[amb]

Yes, the Amphenol Eco|Mate C16-M series is what I used. I prefer the 3+PE version (used two of them on the krmathis amp). The PE pin is a little longer and makes contact first when you plug it in, and that is used for the G in the V+/G/V- triple per side. The fourth pin is used for unbalanced TRS jack ground return to the PSU.

 

[minivan]

hi amb, i happened to have a few of these neutrik loudspeaker connectors laying around
Neutrik - Audio - Cable Connectors - NL4FC
can i used them for the power connection?

 

[compuryan]

hey guys, i was listening to the amp for a while and realized the heatsinks on the sigma22 getting hot. How hot is too hot? Maybe I need better heatsinks?

 

[sachu]

Quote:

Originally Posted by compuryan /img/forum/go_quote.gif hey guys, i was listening to the amp for a while and realized the heatsinks on the sigma22 getting hot. How hot is too hot? Maybe I need better heatsinks?

wow, how long have you been listening.. are the heatsinks the ones supplied in the glass jar audio kit?

The amp is not yet cased up right? what headphones are you driving?

i am now planning on going with the dual sigma22 board setup with dual 160VA toroids..

Ryan, can you comment on the tracking quality of the pot?

I was looking at this as a possibility (as the Joshua tree attenuator is sold out and version 2 is as of now slated for 2011 ?) to use in the balanced setup.

Saachi

 

[amb]

Quote:

Originally Posted by minivan /img/forum/go_quote.gif hi amb, i happened to have a few of these neutrik loudspeaker connectors laying around Neutrik - Audio - Cable Connectors - NL4FC can i used them for the power connection?

Since it is normally used for speaker connections, it's a bad idea to use it for other purposes (especially when it's going to have some large DC voltages on it). Someday, somewhere, someone is going to plug the PSU into a speaker and blow something up.

Quote:

Originally Posted by compuryan hey guys, i was listening to the amp for a while and realized the heatsinks on the sigma22 getting hot. How hot is too hot? Maybe I need better heatsinks?

Well, how hot are they? If you have a thermocouple attachment to your DMM, or an IR thermometer to measure the actual temperature, it would be useful info.

Otherwise, measure the voltage drop across the PSU MOSFETs (betweeen the MOSFET mounting tab and the output), and then tell me how much bias you adjusted the 4 amp boards for, we could calculate the power dissipation to determine whether it's safe or not. Are you using the default 1.5" heatsinks?

 

[compuryan]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Well, how hot are they? If you have a thermocouple attachment to your DMM, or an IR thermometer to measure the actual temperature, it would be useful info. Otherwise, measure the voltage drop across the PSU MOSFETs (betweeen the MOSFET mounting tab and the output), and then tell me how much bias you adjusted the 4 amp boards for, we could calculate the power dissipation to determine whether it's safe or not. Are you using the default 1.5" heatsinks?

I am using the default 1.5" heatsinks. I can hold my finger on top of them for about 3-4 seconds and before I have to pull away because of the heat. I checked all my R34 values on the b22 boards and they're all around 55mV. Where is the mounting tab for the PSU MOSFETs? Is that just any one of the three pins soldered to the board? And which output, where is it?

Thank you for your patience with me. Building this has been one big big learning experience.

 

[amb]

If you can rest your finger on the heatsink for a few seconds then it's probably ok, but your case should be well ventilated or the temperature would get much higher.

The mounting tab of the MOSFET is the metal part where the mounting screw goes through. It is internally connected to the drain (center) pin of the MOSFET. Since the two MOSFETs of each rail are paralleled, it doesn't matter which MOSFET you use. One bank is the positive regulator and the other is the negative. Measure the voltage between a "+" bank MOSFET tab and V+ output, and do the same between the "-" bank and V-.

 

[Mellow Mushroom]

hoe do you calculate how much heat the S22 dissipates? it's too bad i was born handsome but have delicate fingers, so i can't touch hot heatsinks to see if they are OK

 

[amb]

Quote:

Originally Posted by Mellow Mushroom /img/forum/go_quote.gif hoe do you calculate how much heat the S22 dissipates?

