CKIII and AKG

[fillemon]

Hello people,

i still have an CKIII pcb lying around. i wonder if it would make a good match with a AKG headphone. at this moment i have a 500, i will buy very soon an 701 or 271. but the ckIII is said to have a bit more forward mid, But that is what akg has a bit too, i mean: not powerfull bass. I don't need that, but if the amp does the same thing, it might get to upfront; i have seen a lot of threads with good remarks on an CKIII with grado and senns, i can very well understand this fine match. still is it okee with a AKG ?

thank you very much
friendly greetings

 

[ericj]

A lot of the sound signature of the CK2III amp is in the output transistors - if you use something other than the standard mje2x3 / bd13x output transistors, you can get a slightly different sound.

on the old millett dDB pages, steinchen has a list of available output transistors and their approximate sound signatures. This is a different circuit, but the descriptions should more or less stand true.

http://www.diamondstar.de/dDB_partslist.html

I used Sanyo 2SC2344 & 2SA1011 in my CK2III and like them pretty well. On my dDB I used Toshiba 2SC2238 & 2SA968, which are truly excellent. you should be able to get most of the exotic output transistors from bdent.

 

[fillemon]

thanx a lot ericj

that is a nice link and some nice descriptions,
i think i will use the 2SC2238; if you say so, and the description suggests it also, but then again, is this a drop-in on the CKIII ?

still i will start off with the suplied opamp. (i'm bying it in kit form)

thanx a lot.

 

[ericj]

Yes, it's a drop-in, but do observe the fact that the pinout is backwards.

The opamp in the CK2III does not have an impact on the sound signature; you can use just about any fet-input opamp because all it is doing is zeroing out DC offset. A tl082 would work almost as well as the opa2134.

 

[fillemon]

thanx ericj,

what do you mean with pinout is backward,

do i have to solder things differently, or can i just put the opamp in it, but with pin 1 in socket 8 ?

what do you mean with the sound signature ? i don't get very well.

ps: what upgrades do you have for the ck2III ? or what did you change in compare with the standard parts ?

thanx a lot
friendly greetings

 

[amb]

Quote:

Originally Posted by fillemon /img/forum/go_quote.gif what do you mean with pinout is backward

The 2SC2238/2SA968 have pin-out as B-C-E whereas the BD139/BD140 have E-C-B. The circuit board layout is marked for the BD139/BD140, so when you put the 2SC/2SA transistors in there you have to put them in backwards.

Quote:

do i have to solder things differently, or can i just put the opamp in it, but with pin 1 in socket 8 ?

That comment was referring to the output transistors, not the opamp.

Quote:

what do you mean with the sound signature ? i don't get very well.

What ericj was saying is that the opamp has no effect on the sound. It is not used for audio amplification. The function of the opamp here is to control the DC offset.

 

[tomb]

Note that BDent does not carry the 2SC2238/2SA968 complementary set of BJT's. They do have the 2SC3422/2SC1359, 2SC3421/2SC1358, and 2SC2344/2SA1011 sets. I would rank them in the order of quality as listed, respectively, with 2SC3422/2SA1359 as best with a very good rocking slam.

The 2SC3421/2SC1358 probably have the lowest bass extension.

The 2SC2238/2SA968 is available at MCMinone, a Newark subsidiary. However, they are currently out of stock, but a rep there told me sometime in mid-October for new stock, which should mean eminent. Those transistors are perhaps the detail kings and have a very solid flat response throughout the audio spectrum.

 

[fillemon]

tahnx a lot people, to point me to those things.

okee, i start to understand it. but what kind of bjt's do you need when you install the 2SC2238/2SA968

cause the 2SC2238/2SA968 is offerd at bdent. i looked at rs-components and see they offer for expample the 2SC2238A (but not the Y version, is this a difference ?)

 

[tomb]

Quote:

Originally Posted by fillemon /img/forum/go_quote.gif tahnx a lot people, to point me to those things. okee, i start to understand it. but what kind of bjt's do you need when you install the 2SC2238/2SA968 cause the 2SC2238/2SA968 is offerd at bdent. i looked at rs-components and see they offer for expample the 2SC2238A (but not the Y version, is this a difference ?)

