[RudeWolf]

also playing so beautifully the K1000. Yes it will demand near or max volume for loud levels on most classical recordings... That said, it is a night and day difference to a 100w Denon receiver I was using priorly to power the AKG, and I didnt listen to anything unpleasant with the volume control at max. The CFA3 tops it everywhere with good marging other than loudness, as expected. Even dynamics didnt suffer IMHO. Of course an AV receiver is not what most here would use to power the K1000.
With the HD800/800S it is transformative compared to the Meier Symphony I mostly used before, more open in all directions, highs are sweet, bass is improved but not overwhelming, it doesn't sound coloured. Same with my 500 series sennheisers, the CFA3 bettered them by far margin. Even the 800, the most hard to drive of my "normal" headphones, gets deafning loud (but not shouty) before 12 o clock to me.
My non elaborate audiophile lingo is probably limiting my description, but well, count me as one more very happy CFA3 user with the most demanding headphone I know. Plus Rudi's build it is the most beatiful audio gear Ive owned and by far my favorite looking SS amp.
Using it with the Spring 3 with preamp and I dont feel need for a tube pre. Actually, Maybe I should mention a non direct comparisson: I had a kgsshv carbon and I would rate it a spot on neutral and SS sounding; the CFA by comparisson sounds more tubey for me already.

I’m super happy that you like it! I really built the amp with most upgrades I could think of, so it should display the best of the CFA3 design. Too bad I didn’t use it enough to justify keeping it.

Might build the tube pre one next.

 

[migo]

I’m super happy that you like it! I really built the amp with most upgrades I could think of, so it should display the best of the CFA3 design. Too bad I didn’t use it enough to justify keeping it.

Might build the tube pre one next.

What was exact specs of this CFA3 build and its upgrades? Thanks.

 

[lsantista]

I believe you’ll find your answers in the first post of this very thread, below for your convenience:

https://www.head-fi.org/threads/kg-cfa3-headphone-amp.938064/

If you need more specifics, RudeW or I can try to help. Edit: I ask him to add speaker taps in the end , havent tested it yet but they look beautiful with their copper finish. I also dig the oversized , dead silent volume knob and its bronze finish
I listened a lot of (non classical) genres yesterday with the k1000 and it was a bliss, plenty of volume and energy/emotion at 12 o’clock and deafening to me some 3-4 hours past that before.

 

[migo]

I believe you’ll find your answers in the first post of this very thread, below for your convenience:

https://www.head-fi.org/threads/kg-cfa3-headphone-amp.938064/

If you need more specifics, RudeW or I can try to help. Edit: I ask him to add speaker taps in the end , havent tested it yet but they look beautiful with their copper finish. I also dig the oversized , dead silent volume knob and its bronze finish
I listened a lot of genres yesterday with the k1000 and it was a bliss, plenty of volume and energy/emotion at 12 o’clock and deafening to me some 3-4 hours past that before.

Thank you, this @RudeWolf build inspired mine build too!

 

[paradoxper]

I'm curious to ask those who use a tube preamp with their CFA-3- if you use the preamp as the volume control, or if you set the preamp to a certain volume and then user the CFA-3 volume control. I believe the second option would really redefine the preamp as a "tube buffer" instead of a "preamp" as the preamp is technically made to be a volume control.

I have little experience with tube amps in the last 15 years but using my audio-gd vacuum tube HE-1 with my CFA-3 and having tested both options- I vastly prefer the "tube buffer" option as I find the bass much tighter and focused and overall detail retrieval noticeably better. Using the audio-gd as the preamp IMHO and in my system is just to bloated, to round, and involves to much sacrifice of technicalities. This could be due to my dac already being extremely saturated in its presentation and therefore in combination with the tube pre, it is to much of a good thing. Using the audio-gd as a "tube buffer" instead of a preamp increases detail, and soundstage while imparting a very linear tube sound with no loss to bass focus and tightness. Meaning- there is ZERO tradeoffs using the audio-gd as a tube buffer and only gains IMHO.

I would appreciate others to share their insights with me on this issue...

May have something to do with the attenuation of HE-1. Or, as you've alluded, perhaps your DAC of which I'm unfamiliar with.

