The Multi Amp aka Dynalo Mk2

[kevin gilmore]

i am pretty sure i never had the gerbers for that but i will look.

Those are the original circuit, not balanced differential, and use hard to find jfet inputs.

best to build one of the new boards

[Thai Tao]

May be i'm the only one who is not pleased with the Dynalo MK2?

I have heard the original dynalo long time ago for brief time and it give me very strong impression, it sound very good. Then i decided to build the susy Dynalo but it doesn't sound good at all, i don't have totl head amp, just some entry level like Cayin C5, O2, Project Polaris and Schiit Vali and my Susy Dynalo doesn't sound better than any of these. Until today, finally i have borrowed the original dynalo and it just sound clearly better then my susy: it sound clearer, detail pickup is easier, better soundstage depth, everything sound more real! And this dynalo even using cheap transformer ( i can get it for less then 5$), the regulator is just basic 7815/7915. My build is pretty normal, the pzta56/06 and that340 is ordered from mouser, dale, vishay,bc resistor, panasonic fc , kemet mmk5 rail decoupling capacitor got from local store, the krell clone power supply board is a kit from ebay seller. My susy measure fine, 0.27V across 22ohm resistor, <5mv output offset, just can't understand how it sound like this.

[mwl168]

What value volume pot are you using with the SS Dynalo? SS Dynalo has BJT input not JFET and requires using a pot that's no higher than 10K. 

[UFN]

What's you connection/grounding scheme?

 

//UFN

[sorenb]

32 minutes ago, Thai Tao said:

May be i'm the only one who is not pleased with the Dynalo MK2?

I have heard the original dynalo long time ago for brief time and it give me very strong impression, it sound very good. Then i decided to build the susy Dynalo but it doesn't sound good at all, i don't have totl head amp, just some entry level like Cayin C5, O2, Project Polaris and Schiit Vali and my Susy Dynalo doesn't sound better than any of these. Until today, finally i have borrowed the original dynalo and it just sound clearly better then my susy: it sound clearer, detail pickup is easier, better soundstage depth, everything sound more real! And this dynalo even using cheap transformer ( i can get it for less then 5$), the regulator is just basic 7815/7915. My build is pretty normal, the pzta56/06 and that340 is ordered from mouser, dale, vishay,bc resistor, panasonic fc , kemet mmk5 rail decoupling capacitor got from local store, the krell clone power supply board is a kit from ebay seller. My susy measure fine, 0.27V across 22ohm resistor, <5mv output offset, just can't understand how it sound like this

Have you checked that you didn't mixup the PNP/NPN's?

 

[Thai Tao]

50 minutes ago, mwl168 said:

What value volume pot are you using with the SS Dynalo? SS Dynalo has BJT input not JFET and requires using a pot that's no higher than 10K. 

Yes, i use 10k pot.

 

36 minutes ago, UFN said:

What's you connection/grounding scheme?

 

//UFN

Here it is:

 

18 minutes ago, sorenb said:

Have you checked that you didn't mixup the PNP/NPN's?

 

Yes, i already checked that, i think if i mixed it up, it was already smoked.

[Arthrimus]

I'm no expert, but this doesn't look right to me.

Could those transposed capacitors have anything to do with it?

[sorenb]

3 minutes ago, Arthrimus said:

I'm no expert, but this doesn't look right to me.

Could those transposed capacitors have anything to do with it?

they are in parallel ... but it does call for a better picture of the entire board

[kevin gilmore]

an early version of that board had the ground missing from one of the capacitors.

put the opamps in and see if there is any sound change. without the opamps there is an additional feedback loop

 

[Bespav]

Those are the original circuit, not balanced differential, and use hard to find jfet inputs.

I'm taking my own here:

http://m.ebay.com/sch/i.html?sid=jianxulia0&_pgn=1&isRefine=true

Matching of 4 quads:

Gate capacitance of N-type:

Gate capacitance of P-type:

They are similar to 170/74 pair, but a little more noisy, 1/2 in gate capacitance, 2/3 in transconductance and P-type are rated up to 40 V.

[guzziguy]

22 hours ago, JoaMat said:

... I want a small portable amplifier to be used in my garden under a cheery tree - resulting in this...

It must be nice to have cheery trees.  Mine are all sad, probably due to the extended drought we've been having.

In seriousness, that's an interesting solution to nice music from portable gear.

[cspirou]

Do you really need to connect the output jack with the power supply ground? Don't they share the same ground plane?

Is there a checklist for voltages at certain points we should be getting for troubleshooting purposes?

[poks999]

12 hours ago, kevin gilmore said:

Those are the original circuit, not balanced differential, and use hard to find jfet inputs.

best to build one of the new boards

You're probably right. I was curious since the rev.c board I think would be easier for me to print, since I have a CNC router but no other resources. Aside from I assume etching my own it would be hard to otherwise get the boards at a decent cost.

[Thai Tao]

10 hours ago, sorenb said:

they are in parallel ... but it does call for a better picture of the entire board

Yes, they're in parrallel so that's fine, i will post a better picture of entire board soon.

10 hours ago, kevin gilmore said:

an early version of that board had the ground missing from one of the capacitors.

put the opamps in and see if there is any sound change. without the opamps there is an additional feedback loop

 

I put 4 tl081 in, offset measure 0mv but i don't think it sound different from before, tried removing the connection between 2 boards input ground ( the ground at input+ and input-), it sound a bit different but when i switch to the original dynalo it's still a whole league better: it's sound smoother and clearer at the same time, the sound is more 3d, more open, imaging is better.

