and now for something completely different part 3

[kevin gilmore]

opa551 is a cheaper opamp that is good to 60 volts

opa445 is good to 90v.

at least that is what the pricing used to be

[audiostar]

So, I am good with my four OPA445. 

Thanks, Kevin for confirming.

Edited April 3, 2022 by audiostar

[audiostar]

On 11/1/2017 at 2:38 AM, mwl168 said:

On a side not here, cooling effect is bigger if sands are put on the lower end of the sink. As heat travels up, sink real estate gets used more effectively. 

[JoaMat]

On the split CFP3 power board it seems to be some pads between the 82R resistors on the bottom layer. What might the purpose of them be? 

[kevin gilmore]

surface mount version of the 47uf cap

[audiostar]

On 3/29/2022 at 8:17 PM, audiostar said:

Thanks, Pars! 

Which pins are you using on the lower side, that go into the 14-pin socket, do you have the p/n handy? Thx

After ordering something from eBay, I just found the following perfect part that is available from Mouser as well. It is 7pin, round, gold flash, Preci-dip p/n 350-10-107-00-001101.

 

 

 

 

Edited April 10, 2022 by audiostar

[audiostar]

Meanwhile in the making... 

[audiostar]

Hey Kevin, what happens with the amp if someone decide to toggle the ZF/SS switch while the amp is powered on?
Just thinking loud that exposing such a switch is actually pretty dangerous, no? 

@kevin gilmore

 

Edited April 19, 2022 by audiostar

[kevin gilmore]

you get a dc glitch in the output. not enough to cause damage to the headphones.

[audiostar]

Would the Headphone Protector trigger? 
Thanks again, appreciated!

Edited April 19, 2022 by audiostar

[kevin gilmore]

probably not. glich is too fast.

try it and let us know.

[audiostar]

Will do, thanks for heads up

[Pars]

When I was repairing Todd's CFA3, I think I did this, and no, the protector didn't trigger. Also I don't recall much noise in the phones from it either. Probably not the best thing to do, and it has been a while since I worked on this.

[Breaklunchdinner]

Hello

 

I'm on the way to CFA3 mountain, and it's my first time to build DIY amp.

Thanks to you guys, I could order PCBs, and buy most parts I need.

 

What I still don't know is how to build my own enclosure(chassis).

 

Is there any reference document or universal(?) enclosure I can use?

(I could'n t find it)

 

I always appreciate all you guys and information you shared.

 

Thank you!

[johnwmclean]

There is no generic or universal enclosure as such.

I recommend having a look at modushop, the pesante dissipante range could be the ticket. But you’ll need to tap heatsinks and drill holes for the panels. Modushop customise as well, so you could have everything done there from your drawings. eBay is another good source for enclosures.

Front Panel Express is a great company for getting drilling of your panels done, you need to work with their proprietary  software which is downloadable and fairly easy to use.

Unfortunately none of this is cheap...

[johnwmclean]

https://goldensound.audio/2022/07/04/kevin-gilmore-cfa3-headphone-amp-measurements/

[mrjayviper]

On 3/14/2022 at 12:29 AM, audiostar said:

Prior I start desoldering any components from my other boards, I thought I'll ask if anyone might need two fully populated (except Opamps and JFETs) wider boards. Not trying to make any profit, will sell at BOM cost, DM me if interested. 

 

what's the width of the PCB including the L-bracket? thanks!

[mrjayviper]

(This is the gerber file I'm looking at => cfp3smt2splitamp - CADCAM.zip dated 2022-Feb-07 in the shared Drive folder)

- what's the minimum voltage I can use with the amp?

- I've been back-reading and I've read mentions of an opamp but I cannot find it in the PCB.

- average power consumption? (or shouldn't even think about it considering it requires massive heatsink? 😁)

 

Thank you.

 

EDIT1: The file I mentioned above does NOT have the transistor portion like what I've seen in other DIY pics. What Gerber file should I be using?

 

EDIT2: What's the difference between cfa3production.pdf vs cfa3productionss.pdf

[mrjayviper]

if going for the split board, what's the input section? I am looking at the shared folder but it's not so obvious which one to get. Thanks

[mrjayviper]

On the left side of cfa3productionss.pdf, there's a schematic on the top right with a 2n4391. But I cannot find it in the cfp3rssfixedss and cfp3rssfixedsssw.

Any ideas? Thanks

[migo]

Another newborn CFA3 dual mono setup here. Thank you Mr. Gilmore and Audiostar and Mirko!

[audiostar]

On 3/13/2022 at 1:42 PM, audiostar said:

Look what the cat just dragged in 🙂

I have some split boards available, anyone in need for them 😀 just let me know.

[JoaMat]

It’s an awfully warm summer here in southern Sweden and it’s too hot to sleep… did this last night…

 

An attempt to make a smd version of CFA3. Same board size as the smd version of Dynahi I built some months ago.

Lots of more work… doubt I’m capable to get this to work though.

[audiostar]

I always do loop outs on my amps in order to daisy chain to other amps, etc. 

So, thinking about adding RCA ins to the CFA3, which is pretty easy.
The question is with the RCA outs - the following pic is from Jensen, I think, where they only connect pin3 to ground on the RCA output only and leave the XLR out floating. Is this something, that is ok with the circuitry on the CFA3? Any thoughts @kevin gilmore? Thanks!

Edited August 20, 2022 by audiostar

[Emooze]

On 8/19/2022 at 4:27 AM, JoaMat said:

It’s an awfully warm summer here in southern Sweden and it’s too hot to sleep… did this last night…

<movie>

An attempt to make a smd version of CFA3. Same board size as the smd version of Dynahi I built some months ago.

Lots of more work… doubt I’m capable to get this to work though.

I am into this. I have been thinking about a CFA3 and an SMD version appeals to me a lot. Hope you can get it working!