Craig Sawyers Posted September 22, 2016 Report Share Posted September 22, 2016 I agree with just about all that. At one stage you could buy thick rectangular washers the same size as a TO220 tab to spread the pressure, but they have not been available for years. I tried M3 PEEK screws on my build, but was unhappy with the very low torque necessary to strip the threads. In the end I used a combination of ceramic insulators (as specified by Kevin) and the really long insulating bushes, and stainless cap screws, nuts and Belville washers. My T2 was one of the first batch made, with casework supplied by Kevin, and I have had zero thermal problems. 1 Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted September 22, 2016 Report Share Posted September 22, 2016 1 hour ago, Craig Sawyers said: I agree with just about all that. At one stage you could buy thick rectangular washers the same size as a TO220 tab to spread the pressure, but they have not been available for years. I tried M3 PEEK screws on my build, but was unhappy with the very low torque necessary to strip the threads. In the end I used a combination of ceramic insulators (as specified by Kevin) and the really long insulating bushes, and stainless cap screws, nuts and Belville washers. My T2 was one of the first batch made, with casework supplied by Kevin, and I have had zero thermal problems. Craig, what size belville washer did you use? And did you have the b- washer just sitting on the insulating bush or did you use them on the other side (which would seem to defeat the purpose of the b-washer)? Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted September 22, 2016 Report Share Posted September 22, 2016 I just followed the recipies in this http://www.onsemi.com/pub_link/Collateral/AN1040-D.PDF . Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted September 22, 2016 Report Share Posted September 22, 2016 Thanks, Craig, I see. So from the underside then. And am I seeing this correctly, that the flared part of the washer faces the nut and not the board? Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted September 22, 2016 Report Share Posted September 22, 2016 The flared part of the washer faces a plain washer, and does not bear directly on the board. Do you notice the "rectangular steel washer"? Unless someone has an obscure source, these are unobtainium. Quote Link to comment Share on other sites More sharing options...
Pars Posted September 23, 2016 Report Share Posted September 23, 2016 Like these? Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted September 23, 2016 Report Share Posted September 23, 2016 Well spotted. But then I saw the price for one that would do a TO220 https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5729-9-4 Quote Link to comment Share on other sites More sharing options...
Kerry Posted September 23, 2016 Report Share Posted September 23, 2016 At qty 5,000 they go to $0.058 a piece. If you split that five ways, that's about $60 per 1,000. Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted September 23, 2016 Report Share Posted September 23, 2016 First of all, check that part is correct for a TO220 package - I didn't spend a vast amount of time verifying it was the right size. Quote Link to comment Share on other sites More sharing options...
Kerry Posted September 23, 2016 Report Share Posted September 23, 2016 I was more looking for fun, but yes if anyone was thinking of moving forward the part should be confirmed. Quote Link to comment Share on other sites More sharing options...
Pars Posted September 24, 2016 Report Share Posted September 24, 2016 On 9/23/2016 at 1:21 AM, Craig Sawyers said: Well spotted. But then I saw the price for one that would do a TO220 https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5729-9-4 Yeah, I hadn't looked at that. Isn't it $2.26 for a package of 100 Guess not... Quote Link to comment Share on other sites More sharing options...
s_r Posted October 5, 2016 Report Share Posted October 5, 2016 So I had another member borrow my T2 to take a look at it. But I was told that the noise is around the normal level for this amp. Am I just the only asshole that finds an audible noise floor to be a dealbreaker? Or are there T2s out there that are actually dead silent (even in a room with no background noise)? Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted October 5, 2016 Report Share Posted October 5, 2016 I could be going deaf (not outside the realms of possibility) but my T2, either through 007's or a 1980's pair of original low bias Lambdas is absolutely silent. Quote Link to comment Share on other sites More sharing options...
s_r Posted October 5, 2016 Report Share Posted October 5, 2016 Is there some meaningful way to measure the noise at the output with a scope? To compare what I measure with other T2s would probably answer the question. Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted October 5, 2016 Report Share Posted October 5, 2016 Yes I can do that. They key is to measure over that audio bandwidth and the A-weight it. I'll give that a bash tomorrow. Quote Link to comment Share on other sites More sharing options...
blubliss Posted October 6, 2016 Report Share Posted October 6, 2016 Mine is very quiet after using the battery adjustment method Craig articulated in this thread. Before that the amp had some consistent background noise which was livable but noticeable. Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted October 6, 2016 Report Share Posted October 6, 2016 22 hours ago, s_r said: So I had another member borrow my T2 to take a look at it. But I was told that the noise is around the normal level for this amp. Am I just the only asshole that finds an audible noise floor to be a dealbreaker? Or are there T2s out there that are actually dead silent (even in a room with no background noise)? I have never heard a stat amp where you couldn't tell if it was turned on or off - ie every one, where it is absolutely silent, will give some extremely light background noise - whether it was a Stax, Mjolnir kgsshv, t2 or carbon. The difference is barely perceptible, but is easier to detect if you place your hands over your headphone cups. Like Andy, my experience with the T2 is that it is extremely quiet. The Carbon is a touch more quiet, but not significantly so. Quote Link to comment Share on other sites More sharing options...
