Author Topic: Tube Preamp Project: advise and discussion  (Read 9329 times)

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #80 on: September 25, 2018, 10:03:35 AM »
For fewer problems with instability (squeals) and noise, pop the grid wires up in the air, and keep them as short as possible.  Keep the plate and cathode wires pushed down against the chassis.  The wires to the tone controls might like to be pushed against the chassis as well.

Thank you. I keep this in mind. And try to apply it this time around. I' doing my 3rd board. The first has to much noise. The second with a different circuit is very weak. I hope this 3rd try i get the sound i was looking for. :)

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #81 on: September 25, 2018, 10:05:59 AM »
> i dont know why the regulator for the 6.3v heater gets hot

You got 9V. You need 6V. Where does the other 3V go?

When I cut 9 foot lumber to 6 foot I get a heap of 3 foot scraps in my way.

Here, the excess 3V doesn't lay on the floor to trip over, thank goodness. Instead it "goes away" as heat.

3V at 0.3A is nearly a Watt. 1 Watt in a TO-220 package may be safe but sure is HOT. Normally we'd bolt the regulator to a heat spreader at about this point. But it may live forever, naked, if it gets good air.

This is so clear. Thank you Sir. Now i get it right. Thanks for the help. :)

thermionix

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Re: Tube Preamp Project: advise and discussion
« Reply #82 on: September 25, 2018, 04:14:48 PM »
For fewer problems with instability (squeals) and noise, pop the grid wires up in the air, and keep them as short as possible.  Keep the plate and cathode wires pushed down against the chassis.  The wires to the tone controls might like to be pushed against the chassis as well.

Thank you. I keep this in mind. And try to apply it this time around. I' doing my 3rd board. The first has to much noise. The second with a different circuit is very weak. I hope this 3rd try i get the sound i was looking for. :)

Another thing for future builds, and I can't see all that is going on in the pic, but it looks like you're basically crossing over the tube, wires running to the farther triode relative to the circuit on the board.  So it might reduce problems to swap triodes.  General rule of thumb is to not have the signal path cross over itself, but to flow from input to output, as much as possible.

printer2

Re: Tube Preamp Project: advise and discussion
« Reply #83 on: September 25, 2018, 06:58:07 PM »
Cross wires at 90 degrees from each other. Keep them short if possible, think of them acting either as an aerial or transmitter antenna, they work best when longer related to the size of the wavelength. Also think in terms of loops, the input circuit loop, the output circuit loop. With that in mind the area that the loop makes catches interference in relation to the size of the loop. Think of it as a net. Of course optimizing one area will compromise another (we can't win every battle). Knowing which one to optimize separates the men from the boys.
Fred

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #84 on: September 26, 2018, 08:03:06 AM »



This is my current wiring. I think i need to layout the board in more organized way.  I hear no squeal or noises as of now even at max gain. But i will test it more and see if there is any problem that will arise. Thanks for the tips..:)

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #85 on: September 27, 2018, 05:23:23 AM »
So the progress is almost there. But a new struggle arise. Haha. No more squeal or loud hum. Thanks for the wiring tips of thermionix. It really helps me quiet down my preamp noises. But this is my problem. I tried to hook my preamp directly to my audio interface but it clips like crazy. I try to lower down the gain and lower the master volume in my preamp, it is as quiet as night but when i put a bit of a volume and gain it clips even a little volume increase.

My amp typology is like a marshall preamp. What could be the cause?

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #86 on: September 27, 2018, 09:04:51 AM »
I found the problem. Its a wrong pot wiring. Wew. Now i'm trying to record the sound. I will post a sound demo when all are in good running condition. :)

MJ_Sound_Cubed

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Re: Tube Preamp Project: advise and discussion
« Reply #87 on: September 27, 2018, 05:10:24 PM »
I would clean the solder joints with alcohol to remove the flux. I will turn another color one day and look a bit disgusting  :)
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johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #88 on: September 28, 2018, 06:20:38 AM »
I would clean the solder joints with alcohol to remove the flux. I will turn another color one day and look a bit disgusting  :)

Thank you sir MJ. I'll post the clips as soon as possible. My habds are not yet ready to play.

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #89 on: October 01, 2018, 09:46:25 PM »
https://soundcloud.com/john-govan-426812247/amp-problem


I have this problem in my sound. There's an ugly distortion or clipping. I dont know why.

thermionix

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Re: Tube Preamp Project: advise and discussion
« Reply #90 on: October 01, 2018, 10:14:42 PM »
Overdriving your audio interface?

anotherjim

Re: Tube Preamp Project: advise and discussion
« Reply #91 on: October 02, 2018, 04:11:10 PM »
I dunno, it sounds like its trying to be good, but I don't think it's clipping the recording. I can hear a fizzy "digital" crackling in the note decays which is present in the silence at the end. I mean "digital" as a description, sometimes it can be something unexpected, like the treble cap in the tone stack... to something actually digital like multiple SMPS noise in the grounds...
Could you hear anything wrong while recording or only afterwards on the recording?
Croeso i Diystompboxes.

