[nightanole]

Well i got all the parts in for my CK2III build. However headwiz is still down, and i cant find a build thread here like the M3. Is there one?

Anyway i have a few questions if some one could help.

1. Im popping in the wee little transformer inside the case for an all in one setup. Its been ingrained in my skull not to mount the tor with a center screw to the chassis. If that is the case how should i mount the unit to the case (hot glue?)

2. I used a shunt style volume control on my starving student and it seemed to really help the super cheap volume control sound good. I was wondering if I could use that style with the blue alps, or should i just stick to stock since its a special $16 unit? In theory if i used a 50k resistor, the source would only see 50k or higher, but the the unit would see variable 100k to 50k instead of a fixed 50k. This would also knock the gain down from 9 to 5, which is fine for my 64ohm or under phones.
shunt style volume control

3. Can the unit be sealed and still use the 30ma quiescent current? I ordered 6 heatsinks instead of just the 2 output ones. Not sure what good a heatsink is gonna do with no air flow though.

4. Guess i should have read alittle further in the build up. it says that if i place the transformer in the case, and use earth ground, i will create a ground loop so i should connect the ground of the board to the chassis via "10Ω 5W wirewound resistor in parallel with a 0.1µF film capacitor rated at least 250VAC". This is what doesnt make sense. If i would have just used a jamaco wall wart maker, and placed the transfomer in that, i wouldnt run a earth ground to chassis, and then i just ground the board to the chassis. So why do i have to connect earth ground to chassis when its in the box? cant i just make it a standard 2 prong device?

 

[ericj]

Quote:

Originally Posted by nightanole /img/forum/go_quote.gif Well i got all the parts in for my CK2III build. However headwiz is still down, and i cant find a build thread here like the M3. Is there one? Anyway i have a few questions if some one could help. 1. Im popping in the wee little transformer inside the case for an all in one setup. Its been ingrained in my skull not to mount the tor with a center screw to the chassis. If that is the case how should i mount the unit to the case (hot glue?)

Why shouldn't you use the center screw?

Quote:

Originally Posted by nightanole /img/forum/go_quote.gif 2. I used a shunt style volume control on my starving student and it seemed to really help the super cheap volume control sound good. I was wondering if I could use that style with the blue alps, or should i just stick to stock since its a special $16 unit? In theory if i used a 50k resistor, the source would only see 50k or higher, and the unit would see 100k instead of 50k. This would also knock the gain down from 9 to 5, which is fine for my 64ohm or under phones. shunt style volume control

Putting a resistor in front of the pot is a stupid way to reduce the total gain. Why not reduce the gain by reducing the gain?

Quote:

Originally Posted by nightanole /img/forum/go_quote.gif 3. Can the unit be sealed and still use the 30ma quiescent current? I ordered 6 heatsinks instead of just the 2 output ones. Not sure what good a heatsink is gonna do with no air flow though.

There are four output transistors. The heatsink allows the heat to go somewhere instead of just building up in the teeny tiny silicon die inside the package and killing it. Even without generous venting.

I don't know if you can do 30ma quiescent current in a fully enclosed case, and here's the thing: you shouldn't try. The output transistors have a positive thermal coefficient and this means that if you set it to 30ma with the case open and then close the case, since there is no airflow the transistors will run hotter and draw more current.

You can use an enclosed case, it'll just run hot, and you have to start low with the biasing and tune it by ear and thermometer until you get to a point where it runs not-too-hot and sounds good to you.

Quote:

Originally Posted by nightanole /img/forum/go_quote.gif 4. Guess i should have read alittle further in the build up. it says that if i place the transformer in the case, and use earth ground, i will create a ground loop so i should connect the ground of the board to the chassis via "10Ω 5W wirewound resistor in parallel with a 0.1µF film capacitor rated at least 250VAC". This is what doesnt make sense. If i would have just used a jamaco wall wart maker, and placed the transfomer in that, i wouldnt run a earth ground to chassis, and then i just ground the board to the chassis. So why do i have to connect earth ground to chassis when its in the box? cant i just make it a standard 2 prong device?

