Reviewing a cheap 6J1 tube preamp.

6J1 tube preamp.

[@bigbasil1908]

Just watching another video about the 6J1 preamp and the guy is testing it out on an oscilloscope. He says the 1 microfarad capacitors on the output are not letting the bass tones through and is suggesting changing those to 3.3 micro farad, or 4.7 micro farad capacitors. The video is called 'Tube preamp budget kit test and review' and channel 'JohnAudioTech'. Maybe the capacitor changes can give you a much better 6J1 preamp.

[@josiaalbano5309]

my native language is not English, I speak Portuguese... so I apologize for the mistakes. I have this preamplifier. I made the suggested modification to the output capacitors to improve the response. really improved. but the best change I recommend is to place a capacitor in parallel with the cathode resistor, the sound has improved a lot. I suggest calculating with the frequency formula for capacitor=1/2πrf to find the ideal capacitance value for a good response from 20 hertz. Now my problem is learning how to control the noise, maybe lowering the supply voltage will solve it.

[@ChristopherSibert]

In regards to your story about getting a shock, similar thing happened to me with a computer power supply when I was in my early 20s, made me extra cautious around AC power from then on!

[@jonathansmith4947]

Thanks for the video! I was looking for a radio project and was hoping someone had made this.

[@makarov138]

Get you a FX-AUDIO TUBE-03 tube preamp to feed your main amp. Replace the tubes that came with it to a matched pair of 5654Ws, and you will hear wonderful base, and all the way up! That is my setup here at home. Mine is driving a 100W per channel class D amp that drives a pair of 12s with tweeters.

[@timothynolan7250]

The cat!!! Lol. I got one too. Wish I could get ride of it! Great video!!! Thanks.

[@UDX4570PalmSprings-yh1mv]

Run the tube fillaments on DC instead of AC using a full wave bridge rectifier, that will eliminate the AC hum.

[@StevDoesBigJumps]

I'm glad to see that suspicious tube glow was just led's. The presence of transistors isn't very inspiring though, unless they're part of a sidechain or the power supply circuit.

[@andvgeo2253]

thanks for the upload

[@rodneyfranks2726]

Thanks for the video very interesting.

[@ea6wu]

Thanks for the video!

[@cryptodream5092]

Glad you went with LED 👍

[@tartarianhobo7741]

Thank You.

[@switzair8756]

The cat adds a nice little distraction. You could use the purring to compare the base outcome with a semiconductor type. People will like it. Since there are no ugly cats it could also be part of the video. // Great Job, because in many reviews they talk a lot. Without any sound example!

[@TheRadiogeek]

I’m afraid that I am one of those people who has to have all my resistor bands going in the same direction. Nice job on the kit build and video. 👍👏🏻

[@rednerdnecktech2474]

It usually doesn't bother me unless there are a lot of resistors. I still can't figure out the buzzing noise problem. I guess the next solution is to replace the tubes with better quality ones.🤷

[@thomasr.5443]

Yeah, me too!! 😅 Allthough on that kit I did it a bit different. I oriented all the tolerance bands to the middle.

[@HappyHermitt]

Me too mostly

[@dogsauce19]

Hey great video! Noticed the multimeter was on DC for reading the voltage. Could you pull 12V DC from that leg and use it to power a 12V DC amp like a TDA 2050? Cheers

[@HappyHermitt]

I bought one but just realized I need a wall wart for it. I'll build it soon. Any idea of swapping for better capacitors will help it? Thanks?

[@vincenzomauro4754]

I've just noted in the video that 2 of the 4 transistors looks not mounted correctly, the flat side should be facing each other. You can check the marks on the pcb. Next time pay attention touching the board when powered, because the tubes works at 70 volts that can be dangerous. Have a nice day!

[@rednerdnecktech2474]

You are correct about the transistors, nice observation. Good thing a npn transistor turned backwards are still a npn 😆. I has been fix.

[@davidlalremruata]

What if I use it along with a 15 watt Marshall amp to play my guitar? Could it work to change my tone for the better?

[@generalleigh7387]

Hey buddy. I ordered the exact same circuit but with the acrylic shell- question, is it possible to bridge the left channel into the right channel making it into a bridged mono………and double the output? Thanks.

[@rednerdnecktech2474]

I'm sure you could but remember this is a preamplifier not a power amplifier its job is to increase the signal strength for high impedance.

[@elsaarmstrong-zp6ng]

Tubes/valves add even harmonics and soft clipping which enhances the mid and bass frequencies which is pleasing to the musical ear! Guitarists like Mark Knoffler, Brian May love this sound! Many audio fans also find this a pleasing to the ear! Although valve power amps are expensive a solid state power amp with a flat frequency response coupled to a valve pre amp is a cost affective solution as the even distortion is added at the pre amp stage! It adds presence to the signal which gives like live music into your listening area, it seems to add an octave above fundamental and a 5th above ! I used to have 2 Leak TL50 power amps and a .1 % plus pre amp but sold it as the TL 50’s power tubes (matched pair) became too expensive (£160 ) to replace! I now have a pre amp like you have here feeding 2 solid state FET power amps that should last a long time I hope! Fraser.

