Group Build: Dynafet

[n_maher]

It's virtually guaranteed that you'll have a higher noise floor with the PS in the same chassis. If pushed I'd recommend a remote trafo triggered by one of amb's e24 boards but again I think heat is going to take careful consideration especially for 4-ch folks.

[Hopstretch]

I'd personally prefer a one-box build for space reasons, and may also listen to the voice of reason from Spain and just go SE myself. Will think on this.

[naamanf]

Naaman: I'd prefer a single box version if the chassis is large enough. I see no reason to waste performance of a low output impedance power supply on 3 feet of wire and a bunch of connectors. However, I'm usually alone in this opinion. I'll leave this direction up to you for estimation purposes. It's not a super critical decision at the moment, as long as the committing parties are away of the potential cost and labor associated with 2 boxes. Also, I'm of the opinion that the bigger the heat sinks the better, so perhaps we can offer two size of cases, one that caters towards the 4-channel / speaker amp builds and one for the 2-channel builds.. again, your call.

I would also prefer a single box version.

I really think we all need to come to a group consensus on how we want this built. One version only. Trying to plan for 10 different amps to meet the needs of 10 different people won't work out IMHO. If people want to do their own or stray from the group version then they can buy sub components of the planned group version. Just my $.02.

[DigiPete]

Well we can consider offering stuffed boards, and a chassis option.

Those who don't like the group chassis, can DIY their prefered chassis.

[naamanf]

Well we can consider offering stuffed boards, and a chassis option.

Those who don't like the group chassis, can DIY their prefered chassis.

Yup.

[laxx]

I'd like to follow up with this and see what the final price comes down to.

• 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
  
• Stretch - 0 - 4
  
• PFKMan23 - 0 - 4
  
• Icarium - 4 - 4
  
• Dreadhead - 0 - 4
  
• laxx - 0 - 4
  

[n_maher]

I'd like to follow up with this and see what the final price comes down to.

• 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
  
• Stretch - 0 - 4
  
• PFKMan23 - 0 - 4
  
• Icarium - 4 - 4
  
• Dreadhead - 0 - 4
  
• laxx - 0 - 4
  

Currently there are (magically) both 44 boards offering to be built and 44 requested. I have not added boards for me since honestly, I don't want any.

[Pars]

I dunno are there clear sonic benefits with active ground? I don't think I've heard any... but I didn't do detailed a/bs either. It certainly wasn't night and day enough for me to say either way. Sure doesn't seem to stop the Meier stuff from sounding like thin ass

IIRC, KG doesn't like active grounds. I'm not sure I've ever seen a 3 channel dynalo or dynahi. I'll let him weigh in and correct me if he cares to however. The ones I've seen are 2 channel for SE and 4 channel for balanced.

[n_maher]

Kevin's designs aren't often fond of unity or even low gain are they?

[Looser101]

I would also prefer a single box version.

I really think we all need to come to a group consensus on how we want this built. One version only. Trying to plan for 10 different amps to meet the needs of 10 different people won't work out IMHO. If people want to do their own or stray from the group version then they can buy sub components of the planned group version. Just my $.02.

Agreed. Looking at what most people have committed to as boards for themselves, it looks like 4 channel builds are the most popular choice. It looks like only Pars and myself were looking at a 2 channel build. If it makes it easier I would up my board count by 2 and go balanced. This would make chassis machining decisions much easier, as they would all be the same.

[naamanf]

It's virtually guaranteed that you'll have a higher noise floor with the PS in the same chassis. If pushed I'd recommend a remote trafo triggered by one of amb's e24 boards but again I think heat is going to take careful consideration especially for 4-ch folks.

I think this would be a good way to go and would not add that much to the final cost. Most expensive parts would be the cannon plugs/jacks.

[Looser101]

I think this would be a good way to go and would not add that much to the final cost. Most expensive parts would be the cannon plugs/jacks.

Wouldn't it be cheaper to just have a transformer shield added even if we have to pay to have it fabricated? Adding an extra case would surely be more expensive.

[justin]

Kevin's designs aren't often fond of unity or even low gain are they?

