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The Cavalli-Kan Kumisa III Stereo Headphone Amplifier has landed - Page 5

post #61 of 75
Hi everyone,

I am just about to begin building(and buying the parts) for this amp.
According to AMB's website, they only recommend BJT BJT BD130/140 as output transistors but I have been reading bits and pieces of people using other transistors.

Can someone comment on the transistors? I will be driving D2000 with this amp when it is done.

Thanks!
post #62 of 75
Oop! Nevermind.
post #63 of 75
Post in the DIY forum you mean?

For some reason, CK2III is so "under-hyped".
post #64 of 75
Quote:
Originally Posted by ezzo View Post
Hi everyone,

I am just about to begin building(and buying the parts) for this amp.
According to AMB's website, they only recommend BJT BJT BD130/140 as output transistors but I have been reading bits and pieces of people using other transistors.

Can someone comment on the transistors? I will be driving D2000 with this amp when it is done.

Thanks!
I used MJE243/253 based on recommendations for a warmer sound. Supposedly the BD139/140s have a somewhat colder sound with more treble. I obviously have no reference other than trusting those who have built multiples of the CK2III. I can say that I am very happy with my MJE243/253 amp though!

PS: Definitely use heatsinks on the output trannies, they really help in setting the quiescent currents.
post #65 of 75
Quote:
Originally Posted by gtp View Post
I used MJE243/253 based on recommendations for a warmer sound. Supposedly the BD139/140s have a somewhat colder sound with more treble. I obviously have no reference other than trusting those who have built multiples of the CK2III. I can say that I am very happy with my MJE243/253 amp though!

PS: Definitely use heatsinks on the output trannies, they really help in setting the quiescent currents.
THANKS ALOT gtp!
Sounds like some transistors rolling might be fun for the Denons

Anyway, just a question here. Do you find the MJE243/253 too warm or bassy for your DT770s? Since closed phones tend to be on the "warm" side, plus the DT770s are already considered to be quite bassy.
post #66 of 75
Quote:
Originally Posted by ezzo View Post
THANKS ALOT gtp!
Sounds like some transistors rolling might be fun for the Denons

Anyway, just a question here. Do you find the MJE243/253 too warm or bassy for your DT770s? Since closed phones tend to be on the "warm" side, plus the DT770s are already considered to be quite bassy.
Not at all. In fact, I find my CK2III to be a very even amp. Nothing is emphasized, but everything is solidly there. I think my CK2III actually tames the bass of the DT770 and tightens it up a lot. Underpowered, the DT770 bass can get too flabby, but with decent power it gets more focused and clean. My CK2III matches up very well.
post #67 of 75
Quote:
Originally Posted by gtp View Post
Not at all. In fact, I find my CK2III to be a very even amp. Nothing is emphasized, but everything is solidly there. I think my CK2III actually tames the bass of the DT770 and tightens it up a lot. Underpowered, the DT770 bass can get too flabby, but with decent power it gets more focused and clean. My CK2III matches up very well.
Ah, sounds great to me, I shall go with the MJEs first. Your case of DT770 is quite similar to the Denons with sensitivity and low impedance of 25ohms, not many amplifier can drive it well, thats what I read. Hope the bass tightens up abit with the CK2III.

I have another question here, hope someone can answer it.
According to AMB's website, ceramic caps are recommended for positions: C5, C6, C14, C15 & C8, C9, C17, C18 and all of them lies in the signal path.
From what I read, ceramics sounds awful when in the signal path.
So what does this mean? Should I change them to film caps instead?
post #68 of 75
Quote:
Originally Posted by ezzo View Post
According to AMB's website, ceramic caps are recommended for positions: C5, C6, C14, C15 & C8, C9, C17, C18 and all of them lies in the signal path.
From what I read, ceramics sounds awful when in the signal path.
So what does this mean? Should I change them to film caps instead?
The capacitors are low-value and acts only in the ultrasonic frequencies for compensation and stabilization. They have absolutely no effect within the audible band, therefore I hesitate to call them "in the signal path". Also, not all ceramic capacitors are alike. NP0/C0G multilayer monolithic ceramics are specified here, and they're very linear. Since the PCB layout fits these capacitors perfectly they are recommended without reservations. If you must, you can put silver mica or polystyrene caps in these positions but they're not going to make a bit of difference in the sound.
post #69 of 75
Quote:
Originally Posted by amb View Post
If you must . . .
I find refreshing your practical perspectives on this hobby and its potential frivolousness that I've observed here and on threads over at headwize.... You clearly know your stuff as this is IMO one incredible amp. I can't thank you enough for the work you and others have done on this project.
post #70 of 75
Quote:
Originally Posted by amb View Post
The capacitors are low-value and acts only in the ultrasonic frequencies for compensation and stabilization. They have absolutely no effect within the audible band, therefore I hesitate to call them "in the signal path". Also, not all ceramic capacitors are alike. NP0/C0G multilayer monolithic ceramics are specified here, and they're very linear. Since the PCB layout fits these capacitors perfectly they are recommended without reservations. If you must, you can put silver mica or polystyrene caps in these positions but they're not going to make a bit of difference in the sound.
Thanks alot!
post #71 of 75