Sorry - that's incorrect. What you are seeing is a computerized replacement recommendation at BDent. They have never carried the 2SC2238 or 2SA968, at least not for several years. I've even contacted them about it, but the replacements already work fine for their purposes (repair technician support).

There are some other vendors that carry the 2SC2238/2SA968 pair - for instance, fibra-brandt.com in Europe has them. There's also a local vendor in Atlanta that gets in about a half-dozen from time to time. Most of the other US vendors are looking for large, multiple buys, unfortunately, that's why MCMinone seems to be the best source in the US, and I can vouch for the good service. There are also some listings on e-bay, but I'm not certain whether they are up to snuff or are cheap copies:
5x 2SC2238 +5X 2SA968 TOSHIBA Pwr AMP Transistor TO-220
They don't look like the ones I have, but that doesn't necessarily mean anything.

As for your first question, "BJT's" is simply the shorthand way to describe any of these type of transistors - as distinguished from another often-used output device around here: MOSFETs. MOSFETs are NOT used on the CKIII.

P.S. I can't tell about RS-Components. There are so many subsidiaries for them, I guess we'd need the country you were looking at. Also, if BDent is showing a different replacement for the 2SC2238A vs. the 2SC2238, then the 2SC2238A may not be the same animal.

 

[fillemon]

waauw tomb,

that is quite some accurate information. thanx a lot.
so i need an pair of 2SC2238/2SA968 (so that makes 4) to stuff the ck2III and i'm there, watch the polarity and i'm fine.

wel bdent doesn't make a difference between 2SC2238 and 2SC2238a.
but when i look around you find these is lots of "last letter" versions.
when i look at rs components on 2SC2238 : i find them, so i suppose these
are the one i need ? (this is the part number 197-9862 )
they have also the 2sa968. i think these are the parts ? if so i just order them along. do they need cooling ? cause turning them other way around makes it a bit hard to connect a large heatsink ? or if i have a high case, i can solder them underneath so that they still can be attached to a side of the case ?

thanx already
greetings

 

[tomb]

Quote:

Originally Posted by fillemon /img/forum/go_quote.gif waauw tomb, that is quite some accurate information. thanx a lot. so i need an pair of 2SC2238/2SA968 (so that makes 4) to stuff the ck2III and i'm there, watch the polarity and i'm fine. wel bdent doesn't make a difference between 2SC2238 and 2SC2238a. but when i look around you find these is lots of "last letter" versions. when i look at rs components on 2SC2238 : i find them, so i suppose these are the one i need ? (this is the part number 197-9862 ) they have also the 2sa968. i think these are the parts ? if so i just order them along. do they need cooling ? cause turning them other way around makes it a bit hard to connect a large heatsink ? or if i have a high case, i can solder them underneath so that they still can be attached to a side of the case ? thanx already greetings

If you order, just make sure you get the TO-220 versions. If you can, check the spec sheets with these to make sure:
2SC2238: http://www.diyforums.org/MAX/bjt/2SC2238.pdf
2SA968: http://www.diyforums.org/MAX/bjt/2SA968.pdf

As for mounting on the CKIII, you may have to get creative. There are a number of smaller stamped metal heat sinks that will fit on a reversed transistor. Also, the use of some short leads is not unreasonable - but you should probably confirm with Amb about that one.

 

[fillemon]

okee, i'll check the data, but from a first view : those are the one.

i'll check with amb what they say about cooling.

thanx a lot already

greetings fillemon

 

[amb]

If you go to the CK²III website and look under "CK²III gallery", ferrari's build shows 2SC2238/2SA968 output transistors mounted in reverse with heatsinks.

 

[fillemon]

thanx a lot amb.

 

[xmokshax]

Quote:

Originally Posted by amb /img/forum/go_quote.gif If you go to the CK²III website and look under "CK²III gallery", ferrari's build shows 2SC2238/2SA968 output transistors mounted in reverse with heatsinks.

completely off topic: i have to ask where your sig comes from, amb. just an unfortunate computerized translation? either way, pretty hilarious.