Group Build: Dynafet

[vvs_75]

That said, I'd still recommend surface mount

May be if people, who are strongly against SDMs and who are for them, can make their cases to show that benefits exceeds in ether case, then we can agreed on this subject and move on.

Same goes for single vs. double box configuration problem.

[Pars]

Pete: You'd be doing it (or the builder). 0805 SMD is the size used on the PINT for example (and perhaps the mini3?). Small but not really hard to solder.

Marc and/or Jacob: For an amp such as this, what advantages do you see in using SMD resistors? This isn't a high speed device (digital), so I wouldn't think that the shorter traces, etc, would be a huge advantage. Matching? Probably not.

Marc: Have you found anyplace that you can buy reasonable quantities of either the KOA or the Susumu 0805s? I saw your thread asking about that in 2007.

Edited February 10, 2009 by Pars

[Beefy]

Although I am not involved and still just a DIY noob, I cannot see what objective benefit using SMD resistors provides other than making it that little bit more difficult for many people to build. RN60's have been good enough for every Dynahi board I have ever seen......

[Looser101]

This is not a portable device. Is anybody asserting that the thermal noise performance of an smd resistor is as good or better than a larger resistor like a RN60? Is this a potential serious compromise?

[j4cbo]

Compare the Vishay TNPW series: http://www.vishay.com/docs/28758/tnpwe3.pdf

... to their RN60D: http://www.vishay.com/docs/31027/cmfmil.pdf

RN60D: Temperature coefficient 100 ppm, noise "Average for standard resistance range is 0.10

[naamanf]

If we are going the SMD route it might be worth while to get the paste stencil and have who ever wants the task to do all the SMD parts.

As far as I/O what do you think would be good? Also should we look into converting the SE input into balanced?

I also have no problem with a single case design as long as we get a good trafo.

[Pars]

Compare the Vishay TNPW series: http://www.vishay.com/docs/28758/tnpwe3.pdf

... to their RN60D: http://www.vishay.com/docs/31027/cmfmil.pdf

RN60D: Temperature coefficient 100 ppm, noise "Average for standard resistance range is 0.10

[luvdunhill]

I'm quoting the TNPW rather than Susumu RG/RGH series because they had noise graphs, though I suspect resistors of the same size and construction (thin film) will have generally very similar performance.

SMD resistors can get very exotic. Susumu has some 5ppm, 0.1% parts as does Alpha:

http://www.susumu.co.jp/english/pdf/products-j01-04.pdf

[url=http://www.alpha-elec.co.jp/e_machine.html]Alpha Electronics Corp.

Edited February 10, 2009 by luvdunhill

[DigiPete]

Let's add the 0.3" pads, I think this is fine and we can move forward.

That's my vote as well.

I concur with Pars - (RN55 class or the 0.3", which would allow PRP 1/4W)

[Dreadhead]

If we are going the SMD route it might be worth while to get the paste stencil and have who ever wants the task to do all the SMD parts.

As far as I/O what do you think would be good? Also should we look into converting the SE input into balanced?

I also have no problem with a single case design as long as we get a good trafo.

SE to balanced would be awesome but it doesn't need to be a transformer on my GS-X it appears that it just puts the ground to the -VE boards on the SE inputs.

[Hopstretch]

SE to balanced would be awesome but it doesn't need to be a transformer on my GS-X it appears that it just puts the ground to the -VE boards on the SE inputs.

I'd appreciate this too, if it's not a technical PITA.

[justin]

SE to balanced would be awesome but it doesn't need to be a transformer on my GS-X it appears that it just puts the ground to the -VE boards on the SE inputs.

there are several ways to do it, a transformer would be one of them

some other options:

- create an inverted signal with a pre-amp such as a Dynalo circuit, but there would be nothing in the non-inverted signal path before the Dynafet. This is done in some expensive stuff like the Pass Labs Ono phono pre-amp

- convert SE to balanced with a pre-amp like a Dynalo; see the "Balanced Bridge" version on Headwize

Both of the above methods add active circuitry to the signal path that you really don't need.

