[luvdunhill]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif Ti: Looking at your drawings for the angle bracket attachment for the beta22 and sigma22, I notice that the very edge of the casing of the MOSFETs will actually be off the angle bracket a bit. You specify the hole being 0.4" from the edge of the angle bracket, and many TO-220 devices are ~0.5" from the center of the hole to the edge of the casing. Does this pose any thermal issues?

nevermind

helps to look at the devices themselves sometimes rather than drawings

 

[iamwhoiam]

That's amazing, can't wait to read the amb.org pages on this!

 

[L_and_P21]

Quote:

Originally Posted by amb /img/forum/go_quote.gif lol, the β22 is already quite an over-the-top headphone amp, and β24 would be borderline insane as one. It has a gain of 20, which is appropriate for a speaker amp of its class (just a bit under 2Vrms input will drive it to full output), but this is too much gain for most headphones. Also, its 5K ohm input impedance does not lend itself well to having a volume control pot there, so it really needs to be used with a preamp, or a source with a volume control. Currently I use a Benchmark DAC1 (which has a volume pot) feeding the β24 directly in fully balanced mode.

i have quite a crazy idea for a massive diy build. i have a pair a K701's and was wondering if the β24 would be ok for a headphone amp with them, with a β22 as a pre-amp.

Edit: by ok, i mean i dont want to harm them in any way.

 

[aloksatoor]

and a sound that can start earthquakes

Quote:

Originally Posted by L_and_P21 /img/forum/go_quote.gif i have quite a crazy idea for a massive diy build. i have a pair a K701's and was wondering if the β24 would be ok for a headphone amp with them, with a β22 as a pre-amp.

 

[compuryan]

Quote:

Originally Posted by L_and_P21 /img/forum/go_quote.gif i have quite a crazy idea for a massive diy build. i have a pair a K701's and was wondering if the β24 would be ok for a headphone amp with them, with a β22 as a pre-amp. Edit: by ok, i mean i dont want to harm them in any way.

Why not just drive the headphones straight from the β22 and use the β24 (w/ β22 as preamp) strictly for speakers? I don't think you'd hear much improvement with β22>β24 than with just a β22 because the two amps hold very similar designs, one just has more power. Not to mention the β24 is so powerful you'd really have to be careful that you wouldn't damage the headphones.

 

[grawk]

The B24 with Ti's speakers was the highlight of canjam, for me. Sunday night was a revelation. Thanks for bringing them Ti!

 

[sachu]

Quote:

Originally Posted by grawk /img/forum/go_quote.gif The B24 with Ti's speakers was the highlight of canjam, for me. Sunday night was a revelation. Thanks for bringing them Ti!

hehhe..I egged him on to turn it on..he was afraid folks would make a scene for playing speakers in a headphone econvention...10 minutes later everyone in the room was sitting around listening to magic from Ti's DIy Dynaudio speakers and awesome B24 amp.

 

[L_and_P21]

Quote:

Originally Posted by compuryan /img/forum/go_quote.gif Why not just drive the headphones straight from the β22 and use the β24 (w/ β22 as preamp) strictly for speakers?

if i were to just use the β22 for the headphones i would just use it make it fully balanced. plus i dont have any speakers... yet.

Quote:

Originally Posted by compuryan /img/forum/go_quote.gif Not to mention the β24 is so powerful you'd really have to be careful that you wouldn't damage the headphones.

this is what i would like to avoid and why i asked.

i know its a crazy idea. but i just like to build and play around with electronics.

 

[amb]

Thanks, even though my β24 sat quietly on the table through most of CanJam '09, it generated a lot of curiosity and excitement. When I finally cranked up the sound at the end of the meet, just seeing people's reactions was worth all the effort (of lugging the heavy beast hundreds of miles).

