MH Diamond Buffer Output Transistors
Mar 13, 2006 at 6:55 PM Thread Starter Post #1 of 24

abcheng

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I'm about to build my diamond buffers for a MH, and I saw this output transistor on the webpage:

2SC 2238 y 2SA 968 y 160 1.5 100 neutral and balanced sound, tight bass. detailed and clear highs without being bright, easy to listen to
excellent choice but note reversed pinout!

Where can I order these and which one ( 2SC 2238 y / 2SA 968 y) should I order for Q8 and Q9?
 
Mar 13, 2006 at 7:33 PM Post #2 of 24

Clutz

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Quote:

Originally Posted by abcheng
I'm about to build my diamond buffers for a MH, and I saw this output transistor on the webpage:

2SC 2238 y 2SA 968 y 160 1.5 100 neutral and balanced sound, tight bass. detailed and clear highs without being bright, easy to listen to
excellent choice but note reversed pinout!

Where can I order these and which one ( 2SC 2238 y / 2SA 968 y) should I order for Q8 and Q9?



Both of those transistors are difficult to find in North America. I ordered them through a friend in Germany. Further, you need both the four 2SC 2238Y and four 2SA 968Y transistors for each diamond buffer.

Cheers,
Clutz
 
Mar 14, 2006 at 12:53 AM Post #4 of 24

abcheng

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I think i'll just stick with the MJE243 and MJE253. The problem is, the MJE243 output transistors are only sold in quantities of 2000 :/. Are there any other output transistors anyone can recommend me that can be purchased through digikey or mouser? Also, speaking of buffers, where can I purchase BUF634s? Digikey and mouser are out of them.
 
Mar 14, 2006 at 1:18 AM Post #5 of 24

[AK]Zip

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Quote:

Originally Posted by abcheng
I think i'll just stick with the MJE243 and MJE253. The problem is, the MJE243 output transistors are only sold in quantities of 2000 :/. Are there any other output transistors anyone can recommend me that can be purchased through digikey or mouser? Also, speaking of buffers, where can I purchase BUF634s? Digikey and mouser are out of them.


http://www.alliedelec.com/Default.asp

They sell the MJE243 and MJE253. As for the buffers; I have 2 I can sell you. PM me if you want them.

-Alex-
 
Mar 14, 2006 at 3:29 AM Post #6 of 24

abcheng

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So I won't be able to get MJE253 transistors or something similar to it from digikey from mouser right? If so, that sucks
frown.gif
.
 
Mar 17, 2006 at 7:01 AM Post #9 of 24

abcheng

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I noticed on the Diamond buffer webpage that Q8, Q9, along with R8, and R9 are optional. Is there a negative effect if I don't use these parts? I don't really want to order from Allied or RS Online unless they have no minimum order and cheap shipping.

Any thoughts?
 
Mar 17, 2006 at 9:21 AM Post #10 of 24

steinchen

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Quote:

Originally Posted by abcheng
I noticed on the Diamond buffer webpage that Q8, Q9, along with R8, and R9 are optional. Is there a negative effect if I don't use these parts? I don't really want to order from Allied or RS Online unless they have no minimum order and cheap shipping.


the parallel stages Q8b and Q9b are optional, not the whole output stage!
 
Mar 17, 2006 at 2:35 PM Post #11 of 24

NeilR

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Quote:

Originally Posted by steinchen
the parallel stages Q8b and Q9b are optional, not the whole output stage!


Hi steinchen,

I'm curious about something.... the PPA, for example, is a pretty "high end" amp and it is using the identical diamond buffer, except with only one complimentary pair of output transistors. I am just curious what led you to pack two pairs onto the boards and what differences you have heard. I am not trying to save a dollar; just very curious about the technical issues related to these output buffers. I think it is cool that you packed a pairin there
k1000smile.gif


Regards,
Neil
 
Mar 17, 2006 at 2:56 PM Post #12 of 24

n_maher

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Neil,

Certain things just were not possible on the PPA given the space available, that board is literally PACKED with components. I think that Steinchen has commented a bit on the sound of the MH buffers w/ 1 vs. 2 in the past but I can't find it right now. My recollection is that it improved sonics slightly. For the $2 that the add'l trannies cost I figured why not
smily_headphones1.gif
. Then again my output caps (C7) each cost more than the diamond buffers so clearly I have issues
evil_smiley.gif
.

Nate
 
Mar 17, 2006 at 3:16 PM Post #13 of 24

NeilR

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Nate- let me get this straight. The PPA board is 6.3"x 4". The Millet dDB board is about the size of my thumb. There was room on the dDB for two sets but only room for one on the PPA?
evil_smiley.gif


(You don't have to explain- I doubt that the pack job that Steinchen and crew did would be acceptable to Tangent & Crew. I just couldn't resist).

I have a rainy day project lined up to make a Millet dDB with only one buffer, just to compare and satisfy my own curiosity. This is the cool thing about DIY. We learn so much that we could never do with commercial gear. I think these dDB's are a great and cheap way to experiment with a complex discrete output circuit, which is why I loaded up on the boards.

I noticed that Mouser carries the BD139/BD140 output transistors. I might throw a set or two on my next order. I think someone here was asking about a US source for those. I think Steinchen favored the BD137/BD138 transistors. I for one would like to experiment with those "European flavors". Maybe someone "over there" would like to arrange a package that could be sent here and redistributed locally. I wouldn't mind doing that; a pretty simple mailing process.
 
Mar 17, 2006 at 5:53 PM Post #14 of 24

n_maher

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Quote:

Originally Posted by NeilR
Nate- let me get this straight. The PPA board is 6.3"x 4". The Millet dDB board is about the size of my thumb. There was room on the dDB for two sets but only room for one on the PPA?
evil_smiley.gif



SMD vs. thru-hole I think makes up for the difference
smily_headphones1.gif
.

Quote:

I have a rainy day project lined up to make a Millet dDB with only one buffer, just to compare and satisfy my own curiosity. This is the cool thing about DIY. We learn so much that we could never do with commercial gear. I think these dDB's are a great and cheap way to experiment with a complex discrete output circuit, which is why I loaded up on the boards.


I had thought of doing this as well but then decided that I just don't care enough to go through the permutations like that. Working with the information I already have (having tested fully populated DBs) I know they sound good like that and are still cost acceptable (to me). But I'd certainly be interested to hear what you have to say on the subject the next time it rains.

Nate
 
Mar 17, 2006 at 6:53 PM Post #15 of 24

ppl

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I am Glad you guys are having fun at this. The parallel output transistors will give more current gain under load as the Hfe starts to fall above 200 mA on the MJE and something like 30 or 40 mA on the BD types so doubling up the output stage should give more punch and better defined Bass. Now just add another Predriver stage for a three stage output buffer and get some real drive plus seriously rise the Buffers input impedance and Reduce input Bias current under load
 

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