Group Build: Dynafet

[pabbi1]

I just can't do this as I am building a trafo coupled amp with 5 Lundahl trafos.... but, I do have 3000' of 1kv 16878/1 in 4 colors I would gladly share. Besides, there is this electrostat to finish, and cases to make... this doesn't even have _any_ tubes - wtf?

[DigiPete]

First stab at a BOM. I took the Google one from Headwize and started updating it with some info Marc provided.

http://home.comcast.net/~youngc1/DynaFET BOM.xls

That does not look too bad price wise. With volume discount it may be

around $100 per board stuffed (just guessing)

[DigiPete]

I just can't do this as I am building a trafo coupled amp with 5 Lundahl trafos.... but, I do have 3000' of 1kv 16878/1 in 4 colors I would gladly share. Besides, there is this electrostat to finish, and cases to make... this doesn't even have _any_ tubes - wtf?

traitor... away with him... away with him....

[Torpedo]

I'll try again, please read.

To make a SE Dynafet do you need just 2 boards, or a third one for active ground is required as in the B22?

If the answer to that question is no, then to make a Dynafet to work in SE and balanced with separate outputs, would it be advisable/preferable making it with 6 boards?

I'm interested in trying the thing, and I'm convincing a friend to build his and mine, so I wouldn't overload you guys building more boards for me. If he accepts, I think it would be desirable he got Casino access to follow this thread. Would that be possible? He's not a Headcase member yet.

[Icarium]

Three boards are not required for either the beta22 or dynafet as far as I know unless you want active ground.

You do not need 6 boards for what you are talking about except for if you want 3 channel for the single ended outputs.

Separate outputs is not a problem with 4 boards.

[Torpedo]

Thanks for the reply Icarium. OK, I'll rephrase my question since "required" isn't the proper word to mean what I wanted to. Are there clear benefits sonically for using active ground in the Dynafet as there are in the B22?

Considering that a project like this is better to have it made right at the first trial, I'd like to know if it's worth the expense and trouble building it with active ground or not. For this same reason, I'd like to know too if having a power supply for every 2 boards is overkill or just the way to go.

[Icarium]

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

[Torpedo]

Thanks again for the reply. Well, if there's not a clear benefit, we may leave it without active ground. Much cheaper and easier to build and adjust.

As soon as my friend says whether he'd be building some boards for himself and me, I'd contact mods to let him having Casino access and would update the "order status" accordingly. Thanks.

[Icarium]

Well don't take that to mean there isn't one... let people more experienced in the matter or familiar with the science comment

I was more curious to see if you have experienced the difference/benefits yourself.

[Torpedo]

Nope, I'm not that skilled as to convert my 3 boards B22 into a non-active ground device for comparison I'm no DIYer/tweaker so I take things "as is" but for some tube rolling on the gear allowing it.

I not even know if the Gilmore Reference balanced has active ground

[MASantos]

Torpedo, if you need I can build your boards, in case your friend can't.

I'm right next door to you so shipping shouldn't be a problem. I could even take the trip, Spain's always a pleasure to visit!

[Torpedo]

Hi Manuel, thanks a million for your kind offer . My friend Rodrigo is interested in the project and would build his boards and mine too. The active ground issue interests him, so we would wait until there are more opinions about it, eventually Kevin could provide his too.

If we decide to go absolute overkill and making two balanced with active ground in SE amps, he'd be building up to 12 boards... Maybe he hasn't thought about it carefully yet And we have no idea about costs yet

[MASantos]

Hi Manuel, thanks a million for your kind offer . My friend Rodrigo is interested in the project and would build his boards and mine too. The active ground issue interests him, so we would wait until there are more opinions about it, eventually Kevin could provide his too.

If we decide to go absolute overkill and making two balanced with active ground in SE amps, he'd be building up to 12 boards... Maybe he hasn't thought about it carefully yet And we have no idea about costs yet

Where in Spain do you live? Can I come for a visit when they're done?;D;D

[swt61]

Where in Spain do you live? Can I come for a visit when they're done?;D;D

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

[Torpedo]

In Madrid, but my friend lives in Galicia, which depending where in Portugal you are, might be closer to you. There's a very active headphones aficionados group over there, they all participate in the Spanish Auriculares.org forum, and we set several meetings along the year. I suppose there will be one when this cold and snow passes. Of course you can come by my place whenever you want, you'll be very welcome

[luvdunhill]

trouble building it with active ground or not

FWIW, I think it will take some work to make this amp stable with lower gains.

[Torpedo]

FWIW, I think it will take some work to make this amp stable with lower gains.

So your advice is not trying the active ground configuration unless you're very knowledgeable and skilled?

[DigiPete]

So your advice is not trying the active ground configuration unless you're very knowledgeable and skilled?

It may not be feasible/advisable to try to get this design to unity gain for an active ground channel.

A balanced amp (4 ch) does not use an active ground, and one 4-ch amp can play balanced or unbalanced

[luvdunhill]

...that and there would be a lot of heat to deal with both in the amp and the power supply.

[Hopstretch]

Blockhead question, but where will the PS be located? External?

[DigiPete]

Blockhead question, but where will the PS be located? External?

By the size of the case some have posted it seems internal.

I would prefer a two box solution, personally, and I may still do that.

[DigiPete]

Well, I made contact with Jacob

Originally Posted by DigiPete

Jacob,

There is a serious effort to group build the Dynafet.

If you are interested, we could use someone to perfect the boards.

Let me know if you are interested to help.

Cheers

Pete

Dammit. I was just about to finally get my Dynahi into a case and stop DIYing amps for a while. So much for that...

Is there a thread I should be looking at? I don't see anything recent in Head-Fi's DIY section.

[n_maher]

For heat reasons alone I think a 2-box solution would be prudent. Overkill perhaps, but better safe than sorry.

[Torpedo]

Thanks for the input mates. I was considering going just SE for myself. My favourite cans are all SE and I'm not planning to recable them anytime soon. Unless the new HD800 sound damn better balanced, I wouldn't be taking much profit from a balanced amp. Hence my interest to know if it'd be a good thing building it with active ground.

In your opinion, what's the ideal gain setting for this circuit?

[luvdunhill]

guys I may not be around here much today and tomorrow.

If possible, I'd love to have the owners of the various sourcing efforts drop in a rough estimate in the next few days so we can get some commitment by the interested parties, as we may be looking at some lead time for some of the semiconductors to keep prices down. Also, there will be another run for the dual heat sinks and that will take time as well. Then there is the board finalization and fabrication. As soon as we can get these items moving, the better, as we could be talking 4-6 weeks easily.

The next steps forward as I see it is a rough cost with a few options, then a final commitment to at least the above costs (boards, semiconductors, and tiny heat sinks) then finally a deposit made for the above items.

Chris: as far as the boards go, I think a rough cost based on the board size in the original files would be good enough for now. Looks like 50 is a good number. If/when Jacob Potter wants to get involved, you guys can go to town on the boards.

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.