Manolo, I just noticed from pictures; you mounted mosfets backward. Mosfets must face outerside of the board.. not to inside..
Remove them. And correct.
Change 500ohm trimpots to 1k for p1 and p2.
Remove them. And correct.
Change 500ohm trimpots to 1k for p1 and p2.
Input of output cap to ground for dc offset. Bias across resistors per schematic.
Hey Star, your're right. I cannot believe I did that. I had noticed the double line in the the board as a guide I guess but missed that. Will reverse. Already ordered 1k pots.
Hi all-just built the Ba3. One channel not working. Issue somewher. The other channel works BUT R10 dials to 1V per instructions but R11 stays at 0 no matter how I turn the pots. Instructions say 1V across R10 and R11. Any ideas? thanks
Well, removed mosfets and reinstalled them facing outward, as they should be, and still no hint of any activity as far as measurements. I'll replace the 500 ohm trims with the 1K trims when they arrive this week. Worried that something more insidious is at hand because of lack of readings. I had to cut the mosfet leads, install posts and then solder the mosfets to the posts. Hope this did not damage the mosfets or having had them backwards. R12 to the right seems strange but it is OK, ripped it with the alligator clips, bit soldered.
I am going to fashion some some measuring posts because getting those clips inside that cramped space and connecting to such small resistors is very difficult. Thanks for looking!
I am going to fashion some some measuring posts because getting those clips inside that cramped space and connecting to such small resistors is very difficult. Thanks for looking!
Attachments
Dual Primary transformer
Hey Guys
I have a real newbie question here. I am starting to wire up my BA3 preamp but my transformer has 4 primaries instead of two. How do I hook this up for 120v? The trannies for my F5T have single primaries only.I have a normal set up with a power switch, separate fuse holder, and IEC inlet.
Any pictures or advice would be greatly appreciated.
Thanks
Hey Guys
I have a real newbie question here. I am starting to wire up my BA3 preamp but my transformer has 4 primaries instead of two. How do I hook this up for 120v? The trannies for my F5T have single primaries only.I have a normal set up with a power switch, separate fuse holder, and IEC inlet.
Any pictures or advice would be greatly appreciated.
Thanks
Blue and Violet together to the AC Live -> Fuse -> power switch
Grey and Brown together to AC Neutral
Grey and Brown together to AC Neutral
Preamplifier up and functioning
Thanks to all who helped here and privately. Preamp. is running ok. This morning I received my Digikey package with the 1k pots and managed to get all the biasing. Pretty quick I might add. If you notice in the photo, I have not decided what to do about the final coupling cap. You can see that I have, for C3, Nichicons Muse bipolar capacitors, 10uf. I couldn't resist to bypass these with 2 Auricaps lying around though. Have to coordinate with good caps that fit. The caps I have are 600v, for tube equipment, and too big. So, I'll keep listening and check bias again tomorrow. -Offset was practically zero v and bias across the resistors 1.08v- And then, the power supply wiring will be better dressed and routed as well as the signal wires. Have to also wire the input selector in the back panel.
As far as the enclosure, I am not planning to use the bottom black panel, only the subchassis, this provides for less resonance surfaces. And see how it compares to my tube preamp.... So far pretty smooth and the bass is impresive.
Thanks to all who helped here and privately. Preamp. is running ok. This morning I received my Digikey package with the 1k pots and managed to get all the biasing. Pretty quick I might add. If you notice in the photo, I have not decided what to do about the final coupling cap. You can see that I have, for C3, Nichicons Muse bipolar capacitors, 10uf. I couldn't resist to bypass these with 2 Auricaps lying around though. Have to coordinate with good caps that fit. The caps I have are 600v, for tube equipment, and too big. So, I'll keep listening and check bias again tomorrow. -Offset was practically zero v and bias across the resistors 1.08v- And then, the power supply wiring will be better dressed and routed as well as the signal wires. Have to also wire the input selector in the back panel.
As far as the enclosure, I am not planning to use the bottom black panel, only the subchassis, this provides for less resonance surfaces. And see how it compares to my tube preamp.... So far pretty smooth and the bass is impresive.
Attachments
A good output cap is a must. Does not have to be expensive but a decent one, Solen, Jantzen cross cap, Audyn $5 cap etc.
First impressions and output cap....
The linestage is doing ok as far as function goes. Only 10 or 12 hours on it. With my F4 I certainly would like it to have more gain. Music does not get alive until the 12 o'clock attenuators position and nothing much happens -dynamically- below that. I'll try to parallel R5 with a 200 ohm R to raise gain a little, as described in the other ba thread. So far it's very smooth and musical.
Wondering, which of the First Watt offering amplifiers is the better match for this preamplifier. And, I'm using a single 0.68 uf coupling cap and no problem, it seems to work pretty well. No need to go to 10uf I guess.
The linestage is doing ok as far as function goes. Only 10 or 12 hours on it. With my F4 I certainly would like it to have more gain. Music does not get alive until the 12 o'clock attenuators position and nothing much happens -dynamically- below that. I'll try to parallel R5 with a 200 ohm R to raise gain a little, as described in the other ba thread. So far it's very smooth and musical.
Wondering, which of the First Watt offering amplifiers is the better match for this preamplifier. And, I'm using a single 0.68 uf coupling cap and no problem, it seems to work pretty well. No need to go to 10uf I guess.