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Group Build: Dynafet


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I assume you mean have both sets of boards installed in a chassis at the same time? The inputs wouldn't be so bad I wouldn't think because they've already gone thru the pot at that point, so it would be like a selector switch (stereo or balanced). The outputs you might be able to wire in parallel if only one set of boards was powered. Otherwise, 2-4 more poles (or relays). Then there is power, which is the easiest as you would only need a DPDT switch for that (switching V+/V- DC power).

Doing this all without pops, etc. is another matter.

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Did some work on mocking up the chassis and getting into a more listenable state. I will need to get aluminum top/bottom and rear panels for this (not using the steel ones that it came with). I'm also

Got both boards up and running with mods 1 and 2 above. Ran RMAA on it at 150mA, 100mA and 75mA bias. I think 150mA is probably the best. See what any of you think of the plots attached. Als

Documenting how these are configured: Vbe multiplier: R17-R18: 3.3K R62: 1K VR3: 20K R19-R20: 2K Mods: Cordell zobels: 100pf / 90.9R from gate to ground (Cordell use

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What do I need a spreadsheet for? :confused:

I just had him write you a quote up for 2 kits with standard options as an aid to help you decide if you want to grab a few or not.

If you are not interested or already have all the information you need to come to a decision then no need for the spreadsheet :)

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The one board layout from jacob that I saw had +/-15V regs for a more typical servo opamp in it...

right, but it's quite simple to adapt. Just leave off the regulators and the bypass caps, two pieces of wire and you're done!

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right, but it's quite simple to adapt. Just leave off the regulators and the bypass caps, two pieces of wire and you're done!

I guess I must be missing something here... why would you want to? Are these higher performance than a TL071, etc. as a servo? Increased pull in range (or whatever you call it in a servo) due to the higher rails? Free (kinda)?

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On my question, yes I'd be treating them as two separate amps that happen to share one case with two sets of inputs, two volumes and two headphone sockets so umbilical plugging isn't any problem. I'm not looking at a complex solution, just a simple and neat one.

Switch off power, swap umbilical socket, power on... Is that reasonable?

Edit:

I will be feeding both from a Pico DAC so parallel input would be nice as my source will be USB for 90% of the time

Edited by Smeggy
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If both amps use the same rail voltages and the PSU can cope with the load I see no reason why you can't use a single PSU to power both amp sections, one at a time. The loop out is just another set of sockets wired in parallel.

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Ok, so I am in for two populated boards and will send $160 this weekend if that's ok. Hopefully DigiPete is still willing to populate my boards.

I also hear my B22 Sigma may not have enough juice to run the Dynafet boards, is there a specific transo that will do the job as I don't currently know what is in there.

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So if the transo needs upgrading to feed the Dynafet boards, will that screw with the beta in any way? I don't want to be underpowering or overpowering either set of boards and I don't know enough about this stuff to know. :confused:

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Ok, so I am in for two populated boards and will send $160 this weekend if that's ok. Hopefully DigiPete is still willing to populate my boards.

.

Sure :) A larger trafo should not hurt your Beta, so long as it does not cause any more hum/emi than your current unit.

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Ok, so I am in for two populated boards and will send $160 this weekend if that's ok. Hopefully DigiPete is still willing to populate my boards.

I also hear my B22 Sigma may not have enough juice to run the Dynafet boards, is there a specific transo that will do the job as I don't currently know what is in there.

Actually for now you only need to send 120 dollars + fees to Luvdunhill. I think there's still space.. have a couple people interested. Perhaps he'll post here if its kosher.

I'm not sure but heatsinking may become an issue as well (Not sure at all).

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Actually for now you only need to send 120 dollars + fees to Luvdunhill. I think there's still space.. have a couple people interested. Perhaps he'll post here if its kosher.

I'm not sure but heatsinking may become an issue as well (Not sure at all).

Thanks

It's all cool as long as I can successfully strap it all together to work I'll be extremely happy. Two awesome amps in one case? What's not to love :D

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if/when Jacob reads this thread :) I'd like to offer another suggestion of adding another set of pads right next to the current pads, but spaced out slightly axially so a second resistor can be piggybacked on top of the (currently) single ballast resistor per output device. I'd like to experiment with lowering the ballast resistor, as I'm expecting we will get good matching...plus this will allow more power handing here in case we want to up the bias substantially.

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Updates from my end:

Dynafet Group Order - Google Docs

Spreadsheet is updated.

So this week it's time to lock down input transformers. Now that Cinemag is an option please recommunicate your input transformer needs to me. If you have locked down your needs on the diyaudio wiki then that is fine. I will check that to make sure you are covered.

Otherwise please let me know if you do not want input transformers, if you want sowter or Cinemag.

I am in talks with SumR as well and waiting on a few more quotes:

What I have now is this:

2/ The Encapsulation can for 160VA to 230VA is OD: 5.3", HT: 2.75"

3/ Price of the 150VA is US $ 8700 Fully encapsulated in toroid can.

4/ Price of the 230VA is US $ 98.00 Fully encapsulated in toroid can

Price of a 200VA transformer with 120/240Vac primary, encapsulated into toroid can,

is US $ 95.00/e

10 pcs given the above arrangement is US $ 87.00/e.

