With the BA3 as a pre and looking at the guide here it states
So, do I need the bias boards and output stage? + the Gain Stage (out of stock 🙁 )
OK does this look good for a starting point with my order. I'm leaving the cases etc. for the moment.
Pre-amp
1 x Burning amp Gain stage
1 x Power supply
1 x Super regulator
1 x Matched Jfets
Amp
1 x F4
1 x Power supply
1 x Soft Start & Speaker Turn-On Delay
1 x Transistor Kit
1 x Matched jfets
Is the super regulator a good (worthwhile) option for the pre-amp?
But how do I source my BA-Gain stage? These are currently out of stock and guessing may be for some time 🙁
Do I need a transistor kit for the BA-Gain stage or will this just be with my Mouser order?
Pre-amp
1 x Burning amp Gain stage
1 x Power supply
1 x Super regulator
1 x Matched Jfets
Amp
1 x F4
1 x Power supply
1 x Soft Start & Speaker Turn-On Delay
1 x Transistor Kit
1 x Matched jfets
Is the super regulator a good (worthwhile) option for the pre-amp?
But how do I source my BA-Gain stage? These are currently out of stock and guessing may be for some time 🙁
Do I need a transistor kit for the BA-Gain stage or will this just be with my Mouser order?
@pmeeke :
It will help other members suggest part sources if you fill in your location in your user profile.
As others have mentioned P3 adjustment really requires the ability to measure distortion. Have a look at 6L6's demonstration here:
For now either leave out P3 or just set it to the midpoint (measure with meter)
Since you're using the BA3 FE as a preamp feeding an F4, I highly suggest you use a regulated power supply with target voltage greater than +/-24V. Higher voltage rails give slightly lower distortion and keeps the BA3 FE well away from voltage clipping at the output level needed for max output for the F4. The Superregulator should work fine.
I didn't see a transistor kit for the BA3 FE so I think you'll have to source the parts yourself. I recommend that you make a list from the BA3 article: https://firstwatt.com/pdf/art_ba_3.pdf
Please note the change in P1/P2 values if you use the Fairchild output mosfets.
It will help other members suggest part sources if you fill in your location in your user profile.
As others have mentioned P3 adjustment really requires the ability to measure distortion. Have a look at 6L6's demonstration here:
Since you're using the BA3 FE as a preamp feeding an F4, I highly suggest you use a regulated power supply with target voltage greater than +/-24V. Higher voltage rails give slightly lower distortion and keeps the BA3 FE well away from voltage clipping at the output level needed for max output for the F4. The Superregulator should work fine.
I didn't see a transistor kit for the BA3 FE so I think you'll have to source the parts yourself. I recommend that you make a list from the BA3 article: https://firstwatt.com/pdf/art_ba_3.pdf
Please note the change in P1/P2 values if you use the Fairchild output mosfets.
I have built three BA3 preamps: high/low gain, low gain and balanced version. Never felt the need to change to adjust P3, but doesn't mean you shouldn't experiment. Might be obvious, but a good power supply matters. Having tried two simple and slightly different factory assembled power supplies in the H/L version, the power supply with slightly better filtering was more liquid and less harsh. Main difference I could see is filtering around the rectifiers.
Good luck!
Good luck!
You don’t need a scope (but extremely helpful) to adjust the BA3 front end. Just adjust. measure and track values on a piece of paper for both P1 / P2 and listen (that’s the key.
That’s an excellent point. PSU quality makes a huge difference (within a range). I see alot of new builders on the forum today using SMPS for line stage and power amp projects and it’s good that they are actually building. However, they just don’t do these great designs justice.
I use Salas’ DCST supply for my BA3 and it’s super smooth.
Power supply: This one is fairly inexpensive, and comes with the parts to stuff it. It can be run as a dual power supply or it can be tied at the GND to be a bipolar power supply. You would run it as a bipolar. I recently used it to power a ACA mini which was biased pretty high. It didn't break a sweat. You will need a transformer for it. I recommend 22vac transformer for a 24v supply. Antek AS-0522 works good for this. You will want to run it at 24v like mentioned above so you will have the gain needed for the F4.
https://glass-ware.stores.yahoo.net/dulv.html
JFETs: Regarding the JFETs, take note of what IDSS range you need. I tend to use the higher range so long as it will work so I can scavenge them for other projects.
