Topic: My DIY tube amplifier and preamplifiers

[wufei]

Looks like my threads were merged into one and so I have to modify the title of this thread so as to represent all of my DIY tube projects. 

List of my projects currently posted:

1. 6BM8 base power amp
2. EL34 Power Amp
3. 12AX7, 12AU7 all tube phono and line stage preamplifier




Hello, let me share my first DIY tube amp that I just recently completed.  It is 6BM8 based single ended amplifier, the schematics I got from the web.  This build has a good story in it, I met bro remington via sulit when he posted a small amplifier with 6BM8 tube in it, I bought the amp and played with it until I managed to blow her up due to experimentation, due to frustration I salvaged the tube and set out of building a completely new amplifier.  Remington introduced me to Master Tony, the latter is so very kind to sell me one of his power transformer (I got the old transformer shorted in the secondary winding, dont ask how I did it, its a complex one).  With all the parts sourced I set out to build my very first tube amp project, my first is a solid state amp based on 2n3055 and mj2955 but that was 25 years ago. I have to give credit to Remington for influencing me to go back to the audio hobby once again.

Though this is not a unique project but for me who just got back Im really happy on what I have achieve that I am proudly sharing my work in this thread, I didnt know the pinoydvd it is sir remington who told me about this site and Im glad that there is such site for the hobbyist to go and ask questions.  My new project that I working now is the single ended EL34 based Amplifier.

[tony]

welcome to the forum wufei, another tubero is discovered by me....

i think you have room in there for 3/4 inch OPT's....

[RXV]

Once you get to meet Remington, get ready to get back to the audio addiction! I know I did hehe

[remington]

Nice bro and finally nag member ka na din dito! Welcome to the forum, Pretty sure you will enjoy and discover a lot of audio related stuff here and improve your tube amp building talent more. Looking forward to hear your el34 set. Also a very touching story behind your 6bm8 SET build, it really sound sweet, SET na SET talaga ang SQ and ako ang BI behind it 

[remington]

Once you get to meet Remington, get ready to get back to the audio addiction! I know I did hehe

grabe bro...... BI talaga ako

[wufei]

Thank you master tony for the warm welcome.  Master I lost your home number, I hope you wont mind PM it to me.  Thanks again for the xformer and the tube socket.   Master are you talking about the output transformer? yes sir, the output im using is quite small, it doesnt have much bass as the bigger one. 

Master when I increase the capacitance of the bypass capacitor on the cathode of the triode in 6BM8 I noticed an increase in gain but it also affected the low end, is it the right behavior? I though when you increase it the more low you will get along with the gain. Thanks

[wufei]

Remington,  hahaha oo BI ka bro.   I po post ko na din yung latest build ko,  now preamp naman with baxandall tone control

[tony]

Once you get to meet Remington, get ready to get back to the audio addiction! I know I did hehe

if you can melt solder, you can build tube amps....
did you know that the Dynaco ST70 was built my many
who where not even into electronics?
the only requirement then was
that you understand English and can follow instructions...

[tony]

Thank you master tony for the warm welcome.  Master I lost your home number, I hope you wont mind PM it to me.  Thanks again for the xformer and the tube socket.   Master are you talking about the output transformer? yes sir, the output im using is quite small, it doesnt have much bass as the bigger one. 

Master when I increase the capacitance of the bypass capacitor on the cathode of the triode in 6BM8 I noticed an increase in gain but it also affected the low end, is it the right behavior? I though when you increase it the more low you will get along with the gain. Thanks

i am making a pair slightly bigger than what you have now....
the bypass cap in shunt with the cathode resistor of the pentode section of the 6BM8
forms the negative voltage required at the grid, it is positive wrt to ground and so
grid is negative wrt to cathode...in order not to lose transconductance,
the bypass cap is there so that at ac, the capacitor puts the cathode to ground.
the low frequency cutoff is determined by the time constant formed by the resistor and capacitor combo...
pm'ed you my contact details....

[dana]

congrats and welcome here, Wufei (wats in a name, a bruce lee disciple, jeet kun do practitioner ? 
madaming mababaet dto tsaka BIs.
DIY rin ba ung tube cage?

[wufei]

master tony thanks. i will call you soon, i see, master im referring to the bypass on the triode first stage of the 6bm8, when i increased the cap value it became somewhat like a brightness, the gain up so do the mid and high,  so maybe im not doing anything right, when i completely remove it the low improve. how can i determine the right value. thanks master.

i am making a pair slightly bigger than what you have now....
the bypass cap in shunt with the cathode resistor of the pentode section of the 6BM8
forms the negative voltage required at the grid, it is positive wrt to ground and so
grid is negative wrt to cathode...in order not to lose transconductance,
the bypass cap is there so that at ac, the capacitor puts the cathode to ground.
the low frequency cutoff is determined by the time constant formed by the resistor and capacitor combo...
pm'ed you my contact details....