If the transformer is in the box, and the box is metallic, you must ground the enclosure to earth ground to prevent possible safety issues.

 

[cobaltmute]

from the initial setup page on amb's site:

Quote:

30mA should be adequate quiescent current for most applications. If your output transistors have heatsinks, then you may increase the current up to around 60mA, keeping in mind that the additional heat must also escape the enclosure. Since the Hammond 1455Q case dpesn't have any ventilation slots, it is recommended that you keep the quiescent current at the default setting.

 

[fishski13]

Quote:

Originally Posted by nightanole /img/forum/go_quote.gif Well i got all the parts in for my CK2III build. However headwiz is still down, and i cant find a build thread here like the M3. Is there one? Anyway i have a few questions if some one could help. 1. Im popping in the wee little transformer inside the case for an all in one setup. Its been ingrained in my skull not to mount the tor with a center screw to the chassis. If that is the case how should i mount the unit to the case (hot glue?) 2. I used a shunt style volume control on my starving student and it seemed to really help the super cheap volume control sound good. I was wondering if I could use that style with the blue alps, or should i just stick to stock since its a special $16 unit? In theory if i used a 50k resistor, the source would only see 50k or higher, but the the unit would see variable 100k to 50k instead of a fixed 50k. This would also knock the gain down from 9 to 5, which is fine for my 64ohm or under phones. shunt style volume control 3. Can the unit be sealed and still use the 30ma quiescent current? I ordered 6 heatsinks instead of just the 2 output ones. Not sure what good a heatsink is gonna do with no air flow though. 4. Guess i should have read alittle further in the build up. it says that if i place the transformer in the case, and use earth ground, i will create a ground loop so i should connect the ground of the board to the chassis via "10Ω 5W wirewound resistor in parallel with a 0.1µF film capacitor rated at least 250VAC". This is what doesnt make sense. If i would have just used a jamaco wall wart maker, and placed the transfomer in that, i wouldnt run a earth ground to chassis, and then i just ground the board to the chassis. So why do i have to connect earth ground to chassis when its in the box? cant i just make it a standard 2 prong device?

1. you just need to make sure that the TX has isolating foam/discs. the speced Amveco has an epoxy potted center and foam underneath.

2. use a shunt method if you want, but strictly as a means to reduce gain, it's not the best way.

3. AMB specs the quiescent current at 30 mA with a fully enclosed chassis. the one i built has had no issues.

4. a wall-wart delivering DC to the CK2III from the wall outlet - there's no AC/ground coupling to be concerned with.

 

[nightanole]

Ok so the shunt pot not a good idea ( I ordered the resistors and caps for both gain settings anyway, i was just wondering about sound quality vs the standard method). It was what the new compass amp/dac uses so i was curious about using it with this amp.

The stock tx is the one with the foam disc and potted center with a hole. Do i still use a steel screw to mount it to the chassis?

If the 30ma is with a closed case, then i should be fine since im using additional heatsinks too. I just tune the current with the case closed i assume?

And it looks like im stuck buying more parts to get the 5 watt resistor/cap to ground the board to the chassis.


Anything else I should know?

 

[MisterX]

Quote:

Anything else I should know?

A Zobel network is a very good idea and since you are ordering parts for a ground loop breaker....

 

[nightanole]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif A Zobel network is a very good idea and since you are ordering parts for a ground loop breaker....

SNiff sniff, headwiz is down, i have no access to finding this stuff out. all links to the Zobel network goto the head wiz forums...

 

[Ferrari]

nightanole, a Zobel network can be made from a 10Ω 2W (or 22Ω 2W) metal oxide/film power resistor and 100nF (or 47nF) film capacitor (MKP/MKT 100V or higher) in series. Connect one Zobel network on each channel, from headphone L-out/R-out pin to GND.

 

[nightanole]

So hows this for a shopping list;

Zobel network:

71-CPF2-F-22 vishay/dale 22ohm x2

594-2222-368-45473 visha mkt 160vac 47nf x2

ground interupt:

71-RS5-10 vishay/dale 10ohm wirewould

505-MP3X2.1/275/20P wima .1uf 275vac film


Could someone double check that?

