Oh ok that's interesting. I've recently replaced the THAT in my DynaHi with a pair of 2SC3381-GR/2SA1349-GR and I noticed the gain dropped a lot. Does changing the pot value apply there too? (Sorry for being off topic)

[jose]

4 hours ago, cspirou said:

What is the preferred potentiometer value if I go with 2sk170/2sj74 jfets instead of the THAT chips? Still 10k?

I use 10K  (Dynahi bal. and Dynalo MKII)

 

[Kerry]

8 hours ago, cspirou said:

What is the preferred potentiometer value if I go with 2sk170/2sj74 jfets instead of the THAT chips? Still 10k?

I use 50k with the fet input.

[jose]

Is there much difference between 10k vs 50k?  for balanced it´s easier to find 10k pot.

[Whitigir]

Is anyone running mini Dynalo on battery supply ? Sony claims that battery supply is superior on their most expensive DMP-Z1.  So, I just wonder

[Pars]

I'm using 10K pot with JFETs (Linear Systems).

Batteries have noise as well, so if it were a GRLV, I'd be tempted to think it would be superior. Never tried it though. Can you fit the batteries in the case? And what would you do as far as the power switch goes?

[JoaMat]

1 hour ago, Whitigir said:

Is anyone running mini Dynalo on battery supply ? Sony claims that battery supply is superior on their most expensive DMP-Z1.  So, I just wonder

See below.

 

On 8/30/2016 at 8:06 PM, JoaMat said:

I’ve had a great time the last couple of weeks building the mini Dynalo designed by Kerry.

Here is the Dynalo with a finished (almost) board. Side panels from Modushop, internal height 40 mm. Front and rear panel are copper clad boards milled myself and the top cover is  an aluminum net for better ventilation.

Now, this amplifier turned to be a very nice one, so I started to modify it for my own personal preferences. I want a small portable amplifier to be used in my garden under a cheery tree - resulting in this.

Switching power supplies, all connectors at the rear panel and some other stuff not needed removed to give room for Raspberry Pi 3 with a HiFiBerry DAC+ Pro on top. Changed front panel (easily done with a mill and copper clad board) and rear panel has two holes for connectors for the batteries and a wlan antenna.

Today I got a heat sink for the output transistors. Below is a picture showing them, they are just resting on some soft pad – have to figure out the best way to get them  fastened. I don’t think the sinks are needed but they are very much preferable.

Many thanks to Kerry for an excellent work.

 

[Whitigir]

@JoaMat, thank you very much.  You essentially has DMP-Z1 by yourself  lol

May you please share more info on the battery supply you are using ? Thank you

[JoaMat]

I used the battery pack summer 2016. LiPo 6 cells, one pack each rail, give you  some 22 volts reduced by the regulator. Those LiPo packs are used by RC people. I bought from hobbyking.com.

[cspirou]

My main concern with battery isn't so much noise but the varying voltage as power draws down. Usually this means some sort of power management circuit in between the batteries and the amp which can have their own noise. Also with a bipolar power supply there's an issue of one rail powering down before the other, leading to a large DC offset.

I'm sure Sony has a very competent implementation though.

[JoaMat]

Found this in closet. I guess it’s some kind of charger I built a couple of years ago. Six Mean Wells and charger regulators and each cell has his own charger. Red light will probably turn green when fully charged. I don't remember but I will see in a couple of hours.

 

[Whitigir]

How long do they last ?  

[JoaMat]

I don't remember, but capacity is 3.3Ah when new. How much is the current of the mini? 

[Whitigir]

Nvm, got it.

Please someone clarify on board V1.5

the 1.43M is still 160K value ? Stock board is 402 and 255.  Bridging jumpers 0p2v, 0p8v, 1p6v , 3p2v .  It is expected to run 20V and 14-15mA. ?

Edited October 27, 2018 by Whitigir

[Pars]

Yes to most of it. For the LED resistors, which set the bias, I used 422 402R with LTST-C170CKT Lite-On LEDs. This gave me the 14-15mA bias. Running 402 422R with these LEDs will give you 12-13mA.

You're going to try doing the onboard regs? Good luck, though the 2oz boards will make these easier than the 3oz were.

Edited May 23, 2019 by Pars
Fake news!

[Whitigir]

So, a weird question.  But I have the onboard reg working just fine.  +20.11 and -20.03.  However, when I measure offset, each channel line is fluctuating from -3mV to +3mV, and the R- channel started out at -12mV then come down to +/-3mV.  I have not turned the trim pots or anything ? Should I be worried ? Or should I just throw in the 0 Ohms and see what coming out ?

I have no SE switch in place, I don’t think it should affect anything since I am not looking to use SE input atm.

Edited October 28, 2018 by Whitigir

[Pars]

I wouldn't worry about that offset. I would adjust the trim pots a bit. The channel layout, looking at the top of the board from the front is:

L-    L+

R-    R+

The two pots by the LEDs will adjust the overall offset for its respective channel. The other 4 pots will adjust the channel it is nearest to. If you have two meters and can watch the + and - of each channel at the same time, that would be best, as the pots will have some effect on the opposite + or -. Don't go overboard in adjusting trying to 0 everything out. As the amp heats up, the channels will drift without the servos in place.

BTW, how did you do the onboard regs? Hot air station?

[Whitigir]

12 minutes ago, Pars said:

I wouldn't worry about that offset. I would adjust the trim pots a bit. The channel layout, looking at the top of the board from the front is:

L-    L+

R-    R+

The two pots by the LEDs will adjust the overall offset for its respective channel. The other 4 pots will adjust the channel it is nearest to. If you have two meters and can watch the + and - of each channel at the same time, that would be best, as the pots will have some effect on the opposite + or -. Don't go overboard in adjusting trying to 0 everything out. As the amp heats up, the channels will drift without the servos in place.

BTW, how did you do the onboard regs? Hot air station?

I did the onboard reg by hot-air, and using chip-Quik paste.  It turned out pretty ok, and only the jumper legs were tricky as I had to sneak-in a piece of solid silver conductor as I think it would conduct better.  Needless to say, I was doing it and praying, and it turned out ok.  I spread the paste by the pointy tweezers as I don’t have any stencils

 

Edited October 28, 2018 by Whitigir

[cspirou]

3 minutes ago, Whitigir said:

It turned out pretty sweet, and only the jumper legs were tricky as I had to sneak-in a piece of solid silver conductor as I think it would conduct better.  Needless to say, I was doing it and praying, and it turned out ok.

The jumpers don't transmit any significant current, they just are used to set the voltage. So silver solder is definitely overkill.

[Pars]

Yep, when I tried the onboard regs, I had problems getting the jumpers to bridge properly as well. They do go to ground, and anything going to ground on the 3oz boards was a problem, particularly if you were trying to use a sane tip size for the application.

The tab on O23 looks a bit light on solder... looks like you used hot air and paste on most of the SMD?

Edited October 28, 2018 by Pars