4 hours ago, cspirou said:

Do you really need to connect the output jack with the power supply ground? Don't they share the same ground plane?

Is there a checklist for voltages at certain points we should be getting for troubleshooting purposes?

Yes they share the same ground plane, but from my understanding, the output ground have high current flowing, and it should go back to the power source, where the current come from with it own path to reduce ground loop and interact with clean signal ground. 

[Pars]

Strange... I also have an original Dynalo (built on one of Justin's headamp boards, back when he sold them), plus another one that is built on rev. b/c boards, but powered with an Elpac wallwart. While I still don't think the SUSY version sounds massively better, it is at least as good, and certainly not inferior. My SUSY is using the FET input (K179/J74), and a 10K pot.

What is your biasing on the SUSY? Mine is using +/-16V supply IIRC, and running around 17mA. I don't recall what I have in there for resistors, maybe 301R?

 

Also, I recall that I was not impressed with the SUSY initially, but had some pot wiring problems. Once corrected, it sounds very good.

[Thai Tao]

1 hour ago, Pars said:

 

Strange... I also have an original Dynalo (built on one of Justin's headamp boards, back when he sold them), plus another one that is built on rev. b/c boards, but powered with an Elpac wallwart. While I still don't think the SUSY version sounds massively better, it is at least as good, and certainly not inferior. My SUSY is using the FET input (K179/J74), and a 10K pot.

What is your biasing on the SUSY? Mine is using +/-16V supply IIRC, and running around 17mA. I don't recall what I have in there for resistors, maybe 301R?

 

Also, I recall that I was not impressed with the SUSY initially, but had some pot wiring problems. Once corrected, it sounds very good.

 

Yes, i know i should sound better than this, i left it cover in dust for months because it doens't sound so boring and i don't have a real reference (dynalo 1 or 2) to compare to, until now i have confident to say that it doesn't perform its true level so i finally ask here for advice. 

My power supply is +/-17v, ouput current for each transistor is about 13ma ( 0.27V across 20r).

The power board kit i got from ebay, the kit is supplied with op27 and it sound awful, i swap for opa134, ad797 and lm6171 and it get much better, i find it sound best with lm6171.

I also have the golden reference board, it sound slightly better than the Krell PS.

I also modify another golden reference board back to walt jung super regulator with d44h11/d45h11 output transitor and this PS sound really good too.

Right now i think i will make a power supply in perfboard with mc7812/mc7912 (which i have in hand) to try if it sound any different.

[kevin gilmore]

got a scope and signal generator?

pics of the 2 phases please at about 1vpp

[Thai Tao]

4 hours ago, kevin gilmore said:

got a scope and signal generator?

pics of the 2 phases please at about 1vpp

Yes, i have, input is 1Vpp sine wave or squarewave, output get from gnd-O+ and gnd-O-. The trace is a bit blur because steam get stuck on the screen, in reality, it look sharp.

1Khz, 1V/div

20Khz, 1V/div

1Khz/ 1V/div

20Khz, 1V/div

[StrawHat]

I don't know if it can help but one thing I never do is run the wires from the psu to the amp boards in series, I always use separate power wiring for each amp board and join them at the power supply. You seem to know what you're doing so it's just my humble 2 cents. I can't remember why I do this but I think I had some problems with that kind of wiring in the past with two Beta22 boards and I have been avoiding it ever since. Maybe it's just builder's superstition

I think that if you changed the stock gain you also need to change the compensation capacitors.

[cspirou]

I ordered some PCBs from easyeda.com to build this with the following specifications.

139mm Max* 78mm Max;
- Layers: 2;
- PCB Thickness: 1.6mm;
- PCB Color: Green;
- Surface Finish: HASL(with lead);
- Copper Weight: 2oz.;
- Material Details: FR4-Standard Tg 140C;
- Smallest Holes: 0.30mm↑;
- Min. Tracing/Spacing: 6mil↑ / 0.152mm↑;

After reading through many pages here I am pretty sure my boards will be fine but someone can correct me if I am wrong. I ordered 10 boards which makes 5 pairs for 5 amps. I plan on keeping 2 pairs so the other three are up for grabs. I got a discount code since it was a first time order so they workout to about ~$10 a pair. If anyone is interested in the three remaining pairs just send me a PM. I will only charge exactly what it cost me + shipping. I am based in Europe so anyone from the US will have to pay more, but the boards are so cheap that it might be worth it. I will also consider trades for a GRLV PCB, 3oz copper.

Edit: got a picture

[kevin gilmore]

final board file for the transportable just posted

http://gilmore.chem.northwestern.edu/boards/SSDynalo-v1-4.zip

this is Kerry's work, very amazing

 

Edited September 22, 2016 by kevin gilmore

[mypasswordis]

Many thanks, Kerry! @sbelyo want to change the Dynalo board to this version or add these to the group buy?

[Kerry]

I've been enjoying the amp now for a bit.  Looking to case it up shortly

I'll publish the BOM shortly.

[cspirou]

Did you figure something out for the heat problems?

where can I source some Alpha pots for this?

Edited September 23, 2016 by cspirou

[Kerry]

If we set the current down to original spec, it reduces the heat.  At that point some heat sinks with some thermal tape and chassis venting should do the job.