I also found it a little too bright with the project settings of 9.5v on the pots when combined with my M2-x (ishikawa input board). For me the remedy was to raise the pots adjustment voltage until I liked what I heard, and Ended settling on 10.5v
Great little preamp!
Hi Hikari
Nice reading, thanks.
Based on my own experience withthe B1 Korg I would say:
1) fit better pots and possibly better caps
2) once done, adjust the bias to your liking, sounds like you may have despite the quick prototype parts a bit of too much H2 bias for your liking?
Have fun, indeed great bit of kit!!!
Claude
Nice reading, thanks.
Based on my own experience withthe B1 Korg I would say:
1) fit better pots and possibly better caps
2) once done, adjust the bias to your liking, sounds like you may have despite the quick prototype parts a bit of too much H2 bias for your liking?
Have fun, indeed great bit of kit!!!
Claude
B1 replaced by B1 Korg sounds gooood
I removed my B1 to resolve the ringing when changing input and listened to my straight B1 for a while. Sounded good with the improved 24v supply, should have done that sooner.
The Korg is now sat on some sorbithane I had. Can't get anything to stick to it so ended up clamping using what I hhad around. The PCB is mounted on the rubber stand offs suggested earlier. These probably do more to suppress than the sorbothane. Removind the Korg was not easy, so good luck to anyone with ringing that isn't solves by the rubber stand offs.
The b1 Korg is back in, and staying. Bothe are using the same caps. Standard 9.5v setting with speaker polarity reversed. I get the deeper sound stage described by others. But its the tone that seems to have got more full and lush that I'm really enjoying. Didn't expect that.
Thanks again to Nelson and all the contributers that helped this design become available to the likes of me.
I removed my B1 to resolve the ringing when changing input and listened to my straight B1 for a while. Sounded good with the improved 24v supply, should have done that sooner.
The Korg is now sat on some sorbithane I had. Can't get anything to stick to it so ended up clamping using what I hhad around. The PCB is mounted on the rubber stand offs suggested earlier. These probably do more to suppress than the sorbothane. Removind the Korg was not easy, so good luck to anyone with ringing that isn't solves by the rubber stand offs.
The b1 Korg is back in, and staying. Bothe are using the same caps. Standard 9.5v setting with speaker polarity reversed. I get the deeper sound stage described by others. But its the tone that seems to have got more full and lush that I'm really enjoying. Didn't expect that.
Thanks again to Nelson and all the contributers that helped this design become available to the likes of me.
Jim, all is well now. I have a Hakko powered solder sucker. I removed each of the active devices using it. Put everything back and resoldered.
Now all of the voltages are correct and I can vary the voltage at the T7 and T8.
I have two theories, one mostly likely is poor soldering on my part, the other might be on some of the holes or perhaps just it didn't plate through.
Oh well, it works and music flows from it.
Now all of the voltages are correct and I can vary the voltage at the T7 and T8.
I have two theories, one mostly likely is poor soldering on my part, the other might be on some of the holes or perhaps just it didn't plate through.
Oh well, it works and music flows from it.
Attachments
Fantastic news!! 
Now you get to sit back and listen, enjoy the project! It's a special one, I'm sure you'll like it. (Don't forget to play with speaker phase)
Now you get to sit back and listen, enjoy the project! It's a special one, I'm sure you'll like it. (Don't forget to play with speaker phase)
An externally hosted image should be here but it was not working when we last tested it.
My current plan of attack:
A) more capacitance between SMPS and PCB. Will try 33,000uf...and I'll see if it shuts down the smps.
B) Better pots. I really like having two volume pots but two volume pots makes stepped attenuators tricky to use. Any suggestion on a good non-stepped mono pot? I guess I could use two Alps Blue Velvets.
C) I am not sure about the polyster caps. Obviously, size is an issue. I have Silmics on hand but I've tested Silmics vs poly caps before...and I prefer poly.
D) This amp deserves a real PSU. If I can get this preamp a little closer to where I want it (less grain, a little less harsh) then I will go all out on the PSU for it.
Attachments
Poorly matched Jfets, wrong value R1, or poorly matched NuTube sections.
you could try a higher value pot if you have one.
All supplied in the full kit, I let it run for 30 mins and eventually was able to balance the pots.
Now only have sound from 1 channel.
Hi Hikari1
Of course you can try everything, that's DIY!
I have been there investigating a while ago, and found IN MY CASE what I posted here. My humble view would be:
My current plan of attack:
A) more capacitance between SMPS and PCB won't do anything... Admittely with an already very low ripple SMPS (better than recommended), moving from 1000 to 2200uF made a small (but existing) difference, so I stopped there the PS caps increase: diminishing returns. 33,000uf sounds like a lot... Bottom line is Papa has (of course) already designed a nice Pi Filter that can be only slightly improved by increasing a bit the caps value, but there is no miraculous bottleneck there
B) Better pots of course. No clue on mono pots but the Tocos Cosmos I tested and posted here, and commented again last week, is really a great pot vs a pure resistor network as reference. I believe they do also mono pots. That is a big step up from the std but good Blue Alps, more in the old Black Beauty league if not better (but long time durability beoing a question mark of course).
C) I was not advising polyster caps but polypropylene ones. Size isn't a real issue but for the output ones, these probably need some creativity. Read my posts on caps re values you can use / realy need, the ones in the BOM are just goiven as std values but can be optimised once you go the trouble purchasing different caps and understanding what they are doing. BTW, I found the Silmics to be quite a bottleneck vs PPP caps, again you can efer to my post / report for more details (search function is your friend).
