Hi,
I'm new to amp builing and have just took delivery of my ACA kit. owing to a p&p cost of $90 i decided just to buy the components/connectors and supply my own chassis and heatsinks. I think I will be going for one of the chassis from ebay previously mentioned.
Anyway... my question is to do with the thermal paste and the.mica pads. I've done some searching and found some goo at maplins for a good price however are there any specs I should be looking for; thermal conductivity values for example? The same question goes for mica pads except I'm still looking for somewhere to buy them in the UK. (mica pads just look acetate sheets to me)
thanks
anima
I'm new to amp builing and have just took delivery of my ACA kit. owing to a p&p cost of $90 i decided just to buy the components/connectors and supply my own chassis and heatsinks. I think I will be going for one of the chassis from ebay previously mentioned.
Anyway... my question is to do with the thermal paste and the.mica pads. I've done some searching and found some goo at maplins for a good price however are there any specs I should be looking for; thermal conductivity values for example? The same question goes for mica pads except I'm still looking for somewhere to buy them in the UK. (mica pads just look acetate sheets to me)
thanks
anima
My friend sent me few WIP pics for ACA cab.
Internal dimensions are 70mm x 152mm x 196mm (HxWxD).It still needs powder coating ad front panel of Wood or Acrylic.I am planning to use laptop power supply,any suggestion of chassis mount DC power jack.
Regards,
Sachin
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Internal dimensions are 70mm x 152mm x 196mm (HxWxD).It still needs powder coating ad front panel of Wood or Acrylic.I am planning to use laptop power supply,any suggestion of chassis mount DC power jack.
Regards,
Sachin
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Nice, compliments to your friend, he has great metal working skills, the bending and cutting
Thaks Walter,
He has also built B1 cab for us
Sorry for little OT
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Regards,
Sachin
Wow this is one good sounding machine.
Finished up the bias adjustments... Easy. 10.01 on one and 10.1 on the other... The temp on the heat sinks around 108 to 107f.
Plugged in speakers and turned on the fm radio and left the room for an hour. No smoke. But a beautiful warm and rich mid range. Sweet very sweet.
Today I'll turn it no again for a good 100 hour burn in. Then give a listen on main system.
Nelson, thank you!
Finished up the bias adjustments... Easy. 10.01 on one and 10.1 on the other... The temp on the heat sinks around 108 to 107f.
Plugged in speakers and turned on the fm radio and left the room for an hour. No smoke. But a beautiful warm and rich mid range. Sweet very sweet.
Today I'll turn it no again for a good 100 hour burn in. Then give a listen on main system.
Nelson, thank you!
Finished my ACA a few weeks ago. Just breaking in along with a new pair of PSB Alpha B1s. I am using a CMoyBB headphone amp I built from JDS Labs--the one in the Altoids tin--as a pre and volume control. Listening to Pandora (Ry Cooder and Taj Mahal Radio mostly) from my computer or my songs on ipod. Costs: $270 ACA, $300 PSBs and $50 for the CMoy plus a few bucks for cables. Everything works well together.
My computer room is small, about 12 x 15 and the speakers are on a table near the far wall. Sound is great. PSBs started out a bit harsh, but they a mellowing out. Music is clear and detailed, and there is a certain sweetness on the more acoustic tunes. Loud rock gets a bit confused; bass is not overwhelming by any means, but I am not a fan of rumbling house shaking bass. There is plenty of headroom with this set up in this room. I was worried that the 5 watts per channel would be limiting; it is not. The cMoy does provide some boost.
Weak link is the source. Line input is just not the same as with my old dependable Rotel, but I'm feeding that into Sonic Frontiers tube amp and preamp in my listening room. But for my purpose in the computer room this set up is great.
Future considerations would include a Fostex or similar full range speakers with an open baffle set up. Also an O2 headphone amp (kit) from JDS Labs to replace the cMoy.
Anyway, I'm very happy, except that I need more to do.
My computer room is small, about 12 x 15 and the speakers are on a table near the far wall. Sound is great. PSBs started out a bit harsh, but they a mellowing out. Music is clear and detailed, and there is a certain sweetness on the more acoustic tunes. Loud rock gets a bit confused; bass is not overwhelming by any means, but I am not a fan of rumbling house shaking bass. There is plenty of headroom with this set up in this room. I was worried that the 5 watts per channel would be limiting; it is not. The cMoy does provide some boost.
Weak link is the source. Line input is just not the same as with my old dependable Rotel, but I'm feeding that into Sonic Frontiers tube amp and preamp in my listening room. But for my purpose in the computer room this set up is great.
