my first solid project, discrete WJ/diamond buffer

[digi01]

my first solid project,discrete WJ buffer

hi all,I am new here.
this is my first try at solid based design.I build this buffer for replacement buffer IC, eg.BUF634.the buffer is biased in CLASS A,purpose for generic use.
thanks sijosae(headwize.com member,diy headphone amp master) for archetype try out,url at here.

original article at here,(Walt Jung's buffer)
LINK

cheers
Zang

 

[digi01]

sch,any suggestions?

 

[f.k.l.chan]

Hi digi01

How does it sound compare with the BUF634?

 

[maxw]

Hi digi01

How does it sound compare with the BUF634?

and will it drive the same load?

 

[peranders]

First, Zang, if you draw the schematic like everyone else it's easier to read but you have maybe used some software with limited drawing area?

Strive to have power supply a the top and then potentials get lower vertically. Compare Walt's original schematic or mine or anyone's....

A diamond buffer is pretty simple to get working but beware of that this discrete buffer is probably not as good as BUF634. Why? The BUF634 uses GHz transistors probably and they are matched since it's a monolithic device. The current capability is probably not an inssue either.... but it's fun to do something of your own, sure.

I'll guess you already have seen my diamond buffer and also Glassman's?

Notice that both my and Glassman's buffer have something extra to offer. In both cases it's more output power and more current.

If you are after copying sijosae's artwork, ask him first if he do mind.

 

[Upupa Epops]

VJ's based buffer give better sonic results than 634, but not with this working points ( iddle current ). Current must be higher ( class A ref. to lower load ), so output transistors must be types with higher Pc , for example BD 139/ 140.

 

[X.G.]

sch,any suggestions?

The sch have a mistake,I.E.,the CCS (of LED and tr) is wrong

 

[peranders]

Indeed, that's the drawback of making "odd" schematics. So Zang, the how the LED's should be connected.

 

[digi01]

First, Zang, if you draw the schematic like everyone else it's easier to read but you have maybe used some software with limited drawing area?

thank you P-A,I draw the sch via protel basis on mine understanding of Wj buffer.I think it is clear,but...who knows this is my first draw a sch file use protel.

The sch have a mistake,I.E.,the CCS (of LED and tr) is wrong.

thank you X.G. there are two wrong route of ccs.I have revised it.new file attached,PDF version.

A diamond buffer is pretty simple to get working but beware of that this discrete buffer is probably not as good as BUF634. Why? The BUF634 uses GHz transistors probably and they are matched since it's a monolithic device. The current capability is probably not an inssue either.... but it's fun to do something of your own, sure.

really,those transistor must be fine mached.I have do it.infact,the buffer that I assembled nothing special.
there are some different to BUF634:
1, buf634 is biased in classAB,with output current limit and bandwidth limit
2,the inner circuit of buf634 is un-adjustable,mine has a number of options.
3,mine is rough compare with factory IC but more fun.

I'll guess you already have seen my diamond buffer and also Glassman's?

yes,I am happy to surf net and search information that I'm interested.

If you are after copying sijosae's artwork, ask him first if he do mind.

I have ask for some ideas and experiences from sijosae before,he is my teacher and good friend.

so output transistors must be types with higher Pc , for example BD 139/ 140.

I use Mhz small power transistor(1A,0.9W)

 

[digi01]

Hi digi01

How does it sound compare with the BUF634?

and will it drive the same load?

I will build another opa637 plus buffer amp for test,I am very glad to compare with the BUF634.Wish it can over...

Z

 

[f.k.l.chan]

I am quite worry the DC offset, since need match all the LEDs and Tr.

 

[peranders]

You only have to worry about offset if you have a high impedance signal source and/or don't use feedback.

 

[peranders]

I use Mhz small power transistor(1A,0.9W)

If you make you pcb equally tight as sijosae's be prepared that the maximum power dissipation willl be 0.6-1 W. When you place parts so tight the cooling won't get so good.

 

[peranders]

Zang, your latest pdf is blank here.

 

[digi01]

Zang, your latest pdf is blank here.

Sorry,it includes GB2312 code,I can look it via my pc.

the screen copy attached,

 

[digi01]

If you make you pcb equally tight as sijosae's be prepared that the maximum power dissipation willl be 0.6-1 W. When you place parts so tight the cooling won't get so good.

Yes,the buffer getting hot.How did you deal with that?I have seen your buffer unit,it is hot too?

P.S.
mine board can mounting 0805 resistors,I think it could help me save some room for dissipation.ygpm

 

[peranders]

My solution is that I don't run it so hot

 

[digi01]

My solution is that I don't run it so hot

then run at low biased?non class A?I have a idea,,,have you try to stack the discrete buffer in order to get more curret output?

Z

 

[peranders]

Don't forget that class A is dependent of the load. If you have 1 kohm load and 5 mA class A you will get 5 V peak out in class A.

 

[LennyK]

Upupa - you mentioned BD139/140 - did you compare "our" popular European type transistors, like BC550 or BD139 to those 2scxxx toshiba ones ??

And my second question - did enybody compare sound or distortion of "diamond" buffer to "White" fet buffer??

regards

Lenny