[@weareelectricgi]

yeah! i have a project converting a hifi audio amplifier into a decent tube sounding guitar amplifier and i'm planning to use that hifi tube preamp to replicate the tube vibe and still use the stock power amp. i hope it will work perfectly

[@weebo19]

your cat was definitely in heat lol

[@jeffwigle9154]

Hi just wondering way can't we hear what it sounds like copy right for testing a product?

[@frequeencytv8130]

Does anyone knows here adding 2 or 4 more tubes meaning it will 4 6J1 or 6 6j1

[@kennethiman2691]

Which side is your input?

[@overbuiltautomotive1299]

howdy from Tn i looked that thing up and found this video thanks ..i sUbeded

[@rednerdnecktech2474]

Thanks for the sub.

[@trankhanhzui]

good audio

[@airmicrobe]

Thank you for this video what if I put 12volts and 1.5A adapter for this kit?

[@rednerdnecktech2474]

As long as it is 12 volt AC, 1.5 amps should be enough , like I said it has to be 12 volt AC.

[@airmicrobe]

@@rednerdnecktech2474 I like to talk about it. I did it long a few weeks ago and I heard really warm music with a big sound after I got the item from AliExpress. Unchained melody from Leann, then a few hours had passed and it permanently turned off. I thought it was too hard for this tiny amp to make the sound or impedence magnifying whatever? I am not good at it. I inspected for a long time and found the adapter is broken not the tube. For the soul music the adapter was victimized I thought but it is not. Thank you for letting me know that. I think adapter was almost broken... I purchased a new one 12 V with 1 A and working so nicely. I ordered the same one in this video and the case suited for the one but AliExpress sent me double of them without a case... And just one pair of tubes. I got two boards.

[@rednerdnecktech2474]

@@airmicrobe I don't use it much but it still works. I would buy extra tubes if you use it a lot. Good luck.

[@airmicrobe]

@@rednerdnecktech2474 I appreciate a lot for ur reply. I DIDN'T ASSEMBLES TWO BOARDS YET. I BOUGHT AIYama one which already assembled. But I don't understand the circuit and just know how to soldering which is also a kid's level. I am a kid. Thank u that is exactly same model.

[@greggb681]

Transistors for a tube preamp? So the transistors do the amplification, not the tubes?

[@rednerdnecktech2474]

No the transistors are for the power rails.

[@christopherdicintio6291]

Don't hate the cat, man.

[@switzair8756]

Here is the layout/plan/schematic of the circuit (and improvement), from an Italian video, 1:02: kzbin.info/www/bejne/pXKppGCvnZdgeKs

[@upside-down6211]

how to add 6.35 jack instead RCA jack?

[@bassieadriaan4278]

You can buy a rca to 6.35 cable

[@upside-down6211]

Can i use 12vac to 12vdc rectifier to use with battery?

[@rednerdnecktech2474]

No you would need an inverter not a rectifier to use this preamp from a battery. This is an expensive solution. There may be a way to power it with (2 ) 12 volt batteries. Having one power the positive rail and one power (reverse)the negative rail but I would have to go back and look at the schematics to figure out where to connect the power supply and test the circuit.

[@tehanindeepapalliyaguru2773]

Can you use dc 12v

[@rednerdnecktech2474]

No it has to be 12v ac.

[@joakojo8470]

Can I change leds? cause It has 2 blue leds and I'd like to put orange leds

[@bigbasil1908]

You would probably need to change the LED resistors to different values depending on the voltage of the new LED's. I don't know very much about electronics but I know LEDs need the correct resistors to prevent burning the LEDs out with too much power

[@joakojo8470]

@@bigbasil1908 thanks for sharing info... Have a great day

[@bigbasil1908]

@@joakojo8470 You too, and have a great christmas friend 😃

[@VPROXE-HELLRAISER]

If I touch the insides of my compressor I'm dead

[@TheAkiiscool]

This thing works on 12volts ac supply... and you have not put those transistors correctly...I have built a couple of these and mine works fine, no hum in my preamps.

[@rednerdnecktech2474]

I have since corrected the problem good observation. Good thing a npn backwards is still a npn which allowed it to work.😊

[@elsaarmstrong-zp6ng]

I think there is a voltage doubler in the circuit! Fraser

[@elsaarmstrong-zp6ng]

Also screening is very important in valve circuits!

[@asharahmadarrauf]

Is it class A

[@rednerdnecktech2474]

Yes

[@SalvvOrtiz]

Scissors would work better on those bags.