Wayne's BA 2018 linestage

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Mark Johnson

Mark Johnson

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Joined 2011
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FYI, Mouser finally shipped me the KSA1220AYS parts today, which I ordered back in December. (It is the PNP transistor in the higher power TO126 package, that Wayne suggests for driving difficult loads). Let's hope this means they will now be in stock and on the shelf at Mouser.
 
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Russellc

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Joined 2003
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xrk971 said:
The Edcor’s impedance is 600ohms and the offset on the WBA18 can be as high as 200mV to 300mV when first turned on an warming up. 300mV/600ohm = 0.5mA. Is a 0.5mA current enough to magnetize the Edcor’s core? Safest thing to do is figure out how you can sneak a coupling cap in there. Either cut the trace on the main M2X PCB and add a cap. Or cut the trace on WBA18 beyween ouriur and boot hole and add a cap. I think you have more room on the M2X mainboard.
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One member here uses the linestage (Wayne's) with the edcors on the outputs to raise gain for his F4. He hasn't written about any problems in regard.

The initial DC offset made me wonder about effects on the Edcors generally (I also have a Teabag board M2) and was told by knowing members here that it wasn't a problem. Still makes me a touch uncomfortable. Could install caps on outputs, bought some silmics but not installed.


Russellc
 
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manniraj

Member
Joined 2012
I populated the boards and those SMD mosfets with the help of one of my friends :)

One question regarding the trimmer position, I brought the part as per the published BOM from mouser but then I also see that the position has 680R marked. So I believe either the trimmer or the 680R resistor needs to be soldered correct and not both?

Thanks
 
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manniraj

Member
Joined 2012
manniraj said:
I populated the boards and those SMD mosfets with the help of one of my friends :)

One question regarding the trimmer position, I brought the part as per the published BOM from mouser but then I also see that the position has 680R marked. So I believe either the trimmer or the 680R resistor needs to be soldered correct and not both?

Thanks
Click to expand...

Can someone please confirm before I power it up as I did not find any mention of this in the documentation.

Thanks
 
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gary s

Member
Joined 2002
Refer to schematic in post #1, it shows R6 as being a 1k5 resistor in parallel with trimmer P1 at 5k ohm. The marking is wrong for the resistor value.

Also post # 69 from 6L6 (Jim) refers also to the resistor R6 as being 1k5.

So you use both the resistor soldered to the rear of the board with a 25 turn 5k trimmer pot - use a good quality pot (Bourns /Vishay Spectrol) and not a generic no name Chinese made pot.
 
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manniraj

Member
Joined 2012
gary s said:
Refer to schematic in post #1, it shows R6 as being a 1k5 resistor in parallel with trimmer P1 at 5k ohm. The marking is wrong for the resistor value.

Also post # 69 from 6L6 (Jim) refers also to the resistor R6 as being 1k5.

So you use both the resistor soldered to the rear of the board with a 25 turn 5k trimmer pot - use a good quality pot (Bourns /Vishay Spectrol) and not a generic no name Chinese made pot.
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Thanks Gary, yes I got a bourns one as per the BOM from Mouser. Will solder a 1.5k resistor underneath the board. I am planning to power it up with my existing Salas Ultra BiB 1.3 boards with +/-18 to 20v as I am going to reuse these boards from my DCG3 preamp.
 
Mark Johnson

Mark Johnson

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Joined 2011
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FYI, Wayne's original choices for the higher power transistor option (KSC2690AY and KSA1220AY) are now in stock at several distributors. It might be wise to buy a few tubes of them now, while they're easily available.

_
 

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chede

chede

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Joined 2016
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From what I read in the thread, the original transistors are perfect for line stage duties.

I have only built the preamp with higher-power transistors, so can't comment on sonic benefits ... I have put the transistors in sockets now, and also the resistors that would needed to be changed for putting in the smaller transistors, so I could try one day ...:D

Jim (6L6) may be able to comment, as he has built both versions ;).

I did have in my first iteration 2SA1220A / 2SC2690A from Inchange Semi in my preamp, and did change them to the Toshibas when they got pointed out in this thread by Patrick (EUVL).
Not sure if there was a real difference soundwise, maybe the preamp is a bit smoother and more engaging sounding with the Toshibas, but that could be imagination ...:p

Best regards,
Claas
 
6L6

6L6

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The intent of the larger (TO-126 package) output transistors was to give effortless power for headphones. It also happens to sound outstanding in line stage duties.

I have built it with the TO-92 outputs and with the A1220/C2690, and both versions sound wonderful. Build it in which ever configuration appeals to you, you will be very happy with the results. :yes:
 
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Centurion53

Member
Joined 2018
6L6 said:
The intent of the larger (TO-126 package) output transistors was to give effortless power for headphones. It also happens to sound outstanding in line stage duties.

I have built it with the TO-92 outputs and with the A1220/C2690, and both versions sound wonderful. Build it in which ever configuration appeals to you, you will be very happy with the results. :yes:
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6L6

I have completed my line amp with the boards that you sent me back in the spring but have not had a chance to fire them up as I have been working about 80 hours a week this summer. :( However, that is over and I should be getting a chance to try them out as soon as I get the power supply board done. My question is, there was mention earlier in this thread that there would be boards available for this preamp through the diyaudio store. Do you know if this is still going to happen, I would like to build another one down the road.
 
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