 

[normie610]

CFA3 truly is the GOAT! Using it now with my newly acquired CRBN, paired with Mjolnir’s SRD-7 (and of course my trusty Elrog equipped 300B preamp ) and the CRBN sounds sublime! After 10 hours of burning in, the bass is really incredible for an estat. For me CFA3 is the one amp to rule them all

 

[paradoxper]

CFA3 truly is the GOAT! Using it now with my newly acquired CRBN, paired with Mjolnir’s SRD-7 (and of course my trusty Elrog equipped 300B preamp ) and the CRBN sounds sublime! After 10 hours of burning in, the bass is really incredible for an estat. For me CFA3 is the one amp to rule them all

Makes me wonder how Uberamp would scale and how a better transformer would play. Great versatility you're utilizing with CFA3.

 

[normie610]

Makes me wonder how Uberamp would scale and how a better transformer would play. Great versatility you're utilizing with CFA3.

It is indeed very versatile and capable. I know it’s not specifically designed to drive ribbons or estats, but with high quality components such as Raal’s interface and/or transformer box + Mjolnir SRD-7, it can drive them beautifully. Glad I asked Miroslav from the beginning to have those speaker posts installed as I did want the maximum versatility out of CFA3.

 

[paradoxper]

It is indeed very versatile and capable. I know it’s not specifically designed to drive ribbons or estats, but with high quality components such as Raal’s interface and/or transformer box + Mjolnir SRD-7, it can drive them beautifully. Glad I asked Miroslav from the beginning to have those speaker posts installed as I did want the maximum versatility out of CFA3.

I think you only need to try MySphere with CFA3 now. I'm thinking full Elrog transformer box. Ha.

 

[normie610]

I'm thinking full Elrog transformer box. Ha.

With double-quad Elrogs

 

[paradoxper]

With double-quad Elrogs

We have a serious issue.

 

[RudeWolf]

As I've sold my CFA3 due to not using it fully (my headphones can't have a BAL connection), my mind has dwelt on the KG Tube Hybrid circuit. It's a 6DJ8 front end powering a half of the CFA3 darlington output for SE duties. Needs only one 6DJ8, so tube shortage shouldn't be much of a problem. At least for now.

The good:
1. Still no overall negative feedback
2. Toobs (no need to hunt for exotic JFETs)
3. That tasty darlington output we know and love
4. On-board turn-on delay/DC protector
5. DC-coupled

The bad:
1. The circuit needs FIVE different voltages to run (+/-15VDC, +/-30VDC, -5VDC, +100VDC, 6.3V/0.3A heater of infinite variety)
2. The stock PCB needs outboard cooling and I still haven't found a good enclosure for it
3. SE-only

The ugly:
1. Going all fancy with powering will make the resulting device not much smaller than the CFA3
2. 100VDC will happily kill you, if you let it
3. Part availability currently is all over the place (currently KSA1156/KSC5026 seem extinct from the regular sources, KSA1381/KSC3503 seem like alternatives)

Currently my plan is to redraw the existing PCB for a commonly available (dissipante/rando-china) enclosure. Maybe I'll replace some parts with SMT analogs and add some filtering/decoupling to make the circuit more resistant to RFI. I don't see much possibility for shrinking the PCB down, so don't hold your breath.

 

[kevin gilmore]

a fully balanced version of this is easy to do. also no feedback.

IF you can get the parts.

The +/-15 supplies can be eliminated if you use high voltage servo opamps.
One of a number of projects i am working on, waiting for the parts situation to at least stabilize.
a much higher power CFA3 is also in the works.

 

[RudeWolf]

If we substitute KSA1156/KSC5026 for KSA1381/KSC3503, then it should be buildable now. The THPS should have all of the parts readily available as well. With say OPA445 and everything running from +/-30VDC, a single GRHV100 and GRLV should power it all. Of course, there's still the -5VDC, so a local regulator for the protector might be needed.

So far with large heatsink brackets this case seems like the most likely candidate. Or we stretch the PCB to fit better. I personally have some huge brackets which would reach the board fine.

 

[kevin gilmore]

that particular design is a dual opamp, so you have to make an adapter for that, otherwise correct.