If they didn't hear you then you didn't say it.

johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #92 on: October 03, 2018, 07:06:36 AM »
I dunno, it sounds like its trying to be good, but I don't think it's clipping the recording. I can hear a fizzy "digital" crackling in the note decays which is present in the silence at the end. I mean "digital" as a description, sometimes it can be something unexpected, like the treble cap in the tone stack... to something actually digital like multiple SMPS noise in the grounds...
Could you hear anything wrong while recording or only afterwards on the recording?

i can hear it even i hook my preamp into the power amp of my guitar amp. i think it is my wiring. or i'll try to replace my treble cap since it is a multi layer cermaic. i think it is not a good treble cap. Mica caps are pretty expensive. thank you sir.

amptramp

Re: Tube Preamp Project: advise and discussion
« Reply #93 on: October 03, 2018, 09:37:05 PM »
I dunno, it sounds like its trying to be good, but I don't think it's clipping the recording. I can hear a fizzy "digital" crackling in the note decays which is present in the silence at the end. I mean "digital" as a description, sometimes it can be something unexpected, like the treble cap in the tone stack... to something actually digital like multiple SMPS noise in the grounds...
Could you hear anything wrong while recording or only afterwards on the recording?

i can hear it even i hook my preamp into the power amp of my guitar amp. i think it is my wiring. or i'll try to replace my treble cap since it is a multi layer cermaic. i think it is not a good treble cap. Mica caps are pretty expensive. thank you sir.

Film caps are the best deal for audio and they are normally cheap.

SMPS noise is a problem that takes effort to understand and fix and frequently it helps to sacrifice a goat to the EMI gods.  Start with figuring out what the SMPS circuit does and figure out some filtering for it.

Marcos - Munky

Re: Tube Preamp Project: advise and discussion
« Reply #94 on: October 04, 2018, 05:07:24 PM »
At this exact moment, I'm building an Alembic F2B and having noise issues, like static noise. Did this happened in your previous builds? I'm using the same smps, so we may be having the same issues.

anotherjim

Re: Tube Preamp Project: advise and discussion
« Reply #95 on: October 05, 2018, 05:35:57 AM »
Quote
i think it is not a good treble cap. Mica caps are pretty expensive. thank you sir.

I found that a good cap for that role is surprisingly difficult to source. Mylar/Mica/Polystyrene in 100-400pF range with sufficient voltage rating - either very expensive or just not listed, at least at many hobby electronics suppliers. I've found ceramic disc caps with 1kV or 2kV ratings can work well, despite not ideal audio types, they have more than enough voltage handling. For the rest of the caps in the nF ranges, they are cheap and very easy to find as film caps with at least 400v rating.
BTW, the scheme may call for 250pF and you can only find 220pF, it will work fine as a tone control.
Croeso i Diystompboxes.

If they didn't hear you then you didn't say it.

rankot

Re: Tube Preamp Project: advise and discussion
« Reply #96 on: October 05, 2018, 07:58:20 AM »
You can always put HV coupling capacitor before the tone stack, than you can use low voltage capacitors inside it.
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PRR

Re: Tube Preamp Project: advise and discussion
« Reply #97 on: October 05, 2018, 08:51:20 PM »
> ceramic disc caps with 1kV or 2kV ratings can work well, despite not ideal audio types

Ceramics under 1,000pFd will be "NP0" which is totally perfect and fine for audio. 500V is enough for tube tonestacks.

You can get NP0 in larger values but typically not at tube voltages.

There are Tube Guitar Amp web-shops who stock the usual tonestack parts in appropriate ratings and values.
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johngovan1234

Re: Tube Preamp Project: advise and discussion
« Reply #98 on: October 05, 2018, 09:57:42 PM »
Based on your help and informations and the forums i read. It really helps a lot in my learning. Let me share the learning  i get from all of you and from reading forums and discussions of other peoples build.

1. Google search engine is very helpful
2. Tube amp DC Voltage will shock you to the bones if you accidentaly touch the B+. 😁
3. WIRING is so crucial! Yes. You guys are really awesome. Wiring tube amp is far more sensitive than wiring a guitar pedal. An understanding of each wires are really important.
As stated by one of our fellow, make sure that we minimize wires crossing each other in the tube connections. The most troublesome wire is the grid wire. We must use a good shielded wire in this triode pin. Because this gives a lot of noise and those nasty tube overdriven artifacts.
4. Grounding is also very important. Don't forget the star ground and be aware of ground loops.
5. I love youtube tutorials.
6. Capacitor are important to what kind of caps to use. Mylar and poly are good for audio. Ceramics are as much as possible be avoided. They are sensitive to thermal changes and suceptible to piezo effect. Sometimes it becomes a noise anthena. Mylar or Mica or NP0 are good choices.
7. Measure voltages and understand basic functions of what you are doing. Learn how tube functions, how capacitor functions, how resistor fuctions and everything. My downsides are computations and other terminologies i do not know. I'm no engineer nor an electronic expert. I learned things tru forums, and internet searchings.

And many more things i've learned in this forum. I will continue to update as soon as everything is in good shape..as of now, the nasty tone are gone. It is a wiring and capacitor issue. :)

PRR

Re: Tube Preamp Project: advise and discussion
« Reply #99 on: October 06, 2018, 12:30:39 AM »
> Ceramics are as much as possible be avoided.

"Ceramic" covers a w-i-d-e range of stuff.

Think of a baked clay flower-pot versus the glaze on a fine dinner plate.

A 0.1uFd, even 0.01uFd, has historically been a "salted" ceramic, like X7R or Z5U, with funny adulterants to raise the value per unit of space. These high values tend to vary with voltage, temperature, and mechanical stress.

A 1,000pFd or smaller can be made with a "glass-like" ceramic which really is good as glass (but easier to make thin) and shows very-low variation. Under 1,000pFd there's no reason to use "salted" ceramics, the pure stuff is small and cheap. FWIW, small ceramics are good-enough for the Jensen 990, a very high-quality audio studio op-amp.
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