- Use 2 Dynafet boards per channel, one + and one -; Use switches/relays so the inverted board can also be used as only a balanced bridge output from the non-inverted board.

- Use 3 Dynafet boards per channel, one +, one -, and one partially populated board as a balanced bridge output. Uses more power and will need bigger heatsinks. It's redundant but it's probably the most reasonable DIY solution if you don't want to add a transformer or additional active stages to the amp

[Dreadhead]

there are several ways to do it, a transformer would be one of them

some other options:

- create an inverted signal with a pre-amp such as a Dynalo circuit, but there would be nothing in the non-inverted signal path before the Dynafet. This is done in some expensive stuff like the Pass Labs Ono phono pre-amp

- convert SE to balanced with a pre-amp like a Dynalo; see the "Balanced Bridge" version on Headwize

Both of the above methods add active circuitry to the signal path that you really don't need.

- Use 2 Dynafet boards per channel, one + and one -; Use switches/relays so the inverted board can also be used as only a balanced bridge output from the non-inverted board.

- Use 3 Dynafet boards per channel, one +, one -, and one partially populated board as a balanced bridge output. Uses more power and will need bigger heatsinks. It's redundant but it's probably the most reasonable DIY solution if you don't want to add a transformer or additional active stages to the amp

Justin, Was "Use 2 Dynafet boards per channel" what you do in the GS-X (of course with dynalo boards)? It appear to be but I'm not sure.

[justin]

No, the GS-X does not convert SE to balanced

[Dreadhead]

No, the GS-X does not convert SE to balanced

Could we do what the GS-X does too? You can certainly still hear sound with the RCA input on balanced headphones though I guess it's not the same.

[luvdunhill]

With the GBP in the crapper, I think now would be a good time to try some Sowther transformers for conversion

[Icarium]

I'm down to do that buy as well if you know specs. (I still need that info for the toroids, or a confirmation on some specs I saw earlier.. I think they were for beta22s).

[DigiPete]

With the GBP in the crapper, I think now would be a good time to try some Sowther transformers for conversion

I got a great deal on my SME 309 tonearm at $1.45 vs. $1.90 GBP/USDollar !!

[Hopstretch]

• luvdunhill - 8 - 4
  
• Naamanf - 6 - 4
  
• looser101 - 4 - 2
  
• n_maher - 4 - 0
  
• Digipete - 8 - 4
  
• Pars - 6 - 2
  
• Fing - 4 - 4
  
• Asr - 0 - 4
  
• PFKMan23 - 0 - 4
  
• Icarium - 4 - 4
  
• Dreadhead - 0 - 4
  
• laxx - 0 - 4
  
• Torpedo - 0 - 4
  
• PICaudio - 8 - 4
  
• vvs_75 - 8 - 4

Sorry guys, I am out. We've just suffered an unexpected flying kick in the financial crotch. Have removed myself from the list. Peace and yoghurt etc.

[Torpedo]

Sorry to read that mate. PICaudio and I have a friend who is very interested in the project. He would take 4 boards and would build them, so he wouldn

[luvdunhill]

Sorry to read that mate. PICaudio and I have a friend who is very interested in the project. He would take 4 boards and would build them, so he wouldn

[Torpedo]

Ok if no one is against it, then I

[Dusty Chalk]

Perhaps we could make a special place that is not casino and not outside world? Dan?

[Smeggy]

Don't forget to add two boards for me that Pete will be making

[luvdunhill]

Perhaps we could make a special place that is not casino and not outside world? Dan?

I'd appreciate it not being open to the outside world. I got all kinds of spam from the Pearl deal and I'm trying to keep this small enough to be advantageous from a cost standpoint but not unwieldy. Plus, I'm counting on the group to help weed out :asshat:s, as this could be a serious drag.