Group Build: Dynafet

[grawk]

I'll just add him to the casino

[Torpedo]

Great, thanks a lot mates I'll let him know.

[naamanf]

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

I think you might be right. Looks like about $75 for each transformer. Maybe less since we would be buying in bulk. Hmm....OEM purchase me thinks.

[j4cbo]

New board: http://b.j4cbo.com/temp/gbf2-brd.png

Hopefully this will satisfy more people

[luvdunhill]

I think you might be right. Looks like about $75 for each transformer. Maybe less since we would be buying in bulk. Hmm....OEM purchase me thinks.

hey, do you have any rough costs for case cost? any estimates from your beta22 builds would probably be right on, plus the differential cost in the cases.

Also, the transformers come in a PCB version.. it would be cool if those got integrated into the I/O boards. If you can get OEM cost, I could probably get some other people interested as well to help the numbers.

Edited February 12, 2009 by luvdunhill

[luvdunhill]

New board: http://b.j4cbo.com/temp/gbf2-brd.png

Hopefully this will satisfy more people

so, is there a ground plane on both sides of the board? I know amb does this with his boards a lot... I'll look over it some more tomorrow...

edit: also, I would recommend cutting off the ground plane around the output devices, or is that what the dashed line is for? I'm confused I suppose

Edited February 12, 2009 by luvdunhill

[n_maher]

hey, do you have any rough costs for case cost? any estimates from your beta22 builds would probably be right on, plus the differential cost in the cases.

Also, the transformers come in a PCB version.. it would be cool if those got integrated into the I/O boards. If you can get OEM cost, I could probably get some other people interested as well to help the numbers.

1. When you say case costs are you including the various finishing bits and pieces or do you just mean raw chassis including panel fab? If it's the latter and you go single chassis figure $200 for just the bones. The chassis once it gets shipped will probably run ~$100 and having both panels done will probably run another $100 (maybe less, maybe more). Of course that leaves you a long way from a finished case but you know that. I'd bet I spent ~$300 on Mike's beta22 including the knobs, switches, RCA's, IEC, etc.

2. You do not want to be mounting the trafo to a PCB, or at least I wouldn't. For me and my money and with the size of the sucker you're talking here I'd want that beast bolted to metal and no chance of shock loading a solder joint or pcb with anything else attached to it.

[luvdunhill]

2. You do not want to be mounting the trafo to a PCB, or at least I wouldn't. For me and my money and with the size of the sucker you're talking here I'd want that beast bolted to metal and no chance of shock loading a solder joint or pcb with anything else attached to it.

I was referring to the input transformers

[n_maher]

Right, that would make a lot more sense.

[j4cbo]

so, is there a ground plane on both sides of the board? I know amb does this with his boards a lot... I'll look over it some more tomorrow...

edit: also, I would recommend cutting off the ground plane around the output devices, or is that what the dashed line is for? I'm confused I suppose

There's a ground plane across most of the top; its area is marked by the dashed line, but it isn't rendered out in that image so that you can see what's underneath. The bottom left and right halves of the board have V- and V+ planes, so that there's a very low-impedance connection between the power connector, rail capacitors, and output devices; those planes do show up in the image.

[kevin gilmore]

By the way i would like 4 boards minimum 8 boards maximum.

I'll build them myself...

[DigiPete]

I was referring to the input transformers

Not interested in those... maybe a separate purchase item for those who indicate they are interested?

[Pars]

New board: http://b.j4cbo.com/temp/gbf2-brd.png

Hopefully this will satisfy more people

Had a brief look at it and from what I saw, it looks good. It appears you have provisions for 0805 SMD, 0.200" and 0.300" resistors?

hey, do you have any rough costs for case cost? any estimates from your beta22 builds would probably be right on, plus the differential cost in the cases.

Also, the transformers come in a PCB version.. it would be cool if those got integrated into the I/O boards. If you can get OEM cost, I could probably get some other people interested as well to help the numbers.

For the I/O boards, these would I assume be mainly geared towards the balanced builds (certainly the SE->bal transformers )? This is probably for Naaman: What jacks do you normally use for both XLR and RCA on such boards? If it would be possible to do a board that would suffice for both SE and balanced builds, that would be greaaaatttttt. Not sure how plausible that is though.

Also, the rear panels on the hifi2000 Pesante Dissipante cases are painted steel, which FPE won't work with. I would suggest shipping the 10mm front panels to them, and then designing an aluminum rear panel that they would supply? Otherwise, find some place that would work the steel panels.

[n_maher]

Also, the rear panels on the hifi2000 Pesante Dissipante cases are painted steel, which FPE won't work with.

I believe that you can request that they send an additional front panel in lieu of the back panel. I'm pretty sure that's what amb did with his beta24.

[Pars]

I believe that you can request that they send an additional front panel in lieu of the back panel. I'm pretty sure that's what amb did with his beta24.

