This was intense, Incredible, informative. Tubes are the only thing that terrify me. Thanks for the info. Instant sub.

@CircuitSecrets

3 ай бұрын

Thank you so much!

The BEST tube preamp video to date!!! Why are you not an Astronaut!

...instantly subscribed!!! Thank you for you absolute professionalism!!!

@CircuitSecrets

3 жыл бұрын

Thank you, and thank you for your kind words!

Yep. It's not the killing part of the voltage/current you need to be afraid of, it's the maiming part. If you're dead, you don't need to worry about being maimed, and trying to do anything with half an arm is an exercise unto itself.

Thank you.Great video.Waiting for the next video.

@CircuitSecrets

4 жыл бұрын

Thank you so much! The next video in the tube preamp series will be released next Thursday.

it does add some flavor to your voice, a little bit of breakup and harmonics, noice.

same thing that dude said.. instant sub. Fantastic video. I will now consider all DIY videos not done to this caliber garbage.

@CircuitSecrets

2 жыл бұрын

Thank you so much!

Cool

@fmercer54

3 жыл бұрын

Is it ok to say D Lab, or, Uncle Doug? These are two of the most biggerest of besteress tube amp men for theory and practical , good luck you guys, and your all beloved ....Merry Christmas.

@CircuitSecrets

3 жыл бұрын

Thank you, sorry I didn't see this before. I checked them out because you mentioned them, good stuff!

dude! I use a 12vdc smps form a laptop....works just fine for dual triode tubes and radio pentodes when triode strapped like 12BA6,12AU6, 12AB4, chi-comm 6J1 or the two 6AH6s I'm currently using for my stereo preamp....they got a 3 AMP filament draw between the two connected in series for 12vdc...so careful when selecting components

@CircuitSecrets

2 жыл бұрын

Yeah a lot of 12 volt smps work great for filament to keep the audible noise down, using the 200 volt smps for the plates with a 12 volts smps to supply it and the filaments eliminates the need of a heavy expensive power transformer.

what is the current required for this project? can build multiple channels with the same smps?

@CircuitSecrets

3 жыл бұрын

You need a D.C. supply of around 2 amps to drive both the filaments(heaters) of the 2 tubes and the plates through the SMPS. Because the output of the preamp is a current amplifier I don't think I would try driving more than one channel per smps. Even if it could handle it you would run the risk of causing parasitic osculations and noise . The smps will supply around 37 milliamp at 200 volts and each plate of a 12ax7 can pull a max of 6 milliamp for a total of 24 milliamp max draw for both plates in both tubes. The bottom line is you could try it, but it would take a lot more filtering and you would have to bias it to limit the current draw on the plates which may change the character quite a bit.

This preamp can be used with solid state amps?

@CircuitSecrets

3 жыл бұрын

Yes it should work fine with a solid state amp but depending on the amp it may require some modifications. Make sure you are loading the output of the preamp with a big enough resister or inductive load like a speaker and adjust the value of R9 to limit the output and not exceed the input rating of the solid state amp. The value I used puts it in the ballpark of standard line in signal, you may need a stronger or weaker signal. Depending on the solid state amp design you may want to use capacitive coupling between the preamp and the solid state power amp. Watch for ground loops and use extreme caution, triple check everything, good luck and happy building.

@ManuLeisure

3 жыл бұрын

@@CircuitSecrets thank you for quick reply ! one more question what is the frequency response of this preamp ?

@CircuitSecrets

3 жыл бұрын

I have not checked it with a signal generator and spectrum analyzer, but I have looked at spectrum analyzer results from a few recordings and it seems pretty solid from around 25-30 hz to 18 khz with a real strong mid peak between 500 hz and 1 khz. A heavier output transformer could boost the lows, and a bright cap could be used to reinforce the highs. C2 and C3 could also be changed to expand the bottom end. If these were swapped for say .1uf the bottom end would be expanded but it would probably need more filtering to prevent parasitic oscillations. I tried to keep it as simple as possible to capture the vibe and tone of the old mixing board preamps with less noise in the audible spectrum and lower cost by using the smps for plate supply.

@ManuLeisure

3 жыл бұрын

@@CircuitSecrets hope i will be replicate your project! thanks for making such an easy video !

@CircuitSecrets

3 жыл бұрын

@@ManuLeisure Thank you! Good luck with your project.

I do not mean to criticize, but for whatever reason the audio sounds ... less than ideal and there is also clipping somewhere in the chain. Could the phase be reversed? Double check pinouts. ill be honest its not great sounding.

@CircuitSecrets

3 жыл бұрын

Good ear on the phase inversion! The preamp has 3 gain stages and each stage inverts the signal. An option to correct the phase is to use both triodes in the first tube in a parallel configuration instead of series, or to simply use only one triode of the first tube. An odd number of typical gain stages makes the output inverted. The extra gain stage also increases the chance of clipping or distortion. If you listen to a lot of old recordings you will notice similar artifacts. It is not an audiophile preamp, but an attempt to emulate the old mixer preamps that were prone to overdriven clipping and distortion, but using a modern smps plate supply to reduce the chance of power supply noise while reducing cost. It is also in one of the simplest configurations possible to help other builders figure out the operation of tube preamps so they can experiment and modify it to suit their taste and needs.

@manelliriaromero345

3 жыл бұрын

@@CircuitSecrets Well, that microphone doesn't meet minimums. I have one that I bought just to reuse the body to make a DIY mic. There are tons of low budget mics that sound many times better. That itself might be the cause of not so great sound. I love the content though, and I subscribed.

@CircuitSecrets

3 жыл бұрын

Yeah the mic was pretty bad, I recently changed to an at2020 and in the most recent video Raspberry Pi Pico I used it with the this preamp and recorded with a scarlett solo interface. I was thinking on using the body from an old MXL to build a mic. Let me know how yours turns out and what parts you use. I was thinking a smps powered tube mic but have not gotten to sourcing parts. I have been tied up working on more content on microcontrolers and grbl compatible DC motor controllers. Thank you for subscribing!

@43audio89

2 жыл бұрын

@@manelliriaromero345 How in the hell did you hear the phase? I'm engineer, need a intern? lol

@sshrugg

Жыл бұрын

@@43audio89 This

Great little viceo, but Switch Mode Power Supplies add a lot of noise, so saying they add less audible noise is incorrect. Also, no offence here, but saying you are using the pre-amp for your recording on this video really makes me want to totally avoid it. The sound quality of your voice is really poor, even compared to most KZread videos from 10 years ago. It definitely does not sell me on this preamp at all.

@CircuitSecrets

Жыл бұрын

Different taste for different people, it has a very primitive sound like something from sixty years ago and that was intentional. The mic I was using at the time is very poor quality so that could be part of what you are hearing. The thing about this particular smps is it operates at a frequency above human hearing so the "audible" noise is very low. The added filtering eliminates nearly all the noise even in a spectrum analyzer. If it is used to direct record an electric guitar the lack of audible noise is very apparent. But it is not for everyone, it is just a simple starting point for a primitive tube preamp with a modern twist.