[analogbox]

Did anyone get a chance to try it with K1000s?

 

[amb]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif I always wondered how you managed to use sigma22 with your power amp. Now I understand. Pretty smart idea with the split power supplies. Is this something that you've seen in other designs, or yet another (yawn) stroke of brilliance on your part

Lol. It is fairly common practice in high-end power amps. Typically, though, a far less fancy design than σ22 is used for the regulated sections.

 

[digger945]

Thanks for the images Ti.
I noticed that cmoy has a post dated 5/25 on HW stating that he is in the process of moving and should be unpacked and set up in a few weeks. Maybe we can browse the forums soon.

 

[TheRobbStory]

For anyone interested, I've decided to pass my partially complete Beta24 on: http://www.head-fi.org/forums/f44/fs...pplies-438031/

 

[qkizz]

I'm so sorry to heat that. Hope you won't regret it in future. My Beta24's never stops to amaze me and makes me feel proud that I managed to complete such a complex project with my mediocre knowledge of electronics wizardry. BTW what's going on with other people projects?

 

[nattonrice]

I got my boards and the s22 supplies last week...
I gotta polish off a certain b22 and buff32s first then I'll look at getting the toroids and case I want... then finally the actual components :S

Somewhere in there is a sohaii... after all of this I think I need to diy-sleep for a year lol.
It's just too much fun~! ^^

 

[compuryan]

I've got all my boards populated, and one channel mounted to it's heatsink. I just need to mount the other channel and put together the unregulated power supply. Back panel is done too. I really hope I finish it before I have to go back to college...

 

[Iniamyen]

Mine's still coming along slowly but surely, as funding permits

I got a big 10.125" heat sink extrusion off of ebay awhile ago, and it's been sitting around until I can lap it, drill/tap it, and paint it properly. Most of this stuff I can't do at home so it's more of a time and effort issue.

I'm also in the process of getting some custom SumR transformers. After that, one quick order to Digikey and I'll at least be able to test out the regulated power section of the amp.

So the remaining tasks are the unregulated power section and the casing (single enclosure.) I haven't given very much thought to these yet, plus I'm sure they will be the most time consuming.

 

[akcrusier]

Another B24 lives! It took me almost exactly a year (high school interfered during the winter) After many mistakes, and alot of help from AMB my amp finally works! Picasa Web Albums - Gregory - B24
I have yet to listen to it with a good pair of speakers yet (the veneer is still drying on those) Shame I will have to leave it all for college in about a month, though with as much power as it has I might be able to hear AMB's B24 from my dorm a few miles away.

 

[nattonrice]

Quote:

Originally Posted by akcrusier /img/forum/go_quote.gif Another B24 lives! It took me almost exactly a year (high school interfered during the winter) After many mistakes, and alot of help from AMB my amp finally works! Picasa Web Albums - Gregory - B24 I have yet to listen to it with a good pair of speakers yet (the veneer is still drying on those) Shame I will have to leave it all for college in about a month, though with as much power as it has I might be able to hear AMB's B24 from my dorm a few miles away.

Holy crap! Is that a 5U case? Looks massive

Congrats on getting it working!

 

[qkizz]

Congratulations! Hope to hear your impressions soon. Great looking! What are the caps you have for unregulated PSU. I see 4 big blue and 4 smaller ones.

 

[akcrusier]

Quote:

Originally Posted by qkizz /img/forum/go_quote.gif Congratulations! Hope to hear your impressions soon. Great looking! What are the caps you have for unregulated PSU. I see 4 big blue and 4 smaller ones.

The big caps are 15,000 mfd ones that I got off of ebay and thge small black ones are 10,00mfd that are listed in the bom.

I have been listening to my B24 for two days with the new speakers I made and I am very impressed. It sounds great with the 3 ways. It is a very big upgrade from the Cambridge audio bose wave radio clone that I had before...
I have identified a couple of issues with it so far. One is that I discovered that my main power transformer buzzes under normal use. I cant hear it unless I get close but its still a bit disappointing after I paid extra to get a SumR transformer. Another is that the main heatsinks get really really hot even if the music is played quietly. When I went to touch them during LOTR (which I had turned up) I was afraid there were getting close to that 170 degree mark where the thermal breakers would go. I am borrowing an IR temp sensor to get an accurate reading. I think for now I will reduce the bias on the main MOSFETs to about 150 mA and perhaps investigate some active cooling. They make computer fans that are virtually noiseless now and combined with a micro controller that I could program to control their speed depending on temperature I dont think I would notice them too much. I know its a bit unusual for hi-fi gear to have active cooling but I would rather break a convention than shorten the life of my amp.

 

[qkizz]

thanks akcrusier.

Mine transformers form diycable are also buzzing but rather quietly. As of temp of heatsinks, yours looks adequate enough but temp is propably way too high. Mine is about 100-110F with 200mA quiescent current. I've had a few class A/B amps and they were never getting hot like one of my class A, which would be about 170F.

 

[amb]

akcruisier, your temperature is too hot. Your heatsinks are internal to the case, does the case have good flow-through (bottom to top) ventilation? On my β24, the heatsink fins normally idle at around 46°C (114°F), with 200mA quiescent current through each output stage. It's warm but still comfortable to touch.

 

[Iniamyen]

I notice that most people are using the relay (per AMB's reference build) for the bleeder resistors. My amp is going to have switching done in the rear, and I'm going to be using a rocker switch to keep things simple. Is there any safety-related reason to not use a 4PDT, and just hook two of the poles up to the bleeder resistor switches, and the other ones to the transformer primaries? I haven't yet seen anyone do it this way.