Anyone have any idea how hot the 2SJ313 and 2SK2013 should run?
I have looked at the data sheet and I see there is a graph with temperatures up to 140deg C but there is no indication of optimal temp. The ones in the amp are running at about 60deg C maybe more which seems a little hot!
Maybe I need to chill again
I have looked at the data sheet and I see there is a graph with temperatures up to 140deg C but there is no indication of optimal temp. The ones in the amp are running at about 60deg C maybe more which seems a little hot!
Maybe I need to chill again
Are your heatsinks at least as large as the ones in the picture?
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O.K. I think I'm ready to bump the bias a bit. The temps in the picture have been consistent all week. I used two different RF temp guns and there is ~ 1 or 2 degrees fudge. The output devices were read at the junction of the center pin and the casing.
The left side is hotter, but I haven't installed the copper or stainless mesh inside the water-box yet. Also going to do a full thermal pad replacement with Andrew's 1 mil mica this weekend. I bought 24 Thermalsil pads also, but want to try it "old school" for the experience
So my question to the experts/veterans is how much room do I have to play with, and what value resistors are recommended. If there are any FE or bias adjustments to consider - that would also be appreciated. I haven't tried the P3 adjustments in the article as I'm under the impression a distortion analyzer is required. If that's something I can detect with my ears I'm willing to give it a go. Again, I'm not looking for more power/SPL - just thinking about the lower distortion that comes from higher bias. I don't hear distortion now, but it may be one of those "You don't know what you got till it's gone" things. Opinions welcomed.
BTW, this thing really sounds good. Over the past week is has warmed up quit a bit and the stage is enormous and very detailed. The extra two output boards don't make significantly more power - but the sound is really full and colorful (in a good way). Those giant bass drums in the orchestra are fully resonant yet controlled. There is more sparkle and brilliance on the top end than I expected.
Haven't placed the order for the new Mundorf AG 33,000 or 47,000 uF caps yet. They made a big difference on the MyRef amps but I need some confirmation that those would be a worthwhile upgrade for the BA-3. I'm using 27,000 Panas now.
What say ye all?
The left side is hotter, but I haven't installed the copper or stainless mesh inside the water-box yet. Also going to do a full thermal pad replacement with Andrew's 1 mil mica this weekend. I bought 24 Thermalsil pads also, but want to try it "old school" for the experience
So my question to the experts/veterans is how much room do I have to play with, and what value resistors are recommended. If there are any FE or bias adjustments to consider - that would also be appreciated. I haven't tried the P3 adjustments in the article as I'm under the impression a distortion analyzer is required. If that's something I can detect with my ears I'm willing to give it a go. Again, I'm not looking for more power/SPL - just thinking about the lower distortion that comes from higher bias. I don't hear distortion now, but it may be one of those "You don't know what you got till it's gone" things. Opinions welcomed.
BTW, this thing really sounds good. Over the past week is has warmed up quit a bit and the stage is enormous and very detailed. The extra two output boards don't make significantly more power - but the sound is really full and colorful (in a good way). Those giant bass drums in the orchestra are fully resonant yet controlled. There is more sparkle and brilliance on the top end than I expected.
Haven't placed the order for the new Mundorf AG 33,000 or 47,000 uF caps yet. They made a big difference on the MyRef amps but I need some confirmation that those would be a worthwhile upgrade for the BA-3. I'm using 27,000 Panas now.
What say ye all?
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You could put two heatsinks back to back (then crank up the bias
)
How high have you taken the bias?
I upped the bias on the power boards to 400mV today and ran it for a while and was most impressed by the way the heatsinks handled the pressure. These are the 165mm x 400mm from MODU in Italy. They are comfortably warm and nowhere near the hand-on-for-ten-seconds level. So I reckon they would be very comfortable at 500mV but I'll probably leave them like this at present. They sound great. Fiddled with P3 until they sounded 'airy'. Thumbs up then for the big heatsinks from Italy.
I almost forgot to mention that the power supply is reading 0.317v across the C-R-C resistors which are two 0.5ohm in parallel (on one rail).
I almost forgot to mention that the power supply is reading 0.317v across the C-R-C resistors which are two 0.5ohm in parallel (on one rail).
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Can you confirm that the process was simply reducing the size of the resistors, and what value did you use? Any other adjustments needed?
They produce the chassis for the diyaudio store but if you are in Europe best to order direct from them. However, good idea to use the specs provided by the diyaudio store when ordering because you will then get the heatsinks drilled and tapped for the mosfets on the power board and the back plate ready for speaker posts and mains sockets etc. Also the base plate in the amp chassis that I got doesn't align with the holes in the pcb modules but they now have one that addresses this issue. None of these things is that important it just means you spend a bit longer away from your nearest and dearest. Can be good can be bad!
I couldn't explain it better than Nelson does in his build instructions.
Thanks, Just wanted to make sure I wasn't missing any secret tips and tricks.
This paragraph in the B-1 Buffer article caught my eye:
"At the moment I’m driving a pair of Lowther DX55’s with some passive baffle-step correction (6 dB loss there) and an F3 amp with only 12.5 dB voltage gain. The preamp is fed by an Xono phono stage with a low output cartridge (Grado Statement).
The sound is extremely neutral without being clinical - just about what you were looking for when you were thinking about a passive preamp. A teensy bit of second harmonic and no noise at all.
There’s just enough gain. If you were using any other power amp, you’d get 8 to 18 dB more gain, and would be able to break your lease or the speaker, or both."
The 8 to 18 db more gain is what I'm curious about. Anyone want to take a guess, or provide a formula that can predict how that would translate to the BA-3 when compared to the F3 Mr. Pass was using ?
"At the moment I’m driving a pair of Lowther DX55’s with some passive baffle-step correction (6 dB loss there) and an F3 amp with only 12.5 dB voltage gain. The preamp is fed by an Xono phono stage with a low output cartridge (Grado Statement).
The sound is extremely neutral without being clinical - just about what you were looking for when you were thinking about a passive preamp. A teensy bit of second harmonic and no noise at all.
There’s just enough gain. If you were using any other power amp, you’d get 8 to 18 dB more gain, and would be able to break your lease or the speaker, or both."
The 8 to 18 db more gain is what I'm curious about. Anyone want to take a guess, or provide a formula that can predict how that would translate to the BA-3 when compared to the F3 Mr. Pass was using ?
I think what he is saying is that 12.5db is a very low voltage gain and a typical amp will have 20 - 30db of voltage gain.
The B1 is a buffer so what comes in is what comes out (voltage wise) so with a low gain amp (perhaps designed to work with a preamp with gain) you might not get enough volume to shake the rafters.
As the BA3 has 30db of gain by default it should be absolutely fine with a B1. As I posted earlier I'm looking at dropping it to 20db which I think should be adequate and I will effectively be using a B1 with it. I say effectively because there will also be active filters in the circuit.
Tony.
The B1 is a buffer so what comes in is what comes out (voltage wise) so with a low gain amp (perhaps designed to work with a preamp with gain) you might not get enough volume to shake the rafters.
As the BA3 has 30db of gain by default it should be absolutely fine with a B1. As I posted earlier I'm looking at dropping it to 20db which I think should be adequate and I will effectively be using a B1 with it. I say effectively because there will also be active filters in the circuit.
Tony.