http://citrus-w...z021v9m6xn7.jpg

[Edited by Gautama on 02-10-2009 at 07:41 PM.]

[Edited by Gautama on 02-10-2009 at 06:05 PM.]

Time to finish my second CK²III so that I can finally usee parts reserved for it I was planning to include transformer in the same chassis than pcb but I found out that those miniature toroidal transformers are pretty hard to get here in Finland. On the other hand, local suppliers have tons of small PCB transformes but only up to 6 VA.

So does anybody know if 6 VA transformer (3 VA per winding) is enough for this amp? Initial specifications found from original discussion thread recommends 6 VA trafo, but amb's page specifies 7 VA trafo. I have distant memory that required rating was made higher but I cannot find exact posting from original thread...

Thank you very much in advance again

Best regards,
Jari

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Edit: Ah, never mind. I think I will order those miniature transformers from Farnell. They are actually not so expensive I initially thought. May as well order bunch of them for future projects

[Edited by jarpatus on 02-15-2009 at 06:10 AM.]

Is there a coating on them responsible for this that I could file off?

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[Quoting amb]

See this post for a discussion.

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Do we have to?
It's pretty bad when someone starts a "help thread" and then argues with everybody that posts a "helpful reply" because he is to stubborn to just accept their advice.
In fact.... that is the best case I have I seen for a forum's ignore feature in a long long time

Thank you very much.

OP27 is not a dual unit and is not JFET-input. OP275 is dual, but has somewhat high input bias current and would not work as well in a DC servo application.

I attach the attachment. One-sided PCB for economic home made. One channel without suuply. (For better stereo distance - each channel separate supply).

First of all, thanks for a great sounding amp amb! Sounds really good together with my HD650's. I have one slight problem with my amp, if I have both low level inputs (l+r) connected I get a slight 50 Hz hum in my headphones, very subtle on my 650's but louder in my test headphones with higher sensitivity. I have tested some different ways to connect the amp and I found out that if I connect one channel correctly, doesn't matter which one, and attach the other rca connector so that only the signal and not ground get connected then it's noise free and I get sound in both channels. Another test I made was to connect the ground from left and right channel to each other (no signal source connected) then I get the same hum. The hum is independent of the volume control position.

Any idea?
Thanks!

/Roger

Yes the amp is in the recommended Hammond case. The transformer is quite close to the board, not very much room to move it away. The transformer is a Noratel AA-021504. The ground from the AC plug is connected to the chassis and the ground hole on the PCB is also connected to the chassis, no ground loop breaker. The source is a Denon 1940 DVD which doesn't have a ground connection but my amp has one. I have a rec out from my amp so I use it as a source selector and I also use the amp's RIAA. I get the same result when I connect the headphone amp directly to the DVD. All equipment is connected to an extension cord with 4 grounded AC outlets. My wall outlet doesn't have a ground connection, I only have that in my kitchen. It's on the to-do list to have grounded outlets in the entire apartment. I tried to connect the ck2III to my grounded outlet and I get the same hum when I attach the 2 signal grounds together.

Regarding the output resistors, which of them should I get, metal oxide 0.47 Ohm 5% or metal film 0.5 Ohm 1% (br.mouser.com/S...ey71-CPF1-F-0.5)?

Is there any measurable difference soundwise aside from the stated specs?

Cheers

/Roger