The dissipation (in Watts) is simply the voltage drop across the MOSFET multiplied by the current it passes. Since there are two MOSFETs per rail on the σ22, each MOSFET handles only half the total current, therefore produces half the heat.

P.S. The total current is the sum of all loads connected to the σ22. Each β22 board draws about 40mA plus the quiescent current through the output stage, which you set with the VR2 trimpot. For example, if you bias the output stage to quiesce at 120mA (55mV drop across R34), then the per-board draw is 160mA. For a 4-board balanced β22 running off a single σ22 board, the total draw would be 0.64A. If you had set the output stage to quiesce at 160mA (75mV drop on R34), then it's 200mA per board and 0.8A total.

To check if the dissipation is too high, you then need to calculate the junction temperature within the MOSFET. This is affected by the thermal resistances of the heatsink, the isolating pads, and the MOSFET's TO-220 package itself. See the σ22 website "Board & heatsinks" section for a discussion about this.

Quote:

it's too bad i was born handsome but have delicate fingers, so i can't touch hot heatsinks to see if they are OK

lol.

 

[compuryan]

Its finished, behold! (and excuse the kitchen counter)

Here a little information about the amp. It sounds absolutely awesome. I was kinda on a budget (haha a budget beta 22 I know) and for the amount I spend on parts I am blown away at the value of this amp. I used Glass Jar Audio to order the kits for the amp and power supply. Jeff was great to deal with. The pot is a 4 channel Alps RK27 blue velvet. The XLR jacks are Vampire and all the solder used was Cardas Quadeutectic. Internal wiring was a mixture of some basic copper wire I had laying around and some thin Cardas copper hookup wire. The transformer is a 100VA Avel-Linding. You're probably wondering if there is hum because of my completely unshielded transformer. With my HD650, its almost inaudible. It bugs me a little sometimes, but I can live with it for now. Might look into getting another σ22 board and putting them both in a separate chassis someday. The chassis I bought at Mendelson's Liquidation outlet for $25, I think it was some sort of audio/visual processor before I got it. I painted it with Rustoleum hammered finish satin black paint. I bought a piece of finished particle board from Lowe's and cut it down for the faceplate and painted the edges. The knob I bought for like $4 in a pack of two at Radio Shack. I am very tempted to order a nice black aluminum one from GoldPoint. The feel of the plastic RatShack knob does not do the amp any justice.

 

[sachu]

NIce work Ryan..Congrats!..can you give info as to how bad the hum is with low z headphones?
like in the 80-300 and 32 ohms ones if possible?


What was the final cost if i may ask?

 

[compuryan]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif NIce work Ryan..Congrats!..can you give info as to how bad the hum is with low z headphones? like in the 80-300 and 32 ohms ones if possible? What was the final cost if i may ask?

I actually can't compare because the only balanced phones I have are my HD650. I wish I could. The final cost of parts was right around $640. Plus the cost of me driving to Lowe's like a zillion times!

 

[sachu]

Quote:

Originally Posted by compuryan /img/forum/go_quote.gif I actually can't compare because the only balanced phones I have are my HD650. I wish I could. The final cost of parts was right around $640. Plus the cost of me driving to Lowe's like a zillion times!

That's a heck of a lot of value....I know how it is about driving to the store every few hours for some part or thing that you forgot or didn't think you would need.

One thought, the transformer could have been placed more to the left me thinks. (?)

What is that thing in the middle of the case?, ground loop breaker on a terminal bar?

 

[compuryan]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif That's a heck of a lot of value....I know how it is about driving to the store every few hours for some part or thing that you forgot or didn't think you would need. One thought, the transformer could have been placed more to the left me thinks. (?) What is that thing in the middle of the case?, ground loop breaker on a terminal bar?

You're right. It does look like I could scoot the transformer back and over a little bit, that might help. The thing in the middle is indeed a ground loop breaker on a terminal bar.

 

[Uncle Erik]

Nice work! It's good to see that you repurposed a case - more people should do the same to keep costs down.

As for a proper knob, have you looked through the offerings at Nebraska Surplus Sales? I like their selection and the prices are fair.