You're right I have not read all the posts. I always felt that the higher the operating voltage the better. I can see that raising the very low 10 ohms would bias the FET differently and provide a little more local negative feed back.
The top end appears a slightly shrill where the B1 seems a lot smoother in the upper-mid to treble region. BoZ has more bass though.
I have just finished a capless SE BoZ. Listening to it now.
My new Oppo BDP=83SE has input caps but my 6AS7 SET has no input caps. So make a preamp with no input caps but good output caps. In this capless SE version of BoZ I have no input caps but retained the 10uf polypropelene caps for the output. Also the output caps have been snubbed by 0.1uf polies.
Nelson suggests a total of 30,000uf for his B1 whose PS I stole a few ideas from. But only having 10,000uf caps I used three to get the filtering/storage up. Also I used a simple RCRCRC filter network. 1ohm/10,000uf/10ohm/10,000uf/1ohm/10,000uf. Each 10,000uf cap is snubbed. Silver plated wire wrap wire is used throughout. Input hookup wires and power wires were threaded through tiny bead chokes. Multiple earths (negative voltage) connections were made. Bitumanised Al foil laid in the top and bottom of the Hammond anodised Al case. Silver solder, Alps pot and 4oz brass added once more to a quality build.
Hard to judge sound quality at this point with only a brief listen. I will follow up. Not sure it can out "B1" the B1 but it does have stacks of gain. Huge sound stage - massive.
My new Oppo BDP=83SE has input caps but my 6AS7 SET has no input caps. So make a preamp with no input caps but good output caps. In this capless SE version of BoZ I have no input caps but retained the 10uf polypropelene caps for the output. Also the output caps have been snubbed by 0.1uf polies.
Nelson suggests a total of 30,000uf for his B1 whose PS I stole a few ideas from. But only having 10,000uf caps I used three to get the filtering/storage up. Also I used a simple RCRCRC filter network. 1ohm/10,000uf/10ohm/10,000uf/1ohm/10,000uf. Each 10,000uf cap is snubbed. Silver plated wire wrap wire is used throughout. Input hookup wires and power wires were threaded through tiny bead chokes. Multiple earths (negative voltage) connections were made. Bitumanised Al foil laid in the top and bottom of the Hammond anodised Al case. Silver solder, Alps pot and 4oz brass added once more to a quality build.
Hard to judge sound quality at this point with only a brief listen. I will follow up. Not sure it can out "B1" the B1 but it does have stacks of gain. Huge sound stage - massive.
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I thought you may be interested in this. Because BoZ has such a low parts count I figured it could build it on itself. I don't need input caps or attenuator in my system so these have not been added here. I do need output caps. Big brown polys (10uf) are perfect for constructing the whole preamp on.
No 20,000uf of storage in this build but still some low ESR storage caps to help with smoothing and the bottom end. With no interconnecting wire and true component-2-component construction signal path is as long as the components and solder joints (silver solder) are all halved.
I should have this cased and playing in the next few days.
BoZ on a Cap (minimalist BoZ) • DIY Audio Projects Forum
No 20,000uf of storage in this build but still some low ESR storage caps to help with smoothing and the bottom end. With no interconnecting wire and true component-2-component construction signal path is as long as the components and solder joints (silver solder) are all halved.
I should have this cased and playing in the next few days.
BoZ on a Cap (minimalist BoZ) • DIY Audio Projects Forum
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J310
Hi JUMA,
I have your version of the pre and sounds excellent with the power supply borrowed from the half completed Bf862 .
I would like to know whether with the input of 21V dc, do I need to change any values ? I refer to the voltage at R3 after the BC548.
thanks
regards
kp93300
Hi JUMA,
I have your version of the pre and sounds excellent with the power supply borrowed from the half completed Bf862 .
I would like to know whether with the input of 21V dc, do I need to change any values ? I refer to the voltage at R3 after the BC548.
thanks
regards
kp93300
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If you use shunt reg from BF862 preamp you don't need cap multiplier.
With 21V PS voltage you can expect a bit less swing at the output (about -15%).
The drain of the JFET should sit at voltage of +V/2 + 1V and the ratio of Rs and Rd should be 1:3.
Rs defines Id and Rd defines voltage at drain.
Finis: Yes it is complete and in it's hand made plastic case (lel). All wiring is wirewarp wire. Here three lithiums power the preamp. Of course any high performance 9V battery, even rechargables could be used. I like lithiums.
At the last minute I added a 0.01uf poly to the power section right at the input to the BoZoaC engine (I could hear Gio whispering "de-couple"). Just one 0.01uf poly to ensure no HF gets into the PS. I'm pleased with the build and assembly.
I am listening to it now from my new Oppo BDP-83SE. It sounds better than my BoZSE capless-or is it. Though this preamp requires 10 or so hours of use to relax the big 10uf 100V ploypropelene output caps and settle the 2 X 1000uf 35V low ESR electros the sound is very immediate, bass seems to be at full weight (I don't believe it) and in all a very natural balance with, comparitively, mids slightly forward.
I thought BoZSE had added additional bass weight due to its 30,000uf of storage caps. But I am sensing this minimalist BoZ has the same bass performance with a fraction of the storage caps? Is it the 27V battery PS?? And I may have better mids??!!??
I cannot play LPs due to the fact I cannot attenuate my phono preamp enough. I may add a pot or an attenuator switch to this BoZ build. So far I'm very pleased. Very impressed. It sounds very quick!
At the last minute I added a 0.01uf poly to the power section right at the input to the BoZoaC engine (I could hear Gio whispering "de-couple"). Just one 0.01uf poly to ensure no HF gets into the PS. I'm pleased with the build and assembly.
I am listening to it now from my new Oppo BDP-83SE. It sounds better than my BoZSE capless-or is it. Though this preamp requires 10 or so hours of use to relax the big 10uf 100V ploypropelene output caps and settle the 2 X 1000uf 35V low ESR electros the sound is very immediate, bass seems to be at full weight (I don't believe it) and in all a very natural balance with, comparitively, mids slightly forward.
I thought BoZSE had added additional bass weight due to its 30,000uf of storage caps. But I am sensing this minimalist BoZ has the same bass performance with a fraction of the storage caps? Is it the 27V battery PS?? And I may have better mids??!!??
I cannot play LPs due to the fact I cannot attenuate my phono preamp enough. I may add a pot or an attenuator switch to this BoZ build. So far I'm very pleased. Very impressed. It sounds very quick!
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HI andrew,
I tried it without any change in the values and it sound fine.
thanks
kp93300
I measured the V at the drain is 14.3 V with an input of 21.2 V power supply.
By your formula, the ideal V at drain is 11.6.
The v at source is 2.3 V .
Can you suggest some approx values of R3 and R5 to try ?
thanks
kp93300
HI mhouston,
which circuit do you used ? 2sk 170 ??
Can you post the schematic ?
I use j310 .
thanks
kp93300
It's nice - you don't have to change anything.
Further adjusting would bring a bit more swing, but it's marginal...
This one on this link: 2SK170 BL
http://www.diyaudio.com/forums/pass-labs/103050-jfet-boz.html#post1226532
http://www.diyaudio.com/forums/pass-labs/103050-jfet-boz.html#post1226532
Funny you should ask. Just yesterday I switched out my BOZ-J for the B1.
I find the B1 to be a bit more bloomy in its character. It does have very nice imagining and depth. BOZ-J is a bit more edgey, and with obviously better drive.
I find them to be completely different in tone.
I went back to the BOZ-J for the drive capability.