 

[grawk]

It's the most amazing thing I've ever seen. You wanted something, so you designed and built every part in the chain. Just spectacular. It's what every nerd aspires to

 

[akcrusier]

Someone on another thread asked for details on my uncompleted B24 build so here they are. I have finished one channel so far and tested it with a very poor pair of old speakers. I am not really sure how it sounds beyond the fact that it obviously has tons of power (more than I will ever need) Unfortunately in the process of troubleshooting my other board i ruined enough of the traces that I decided it would be best to simply start over. So I bought another board and am almost done populating it. Hopefully it works ok. For the power supply I have to O22 boards that are both up and running supplied by a 30VA SumR transformer. For the unregulated power supply I have a 500VA SumR transformer and 4 15,000 mfd capacitors. With that much capacitance I think i will have to do an inrush current limiter. I have an extra solid state relay and think i'll make a delay circuit out of a 555 timer to short the caps a few seconds after start up. The entire amp is contained in a 400mm deep 5 rack unit tall HI FI case. The heatsinks are ones I bought off ebay and cut to 8 by 8 so that they will be able to both fit totally in the case unlike versions of the amp done by others.
Picasa Web Albums - Gregory - audio

One question for AMB. On my one finished/working board I mounted diodes 7-10 flush to the board. I recall reading on headwize some time ago that those needed to be mounted 1/8 above the board because they get quite warm. When I tested my amp (it was at low volume and for no more than 20 mins) the diodes did not seem to get hot even though the amp seemed to be working just find and heat was pouring off the heat sink. Should I replace them and re-adujust my amp?

For the rest of the system I am working on I have the following that are in various states of completeness:
RelaiXed preamp (i wanted to do a B22 but I ran out of cash...)
Buffalo 32 DAC
a pair three ways with Dayton RS270 for bass, a 5.5 SBacoustics for the mids, and a Vifta XT25 for a tweeter. As these are my first pair of speakers I did not want to get to expensive so perhaps later i'll upgrade to something with better drivers (hopefully I can afford some scanspeak drivers by then)

I also have an 18" Mal-X sub that will be used with the system for movies.
I will have the system done by the end of August as I am going to college in early september so I have to finish it by then....

This all started about last August when my logitech speakers died and I heard a real sound system (McIntosh) for the first time. I decided I wanted something that sounded that good. Its my first real DIY audio project, and first project that deals with AC circuits. Starting with a B24 was probably not a good idea but I have learned quite a bit. I will post more pictures when I am done.

 

[amb]

Quote:

Originally Posted by akcrusier /img/forum/go_quote.gif One question for AMB. On my one finished/working board I mounted diodes 7-10 flush to the board. I recall reading on headwize some time ago that those needed to be mounted 1/8 above the board because they get quite warm. When I tested my amp (it was at low volume and for no more than 20 mins) the diodes did not seem to get hot even though the amp seemed to be working just find and heat was pouring off the heat sink. Should I replace them and re-adujust my amp?

D7 through D10 are 18V zeners, and normally they should have a little more than 30mA flowing through them, regardless of whether the amp is idling or playing music. The power dissipation on each diode is W = V * I = close to 0.6W. On a little DO-41 package without heatsink, that should be pretty hot. The diode can handle it -- it's rated for 3W, but you should mount it elevated off the board, so it doesn't burn a mark on the board over time, and the extra lead length actually acts to help dissipate a little of the heat.

If your D7-D10 aren't hot, then make sure they're the right diodes (1N5931B) and that they are mounted in the correct orientation. A zener in the reverse direction becomes like a regular diode, the voltage drop is less than a volt.

Do your DN2535 MOSFETs (Q21-Q24) get warm? They should.

 

[digger945]

Is there another place to find more info on the unregulated PS that feeds the output MOSFETs in this design, besides HW or AMB.com?

 

[amb]

digger945, the unregulated portion is just a big transformer, big rectifier bridge with snubbers, and two big filter/reservoir caps. You can either use one such PS for both channels, or a separate one for each channel. Minimum required voltage is +/-30V under full load.

Here is the schematic/block diagram of what I did for my "reference" build:

 

[luvdunhill]

Ti:

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