and now for something completely different part 3

[Pars]

For the amp portion, I like the layout on the right better, with the tube input boards right along the center.

You really are going dual mono, aren't you? For the PSU, that does look tight. I think you might need more heatsinking for the GRLVs, particularly if you are going to be running some speakers judging from the binding posts I see. The GRHV100 is too close to the IEC as it is. How big in VA are the low voltage transformers for the GRLVs?

And being team crimped connectors, I'll ignore those phoenix blocks

[Satyrnine]

3 hours ago, Pars said:

For the amp portion, I like the layout on the right better, with the tube input boards right along the center.

You really are going dual mono, aren't you? For the PSU, that does look tight. I think you might need more heatsinking for the GRLVs, particularly if you are going to be running some speakers judging from the binding posts I see. The GRHV100 is too close to the IEC as it is. How big in VA are the low voltage transformers for the GRLVs?

And being team crimped connectors, I'll ignore those phoenix blocks

Hi Pars,

Maybe I need to find a new power switch. This one sticks out about 1.5”. That’d let me shift everything back. I could also remote-mount the grlv regs to side panels with an added alum/copper bar. 

The lv transformers are 100VA Antek

About the phoenix blocks, I think I may agree with you. The amount of times these became loose on me makes one question their reliability.

 

[Pars]

I was just poking fun. The reason I don't like them is there is too much chance of misconnecting something in the future. Crimped connectors (Molex KK, Spox, etc.) do it once and done. I haven't used the phoenix connectors enough to know whether they loosen up over time or not. I suppose they can/could. I do use them when initially building/troubleshooting if applicable, but replace with something else once done.

[Satyrnine]

On 12/2/2023 at 9:06 AM, Pars said:

I think you might need more heatsinking for the GRLVs, particularly if you are going to be running some speakers judging from the binding posts I see.  How big in VA are the low voltage transformers for the GRLVs?

Hi Pars, could you (or anyone!) elaborate on the extra heatsinking for the grlvs? I admittedly have only tested with 50-600ohm headphone loads, but the small sinks I had on the grlv's then barely got warm at all. Maybe 105*F max. I have 100VA 30v transformers. I seem to recall someone mentioning that big transformers (and the 30vac secondaries) mean less reg heat from the grlvs? Below is what I was thinking of doing. I could also rotate them 90* left, bolting the L bracket to the side plate but that's even thinner steel than the bottom plate, and would move the DC outputs closer to the 90vac input on the grhv to it's right. I could also rotate the grlv 180* and remote mount the regs to the ~1.5mm aluminum back plate, but that would bring the grlv 30vac inputs closer to the DC jacks as well. 

Second, here's what I can get away with for IEC - grhv proximity. Think it will be a problem?

It would give me enough room for the power switch at the top, plus room for distribution blocks for mains/grounds.

Big thanks to anyone willing to share their wisdom.

Edited December 25, 2023 by Satyrnine

[Pars]

I wouldn't think that large transformers would equal less heat; maybe more since the unloaded voltage will be higher. You can remote mount the pass devices for the GRLVs; I'm doing that on my DynaFET. You are doing dual mono, so you have 2 CFP2 boards per GRLV. The DynaFET is similar, with a pair of DynaFET boards powered by one GRLV. I have that in a 300mm deep Pesante case, with the pair of DynaFETs on one heatsink, and the GRLV on the other. The GRLV heatsink gets almost as warm as the DynaFET side does. In your case, I might consider rotating the GRLVs 90 degrees to point the pass devices at the sides of the case and mount the pass devices there, either directly to the side or on your L bracket?

Also, are you sure you have the rectifier boards in right on the GRLVs? I guess one side wouldn't work if it was backwards, and you are using the 3 bridge boards, which I'm not.

Edited December 25, 2023 by Pars

[Satyrnine]

4 hours ago, Pars said:

I wouldn't think that large transformers would equal less heat; maybe more since the unloaded voltage will be higher. You can remote mount the pass devices for the GRLVs; I'm doing that on my DynaFET. You are doing dual mono, so you have 2 CFP2 boards per GRLV. The DynaFET is similar, with a pair of DynaFET boards powered by one GRLV. I have that in a 300mm deep Pesante case, with the pair of DynaFETs on one heatsink, and the GRLV on the other. The GRLV heatsink gets almost as warm as the DynaFET side does. In your case, I might consider rotating the GRLVs 90 degrees to point the pass devices at the sides of the case and mount the pass devices there, either directly to the side or on your L bracket?