And some more questions. On the Zobel network, it goes in parallel with the speaker to remove inductance of the speaker coil. So one end goes to the positive of the speaker out, and the other to? negative speaker out? star ground? earth ground?


Also found this little guy on ebay.

SMT Resistor Step Attenuator 50K Volume Control

Im not sure if it would sound better then the alps or not, but its the same cost.

 

[Forte]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif A Zobel network is a very good idea and since you are ordering parts for a ground loop breaker....

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif nightanole, a Zobel network can be made from a 10Ω 2W (or 22Ω 2W) metal oxide/film power resistor and 100nF (or 47nF) film capacitor (MKP/MKT 100V or higher) in series. Connect one Zobel network on each channel, from headphone L-out/R-out pin to GND.

What is the purpose of the Zobel network on a headphone amp?

This is the 2nd time this week I have seen people recommend adding this to a CKK111 amp but all the search results I found related to speaker amps, even amb's B22 site says it could be omitted for a headphone amp.

 

[cobaltmute]

Compare that attenuator to these. The switch quality on the one you linked looks very poor. I suspect it won't last very long. I would also suspect there is very little matching of resistors going on.

 

[amb]

A Zobel network is sometimes necessary at the output of a headphone amp, depending on a number of factors including your headphone load and the wiring. Many builders have found that a Zobel tames certain stability issues. While I stop short of recommending a Zobel on every build, it should be harmless on most.

 

[ericj]

Quote:

Originally Posted by cobaltmute /img/forum/go_quote.gif Compare that attenuator to these. The switch quality on the one you linked looks very poor. I suspect it won't last very long. I would also suspect there is very little matching of resistors going on.

How can you tell? The switch mechanism isn't shown.

If they used 1% resistors, they're probably matched better than the tracking on most pots.

The thing to look out for with stepped attenuators though is switching noise. You often get a loud SNAP on each detent. I have two of the 'fake alps' attenuators and one of them was made silent by taking it apart and hosing it down with a silicone-based contact cleaner. The same treatment on the other one didn't completely silence it.

This was very very annoying. And on the worse one, before i cleaned it, there were points on it's travel where there was enough crud in the works that the wiper would sometimes lift.

IMHO the goldpoint attenuators are overpriced, but i can't say i've actually used one. I also think it's pretty lame that they discontinued the ladder attenuator (iirc).

 

[cobaltmute]

I have no doubt that the Goldpoints could be over priced (especially the bare boards version with no resistors).

for the attenuator in question, it may be a great deal if it can hold up. My worry with it would be the physical integrity of the switch mechanism and how the decks are held together. You also have no idea what resistors are in it - it could be 5% carbon film.

But as I said, until someone orders one and uses it, my comments are based upon looks and only suspicions.

 

[MisterX]

Quote:

Originally Posted by nightanole /img/forum/go_quote.gif So hows this for a shopping list; Zobel network: 71-CPF2-F-22 vishay/dale 22ohm x2 594-2222-368-45473 visha mkt 160vac 47nf x2 ground interupt: 71-RS5-10 vishay/dale 10ohm wirewould 505-MP3X2.1/275/20P wima .1uf 275vac film Could someone double check that?

While I would pick different capacitors there is nothing wrong with the parts you selected.

It may be a good idea to add a terminal strip so you have a way to hard mount the ground loop breaker.
Here is one from Mouser---->

158-1006
(I like that one because it has two mounting holes but you could aso use #158-1005 if space is a concern )


Quote:

Originally Posted by nightanole /img/forum/go_quote.gif And some more questions. On the Zobel network, it goes in parallel with the speaker to remove inductance of the speaker coil. So one end goes to the positive of the speaker out, and the other to? negative speaker out? star ground? earth ground?

Out ground and you can mount the zobel network right on the headphone jack if you wish (which is one of the reasons why I would pick different caps)