Wayne's BA 2018 linestage

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chede

chede

Member
Joined 2016
Paid Member
I'm now using my BA2018 preamp with an EL84 PP amp I am currently building.

I have a very slight noise (broadband noise / tube noise, not hum) through the speakers that is not there with the preamp switched off. It is barely audible with my ear at the driver, but still ... :p

Because my BA2018 linestage has bandwidth out to something like 2 MHz, I may try to limit the bandwidth to see if this lowers the noise.

In the BA2018, I'm using the Toshiba TTA004B / TTC004B as outputs, loaded through R11/R12 at 15R, referring to the schematic in post #1. I have put R23/C4 in already, and have 10 pF for the feedback cap C1. I guess I could restrict bandwidth at the preamp by raising the value of C1, any downside to that ?

Looking at it from the other side, there is probably an easy way to restrict input bandwidth on the EL84 poweramp in order to prevent RF ingress. I think I have seen some easy circuit trick to do so, but can't remember where. Could you point me to a simple way to prevent RF ingress in the power amp ?


Best regards,
Claas
 
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manniraj

Member
Joined 2012
I have my Salas Ultra BiB 1.3 PSU boards ready with the output voltage set at +/-20v for BA2018 preamp purple boards without the mounting holes. I have connected the 0 from both the positive and negative PSU boards together and from there taken couple of wires to connect to the GND of the BA2018 boards. Then 2 positive and 2 negative wires from PSU goes to the V+ and V- respectively on each BA2018 board. No inputs and outputs RCA jacks are connected to the BA2018 board as of now. Before powering up just wanted to make sure that my connections are fine especially the ground from psu to the BA2018.

Can someone please confirm on the connections and the voltage to be fine?

Thanks
 
M

manniraj

Member
Joined 2012
Now I am getting a weird issue. When I connect the psu via a small junction where I connected the wiring like = +ve, 0, -ve and the 0 here is joined from both the positive and negative boards. After connecting this to the small molex type junction and power up I measured exactly +20,0 and 0,-20v on the above wiring. From the other end of the molex junction when I connect to the Wayne's line stage which needs +,0,- wiring as (V+, Output GND, V-) and power up. The line stage is powered with the LED switching on but the positive psu board LEDs are not lighting and output DC shows 0.05v but the line stage is powered up.
And curiously when I switch off the mains the line stage LEDs goes off and then the positive psu board LED lights up and I get the voltage back and slowly gets switched off in some seconds.

I checked the shortage of the mosfets which look fine but whenever I connect to the line stage which actually is hanging in the air, so not mounted on the cabinet yet because the line stage does not have mounting holes. I have used double sided tape to mount it so that nothing touches the cabinet.




thanks
 
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manniraj

Member
Joined 2012
william2001 said:
What value do you have at R1 on the UltraBiB? I use 3.9 ohms there on my own build, pictures at post #672.
Click to expand...

I think you are right, I am using a 12R 2W carbon film resistor which Salas also pointed me out on the BiB thread :)

I will try and replace it with a spare 3.3R 3W resistor on R1 and test it out. Can you please point me out to what setup should I be doing once powering it up using the trimmer to set the offset. Or point me to the posts as the search on the thread does not show me the exact setup guidance.

Thanks again.
 
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manniraj

Member
Joined 2012
william2001 said:
3.3R will be good on the BiB. For trimmer P1 on the linestage, I simply used it to set the output offset voltage to 0 VDC. Mine only varies a few mV even after warm-up, which is completely acceptable to me.
Click to expand...

Thank you will do that and report back.

Regarding the psu ground wiring how did you connect to the BA2018? I see that it has a GND near the Input signal and then another GND along with the output signal. To which GND did you connect the psu ground? Also I see that some of them have connected this psu ground to the output signal ground.
 
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manniraj

Member
Joined 2012
Ok I am running now and as you pointed out it was R1 which seems to drop the voltage because of less CCS :)

With 3.3R 3W its perfect and I was to power both the preamp boards fine. I was able to set the output offset to 0.03mV on both the boards with the fluctuation of around 2-3mV. Will run for an hour and set the offset again but the trimmer turns are too sensitive with the offset jumping +/-20 to 50mv.

Thanks
 
william2001

william2001

Member
Joined 2001
Paid Member
I really like this linestage. I swapped out my Jensen autoformers for the 80% nickel Cinemags (CMOQ-4H), and I think it's even better. Not sure how this could be taken much further, it's really good into my F4 monoblocks. Maybe by building a second UltraBiB / 2nd power transformer and going full dual mono with the linestage...

The roughness I had noted earlier (after the rebuild) ended up being a poor and intermittent connection with one of my interconnect cable connectors. I now have the interconnect cables hardwired straight to my autoformers, no RCA's at all. And new RCA's on the other end (Eichmann Klei) at the amplifiers. Everything has been great ever since.
 
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Russellc

Member
Joined 2003
Paid Member
manniraj said:
I connected and it does play beautifully with my M2X paired with Ishikawa boards :)

Will keep this preamp in place of my DCG3 and hear for sometime.

Thanks
Click to expand...

william2001 said:
I really like this linestage. I swapped out my Jensen autoformers for the 80% nickel Cinemags (CMOQ-4H), and I think it's even better. Not sure how this could be taken much further, it's really good into my F4 monoblocks. Maybe by building a second UltraBiB / 2nd power transformer and going full dual mono with the linestage...

The roughness I had noted earlier (after the rebuild) ended up being a poor and intermittent connection with one of my interconnect cable connectors. I now have the interconnect cables hardwired straight to my autoformers, no RCA's at all. And new RCA's on the other end (Eichmann Klei) at the amplifiers. Everything has been great ever since.
Click to expand...

@Williams2001:

The Jensons are same transformer as F6? Or am I getting mixed up?

Thanks,

Russellc
 
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