Author Topic: My First DIY 6BM8 Tube Amp (Read 22974 times)

stick · « **on:** Aug 27, 2011 at 09:04 AM »

This 6BM8 Vacuum Tube is really impressive. I purchased transformers from Sir Edrel... He designed the power trans at 200-0-200 and 3.15-0-3.15, and Output Transformers at 6k/8R UL tap... I copied the circuit from various schematics and I used the schematic mainly from http://www.audioxpress.com/magsdirx/ax/addenda/media/205vanWaarde-pt1.pdf ... I made my own revisions based on actual output sound and most of the revisions by Sir Edrel. I will post the final schematic later. Almost all electronic parts came from SirEdrel... except for the tubes, Volume Pot, Chasis..

The Chasis is made of aluminum with acrylic side covers. Chasis are made by me, Benjie and Olan... really a pain in centering holes...

The Sound... really marvelous! Two Thumbs Up.... Sir Edrel heard it.... this 2W/ch can really perform well attached to an 8" Altec Lansing mounted on a gigantic baffles... In the picture this amp is 95% complete... still need to shine or paint the front plate...

edrel sison · « **Reply #1 on:** Aug 27, 2011 at 07:31 PM »

Congratulations James on your first DIY tube amp! More than happy to help out!
Now show us the innards!

ATJr. · « **Reply #2 on:** Aug 28, 2011 at 07:10 AM »

good job!!!

Edrel, ano sukat nung round opt containers? pinasadya mo ba yan?

edrel sison · « **Reply #3 on:** Aug 28, 2011 at 07:49 AM »

those were capacitors tony, the opts are underneath.

ATJr. · « **Reply #4 on:** Aug 28, 2011 at 08:09 AM »

ahh ic......thanks....

edrel sison · « **Reply #5 on:** Aug 28, 2011 at 08:30 AM »

i have heard this amp tony. amazingly loud. sound quality is nice. recommended for a first DIY project. easy to build and fairly simple.

ATJr. · « **Reply #6 on:** Aug 28, 2011 at 09:45 AM »

yes...the 13FM7 that efren did is also nice, i was told....parang gusto ko tuloy gumawa ng SET......

s2kov · « **Reply #7 on:** Aug 28, 2011 at 06:01 PM »

Congrats on your project!

What speaker did you used?

edrel sison · « **Reply #8 on:** Aug 29, 2011 at 09:35 AM »

andy we tried using the 8 inch altec you also happen to have..403 i think.

dana · « **Reply #9 on:** Aug 29, 2011 at 10:14 AM »

congrats stick & edrel!
what value and caps are those round looking tubular ironns?
would be nice to make one too, have this non working reverb(surround) tube amp
from pioneer using 6BM8, I can scavenge..
how does this compare with decware el84 decware SEP amp?...both same output level of 2Wrms/ch...

stick · « **Reply #10 on:** Aug 29, 2011 at 01:05 PM »

Thanks everyone... here's the inside...

@dana.. the caps value is 80uf/240V Oil Capacitors...they are usually used in motors/compressors and aircons... I don't know about el84, but this 6BM8 really impressed me... maybe thats why japanese are very fond of them...

I also bufffed the front plate to mirror finish... will post pictures soon...

ATJr. · « **Reply #11 on:** Aug 29, 2011 at 02:02 PM »

nice work stick........

there are compactrons you can try, they sell for 1$each in the states....13FM7, 6AG9, 6LU8, sounds nice too...

oweidah · « **Reply #12 on:** Aug 29, 2011 at 02:57 PM »

congrats!

i used to own an allied 333/pioneer sx34 6bm8 receiver. napakaganda tumunog.

another 6bm8 thread
http://www.pinoydvd.com/index.php/topic,98720.0.html

stick · « **Reply #13 on:** Aug 29, 2011 at 04:03 PM »

@TonyT... wow so cheap... $1 per tube... pabili naman... hehe...

@ojofool... thanks... i will read your thread...

edrel sison · « **Reply #14 on:** Aug 29, 2011 at 08:54 PM »

One particular trait of Stick's build was that it uses non electrolytic capacitor to bypass the cathode. Instead a 3 X 22uf 63V polypropylene caps in parallel are used.

Dana, very easy to build. You see that allen bradleys?