Damn, I must of missed that

I may have to get one cuz I wasn't looking forward to dealing with steel for an IEC, etc. cutout.

[Pars]

New board: http://b.j4cbo.com/temp/gbf2-brd.png

Hopefully this will satisfy more people

I've looked this over a bit more and here are the comments I have. In general my viewpoint is geared towards making the board more tolerant of any rework required down the road, hence comments regarding pad and trace sizings (bigger usually is more tolerant of desoldering, etc.)

1. Trace width seems rather small on a lot of the circuits.
   
2. Pad size also is small for the thru hole components, particularly on the larger resistors (2 ohm I assume?) up by the output FETs. But really, on all components. Trimpot pads are minuscule (and I realize those are the stock library sizing).
   

I see you have vregs in place to allow for +/- 15V opamp operation (ala Dynahi). Hopefully, this circuit does not require higher voltage swing on the servo (hence the original opa445)? Overall, very nice job!

[luvdunhill]

I agree, looks fantastic!

What about Justin's suggestion of the input filter? Here's one that I used, and I've also swapped the location of R34-R35 to be after the caps. I'm partial to polystyrene caps here (e.g. Newark 96K9640), but micas are another possibility.

While we're on the subject of caps, I've had very good luck using Teflon (PTFE) caps in feedback loops. Would it be possible to add a second pad to support this? This would not be a standard option, but more for me to tweak with The Voltronics stuff at Mouser is good, but very expensive. Another choice would be Vishay/BC sold at Newark. Both places, just search for "PTFE trimmer". All that really needs to be added is one pad... what that be possible?

Finally, what about adding the Wima FKP2 bypasses? I still think this is a good idea wherever possible.

[Icarium]

Mmmm polystyrene. Mica is good too from what I hear.

Mmm teflon as well.

[kevin gilmore]

vintage silver mica !

[Dusty Chalk]

By the way i would like 4 boards minimum 8 boards maximum.

I'll build them myself...

I think the numbers are: number I'll build, and number I'll want to receive, so I think you have to make up your mind.

[n_maher]

I think the numbers are: number I'll build, and number I'll want to receive, so I think you have to make up your mind.

I think Kevin is saying he's either 4 - 4 or 8 - 8, I do not believe he's offering to build for others or asking someone to build for him.

[Dusty Chalk]

I think Kevin is saying he's either 4 - 4 or 8 - 8, I do not believe he's offering to build for others or asking someone to build for him.

I understood that, but I think he was misreading the 0-4 etc. as the range of boards that person was interested in. So he's kind of:

KG: 4?8 - 4?8

[naamanf]

For the I/O boards, these would I assume be mainly geared towards the balanced builds (certainly the SE->bal transformers )? This is probably for Naaman: What jacks do you normally use for both XLR and RCA on such boards? If it would be possible to do a board that would suffice for both SE and balanced builds, that would be greaaaatttttt. Not sure how plausible that is though.

As far as what case we are going to use I think we need to wait till boards are finalized so we know their size and also know everything else we plan to fit in the case.

As for I/O what do people want? I was thinking for the back: SE/balanced inputs, maybe a loop out for each, SE/balanced preamp outs. Speaker if you think it's up to the task. Now do we want to use something like the e24 for switching power on/off with a nice lighted switch on the front? Matching switches for switching inputs and outputs? Single 4 pin XLR on the front or dual 3s? Or both. Two SE jacks or one?

As for the connectors I was thinking Neutrik for the XLRs and Cardas (OEM price) for the RCA and speaker (if we have it). Or if you guys are feeling froggy WBT but they have a minimum order to get the good OEM pricing.

Also what about volume pot? Dact? TP Joshua tree if they are available? If TP had the JT and Femto available we could make it with a nice display and have remote control.

Edited February 12, 2009 by naamanf

[j4cbo]

What's the deal with the Femto? It's mentioned a few places, but Twisted Pear doesn't seem to have a page up for it. If that's not likely to be available, or if it doesn't do what we want, then I wouldn't be averse to designing something custom for volume, input, and so on.

[Icarium]

As far as what case we are going to use I think we need to wait till boards are finalized so we know their size and also know everything else we plan to fit in the case.

As for I/O what do people want? I was thinking for the back: SE/balanced inputs, maybe a loop out for each, SE/balanced preamp outs. Speaker if you think it's up to the task. Now do we want to use something like the e24 for switching power on/off with a nice lighted switch on the front? Matching switches for switching inputs and outputs? Single 4 pin XLR on the front or dual 3s? Or both. Two SE jacks or one?

As for the connectors I was thinking Neutrik for the XLRs and Cardas (OEM price) for the RCA and speaker (if we have it). Or if you guys are feeling froggy WBT but they have a minimum order to get the good OEM pricing.

Also what about volume pot? Dact? TP Joshua tree if they are available? If TP had the JT and Femto available we could make it with a nice display and have remote control.

You are all saying words that I like!

RK50 what? ;p