CKK3 Impressions and Insights

Impressions

Coming from more entry-ish amps such as the LD2++ and TW-J1, and hearing the anecdotal reports of the CKK3 being a "little" Beta22, I set out building it with sky-high expectations. I was not let down--my impressions follow, and please mind that all my impressions are relative to my (limited) experiences with h.p. amplifiers.

Before this amp I had developed a preference for the K701s over the 650s; now the old Senns are king again. As others have noted about the CKK3, there's just better synergy: the type which the 650s must have to be happy. The amp produces mids and treble with more weight and aggression, but never harshness, with a controlled bass that compliments the 650's silkiness there. The result is the most coherent, balanced and involving headphone sound I've heard. This is not to say that other HP's are not well suited to it: the AKGs are certainly enjoyable, but highly AKG-sounding, in a good way. It's all personal preference at that point. Regardless of headphones, the ultimate ecstasy is during musical complexity, where the amp could not be more sure of itself--perhaps this is the defining feature of the CKK3.

My build

Thanks to the amazing Jeff Rossell for the kit; FrontPanelExpress for the FP. The build took two days of obsessive work, something like 18 hours, excluding bias adjustment. I had to make an external PSU--though I'd initially put the tranny and board in the same case, there was a slight persistent hum. Not anymore, the amp is eerily quiet. PSU case from Context Engineering. A massive vintage heatsink I had on hand was cut and installed, providing plenty of cooling for the quiescent current of ~55ma. It's barely lukewarm to the touch, and it made bias adjustment minimally tedious. With this much heat dissipation, the transistors' QC often dropped a little during adjustment and had to be brought back up! Still, expect to spend a good afternoon adjusting the QC especially if you're OCD about getting things equal. Oh, and the zipties--probably a bad idea, but no problems yet!

My advice to prospective builders

-Use the largest heatsinks you can get ahold of, even if you plan to bias to only 30ma. My experience using smaller, individual HSs for 30ma was a pain, full of fluctuations, but doable. I cannot imagine using no heatsinks.
-Solder small leads onto the bias resistors, R23 and R47, on the sides closest to the adjacent transistors (see pic). This way, you can measure the voltage here without shorting anything--one probe at output left (or right) and the other at R23 (or R27)'s safely-distanced lead. The necessity and advantages of this will become clear once you begin bias adjustment.
-Use a separate enclosure for the transformer and mains wires if possible. I tried an all-in-one solution initially, but I was unable to eliminate all hum until the tranny was out of there. It was worth the extra effort.
-My two input grounds (L&R) had to be connected at the volume potentiometer. I don't think this was indicated on the AMB wiring diags. If you find yourself hum-busting, check here first.
-Always wear that anti-stat bracelet, all it takes is one costly zap. Also, have a heat management strategy when soldering the transistors.

Conclusion

I used to not believe different amps made a difference in SQ beyond things like distortion and SNR. I thought this amp would sound about the same as my others, and at least offer a fun DIY project. My smug convictions all changed with the CKK3, as it sounds better with less (or more musical) distortion and it sold me on DIY--it's the best bang for your buck audiophile solution that also brings a unique pride into the hobby.

Gallery

(Hey amb if you get a chance maybe you could add these to your collection )


Great panel manufacturing from FPE.


PSU connected to the ckk3...


Silly zipties!


PSU with trans. and mains stuff


Note the lead soldered to one end of the blue bias resistor
post #72 of 75
I'm very interested in this amp. I just purchased the mini3 portable amp, and am wanting something that can provide a little more "umph".
post #73 of 75
In one or other way, I've got the feeling that this amp is generally a little under-rated.
Have been using this amp for about 2 week or so in the office... I must say that it's a pleasure to listen to (in my limitted free time at work). Considering the cost of the build, its performance is really good.

post #74 of 75
I've been listening to a Ck²III I purchased about 2 months ago from fellow Head-Fier and the builder of this amp, GeWa. I must say that it drives the HD650 well and the Denon 2k even better. The 650's are almost bright now with some music, and the control seems to be very good. I have not owned many amps, but this one is by far the best. I totally look forward to the AMB designed Beta22 soon.
post #75 of 75
Yep, listening to and loving the CKK-III in the office with Denon D2000. Full details in signature.
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