The dynalo is extremely stable at unity gain without capacitor compensation

[Pars]

Wouldn't it be cheaper to just have a transformer shield added even if we have to pay to have it fabricated? Adding an extra case would surely be more expensive.

Shielded transformer from SumR is cheaper than an Avel plus another case plus good connectors (though JAE and whichever ones were used in the krmathis build are good and not that expensive). Heat may be the trump card however, though I was planning a 2 ch. build, so single chassis = win.

[Icarium]

So shielded transformers from SumR probably what people would want? I would need to know specs to communicate to the manufacturer. If someone could help me out

[n_maher]

I can talk with Richard @ SumR if necessary, I have a working relationship with him already.

[Icarium]

Nod I don't entirely know how group buys work... I can cover the initial cost and then distribute cost depending on how exactly we handle the labor compensation if you can make the arrangements Nate Does that seem reasonable?

[Pars]

Marc,

The goal on these boards in terms of the front end and VAS stage is to

1. Use singles (2SJ74/2SK170 and a BJT pair, currently perhaps 2SA970/2SC2240), and
   
2. use the heatsinks per the diyaudio thread?
   

A nice to have would be grouping the 2SJ/2SK together (back to back) and the same with the BJT quad? Not sure if that is doable.

Referring back to the layout in post 192, the individual TO92s for each dual package device are not oriented opposite to one another, which was what I thought you needed to have for the heatsinks?

Let me know if I am making incorrect assumptions on any of this.

[MASantos]

Will they let you in after that tragic Flamenco incident that mamed four poor maidens and a donkey?

what?

[n_maher]

Nod I don't entirely know how group buys work... I can cover the initial cost and then distribute cost depending on how exactly we handle the labor compensation if you can make the arrangements Nate Does that seem reasonable?

Given the magnitude of what we're talking about here I think that there is going to have to be one, central money collector who can distribute funds to the individual buyers prior to purchase. It wouldn't surprise me if we order $1000 or more of just transformers, the potted and shielded units are probably going to run $75 each or so.

[Dreadhead]

Send me your money!!!!! You'll get your amps in 3-4 years if fed-ex doesn't give me trouble

Seriously I'm in for whatever... Probably not a good idea to have me do the money though since my life borders on the insanely hectic nearly all the time

[n_maher]

Serious consideration will have to be given to how to handle the money so that paypal doesn't eat you guys alive for fees.

[Icarium]

Yeah that shouldn't be a problem.. i mean the end build will be at least that. I can just pay for the transformers. Distribute them and then figure out how much I need from others.

It would be good to have a comprehensive cost distribution model though.

Yeah good call Nate.. paypal fees are a serious issue.

[Torpedo]

I'd like to follow up with this and see what the final price comes down to.

• 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
  
• Stretch - 0 - 4
  
• PFKMan23 - 0 - 4
  
• Icarium - 4 - 4
  
• Dreadhead - 0 - 4
  
• laxx - 0 - 4
  

You can add PICaudio and Torpedo so:

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
Stretch - 0 - 4
PFKMan23 - 0 - 4
Icarium - 4 - 4
Dreadhead - 0 - 4
laxx - 0 - 4
Torpedo - 0 - 4
PICaudio - 8 - 4

This doesn't break the magic of having as many boards requested as offered to build.

Edited February 6, 2009 by Torpedo

[luvdunhill]

Marc,

The goal on these boards in terms of the front end and VAS stage is to

1. Use singles (2SJ74/2SK170 and a BJT pair, currently perhaps 2SA970/2SC2240), and
   
2. use the heatsinks per the diyaudio thread?
   

A nice to have would be grouping the 2SJ/2SK together (back to back) and the same with the BJT quad? Not sure if that is doable.

Referring back to the layout in post 192, the individual TO92s for each dual package device are not oriented opposite to one another, which was what I thought you needed to have for the heatsinks?

Let me know if I am making incorrect assumptions on any of this.

yup, looks right. I'm confused why these heat sinks won't work? The 2SC3381 is "BCE ECB" so just flip one of the devices and things should work, just like with the JFETs. I hope I didn't miss anything.