B1 with Korg Triode

[Yaho]

No Microphonic Nutube

BTW, I may have lucked out or poster tack/putty did the job. It does not generate any ringing or microphonic noise even when I hit chassis with a screw driver handle.

 

[AnthonyA]

Yaho,
9. 5 is already close to sweet spot of good staging and warmth.

Have you compared to any dht preamp.. I found the musicality almost similar.

Ba3 is more similar to those 12ax7 or 5687 but better

 

[Yaho]

Have you compared to any dht preamp.

You read my mind. About a year ago, I've gathered all the parts that I needed to build DHT pre with UX201. Then I came accross the Nutube kit. Oneday, I might finish the DHT just for the fun of it. Currenly, I an switching over to the solid states scene...getting tired of hum and tweaking. 😀
I am very happy with the Nutube B1!

I am going to play with higher bias v...9.7 to 11.5 and see what happens.

 

[AnthonyA]

It's a nice party trick playing with the bias. Can basically match Alot of other preamplifier characteristics just by turning the knobs. So B1 korg is a preamp with many characters..

Tubes is very difficult to get right.. Very picky with cable and even types value of supply and capacitor.. Maybe due to its sissy nature, I gave up and just buy off the rack now lol, cheaper and better. Leave to people who knows better. That's why korg B1 is great.. Buffer before and after solved Alot of problems.

 

[AnthonyA]

Oh you can try do jfet boz... And compare to tubes.. It's quite amusing lol

 

[rikiheck]

I'm working on a Mouser BOM for this, following the BOM here. A quick question, though first let me say that my knowledge of electronics is not great, though I'm trying to learn (in part by building such things): Can you just replace the 10uF electrolytics with (say) Jantzen film types? Is that likely to be worth it? (I understand that they are much bigger, so will take some massaging to get onto the board.) It's a few bucks more, but I keep hearing that film caps are much better sounding.

 

[rikiheck]

A kind of draft Mouser BOM, for the PCB parts, is here. Please let me know if you have any suggestions for changes. I've used RN55 types where available, but sometimes they are not, and sometimes they are out of stock.

 

[rikiheck]

Here is a somewhat more detailed list, with links to Mouser and Parts Connexion and in one case Parts Express. Again, please let me know if you have any suggestions.

Resistors

(6) 332K 1/4W (71-RN65C-F-100K)
Parts Connexion (Holco, PRP (330k),)
(4) 33.2K 1/4W (71-RN55D-F-33.2K)
Parts Connexion (PRP, Takman, both 33K)
(1) 7.5K 1/4W (71-RN65D-F-7.5K)
Parts Connexion (Holco, PRP, Takman)
(4) 1K 1/4W (71-RN55D-F-1.0K)
Parts Connexion (PRP, Takman)

(2) 475R 1/4W (71-RN60D4750FTR)
Parts Connexion (PRP, Takman, both 470R)​

(4) 100R 1/4W (71-RN60D1000F/R)
Parts Connexion (PRP, Takman)
(1) 10K 1/4W for LED (71-RN55D-F-10K)
Parts Connexion (PRP, Takman)
(2) 10R 3W (71-CPF310R000FKEE6)
Parts Connexion (Kiwame 5W, Mundorf 5W)
(1) 270R 3W (71-CPF3270R00FKE14)
Parts Connexion (Kiwame 5W)
(2) 10K trimmer potentiometers (652-3362P-1-103LF)
Capacitors

(8) 1000uF 25V (647-UPW1E102MHD)
Parts Connexio: Nichicon FG, ES
(6) 10uF 50V (647-USW1V100MDD)
Parts Connexion: Nichicon FG, ES; Jantzen Cross-Cap
Diodes

(1) 1N4739 9.1V zener (78-1N4739A)
(1) Green LED (696-SSL-LX40FT3GD)
Chassis mount

(1) 50K Audio stereo volume potentiometer
(688-RK12L1210C0L)
ALPS Blue Velvet (Parts Connexion)
(1) volume knob
Parts Express (many options)
Parts Connexion (many options)
(3) RCA jacks Red
(3) RCA jacks White
Connex Tiffany Style (Parts Connexion)
Connex Rhodium Plated Solderless (Parts Connexion)
Basic Jacks (Parts Express)
(1) DC power barrel jack (Mouser 163-R123B-E)
(2) DPDT on-on toggle switches
Mouser (Many choices)
(1) 24V 500mA DC power supply
Mouser 553-WSU240-0500
Digikey 364-1274-ND

 

[der_yeti]

I know that the volume pot is a matter of taste for most people, but I would suggest to use a simple step attenuator or a TKD CP2500 type. The investment rewards with a better channel parity in small volumes.

 

[Erlend Sæterdal]

BTW, I may have lucked out or poster tack/putty did the job. It does not generate any ringing or microphonic noise even when I hit chassis with a screw driver handle.

Same with mine. No microphonic whatsoever.

 

[ghitus]

Same with mine. No microphonic whatsoever.

