The Multi Amp aka Dynalo Mk2

[mwl168]

The last board run I did was the TO92 version and sorry I don't have any spare boards available. 

The boards I had were from SeeedStudio, 1.6mm/2oz. As Pars said, they work fine and the cost was reasonable. 

[FallenAngel]

Which version were they? I don't have the software to look at the files but I might have to install it and figure out which parts are used.

[sorenb]

7 hours ago, FallenAngel said:

Which version were they? I don't have the software to look at the files but I might have to install it and figure out which parts are used.

you might find GerberLogix useful - both an online as well as free downloadable edition available

[MLA]

I think I have a spare pair of the SMD version (v9) at home, will check after work.

[mwl168]

12 hours ago, FallenAngel said:

Which version were they? I don't have the software to look at the files but I might have to install it and figure out which parts are used.

I am fairly certain I used kgdynalobal5.zip from Kevin's site back in January 2015. On the silkscreen it says version 1.02.

However, the current kgdynalobal5.zip on Kevin's site has a June 2015 date and the version is 1.1. IIRC, Kevin fixed an issue of the board on this version - this information is somewhere in this thread.

[congo5]

12 hours ago, FallenAngel said:

Which version were they? I don't have the software to look at the files but I might have to install it and figure out which parts are used.

kgdynalobal5 is MPSW06/56 THAT340     those are through hole

dated 6/5/2015 9:49 AM

you can use the SeeedStudio gerber veiwer on the order page

[UFN]

circuitpeople.com is great for viewing gerbers as well.

//UFN

[FallenAngel]

On 2/26/2016 at 5:01 AM, MLA said:

I think I have a spare pair of the SMD version (v9) at home, will check after work.

Thanks, it would be awesome if I could grab those.

I used CircuitPeople to check out the lateest (2/6/2016 8:25 AM kgdynalobal9.zip)

It says SS Dynalo Rev 1.2 and it looks like it uses PZTA06 / PZTA56 SMD parts (I count 11 of each per board).

Is there a parts list somewhere here?

[MLA]

I did have a pair left, so PM me your address and I'll ship them your way. 11 ptza06/56 sounds about right.

Haven't seen a BOM around, but it's a very straightforward build with no superexotic parts. Square cap markings tend to be film, round electrolytic and oval MLCC. Then put RN60D in the Mouser search engine and select all values you need. 

[Pars]

Just a quick search thru this thread, there is a BOM in this post. This is an SMT BOM, so should be good. And it is 22 ea. ptza06/56 for a stereo board pair, so 11 ea. per board.

[FallenAngel]

Awesome thanks.

Are schematics available for the new amp? Mainly asking because I might not put a pot in this build and run it off a DAC with digital volume control, as well as wiring unbalanced vs balanced outputs. The DAC will be the Soekris discrete R2R DAC and I kind of wanted to skip the buffer section.

I'm assuming I can use the TL81 instead of the OP27 for DC offset control. I think it's a better chip in specs. Similarly the OPA134. Preference on the opamp to use?

Edited February 28, 2016 by FallenAngel

[Pars]

The schematics were available on Kevin's site, but I attached it here anyhow.

As for opamp, I use TL071 or 81; from the discrete I/V stages I've built, both work well. The TL-08x seems to pull the offset down the lowest of anything I have tried, though I did not compare it to the OPA445 (I do have some of those though).

kgdynalobalssproduction.pdf

[FallenAngel]

Very cool, thanks.

It looks like I'll be using unbalanced input from the DAC, unbuffered, with a 10k resistor to ground as fake pot and all should be peachy.

[Thai Tao]

Anyone have suggestion on cable type for power supply wiring?

[Pars]

Teflon SPC, like the stuff from NavShips on ebay is what I use. 24ga for signal, 20ga or maybe 18ga for power stuff.

http://stores.ebay.com/johnssilverplatedptfewireshop?rmvSB=true

[UFN]

FWIW I personally don't use teflon SPC for power because it's too stiff (no laughing in the back please  ) but (surplus) silicone-insulated copper that's pliable and easy to work with. 18-20 ga sounds right for me (app. 0.5-0.75 mm2 in metric terms).

 

//UFN

Edited March 4, 2016 by UFN

[Thai Tao]

Hi KG,

I open the lastest kgdynalobal9.zip and saw one part (the green rectangular) that doesn't seem to associate with the pcb, can i send this file to pcb manufacturer just fine?

[kevin gilmore]

thats an extra board if you want to do surface mount jfets

 

[mwl168]

On 2/28/2016 at 6:11 PM, FallenAngel said:

Awesome thanks.

Are schematics available for the new amp? Mainly asking because I might not put a pot in this build and run it off a DAC with digital volume control, as well as wiring unbalanced vs balanced outputs. The DAC will be the Soekris discrete R2R DAC and I kind of wanted to skip the buffer section.

I'm assuming I can use the TL81 instead of the OP27 for DC offset control. I think it's a better chip in specs. Similarly the OPA134. Preference on the opamp to use?

I may be stating the obvious but the TL081 is rated at +/-18VDC max supply voltage. The OP27 is rated +/- 22VDC, OPA445 is rated up to +/- 45 VDC.

Edited March 8, 2016 by mwl168

[Thai Tao]

On 7/3/2016 at 7:14 PM, kevin gilmore said:

thats an extra board if you want to do surface mount jfets

 

The P-channel is mmbf5460 then is the N-channel mmbf5457?

[FallenAngel]

On 3/8/2016 at 10:59 PM, mwl168 said:

I may be stating the obvious but the TL081 is rated at +/-18VDC max supply voltage. The OP27 is rated +/- 22VDC, OPA445 is rated up to +/- 45 VDC.

Obvious is good. I remember using the TL081 in my Dynalo on +/- 16.4V as originally designed, but this one will be running +/- 20V, so that's important.

I got the following transformer VPT36-690, 2x 18V 0.69V, and I assume that'll be more than enough to run this amp using the GRLV psu.

[Thai Tao]

Hi KG,

I remember in 1 post you said that the default susy has gain of 6db in se mode, that mean 2, but i tried to simulate it in ltspice but it has gain of about 4, this got me confused as the feed back resistor is 25k and 5k, so the gain should be 25k/5k+1 = 6?

[kevin gilmore]

Lots of people changing the gain.  Yes it's Rfeedback/Rground+1

[mypasswordis]

Relatively low open loop gain brings it down some, doesn't it?

 

Edit:

I'd be down for a fully SMT Dynalo...

Edited March 23, 2016 by mypasswordis

[Thai Tao]

3 hours ago, kevin gilmore said:

Lots of people changing the gain.  Yes it's Rfeedback/Rground+1

I have finished my dynalo, everything measured ok, 0.3V across 20R resistor - 15ma for each output resistor at +/-18V rail, output offset for out+/- to ground is about <2mv without servo. Listen to some music, it sounds so so, not very good and gain seem to be low, i feed a 1Vpp sine wave at the input and get only 1.8Vpp sine wave at output, i use default resistor value with rin =5k, rf= 25k, does this seem strange?