[suicidal_orange]

I am going to build a CKKIII for my balanced Grado's, and while researching the build I would like to order the necessary parts as shipping to the UK takes time. I have seen the kits on GlassJar Audio's yahoo page, but it is unclear to me whether I need 2 boards or if there are 2 ground's on the one PCB? The Grado's only have 2 wires so 1 live wire and 1 ground for each (I assume), and RCA's have this - it's just the amp I'm unsure on.

Am I right in just needing separate grounds and 2 channels? Do I need a PCB for each channel as in some designs?

Thanks in advance for any help

 

[jbloudg20]

I think you need to do a bit more reading on balanced operation. Are you sure you mean balanced, as in 4 channels? Do you have the standard plug on your Grados, or have you recabled/reterminated them with an XLR? RCA's are not used for balanced operation.

 

[nikongod]

The 6db more gain means a LOT for an amp that runs open-loop.

I would build it single-ended. Its well documented, and by all accounts sounds great.

 

[suicidal_orange]

Thanks for the quick replies

My Grado's are terminated with two 3 pin XLR's, but on testing with a multimeter only 2 pins are connected in each (I bought them like this). I've been trying to work out if this is truly balanced or not, as I thought balanced needed "hot" and "cold" wires as well as ground, but I can't find any headphones with more than 2 wires per driver - maybe I was just looking in the wrong place?

My last order shipped by USPS priority took nearly 3 weeks to arrive in the UK, so there will probably be plenty of time for doing research while waiting. If not there is no harm in the stuff sitting in a box while more research is done but I'd like to start ASAP as unpacking my portable most days is getting tiresome!

So, do I need balanced? What should I be ordering?


Thanks again

 

[n_maher]

Do you own a balanced source?

 

[suicidal_orange]

No balanced source - yet. My next project will probably be a USB DAC, but for now the amp would be used from my pc or imod. Being able to accept balanced input would be a bonus, unless you are suggesting it is pointless without balanced input in which case I'll just wire a singe ended amp to xlr sockets - at least it will look good


Thanks

 

[JamesL]

If the 2nd pin on each XLR are isolated from each other, it should be fully balanced.
The CK2III is already a 3-channel amp and has most of the benefits of a balanced amplifier. Seeing as you're going to be using a unbalanced source, I would go unbalanced on this one.

 

[Ferrari]

NO disinformation please!

The CK2III is actually a conventional 2-channel amp with passive ground.

 

[JamesL]

Oh! My bad =(
For some reason, I was thinking it had a active ground.
Thanks for catching that Ferrari.

 

[suicidal_orange]

OK, seems unbalanced is the way to go without a balanced source so thats decided (thread title changed).

I have a 10k Vishay/Dale stepped attenuator here, which should sound better than the 50k pot. If I lower the gain can I just straight switch it or is there more to it? I will start reading for myself tonight, but searching is fairly pointless (lots of pot vs attenuator, not many with differing values involved) so it will be read hundreds of posts and hope to find the right info so a quick yes/no would be a good start

Thanks again

 

[Ferrari]

Yes, you can replace the 50KΩ blue Alps pot for a 10KΩ stepped attenuator without any modification on the CK2III amp circuit.
It should work fine!

 

[suicidal_orange]

Thanks for confirming that Ferrari.

I have requested the CKKIII ordering spreadsheet from Jeff (GlassJar Audio) and started reading about the build. As I have low impedance cans the default gain of 9 is far too much, so I decided to switch it to 4.1 with the change suggested on AMB.com, but there are no 22pF resistors on the order form. Should I use 220pF's instead or try and fit 2 10pF's in parallel in each position (maybe one above and one below the PCB?) and hope the extra 2pF was just there for convenience more than extra safety? I'm sure this has probably been discussed before, but searching isn't helping much - I know cheap is good as these are not going to make any audible difference, but the only local electronic component shop here shut down so I can't just pick some a couple, and paying shipping for something so small and cheap seems pointless

Thanks again for any help

 

[FallenAngel]

Quote:

Originally Posted by suicidal_orange /img/forum/go_quote.gif Thanks for confirming that Ferrari. I have requested the CKKIII ordering spreadsheet from Jeff (GlassJar Audio) and started reading about the build. As I have low impedance cans the default gain of 9 is far too much, so I decided to switch it to 4.1 with the change suggested on AMB.com, but there are no 22pF resistors on the order form. Should I use 220pF's instead or try and fit 2 10pF's in parallel in each position (maybe one above and one below the PCB?) and hope the extra 2pF was just there for convenience more than extra safety? I'm sure this has probably been discussed before, but searching isn't helping much - I know cheap is good as these are not going to make any audible difference, but the only local electronic component shop here shut down so I can't just pick some a couple, and paying shipping for something so small and cheap seems pointless Thanks again for any help

Just ask Jeff for some 22pF caps

 

[suicidal_orange]

What an obvious answer! I looked through all the kits he has available and assumed as none used 22pF he wouldn't have any, but it's surely worth asking. Thanks for making me see sense

 

[fishski13]

good luck on the build. it's a wonderful amp. Jeff gives A++ service as well.

PACE