X-PRE musical fidelity preamp. need help modifying - diyAudio
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Old 25th August 2010, 07:39 PM   #1
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Default X-PRE musical fidelity preamp. need help modifying

Im in the process of modifying my MF X-PRE,
so far ive replaced all the capacitors and i need help for the next part.
Firstly, im not sure if there would be any definate improvement replacing the quad opamp, and if i can find the specs of it or it i can afford it.
Im also considering replacing all the diodes.

What i want to know is if anyone has this amp and has modified it, or is any good at finding out specifications for componants.
I need to find out what type of diode to get, there are 2 massive ones and I have no idea what to replace them with (aparently it makes a big difference though)

I will upload some pictures of the componants im unsure about and i would really appreciate it if someone could give me a hand identifying them
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Old 25th August 2010, 10:11 PM   #2
Arnulf is offline Arnulf  Europe
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Quote:
Originally Posted by 04mac View Post
Im in the process of modifying my MF X-PRE,
so far ive replaced all the capacitors and i need help for the next part.
Firstly, im not sure if there would be any definate improvement replacing the quad opamp, and if i can find the specs of it or it i can afford it.
Im also considering replacing all the diodes.
How about replacing all the resistors first ?
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mod verb, transitive /mod/ to state that one is utterly clueless about the operation of device to be "modded" and into "fixing" things that are not broken; "My new amplifier sounds great so I want to mod it."
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Old 25th August 2010, 10:46 PM   #3
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What you might think about is "what is the goal" and "how do I measure my progress towards that goal". A goal of making the Pre sound as good as it can be is reasonable, but wholesale replacement of parts is very unlikely to get you there. Try substituting whole sections of your system. This is much more likely to product quantatative changes that you can hear, and help descover how to get the most bang for your buck.
If we are going to lend helpfull advice we really need to know more about the entire system. Good Luck - Yea pics
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Old 25th August 2010, 10:50 PM   #4
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Is this the right one?
Attached Images
File Type: jpg xpre.jpg (15.5 KB, 232 views)
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Old 25th August 2010, 11:22 PM   #5
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Thanks for everyones help, i apologise for not uploading the pics in time.
To arnulf, ive established that for any difference in resistors i would have to go for audiophile standard carbon composite ones which for the improvement they would give, are a little out of my price range :P
and firecheif, thats the upgraded model. mines a little older than that:

http://is.gumtree.com/image/extrabig/17236840.jpg

il upload the pics in my next post in a sec
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Old 25th August 2010, 11:45 PM   #6
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Default here are the pics of my amp.

CIMG2438.jpg

CIMG2049.JPG

CIMG2439.JPG
Right. These 3 photos are taken during and after the modification. Iím going to go into more detail of what I did and plan to do so everyone has more of an idea of what I need help with.

I've replaced most major caps (all apart from a couple which haven't arrived in the post yet). This HAS made a noticeable difference. It will hopefully make a bigger difference when I get to replace the last few. I used the same capacitance with a higher voltage and a better brand name so hopefully better build. I also stuck to the same types of capacitors e.g. film caps or electrolytic.

Now Iíve been advised that as well as replacing caps, replacing the rectifier will make a good difference. This is where my first problem starts. In the circuit there are 6 small diodes and 4 triacs. One diode is for the LED and one is near the power source. That leaves 4 that are close and near a bunch of filters so Iím assuming this is the rectifier. Iím not entirely sure if I should replace the triacs, and what specs to use on them. Or if that will actually make a difference. so right now the plan for me is to order the 5 diodes (Iím not bothering with the LED one) and wait for some well educated genius to tell me what triode to get

All help is much appreciated guys
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Old 26th August 2010, 12:00 AM   #7
Arnulf is offline Arnulf  Europe
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You wouldn't happen to have schematic of this thing handy for us, would you ? It would show where those components are located so it would be easier to point out how they affect the output. I'm most curious about those 4 triacs you mentioned ... 2 I'd undertand (one per channel for a crappy chopper PSU) but four ?
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Old 26th August 2010, 12:07 AM   #8
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http://www.diyaudio.com/forums/attac...schematics.gif

http://img.photobucket.com/albums/v2...Schematics.gif

though these are actually the schematics for the x10, im 99% sure its the same circuitry inside.

if you can make any sense of this that would be great
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Old 26th August 2010, 12:16 AM   #9
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Default Triacs

Heres a birdseye view. The 4 triac are in plain sight. I may be wrong about them being triacs, but considering the smaller ones have 'tri' written by them and the bigger ones have the stereotypical triac look id doubt im wrong.
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File Type: jpg CIMG9624.JPG (192.2 KB, 220 views)
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Old 26th August 2010, 09:27 AM   #10
Arnulf is offline Arnulf  Europe
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Those are transistors, each pair constitutes a constant current source according to your schematic.

The bigger TO-220 thingies aren't shown in the schematic but print on the board implies that they are linear voltage regulators (probably one for each rail).
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