[wufei]

thank you sir, its my name when im still not filipino 

regarding the tube cage, pareho kayo ng tanong ni bro remington haha,, diy ko yung idea to use yung
lalagyan ng spoon and fork na gawing tube cage, only 80pesos sa supermarket i de dremel mo lang yung mga excess 

congrats and welcome here, Wufei (wats in a name, a bruce lee disciple, jeet kun do practitioner ? 
madaming mababaet dto tsaka BIs.
DIY rin ba ung tube cage?

[tony]

master tony thanks. i will call you soon, i see, master im referring to the bypass on the triode first stage of the 6bm8, when i increased the cap value it became somewhat like a brightness, the gain up so do the mid and high,  so maybe im not doing anything right, when i completely remove it the low improve. how can i determine the right value. thanks master.

in any common cathode stage, removing the cathode resistor bypass caps,
stage transconductance is lowered, gain decreases, output impedance increases,
but you gain more linearity and lowered distortion also ...

if you can measure the voltage accross that resistor and replace that
resistor with a diode string or an led, you will get still another response...

[remington]

very resourceful itong si wufei( joey) sir dana pati lalagyan ng kutsara ginawang tube cage hehe!!! but the amp sounds sweet parang nilagyan ng sugar

[xbase]

Hello, let me share my first DIY tube amp that I just recently completed.

ganda ng cage...

[remington]

and guess what are those footing that he used..... cabinet door handles...LOL ...galing

[tony]

well if you can imagine it, you can do it....this is what DIY is all about....

[RXV]

Very resourceful

[remington]

wait til' he post his newly assembled el34 SET. We listened to it last night, sweet sounding din and dead silent!

[wufei]

Thanks for the compliment bro remington.  post ko medyo busy lang sa work at pag accumulate ng parts para sa 6 tube DIY pre-amplifier ko.

Thanks Master Tony for the Output and Power transformer, youre the man!
 

wait til' he post his newly assembled el34 SET. We listened to it last night, sweet sounding din and dead silent!

[wufei]

Hi, please allow me to share my latest build, its an EL34 base all tube single ended amplifier. 
I got the kit from China, as with many chinese product tradition, Its missing some parts, luckily these missing parts I easily obtained from Deeco, no manual also exist but only a schematic diagram so I need to figure out the layout of every parts for point to point wiring.  It has an EL34 tube for the finals and 6n9p for the driver stage,  I replaced the 6z3p tube for a 5u4g NOS that I have on my bin (for looks and sound tightness).  The amp sound warm and tight, I enjoyed building it as well as listening to it, good with coffee or if im lucky with a bottle of beer.  Here are some pictures of my DIY amp. Thanks

   

[remington]

nice finally na post na din. Very nice and clean build and it has a SQ of a typical SET amp. Keep them coming bro waiting to hear your your pre amp builds

[remington]

Thanks for the compliment bro remington.  post ko medyo busy lang sa work at pag accumulate ng parts para sa 6 tube DIY pre-amplifier ko.

Nice!!! I will wait fot that. nakabit na ba opt's ng 6bm8 bro? parinig ako ha!

[deist]

Nice build sir! congrats 

[dana]

stainless chassis or aluminum chassis clear coated only?
anong wood and finish ung side burns?
pasilip ng ilalim
nice build, clean and ruggedly handsome...nice nice nice .

[xbase]

direct replacement lang ba un 6z sa 5u rectifier?

[tony]

@dana, that is a kit from China.....
heard this amp from the May 1 EB, good sounding too...

nice job as ussual Joey......btw, i have a choke and some caps you can use....

@Jun, there is another tube diy'er from Marikina, i am trying to look for his pm, will forward to you...

there are a lot of other tuberos here in Pasig and i am trying to convinve them to post here....

[wufei]

@deist - sir thank you for your kindness

@remington - bro thanks sorry busy lang lately dalhin ko sayo yung phono preamp

@dana - thank you sir, i will upload the picture.

@xbase - same pin naman po, parang mas malakas yung 5u, master tony can you shed a light on this, than you.

@master tony - thank you for your generosities,  sa filter chokes and other stuff nd for the good discussion.

[wufei]

ayus bro, kaya lang baka igawa ulit ako ni master kasi 7k pala yung primary though pwede humina nga lang yung power. gagawa ata ng 5k opt

[wufei]

Sir eto po. thanks

stainless chassis or aluminum chassis clear coated only?
anong wood and finish ung side burns?
pasilip ng ilalim
nice build, clean and ruggedly handsome...nice nice nice .