D) This amp deserves a real PSU. If I can get this preamp a little closer to where I want it (less grain, a little less harsh) then I will go all out on the PSU for it.
=> Not sure that is needed. Tried a regulated non SMPS enormous lab PS to see what that would bring and differences wheer very small and more taste and colour than any clear winner. I would say not the priority, Papa's idea of an SMPS does miracles here and I am not an SMPS fan, and for sure not wallwart ones, but then I could hear that it works spot on. You may want a low ripple quality one, while increasing perhaps the PS caps to 2200 or so, that's it IMHO.
So pot and caps in the signal path would be action plan in your case, plus playing with the voltage adjustment, but that's just me. On the other hand I tried step by step options and reported here in order to save other's from having to do it if they didn't wished to (or wanted to save money), hence me refering here again to these posts, but of course the fun in DIY is also trying yourself and sharing experience!
Good luck
Claude
Of course you can try everything, that's DIY!
I have been there investigating a while ago, and found IN MY CASE what I posted here. My humble view would be:
My current plan of attack:
A) more capacitance between SMPS and PCB won't do anything... Admittely with an already very low ripple SMPS (better than recommended), moving from 1000 to 2200uF made a small (but existing) difference, so I stopped there the PS caps increase: diminishing returns. 33,000uf sounds like a lot... Bottom line is Papa has (of course) already designed a nice Pi Filter that can be only slightly improved by increasing a bit the caps value, but there is no miraculous bottleneck there
B) Better pots of course. No clue on mono pots but the Tocos Cosmos I tested and posted here, and commented again last week, is really a great pot vs a pure resistor network as reference. I believe they do also mono pots. That is a big step up from the std but good Blue Alps, more in the old Black Beauty league if not better (but long time durability beoing a question mark of course).
C) I was not advising polyster caps but polypropylene ones. Size isn't a real issue but for the output ones, these probably need some creativity. Read my posts on caps re values you can use / realy need, the ones in the BOM are just goiven as std values but can be optimised once you go the trouble purchasing different caps and understanding what they are doing. BTW, I found the Silmics to be quite a bottleneck vs PPP caps, again you can efer to my post / report for more details (search function is your friend).
D) This amp deserves a real PSU. If I can get this preamp a little closer to where I want it (less grain, a little less harsh) then I will go all out on the PSU for it.
=> Not sure that is needed. Tried a regulated non SMPS enormous lab PS to see what that would bring and differences wheer very small and more taste and colour than any clear winner. I would say not the priority, Papa's idea of an SMPS does miracles here and I am not an SMPS fan, and for sure not wallwart ones, but then I could hear that it works spot on. You may want a low ripple quality one, while increasing perhaps the PS caps to 2200 or so, that's it IMHO.
So pot and caps in the signal path would be action plan in your case, plus playing with the voltage adjustment, but that's just me. On the other hand I tried step by step options and reported here in order to save other's from having to do it if they didn't wished to (or wanted to save money), hence me refering here again to these posts, but of course the fun in DIY is also trying yourself and sharing experience!
Good luck
Claude
I power cycled the Korg B1 a couple times over the past few days. It seems to have gotten better...most of my complaints are gone. Seems to have broken in some. Sounding really good now.
"I power cycled the Korg B1 a couple times over the past few days. It seems to have gotten better...most of my complaints are gone. Seems to have broken in some. Sounding really good now."
Yep valves definitely have a break in period can go from OK to harsh and then on to really good over a period of 40 hours - worth sticking with it before you tinker too much.
Yep valves definitely have a break in period can go from OK to harsh and then on to really good over a period of 40 hours - worth sticking with it before you tinker too much.
A few years back I bought a whole sortiment of WIMA polyester caps (MKS4 and MKS2) to refurbish a Revox tape deck and a Revox reel-to-reel machine. No real complaints using them there (but haven't compared to all MKP caps in this application - probably would be hard to fit size-wise).
But when I tried the MKS in my diy amps, I was never satisfied with them. Too harsh, edgy, unmusical ... 🙄
My default go-to poly caps now are WIMA MKP. If I can fit them, MKP10; otherwise, MKP4 or MKP2.
Small value caps; FKP2.
I'm not even using the MKS in power supplies anymore (I like WIMA DC-Link there, or motor-run MKP).
Of course, ZenMod's Philips MKC are nice as well, or the vintage ERO MKPs ...
Best regards, Claas
Anyone compared toshiba 2sk170 vs the Fairchild jfets? Iam using fairchild now.
I have 2sk170...but they are part of my reserve stash. Is it worth it?
I have 2sk170...but they are part of my reserve stash. Is it worth it?
I have both versions in operation currently, however, in different systems. I'm bringing both verions to Burning Amp. I'll try and get an A/B going and post some results. Not scientific, of course, just listening impressions.
Hikari
Search function is your friend.
Short version, I have not, but my understanding is from other posters and from Papa that it doesn't really matter in that build / doesn't really impact sound.
Claude
Search function is your friend.
Short version, I have not, but my understanding is from other posters and from Papa that it doesn't really matter in that build / doesn't really impact sound.
Claude
I have both, and can't tell a difference. The NuTube's signature is much, much stronger than the differences between buffer's active devices.