Very lucky! I tried two different Nutubes and both showed the ringing issue. Nevertheless I stopped it in both cases with two big pencil erasers stacked one upon the other on the Nutube, screwing the pcb to the chassis with the rubber screws for the drones and plugging every hole of the chassis.

 

[Erlend Sæterdal]

No luck but skill. 😉

 

[rikiheck]

I know that the volume pot is a matter of taste for most people, but I would suggest to use a simple step attenuator or a TKD CP2500 type. The investment rewards with a better channel parity in small volumes.

Yes indeed. That was taken from 6L6's rough BOM. I gather that some ALPS pot will be included in the kit.

 

[Dennis Hui]

rikiheck, just a comment that the RN65 resistors are quite large and their bodies are
longer than the 0.5-inch resistor spacing on the PCB. So you may find fitting
them a bit tricky.

 

[rikiheck]

rikiheck, just a comment that the RN65 resistors are quite large and their bodies are longer than the 0.5-inch resistor spacing on the PCB. So you may find fitting them a bit tricky.

Do you have a suggestion for a reasonable alternative? As I said, I could not find RN55s in some of the types on Mouser. Maybe could try Digikey?

 

[Dennis Hui]

I checked the four values (100R, 475R, 7.5K and 332K) where you have RN6x series and I can find these rn55 ones in stock at mouser:

https://www.mouser.ca/ProductDetail...=sGAEpiMZZMsPqMdJzcrNwlT9AI70gOmatExZmgMr3uw=

https://www.mouser.ca/ProductDetail...GAEpiMZZMsPqMdJzcrNwiaZa5aeFZjZoTl%2Bhns3TXE=

https://www.mouser.ca/ProductDetail...=sGAEpiMZZMsPqMdJzcrNwmQKrDNVFgoHxrc53isqL3k=

https://www.mouser.ca/ProductDetail...GAEpiMZZMsPqMdJzcrNwiaZa5aeFZjZmV8rQC%2B/HUs=

 

[rikiheck]

Thanks! I'll update the list.

 

[rikiheck]

Updated list:


Resistors

(6) 332K 1/4W (71-RN55D3323F/R)
Parts Connexion (Holco, PRP (330k), Takman (330k))


(4) 33.2K 1/4W (71-RN55D-F-33.2K)
Parts Connexion (PRP, Takman, both 33K)


(1) 7.5K 1/4W (71-RN55C7501F/R)
Parts Connexion (Holco, PRP, Takman)


(4) 1K 1/4W (71-RN55D-F-1.0K)
Parts Connexion (PRP, Takman)

(2) 475R 1/4W (71-RN55D4750F/R)
Parts Connexion (PRP, Takman, both 470R)​

(4) 100R 1/4W (71-RN55D-F-100)
Parts Connexion (PRP, Takman)


(1) 10K 1/4W for LED (71-RN55D-F-10K)
Parts Connexion (PRP, Takman)


(2) 10R 3W (71-CPF310R000FKEE6)
Parts Connexion (Kiwame 5W, Mundorf 5W)


(1) 270R 3W (71-CPF3270R00FKE14)
Parts Connexion (Kiwame 5W)


(2) 10K trimmer potentiometers (652-3362P-1-103LF)

Capacitors

(8) 1000uF 25V (647-UPW1E102MHD)
Parts Connexio: Nichicon FG, ES


(6) 10uF 50V (647-USW1V100MDD)
Parts Connexion: Nichicon FG, ES; Jantzen Cross-Cap

Diodes

(1) 1N4739 9.1V zener (78-1N4739A)


(1) Green LED (696-SSL-LX40FT3GD)

Chassis mount

(1) 50K Audio stereo volume potentiometer
(688-RK12L1210C0L)
ALPS Blue Velvet (Parts Connexion)
Of course, there are many other options for the pot….


(1) volume knob
Parts Express (many options)
Parts Connexion (many options)


(3) RCA jacks Red
(3) RCA jacks White
Connex Tiffany Style (Parts Connexion)
Connex Rhodium Plated Solderless (Parts Connexion)
Basic Jacks (Parts Express)


(1) DC power barrel jack (Mouser 163-R123B-E)


(2) DPDT on-on toggle switches
Mouser (Many choices)


(1) 24V 500mA DC power supply
Mouser 553-WSU240-0500
Digikey 364-1274-ND

 

[Yaho]

For power supply mouser 709-RS25-24 worked really well for me. No transformer needed (although I've used isolation trans) and the voltage can be adjusted.

Poster tack/putty can come handy to manage vibration for the Nutube.

For 10 uf caps, I used polyprop/film caps. So far no complain. You are building a great sounding preamp. Have fun!

Can you just replace the 10uF electrolytics with (say) Jantzen film types?

It depends on where you want to place them. They won't fit into the board as they are much bigger than Elna silmics. So, you would have to find ways to place them in the chassis.

 

[Yaho]

Can basically match Alot of other preamplifier characteristics just by turning the knobs. So B1 korg is a preamp with many characters..

DIYers dream come true! 😀