Future considerations would include a Fostex or similar full range speakers with an open baffle set up. Also an O2 headphone amp (kit) from JDS Labs to replace the cMoy.
Anyway, I'm very happy, except that I need more to do.
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Easy?
As you change the bias, the temp of the the heat sink changes. As the heat changes the the bias voltage changes. So it just takes time to wait for the change to hit the heat sinks. As the the temp of the sinks goes up the measured voltage goes down. But it takes time to stabilize. About an hour or so. I was lucky, it just worked out that the settings happened to be almost right on. I may go back and get that 10.1 a little closer to 10.01.
But hey it sounds good so WTF. I'll leave it.
Ido that a question...
I have a stash of black gate caps... And I'm wondering if they would be happy I this amp?
That first cap in the signal path... 10 mikes at 25 or so volts... I wonder if it would be better if it were a non polarized cap... One of those little red black gates???
Phil
K5SSR
As you change the bias, the temp of the the heat sink changes. As the heat changes the the bias voltage changes. So it just takes time to wait for the change to hit the heat sinks. As the the temp of the sinks goes up the measured voltage goes down. But it takes time to stabilize. About an hour or so. I was lucky, it just worked out that the settings happened to be almost right on. I may go back and get that 10.1 a little closer to 10.01.
But hey it sounds good so WTF. I'll leave it.
Ido that a question...
I have a stash of black gate caps... And I'm wondering if they would be happy I this amp?
That first cap in the signal path... 10 mikes at 25 or so volts... I wonder if it would be better if it were a non polarized cap... One of those little red black gates???
Phil
K5SSR
My friend received cab after Powder coating in Red:
how does it look Faceplate and footers are still pending.
Regards,
Sachin
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
how does it look
Faceplate and footers are still pending.Regards,
Sachin
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Three comments.
Nelson says that the Elna Silmics sound very good, better than some film caps. Feel free to experiment.
The distortion changes as you adjust the bias voltage, not so much at 1kHz but more pronounced at 10kHz. If one channel sound brighter than the other, try tweeking the bias.
There could be a latchup mode that you can get into when you first adjust the bias. Two builders have reported that the bias got to about 5V and they couldn't adjust it any higher. I'm not sure what causes it, but it might be wise to center the pot before you apply power. I think without a speaker connected, positive voltage comes through the feedback loop (as C1 charges through R4) that reverse biases C3 which leaks to the gate of Q4. Has anyone eles experienced this?
Nelson says that the Elna Silmics sound very good, better than some film caps. Feel free to experiment.
The distortion changes as you adjust the bias voltage, not so much at 1kHz but more pronounced at 10kHz. If one channel sound brighter than the other, try tweeking the bias.
There could be a latchup mode that you can get into when you first adjust the bias. Two builders have reported that the bias got to about 5V and they couldn't adjust it any higher. I'm not sure what causes it, but it might be wise to center the pot before you apply power. I think without a speaker connected, positive voltage comes through the feedback loop (as C1 charges through R4) that reverse biases C3 which leaks to the gate of Q4. Has anyone eles experienced this?
Don't let an opportunity like that go to waste, try it.
Another worth trying is putting a few Elna Silmics in parallel at the output to replace the Panasonic one, and while your at it get yourself a 10uF polypropylene cap and shove that in parallel as well with the simics.
Try everything.
First post in this thread. Just got my ACA kits yesterday and will be using them with a bottlehead Quickie for a minimalist living room background music system with a pair of blumenstein Orca speakers. Is there a good or non-harmful way to increase the input impedance as the quickie is either 2k or 4k output impedance depending on configuration and 10k may be pushing it a bit.
Thanks,
Jim
b
Thanks,
Jim
b
Jim,
We had the B'head quicky hooked up to the ACA in the Deforest room at the BAfest last Sunday. The combo worked well and couldn't hear any strain or thinness that might have been associated with a pre-out/amp-in impedance mismatch.
I think the two together will work well for your purposes. The only issue (or non-issue as the case may be) is that the quicky either has a lot of gain or could use a higher impedance attenuator to better dail-in volume; it played loudly with quicky's volume dail about an eighth around.
Mario
We had the B'head quicky hooked up to the ACA in the Deforest room at the BAfest last Sunday. The combo worked well and couldn't hear any strain or thinness that might have been associated with a pre-out/amp-in impedance mismatch.
I think the two together will work well for your purposes. The only issue (or non-issue as the case may be) is that the quicky either has a lot of gain or could use a higher impedance attenuator to better dail-in volume; it played loudly with quicky's volume dail about an eighth around.
Mario