B1 with Korg Triode

PKI

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Joined 2011
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The new zeners arrived along with various damping materials. I replaced the parts and everything is looking good now. I went overboard with damping and there is no ringing now on volume change. I still think my Nutube is overly microphonic, as moving my finger gently on the top of the damping material will cause low (but audible) ringing.

I also had the chance to measure it with my amateur test suite (ARTA+pmillett SCI+EMU soundcard). In my setup, it's measuring ~1% THD with 1V output at the 9.5V bias point. FR is pretty flat, which is nice. If I ever swap in film caps for coupling, atleast I have a good baseline on what sufficient capacitance should look like.

One nice bonus is that the volume display shows -16db at 0db gain (1V in 1V out).. I thought that was cool since the circuit has about 16db of gain.

Really happy with how this came out.. Thanks Nelson!!!

Beautiful build! Is that selector and volume control from Maxim?
 
Beautiful build! Is that selector and volume control from Maxim?

Yes, good eye!
I bought one in the past for a build that didn't follow through.

As I started the B1 build.. thought it would make it for a very functional unit together (which it did).
Only caveat is that since the Nutube is so microphonic, taming the ringing was a bit of a challenge... but now with all the damping material it is a non-issue.
 
Yes, good eye!
I bought one in the past for a build that didn't follow through.

As I started the B1 build.. thought it would make it for a very functional unit together (which it did).
Only caveat is that since the Nutube is so microphonic, taming the ringing was a bit of a challenge... but now with all the damping material it is a non-issue.

Hi! Where to you find those products? I've looked on maximintegrated.com and it's certainly not consumer friendly.
Are there input switchers that you others might recommend for their transparency? I don't need a remote.
 
Hi! Where to you find those products? I've looked on maximintegrated.com and it's certainly not consumer friendly.
Are there input switchers that you others might recommend for their transparency? I don't need a remote.

No that is not the "Maxim" we are referring. Maxim is an individual that distributes these volume and input selection boards...he mentioned that he is setting up in the Vendor Bazaar for broader selling of his products.

How many inputs do you need? If just 2, then you can use a DPDT or 4PDT switch...
If you need more, you can look at some multi position rotary switches such as the one ClaudeG recommends.

Sonically, I think any decently built switch should be fine!
 
drpro,

The B1 is in a Parmetal series 20, specifically 20-12082N (12x8x2 in, Natural finish).
By default, these come with a front panel frame and blank panel, and the rear panel is fixed. Since I was planning on getting panels through Front Panel Express, I ordered it with frames for both front and rear, without any blank panels.
These are ordered direct through Parmetal's website.

The PSU is in a Hammond series 1455.. these come in many sizes/colors and are available through many vendors, such as Mouser, Digikey, Hawk etc.
 
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Also, NuTubes vary in their microphonics. A good one will exhibit little or no ringing that dies out immediately when tapped lightly with a fingernail. A bad one will ring either a long time or continuously when tapped. This is typically caused by the filament vibrating, usually somewhere around 5KHz.

I've got a bad one then...it will ring continuously. Weird though, it varies depending on which equipment it's paired with.

Examples:
Pearl II -> B1 Korg -> FW M2 = No problems.
NuVista Vinyl -> B1 Korg -> FW M2 = low rumble sound.
VPI traveler -> (built in phono) -> B1 Korg -> Forte M 4 = continuous ringing.
Pearl II -> B1 Korg -> Quad 405 = Screams like a siren. (I mean loud!)

I'll give some different damping materials a try. At the moment the only damping installed is some packaging foam underneath.
 
Hi all...

I am building a Korg Nu Tube Preamp according to the Pass Plan, and all parts and boards from the DIY Audio Store.

This preamp will go in front of a passive line level crossover...using inductors and capacitors. There will be a high frequency output for the tweeter channel and a low frequency output for the woofer channel.

there will be a master volume control in front of the preamp channels. But I would like to trim the gain of each high and low channel separatly. So the signal would go from master volume control to pots after the master volume control to the pre amp channels to adjust the signal to each channel. This way I can adjust Tweeter level and Woofer level to taste.

My question is: how would I do this??? if Master Volume control is say 20k, what should value of following trim pots be? and how connected?

the "adjusting" pots could not go at the output of the preamp because they would change the output impedence of the preamp and alter the response of the crossover filter at different levels...

Thanks in advance for any help on this.
 
Perhaps you may want to consider 2 pots at the output of the B1K, leading to your 2 filters?

The output of the B1K is between 160 and 300R ish depending on the fets you use, so you could potentialy use a 5K pot at the output, or even less. You want is as low as possible as I don't know what input impedance your filters will have, but that needs tp be very high for a filter, say at anything between 10k and 100kish, other wise you will need a kind of buffer at the input.

Just thinking loud, never done this, I guess most people would adjust the required level once once for all in their filter already adjusting levels between bass and treble, as is done in LS Xover?

Good luck

Claude