Also, are you sure you have the rectifier boards in right on the GRLVs? I guess one side wouldn't work if it was backwards, and you are using the 3 bridge boards, which I'm not.

 

Thanks Pars! I’ll give that configuration a look! Are you driving speakers or just headphones with the dynafet? Weird that mine were running so cool, even with a susvara. 

As for the bridge boards, It must be because we have different bridge boards, as these have running great for quite a while, just finally stuffing it all into the chassis. Early on I actually put my bridge boards in like yours and got no output on one side because of it, so must be a board difference. Good eye!

Side question: what value are you using for main filter caps on your grlv’s? They look large. I was contemplating if I could benefit from bigger caps on mine, I have plenty of vertical space. I also see some putting larger local filter caps on each cfa board. 
 

Thank You! Happy Holidays!

[Pars]

I'm just driving ortho's (T50RP modified, and now a pair of DCA Ether C Flows). I wouldn't even consider trying to drive speakers with it. Caps in the GRLVs are Panasonic TSHA 4700uf 63V.

And Merry Christmas to you!

[Satyrnine]

On 12/26/2023 at 12:20 AM, Pars said:

I'm just driving ortho's (T50RP modified, and now a pair of DCA Ether C Flows). I wouldn't even consider trying to drive speakers with it. Caps in the GRLVs are Panasonic TSHA 4700uf 63V.

And Merry Christmas to you!

Nice cans! I just nabbed a pair of HE6SEs, but also have LCD-2 and LCD-X. I surely won't be driving anything large with the CFA, just some small, efficient near field monitors on my desk, supported with a powered sub. Dukei said that his customers had good things to say about it with small nearfield speakers. We'll see I guess. I def have other amps if it doesn't work out. (various modded adcoms, GFA-535, 545, and 555)

This build is taking it's toll, sooooo much work, although I'm admittedly chose hard mode with the dual mono, dual chassis, tube input version. 

[justin]

Has anyone looked into protection from shorting due to 4.4mm jacks being inserted/removed, or partially inserted? The latter seems pretty common as the plug takes a bit of force to push in for the last .1", which is what opens the jack's switch. 

My idea for protection is using a 2-pole relay to disable the L- and R- pins when the switch is closed. This way, there will only be anything connected to L- and R- on the 4.4mm jack when the plug has been fully inserted

I think this will fix the problem by making it impossible for any conductors to momentarily short together, unless I am missing something. 

 

 

 

[luvdunhill]

Seems reasonable. Team 5-pin approves.

[MLA]

On 1/4/2024 at 5:50 PM, justin said:

My idea for protection is using a 2-pole relay to disable the L- and R- pins when the switch is closed.

Very good suggestion; pentaconn is a good idea but the shorting risk sucks. 

Edited January 6 by MLA

[Pars]

I know it wasn't a pentaconn jack, but a normal TRS jack, but this has been an issue for some time, with it causing a number of B22s to fail at meets when people would plug/unplug phones from amps which were on, and blow the output FETs in those. That sounds like a good solution Justin, as disconnecting the L-/R- would ensure open circuit on the outputs. I'm not a fan of the TRxS type plugs/jacks because of this issue, but I don't do or use portable equipment anymore, so doesn't really affect me. They make these things down to 2.5mm in a TRRS, which seems like a really bad idea.

[Satyrnine]

Protector board noise... I still have noise on whichever "side" (dual mono) I connect the protector board power to. If I use low sensitivity cans, like my HE6SE, I can't hear anything, but high sensitivity cans, like my LCD-X, there is still a persistent and annoying very high frequency noise. I'm more and more sure the protector board is causing it. I'm currently running no shield at all from outputs to headphones, just 4 wires. I've tried connecting the protector board ground to the star ground as well as "chassis". No change.

At this point I think I need a separate supply all together, or possibly a RC filter between the grlv and protector board, to both filter and drop the 30v down closer to 12v a bit. Bad idea?

EDIT: I added 1k resistors on the +30v and -30v inputs. Noise is gone! Getting about 13v on the + input after the added 1k, before the regulator, and about 25v on the - input. Everything seems to be functioning properly, looks like that did it, unless anyone can think of a reason this is a bad idea?

Here's the wiring scheme and pics.