Anyway given that the price break isn't amazing... I think we can be somewhat flexible on values. I am also getting pricing/size info for 250VA/300VA to go straight up into overkill.

I am mostly looking at higher valued toroids with 4 secondaries for use with 2 kits. If you are interested in lower values I can get quotes there. If you have a value in mind I can get quotes and see if I can still work a price break if we have a big enough number. If not then yeah might as well just order on your own.

Last thing is chassis:

I think team J4cbo is mostly settled on these chassis:

modushop.biz

Pending confirmation that the layout we are thinking of will fit in this for sure... we will be looking at 4-6 pieces. There is a price break of 20 percent at 10 pieces. We will probably set up a group buy on diyaudio to get the numbers up as well... possibly for a bigger price break. Let me know if you are interested. We may capitalize on I think Nate's suggestion to get 2x front panel to side step the painted back panel issue.

Shipping works as follows:

i can make a discount of 20% for 10 pieces ,

for the transport I have 2 options, to send them in group, with only courier via earth approximately 20 days about 350 -400 euros in total but I must have confirmation from my courier, or with 125 euros I can send 2 pieces for time with Italian air mail to the cost total of 750 euros. (125 x 5 pieces of 2 case ) ,

So we can probably go with the cheaper option since I need 4-6 chassis at my location anyway and then I distribute the rest if people want in on this.

Another option that we ruled out due to 10 inch height but with truly overkill options is detailed in this thread:

diyAudio Forums - Aavid Thermalloy Possible Group Buy - Page 5

Dimensions are there and pictures are below. I believe he is looking at 250 for a drilled/tapped chassis with 4 heatsinks. This is probably more appropriate for pass labs designs but is a pretty sweet chassis overall. I may get one just to horde.

Anyway just food for thought.. really just need action on the input transformers for now.

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Oh yeah people should probably start paying Jeff at Glass Jar Audio if you haven't already. Torpedo hopefully you are arranging things with him for payment for Team Spain.

If you still need a quote or what not please let me know. Any confusion also let me know. I think he's getting in the bigger heatsinks I think Wednesday.

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As I said in the PM I sent, I'm hesitant about those "Power entry modules" which aren't included and I wonder if they're needed for anything, maybe just making connections easier or whatever.

Otherwise I'd be ready to order payment, just needing Paypal address confirmation.

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As I said in the PM I sent, I'm hesitant about those "Power entry modules" which aren't included and I wonder if they're needed for anything, maybe just making connections easier or whatever.

Otherwise I'd be ready to order payment, just needing Paypal address confirmation.

Are you referring to the sigma BOM spreadsheet? You will need either plain IEC power entry (with fusing, some sort of power switch whether it is part of the IEC or not is your choice) or a filtered IEC inlet.

Also, it might be good if Team Spain were to include some spare current diodes of both flavors, as these are getting hard to find reliably, at least here in the US.

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If a much lower gain is possible with the fet(lower than the dynahi), I would be interested in switching capability to use one of the four boards as active ground for a 3 channel SE output. It probably won't get used much but would be great from a resale standpoint.

I need to do some more reading to comment further.

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Oh I never replied to you there? Sorry, my bad :(

Yeah those are useful. If you want those then just change the number from 0 to 1 and then the rest of the spreadsheet should take care of it. Some people like looser101 are sourcing their own with EMI filtering. I think team j4cbo is still pondering ourselves if we want to go with his instead of something similar to looser's.

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Are you referring to the sigma BOM spreadsheet? You will need either plain IEC power entry (with fusing, some sort of power switch whether it is part of the IEC or not is your choice) or a filtered IEC inlet.

Also, it might be good if Team Spain were to include some spare current diodes of both flavors, as these are getting hard to find reliably, at least here in the US.

Ah good call.. if you want more diodes then adjust the numbers accordingly and then email me back the spreadsheet and then I'll send it to him to have him confirm and then we can do payment.

His paypal address btw is:

[email protected]

Also.. were you guys doing separate payments or one big payment? If separate then it'd probably be good to email him a list of names so he can confirm that he's received all the payments.

Oh yeah one last thing.. for the more than 2 kit buys (j4cobs and spains) wait til you hear confirmation from me to actually pay. He just let me know to wait until later today or tomorrow because he is receiving the larger heatsinks today so he can package it up and make sure that the shipping costs quoted are appropriate. You 2 kitters are fine though!

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I thinkk so... someone linked some from digikey(?) and we are getting those. Would you be interested in some kits? I think we could get some for you if you do... they are ~60 bucks depending on options.

The options are larger heatsinks (Not much extra I forget exactly how much)

Upgraded Muse caps (2.15 after discount)

Or you could also go with no heatsinks if you are set on offboard heatsinking.

We are getting it without toroids and it was like 67 bucks stock and then he's giving us an additional 15 percent discount.

I think its these heatsinks:

HS385-ND 4 TO-220 heatsink 2.2 8.8 70.4 32 Aavid-Thermalloy 530001B02500G

If you would like kits then pm me your email/address information and I'll have him write you up and email you a quote.

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