Salas hotrodded blue DCB1 build - Page 103 - diyAudio
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Old 21st May 2011, 03:03 PM   #1021
AndrewT is offline AndrewT  Scotland
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irfp240/irfp9140 are a better matched pair than irfp240/irfp9240, if the lower 100Vds limit is acceptable.
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Old 22nd May 2011, 12:01 PM   #1022
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I finally got around to my dcb1.

I am using a Tent Labs relay volume control with TX2575 resistors and TX2575s in the B1 as well. I am very pleased with the sound. Pretty much everything that has already been said about this buffer I am in agreement with. I must also add that the Tent Labs relay volume control sounded very nice as well on it's own and the buffer helped with the low freq output, keeping the mid and highs unchanged.

I am using 5w 10 ohm resistors as per the 200ma hot rod specs, but am now considering the 600ma upgrade as there was no noticeable temp change after running for several hours. I am using the 12mm thick alu chassis as heatsinking and really could not detect any temp rise over 3 plus hours.

Got 1 and 1.2 ma of set. Will need to recheck this and all other voltages as.dmm battery died.

Brad
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Old 22nd May 2011, 12:50 PM   #1023
Salas is offline Salas  Greece
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Good. Since you got the sinking, its OK to hot-rod further. Pictures?
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Old 23rd May 2011, 08:41 AM   #1024
Siberia is offline Siberia  Lithuania
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I'm getting small-minded, I guess. And there are a couple of things I've unforseen.

After changing my 220Rs to Takman carbons and living happily thereafter for some time, as a beginning DIYer, of course, I couldn't sit still. I made changes again. Replaced an Alps pot to a cheaper DACT type one, just to see what it gives. It sounder more "veiled" and letting it play for a week or so improved things just a tiny bit.

So I thought, ok, maybe that's a resistors and pots combo, that is not working right. And as I had 4x TX2575s by hand, and read so many good reviews, I replaced takmans.

Now the sound got more transparent, but lean and rather bright. That is ok, as I should wait for these resistors to burn in and I could always check what they sound like with Alps pot.

But there's one thing that bothers me. How all this desoldering/soldering activity is affecting the board? It shouldn't do any good. And at one point I've got parranoid that maybe my joints are not that clean now, hence a rather bright sound.

Reading "..symmetrical psu b1.." thread I've found a recommendation for using this thing: 310-43-164-41-001000 Mill-Max IC & Component Sockets

I don't get 64 contacts thing. Shouldn't it be just 2 for resistors? Is it the same thing as this one: Farnell Export

All this pots and resistors trial is getting tiring. But I'm still considering LDR attenuator, hot rodding and final resistors ajusting.
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Old 23rd May 2011, 09:05 AM   #1025
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The pins can be removed from those 64 pin sockets and used individually. Also, hottrodding is recommended, LDR pot is good, but requires a lot of implementation as it needs a power supply all of it's own, perhaps a gimic really. Keep the TX2575s - they are simply better than carbon films - better to change the value to arrive at preferred sound, not technology!

I now have DCB1 blue (hotrodded) with good components and PRP resistors, Mezmerize channel switchers, R-core transformer, remote volume controlled LDR pot. All of this stuff to make a really well designed, tiny circuited, silver wired and low component pre-amp. Is it worth it? Probably...?!
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Old 23rd May 2011, 09:05 AM   #1026
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Hi siberia,
You could use those sockets until you find the ideal parts for your B1.
Word of advice, I've been there as deep as you are now and I didn't like Diy-ing at that moment, like a neverending story, not enjoyable at all. Maybe it's time to do something that hasn't anything to to with electronics, just to get some distance

Best wishes, Erik.
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Old 23rd May 2011, 11:33 AM   #1027
Siberia is offline Siberia  Lithuania
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Lucas & Erik that's encouraging! Thank you. I have no doubts about the design of this preamp. It has already so much more then I expected. And yes, you are right, I should keep TX2575s and a bit of distance to all this stuff. Then go get LDR pot and to see if anything's misssing. Uriahs suggestion was to use a LM317 to get 5V from DCB1's PSU.

I have only one pair of inputs at this time. Not sure if I want to add a swtich with all additional wiring and components. Although it could be useful as I use two sources.
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Old 23rd May 2011, 11:44 AM   #1028
weskoki is offline weskoki  Europe
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Siberia are you saying you prefer the alps pot?
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Old 23rd May 2011, 11:48 AM   #1029
Siberia is offline Siberia  Lithuania
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Let's say, there was configuration where ALPS fitted more.
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Old 23rd May 2011, 12:48 PM   #1030
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Quote:
Originally Posted by johnwmclean View Post
For a pure buffer only build (no volume pot) are there any considerations or additional parts I should use?
Quote:
Originally Posted by Salas View Post
No. As it is.
Thanks Salas, so there is no need to parallel 220k resistors with 20k underneath the board to get the input impedance within the desirable range?

I read this here:

http://www.diyaudio.com/forums/blogs...cb1-build.html
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