---

[Quoting dk123]

ok thanks, unfortunately its really hard to get it from around here, and shipping from overseas, will cost me quite a bit.

---

Got my three board Beta almost done. Being a noob, I'm pleasantly surprised that initial setup went fine. I'm still waiting for the headphone jacks, but I was able to try the amp with some small PC speakers. It seems to work fine except that the volume knob works backwards. (Clockwise = quieter)

I'm guessing I wired the inputs to the outputs and vice versa but wanted to check here first. I thought I did it correctly per the website, but maybe the drawing shows the pot being wired right side up whereas I wired it upside down?

-py

[Edited by pidesd on 03-08-2009 at 03:04 AM.]

pidesd, I am not sure what you mean by "match new mosfets with the good ones while they are still there". You cannot do any MOSFET matching while it's still installed on the board. That said, on the β22 you don't really need to match the output MOSFETs. The circuit design makes it mostly unnecessary.

thanks

true breadboard of my 2ch beta22

case and other things still in progress. but finally, the amp is making sounds. good sounds

Ok, it's not a CMoy but it is in a tin. I still have to wire in the headphone jacks when I get them, but it works with the speaker jacks already. I also will probably mount the tin on a piece of wood or fiber board. It's actually pretty stiff with the lid on, but it's really flexy with the lid off. I'm not too worried about it since the boards are mounted about 1/2" above the surface, but I don't want the boards to be subject to any twisting forces either.

The tin itself used to hold a bunch of Chinese style cookies. Also, I put most all of the wiring at the front of the tin to stay away from the transformer and hopefully get away from any transformer hum. I haven't listened to it with headphones yet so I don't know if I was successful or not, but I don't hear any while listening through speakers.

Besides, I wanted everything up front because I hate reaching in the back of stuff to hookup things. And I figure this will only be used occasionally for speakers and will likely have different inputs relatively frequently so having those connections in front makes sense. It's not as elegant looking, but I figure form over function. I also put the power button on the right side vs. the rear for easier access.

Amb - not sure if you have seen any samples like this one, so if you'd like pictures for the website, you can grab them from flickr or I can email them to you. Thanks for all your help!

Here's the full amp in all it's cookie tin goodness:

The front "panel":

The back right:

The guts:

that's a lot of heatsink AND toroid

very inventive though. sure beats my 'block of wood' (lol).

the particle-board that I am temporarily using gives off a smell when the b22 is in use - so it must be the heat that is doing that.

[Edited by johnwmclean on 03-09-2009 at 09:54 PM.]

BTW, your wiring is much cleaner than mine. I think maybe i should have used 22 gauge wire... the 18 gauge I used was kinda hard to use everywhere, especially where twisting/braiding was called for. One question though, why didn't you use the input/ground pads that were closer to the volume pot?

the reason I put the jacks toward the back is that I was planning on having some stepper relays (custom boards, tbd) in the rear and I wanted the inputs real close by.

for now, its breadboard mode means I have to use SOME volume control and that means putting it up front (or using long extension shafts which I never really cared for).

the layout is still not final, but my initial thought was to keep things symmetric and having all the HS's line up kind of looked good to me and it gives me a center gutter area to 'put stuff' (remote or logic modules) and the rear small side areas can have the attenuator relays.

however, I suspect it will sit on its plank for a good few weeks before my control circuitry is ready

I currently have an aluminum box holding my trafo and I'm noticing the same problem even though my box is meant to be used for electrical things! I will get some plexiglass or something stiff and use that to reinforce the back of my aluminum. maybe you could consider some stiffening on the sides via plastic, also.

I finally got my headphone jacks installed and unfortunately, I think I'm getting the dreaded transformer hum. The hum gets louder as I turn the volume up. I don't really notice when I'm playing music at normal listening levels though. Does that sound like transformer hum to you? Anything else it can be before I make attempts to shield the transformer or move the transformer?

---

[Quoting oneplustwo]

Hey folks,

I finally got my headphone jacks installed and unfortunately, I think I'm getting the dreaded transformer hum. The hum gets louder as I turn the volume up. I don't really notice when I'm playing music at normal listening levels though. Does that sound like transformer hum to you? Anything else it can be before I make attempts to shield the transformer or move the transformer?

---

try to move the transformer around and change it s orientation. if that makes a difference then this is definately transformer hum. normally the farther the trafo from the signal the better. but if everything is in the same enclosure, hum is very likely to happen and difficult to deal with. if moving the trafo doesnt do anything you probably do not have everything wired properly. also, running the amp with that cover on for too long might be dangerous, especially when driving speakers...

[Edited by pidesd on 03-15-2009 at 12:40 AM.]

---

[Quoting oneplustwo]

Hey folks,

I finally got my headphone jacks installed and unfortunately, I think I'm getting the dreaded transformer hum. The hum gets louder as I turn the volume up. I don't really notice when I'm playing music at normal listening levels though. Does that sound like transformer hum to you? Anything else it can be before I make attempts to shield the transformer or move the transformer?

---

Disconnect your source(s) and listen with the volume up. If it's not there anymore, it's from the source and not transformer hum. I had the same type of hum, but it turns out I just need a better source (wish I had more money...)

---

[Quoting amb]

Listening with no source connected and volume turned up is not a good test of the amp. Without source "termination", the input "floats" and acts like an antenna to pick up all sorts of interference.

---

Okay, but at least in my environment, the type of interference it picks up is very low-level white noise whose power is so low compared to any type of systematic hum that it's basically negligible. YMMV I guess; it's at least a useful data point for me.