s_r Posted October 6, 2016 Report Share Posted October 6, 2016 (edited) 5 hours ago, Craig Sawyers said: Yes I can do that. They key is to measure over that audio bandwidth and the A-weight it. I'll give that a bash tomorrow. Thanks, I should ask if it'd be something I could repeat with my rigol DS1054Z though. 2 hours ago, blubliss said: Mine is very quiet after using the battery adjustment method Craig articulated in this thread. Before that the amp had some consistent background noise which was livable but noticeable. I tried a while ago to adjust the battery to see if it would have any effect on the noise. It'd sooner go out of whack than change the noise. Unless there's something I'm missing I'm not sure that's the solution. 1 hour ago, GeorgeP said: I have never heard a stat amp where you couldn't tell if it was turned on or off - ie every one, where it is absolutely silent, will give some extremely light background noise - whether it was a Stax, Mjolnir kgsshv, t2 or carbon. The difference is barely perceptible, but is easier to detect if you place your hands over your headphone cups. Like Andy, my experience with the T2 is that it is extremely quiet. The Carbon is a touch more quiet, but not significantly so. Right, thanks for clarifying. Without another T2 to compare to it's hard to say whether the noise on mine is higher than what's normal. All I can say is that it's high enough to bother me. Edited October 6, 2016 by s_r Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted October 6, 2016 Report Share Posted October 6, 2016 Looking at the spec for the Rigol, you have a choice of 50MHz or a bandwidth limit of 20MHz. Since the noise voltage goes as the square root of the bandwidth, and assuming you have selected 20MHz bandwidth the noise voltage you measure will be 32 times higher than you would get for a 20kHz audio bandwidth. A-weighting applies a correction for the way the ear's sensitivity changes with frequency for quiet sounds. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted October 6, 2016 Report Share Posted October 6, 2016 I consider my T2 to be absolutely silent. I can't hear any noise, might be because my old ears though. 1 Quote Link to comment Share on other sites More sharing options...
blubliss Posted October 6, 2016 Report Share Posted October 6, 2016 (edited) @s_r Did you try that specific adjustment method I mentioned? From Kerry: 6.55V at 22k resistor using 10k pots while keeping 2k centered, then fine tune with 2k. It is different from the original adjustment methods. I do remember having the experience you mentioned, of the adjustments doing nothing for the noise, until I used this other method. Edited October 6, 2016 by blubliss Quote Link to comment Share on other sites More sharing options...
s_r Posted October 7, 2016 Report Share Posted October 7, 2016 I think that's how I did it the first time. Just in case I did it that way just now, but no change in the result. Quote Link to comment Share on other sites More sharing options...
hfhimeka Posted October 17, 2016 Report Share Posted October 17, 2016 Today, my DIY T2 has successfully come to life! After a year on and off working on this amp on my kitchen table, I was able to power up today and get music playing. All 4 batteries are sitting around 743V. The +/- voltages for each channel are surprisingly well balanced, and both L and R sit about +10V offset at power-on and gradually get down to about 2-4V offset at steady state. I measured the heatsink temperature -- looks like it's steady at 124F/51C after about 3 hours continuous burn-in. A shoutout to GeorgeP for enabling this build--one of my good buddies helped me reached out to you about a year ago for the case/amp board/torroid set. Thanks KG, Spritzer, and everyone else who posted all the useful information on every aspect of the amp on this thread. I learned a lot through the process of building this amp! One interesting thing I found while testing the PSU was that when I had both HV toroids hooked up and powered, the combined inrush blew through my 3.15A slow blow fuse (at 120VAC from the wall). I take it that the inrush of the 2x HV toroids (at least on my toroids) are pulling closer, but not quite, to 4A, since I was able to power up one HV toroid with a 2A fuse that I had left over. I have a 5A slow blow in there now, and so far no issues! -Kuen 16 Quote Link to comment Share on other sites More sharing options...
chinsettawong Posted October 17, 2016 Report Share Posted October 17, 2016 Congratulations! Quote Link to comment Share on other sites More sharing options...
Kerry Posted October 17, 2016 Report Share Posted October 17, 2016 Well done. Congrats and enjoy! Quote Link to comment Share on other sites More sharing options...
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