[amb]

For 230VAC mains you should use 1/2 the fuse rating as you would for 115VAC.  If you are using a single 100VA transformer, I would use a 1A slow blow.

 

[Nada]

 
Quote:

Hi guys, I finally got round to taking some pics of my B22 amp. It has taken me over a year to get to this point and I thought i'd share my hard work with you all. First of all, a [size=x-large]MASSIVE[/size] thank you to everyone who has helped me with this project especially, Ti (AMB LAbs), MR Majestic, and johnwmclean. I would not have been able to do it without your help and patience!

The amp sounds bloody amazing, really happy with it. Its safe to say its not the easiest amp I have ever built, there is a lot that can go wrong (and did go wrong!) but got there in the end. I will be adding some more pics for those interested on the post pics thread (I didn't want to clutter this thread too much).

wow, thats art

 

[alamakazam]

where can I purchase a backpane?

 

[MisterX]

The for sale section maybe?

 

[Lil' Knight]

Quote:

where can I purchase a backpane?

You might want to take a look at the group buy at amb's forum.

 

[alamakazam]

Quote:

You might want to take a look at the group buy at amb's forum.

cool thanks dude
 
for the rest
 
http://www.amb.org/forum/group-buys-f29/interest-check-epsilon22-backplane-board-for-3-channel-beta22-t114.html?sid=c6a925623e2bbfd1f095774a50048757

 

[MrMajestic2]

Ok, so now I have more problems with my build I got a new fourth board in working order, it measures correctly, but it the heatsinks get so hot Im afraid to run it for any longer than a minute. None of my other boards get remotely hot with 56mV, but the fourth is burning. I havent dared plugging anything it yet to listen to it. Any ideas why this board is hot and not the others?

 

[amb]

The heat dissipation is simply the quiescent current through the MOSFET multiplied by the voltage across it.  Since the voltage is fixed, then that leaves only the current that's the sole factor.  Simple Ohm's Law.  If you set the quiescent current the same as the other boards, then it should produce the same amount of heat.
 
Now, that assumes a well-behaved amp that's quiet at idle so the quiescent current is all DC.  It doesn't take into any account possible oscillations or noise.  Do you have the inputs shorted when doing the initial setup?  Do you have the correct value capacitors for C1-C5, and are they all mounted in the correct holes?

 

[MrMajestic2]

Quote:

The heat dissipation is simply the quiescent current through the MOSFET multiplied by the voltage across it.  Since the voltage is fixed, then that leaves only the current that's the sole factor.  Simple Ohm's Law.  If you set the quiescent current the same as the other boards, then it should produce the same amount of heat.
 
Now, that assumes a well-behaved amp that's quiet at idle so the quiescent current is all DC.  It doesn't take into any account possible oscillations or noise.  Do you have the inputs shorted when doing the initial setup?  Do you have the correct value capacitors for C1-C5, and are they all mounted in the correct holes?

Inputs are shorted and C1-C5 looks correct. I will reflow and check again.

 

[CafeNoir]

Hi,
 
I have a small issue with my one-chassis 3-channel B22 that I can't figure out: It doesn't seem to have optimally low crosstalk.
 
I have made two experiments:
 
1) I disconnected one rca input  (let us say left) from the cd player, and disconnected the opposite output at the end connection of my HD-650 (where the headphone cable is connected to the cans), therefore the only sound I hear is theoretically crosstalk in the remaining channel. The result of this is I hear music playing at a low level, but subjectively at least three times louder than my reference SPL Auditor (ruling my aftermarket headphone cable inherent crosstalk out of the equation).
The importance of crosstalk increases when the volume is set higher. I would roughly say it is around -70dB.
 
2) Believing the most obvious source of crosstalk would be proximity of right and left input/output wires, I remade the wiring to place them resonably remote from each other. But it didn't change the situation.
Second possible source of crosstalk: the stepped attenuator. For this, I disconnected the left output wire of the attenuator - therefore the input pad of the left board is connected to nothing. The result: still the same amount of crosstalk, plus additional noise ("free air" noise from the disconnected wire?) at high volume level.
 
So now I am a bit puzzled. The only remaining causes of crosstalk are logically contamination between the boards themselves (unlikely) and contamination of the signal ground wiring ( input and ground wires are supended above the heatsinks, touching them lightly, could it be it?). The output wires to the jack are below the boards and resonably remote from one another, so I don't think they are in cause. So would you have any suggestion? Is there another source of crosstalk I have not been thinking about?
 
Sorry for the long post, but I love my Beta so much I want it to be perfect.

 

[amb]

Cafenoir, your method of testing for crosstalk is questionable.  If you simply unplug one channel's input and let it float, it will act as an antenna and pick up noise/crosstalk from the other channel.  This is not a realistic use situation.  In real life, each channel's input would be driven from a low-impedance source (rather than float).

 

[cfcubed]

On the subject of crosstalk, but not directly relating the last 2 posts, I've been learning the +s & -s of using shielded cabling for low-/line-level inputs.  Perhaps better for another thread & matter more for builds w/PS in same enclosure as amp.
 
In builds like those in my sig using shielded input cabling seems to have quieted down/made the background "blacker".  But, not surprisingly, using multiconductor shielded cable allowed crosstalk amongst the conductors.  So going forward I'll be leaning toward single conductor shielded cable for this application FWIW.

 

[fault151]

Quote:

 

wow, thats art

 
 
Thanks :0) glad you like it. Took me long enough to build!!!
 

 

[yuk228]

del

 

[Blasto_Brandino]

*looks at fault151's amp*
I have so much learning to do, it isn't even funny,
Anyway I'm interested in building a 3 channel, but I'm going to have to do some learning first, now other then the tech school classes I'm going to take, does anyone have a good starter amp or project they suggest?