I have some bugle boy 6BM8s. If i will have the time I will make the same amp for an IPOD..

stick · « **Reply #15 on:** Aug 30, 2011 at 11:22 AM »

Sir Edrel, almost finished cutting plywood parts for the first 8" enclosure you recommended, medyo mahirap at maraming parts.... its hard to miter the diagonal sides... but i made it... maybe i can finish 1 today...

edrel sison · « **Reply #16 on:** Aug 30, 2011 at 12:02 PM »

woah james you are fast! would you mind to post some pictures of the raw baffle here, i am very interested with the outcome! make 2 of them before trying them out to have a better outlook of the result in stereo. did you buy just 2 of the altec 403s?

s2kov · « **Reply #17 on:** Aug 30, 2011 at 02:07 PM »

Non-polar capacitor is a better choice for cathode bypass due to its low esr characteristic.

Quote from: edrel sison on Aug 29, 2011 at 08:54 PM

One particular trait of Stick's build was that it uses non electrolytic capacitor to bypass the cathode. Instead a 3 X 22uf 63V polypropylene caps in parallel are used.

Dana, very easy to build. You see that allen bradleys?

I have some bugle boy 6BM8s. If i will have the time I will make the same amp for an IPOD..

ATJr. · « **Reply #18 on:** Aug 30, 2011 at 02:17 PM »

LED's do not have esr and has very low dynamic resistance.....

edrel sison · « **Reply #19 on:** Aug 30, 2011 at 02:23 PM »

Tony there is about 17 to 18V ata on the cathode, how many LEDs or diodes will it require. biased at around 36mA i think..

ATJr. · « **Reply #20 on:** Aug 30, 2011 at 05:02 PM »

Quote from: edrel sison on Aug 30, 2011 at 02:23 PM

Tony there is about 17 to 18V ata on the cathode, how many LEDs or diodes will it require. biased at around 36mA i think..

2 rows of 10 green led's in series parallel should do it.....led's are cheap and abundant....

otoh, film types are a definite improvement over ecaps.....

edrel sison · « **Reply #21 on:** Aug 31, 2011 at 08:01 PM »

james try led biasing as tony suggested above. might make the sound even better!

s2kov · « **Reply #22 on:** Aug 31, 2011 at 08:31 PM »

street light??

Quote from: TonyT on Aug 30, 2011 at 05:02 PM

2 rows of 10 green led's in series parallel should do it.....led's are cheap and abundant....

otoh, film types are a definite improvement over ecaps.....

ATJr. · « **Reply #23 on:** Sep 01, 2011 at 06:35 AM »

^kinda.....

here is a nice thread: http://www.diyaudio.com/forums/tubes-valves/81492-red-light-district-another-pp-el84-amp.html

an array is something like this:

stick · « **Reply #24 on:** Sep 01, 2011 at 08:05 AM »

I'll try this LED array soon... I have this led array but SMT type LED's with 24V requirement... will this work?

have to finish my enclosure first... here's the first one.. Sir Edrel thanks for the Fiberfills... I just discovered and read that it should be placed on top and bottom of the enclosure...

then I buff the front plate of my amp to mirror like...

alexg · « **Reply #25 on:** Sep 01, 2011 at 09:10 AM »

Excellent for a first project!

Another diy'er hitting the dust, be careful, diy is very addicting and educational. You will learn that there are a lot of people out there who are ripping other people! hahahahahahaha....

Edrel's trannies are great.

Keep it up.

edrel sison · « **Reply #26 on:** Sep 01, 2011 at 10:17 AM »

alex long time no hear. what's up? can you send me an sms, i lost most of my contacts my phone died down a week ago..

ATJr. · « **Reply #27 on:** Sep 01, 2011 at 12:11 PM »

Quote

I have this led array but SMT type LED's with 24V requirement... will this work?

24volts is a wee bit high, but you can try....what you can do now is measure your cathode voltage and see what the voltage is, 15 to 18 seems just about right....

stick · « **Reply #28 on:** Sep 01, 2011 at 12:29 PM »

Thanks alexg...

yah your right tonyT... I remembered measuring only 17.6V...

ATJr. · « **Reply #29 on:** Sep 01, 2011 at 12:34 PM »

^nowadays, i use the resistor capacitor combo exclusively for guitar amps, the coloration it introduces is desired by guitarists...