Soft start: You can use the soft start if you like. Or you can just use a 4 position screw terminal board and two CL60's (you will need a 3rd for the ground to the power supply board). Since this is your first from-scratch build, it may be simpler to go that route. Fewer parts to order and you see this on a lot of First Watt amps. If you plan to be building amps, CL60s are used quite often. I tend to order 10 at a time to get a little discount.
Regarding sourcing the BA-3 gain stage, you can make a post to see if someone has an extra board floating around. Get on the email list and contact the store to see if they have an idea of when the stock will be back in.
If you compare the schematic of the F4 to the BA-3, you will see that the bias board circuit of the BA-3 is already implemented as part of the F4. The F4 simply has a JFET buffer stage at the input to the board to get the impedance right since it doesn't have a driver board like you see on the BA-3. Otherwise, the source may see too much of a load. I believe the reason it is separate on the BA-3 is due to the fact that the BA-3 can be bought with a complimentary output stage or a single-ended one.
https://glass-ware.stores.yahoo.net/dulv.html
JFETs: Regarding the JFETs, take note of what IDSS range you need. I tend to use the higher range so long as it will work so I can scavenge them for other projects.
Soft start: You can use the soft start if you like. Or you can just use a 4 position screw terminal board and two CL60's (you will need a 3rd for the ground to the power supply board). Since this is your first from-scratch build, it may be simpler to go that route. Fewer parts to order and you see this on a lot of First Watt amps. If you plan to be building amps, CL60s are used quite often. I tend to order 10 at a time to get a little discount.
Regarding sourcing the BA-3 gain stage, you can make a post to see if someone has an extra board floating around. Get on the email list and contact the store to see if they have an idea of when the stock will be back in.
If you compare the schematic of the F4 to the BA-3, you will see that the bias board circuit of the BA-3 is already implemented as part of the F4. The F4 simply has a JFET buffer stage at the input to the board to get the impedance right since it doesn't have a driver board like you see on the BA-3. Otherwise, the source may see too much of a load. I believe the reason it is separate on the BA-3 is due to the fact that the BA-3 can be bought with a complimentary output stage or a single-ended one.
Are gerber files available anywhere for it. I could get some put together from JLCPCB having surplus left over for any more UK DIYers if they need them.
hi Mike!
Adjust H3 about 2~3 dB higher in the harmonic profile of your BA-3 and the increase in detail will reflect the setting.
What I did was I saved the profile of the ACP + preamp (below) first and emulate it in the BA-3 because in my case, the ACP + sound tube like to me but needs a little boost in the detail department.
Attachments
I will give that a shot. I have a few projects I am in the middle of. After I get through with those, I will be back onto preamps. Thanks 👍
@pmeeke
I have Mouser projects saved for both the BA-3 front end board and the F4. I'm not guaranteeing their completeness or that there may be parts you don't want (i.e. Schurter power inlet), but if they would be helpful I can share those with you. PM if interested.
Also, I used the Salas BIB power supply v1.1 in my BA3-FE which works great!
I have Mouser projects saved for both the BA-3 front end board and the F4. I'm not guaranteeing their completeness or that there may be parts you don't want (i.e. Schurter power inlet), but if they would be helpful I can share those with you. PM if interested.
Also, I used the Salas BIB power supply v1.1 in my BA3-FE which works great!
Guess what I found in the board hoarding drawer? Looks like my "why buy one when you can get two for twice the price" philosophy may pay off...for somebody else anyway.
The BA-3 front end (the red one) is what you’re looking for.
You’ll have to read up on the Salas Power Supply v1.1 (the black one) and determine if you want to go that way.
Start a private conversation with me and we can discuss options.
Also, I want you to understand that you’re taking a pretty big bite of the diyAudio apple. There are simpler ways to start in this hobby (i.e. ACA Mini, ACP+)…just so you know.
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