Messy wiring at top by transformers is temporary, waiting on a proper dist block. 

And no, my speaker jacks are wired yet, my headphone/speakers switch is just a smidge too short to allow a nut on the inside, so I can't tighten it down. Prob going to 3d print a bracket of some sort to hold it.

All wire is silver plated copper/teflon, not that it prob makes any difference.

Edited January 20 by Satyrnine

[Pars]

I don't know where you would put it, but the easiest separate PSU for the protector board only might be to use a pair of Meanwell 15V bricks as Kerry did for the mini Dynalo? The only problem with these is they don't always come up at the same time on power on, but that shouldn't be a huge problem for this application and could be solved with a short delay on the output. These you could wire straight to the AC L/N after the switch.

The amps I've done I've never bothered with tieing the analog grounds to the chassis; just the IEC earth to chassis. You might put a ground loop breaker in between your star ground and the chassis connection.

[mrjayviper]

can someone please share the latest versions for gerber file links for:

- suitable PSU

- headphone amp

- volume attenuator (remote no necessary)

I was looking at the shared folder and I'm getting confused with the amount of duplicate files available.

I would also appreciate it if you can share a BOM. Thank you.

[justin]

I just completed testing both channels of the latest version of the smd version of the CFA3 boards, and here are some distortion measurements:

 

Test Setup: balanced 1KHz/6Vrms from Tektronix SG 505 oscillator, 
to HeadAmp Gilmore CFA3 (balanced output), 
to General Radio 1840-A output power meter 
& to Tektronix AA501A THD analyzer (which has about .001 to .003% THD on its own). 

2Vrms Output THD Test
(Load, THD)
300, .002%
200, .002%
150, .002%
100, .002%
50, .003%
32, .007%
16, .01%

6Vrms Output THD Test
(Load, THD)
300, .002%
200, .002%
150, .002%
100, .002%
50, .003%
32, .013%
16, .15%

20Vrms Output THD Test
(Load, THD)
300, .017%
200, .017%
150, .018%
100, .022%
50, .26% (12W)
32, .42% (18W)

Max Output Level THD Test
(Load, Watts, THD)
300, 2W, .03%
200, 3W, .03%
150, 4W, .04%
100, 6W, .05%
50, 12W, .26%
32, 18W, .42%
16, 20W (meter limit), <1% ZF, <.3% SS

One thing that surprised me was the 2 channels had virtually identical THD (even in ZF mode) out to 2-3 decimal places until getting down to ~16 ohm impedances where there started to be a little variation

Edited February 19 by justin

[wudilmy]

On 8/21/2023 at 9:10 PM, justin said:

I decided to order some of these, 4oz copper, panelized/scored. Gilmore Purple People Eater, because purple is the most uber color

the PCBs will be available if anyone wants a set

 

Hi Justin, how to purchase this monster? Really want this😋, thank you.

[justin]

Production CFA3 enclosure arrived yesterday 😃 

I told the machine shop to not bead blast the heatsink mounting side, just leave it mill finished. 
They must have thought I meant to mill it after anodizing. I can't figure out if it's a win or not but it's different?

[justin]

Last year I ordered a lot of different boards of KG's amps/PSUs and had someone here put them together as a project. One of them was this 6DJ8 hybrid that uses the triple output buffer of the CFA3. Single-ended output only. There was 1 missing trace on the board that prevented it from working, found and fixed that, so possibly nobody had assembled one of these before. Problem is there's a substantial hiss (very easily audible with even sensitive planars, something like 0.3mV rms of 'white noise'. The +100V is coming from a TL783 regulator, tried AC, DC, batteries for heater, different grounding, gate stopper resistors, feedback caps, w/out servo..exhausted a lot of stuff but couldn't get more than a few % improvement on the noise. Anyone have ideas?

 

th.PDF

[dsavitsk]

maybe noise on the tube cathode.

[ang728]

tried to build it last year . mine kinda works but put them away due to output dc sometimes would trigger protection circuit.Likely having oscillation .still looking for any solution/workaround

 

 

Edited July 18 by ang728

[justin]

14 hours ago, dsavitsk said:

maybe noise on the tube cathode.

I did try batteries for just about everything

[RudeWolf]

I almost started that one as well. It would be nice to have the PCB revised.

[justin]

Apparently the PCBs were revised to correct the errors and even add the protection circuit - but nobody remembered

[swt61]

I blame Brent.