Author Topic: My First DIY 6BM8 Tube Amp (Read 23000 times)

s2kov · « **Reply #30 on:** Sep 01, 2011 at 08:47 PM »

Diy is the way to go!

Quote from: alexg 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.

stick · « **Reply #31 on:** Sep 02, 2011 at 07:44 AM »

Quote from: TonyT 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...

When do you recommend the use of LED's?

edrel sison · « **Reply #32 on:** Sep 02, 2011 at 08:37 AM »

james for your hi-fi applications, as they are covering quite a wide bandwith. you do not want coloration on your amps and preamps. kung pang gitara ok yung coloration, some guitarists like that colored tone.

tapos na speakers?

stick · « **Reply #33 on:** Sep 02, 2011 at 01:03 PM »

^ Just finished one.. already sounding great... bass is exceptional... gonna finish the other half tomorrow.. the sad thing is, I still need to sand these boxes (I'm asthmatic)

...

ATJr. · « **Reply #34 on:** Sep 02, 2011 at 03:23 PM »

Quote from: stick on Sep 02, 2011 at 07:44 AM

When do you recommend the use of LED's?

there are a lot of reasons to use led's or silicon diodes since their dynamic resistance is very low and uniform with frequency, but it is better you find out on your own....

the resistor/ecap combo presents a complex impedance that phase shifts with frequency happens all the time, which i consider as distortion....

stick · « **Reply #35 on:** Sep 04, 2011 at 01:58 PM »

^Thanks... maybe your right, I'll just have to find out on my own then... hehe...

Anyway, just finished the second enclosure yesterday... really tiring, but the reward - really amazing sound... I never expected it would sound that way... Stong Bass, voice presence and just about right highs... I'm using Altec 403A with frequency response of 70~11kHz, 95dB sensitivity...

edrel sison · « **Reply #36 on:** Sep 05, 2011 at 08:47 AM »

james a sammi tweeter would complete and add sparkle to your new speaker system. kausapin mo na si hang sub rhee

stick · « **Reply #37 on:** Sep 09, 2011 at 08:01 AM »

Went to Ronald's place last night with an awesome experience with his turntable and CDplayer set-up... we tried to hook-up my amp with his NAD 20-bit CD Player... - again this amp really amazed me... he used his Q-acoustic 6" floorstanders... then BOOM... the sound is fantastic... titles from Jheena Lodwick and some instrumentals, MJ returned from the dead on his turntable ... then we tried his 12" Philips on Open Baffles... put on Noel Cabangon (did i spell it right), original CD... pure clarity was heard all-over...

Thank you Ronald... he even lend me a pair of Dai-ichi PT-6 tweeters for my set-up...

Thanks again till next time...

edrel sison · « **Reply #38 on:** Sep 09, 2011 at 09:09 AM »

Quote from: stick on Sep 09, 2011 at 08:01 AM

Thank you Ronald... he even lend me a pair of Dai-ichi PT-6 tweeters for my set-up...

pinahiram? ipinamigay na lng dapat ni parasound (ronald) yung daichi tweeter sayo at naka JBL alnico tweeter na yan!

dana · « **Reply #39 on:** Sep 10, 2011 at 07:47 AM »

Quote from: edrel sison on Sep 09, 2011 at 09:09 AM

pinahiram? ipinamigay na lng dapat ni parasound (ronald) yung daichi tweeter sayo at naka JBL alnico tweeter na yan!

agree, malamang binigay na ni ronald syo yan

so, bakasyon ba si bigtime ronald?

parasound · « **Reply #40 on:** Sep 10, 2011 at 09:05 AM »

Big Time?

long time no see brod. sana next vacation ko magkita tayo.

Quote from: dana on Sep 10, 2011 at 07:47 AM

agree, malamang binigay na ni ronald syo yan
so, bakasyon ba si bigtime ronald?

alexg · « **Reply #41 on:** Sep 13, 2011 at 04:51 PM »

Instead of LED's, try LM317 current sink on the cathode, on my EL84 amps, I usually get good results with these.

Edrel have the PCB template, he might be able to have his PCB buy make some more.

PM me if you need help how to use the LM317 on the cathode.

ATJr. · « **Reply #42 on:** Sep 13, 2011 at 05:00 PM »

^here you go......http://users.telenet.be/davshomepage/current-source.htm and here....http://diyparadise.com/yhlmccs.html

stick · « **Reply #43 on:** Sep 14, 2011 at 08:13 AM »

wow thanks for the additional knowledge...

just to confirm... does this mean i remove my cathode resistor and bypass cap and replace it with the YHLMCCS? nothing more nothing less?

Sir Edrel was trying to adjust cathode resistor and bypass and we were able to make around 36mA. tube specs is 40mA...

so if I introduce a 32ohm resistor on the YHLMCCS we would then get 39mA on the pentode...

hehe... tama ba mga sinabi ko?

ATJr. · « **Reply #44 on:** Sep 14, 2011 at 12:03 PM »

^yes, it is that easy and uncomplicated......

Quote

we were able to make around 36mA. tube specs is 40mA.

you will find out that for tube work, a 4mA difference is no big deal.....

alexg · « **Reply #45 on:** Sep 14, 2011 at 12:32 PM »

Quote from: stick on Sep 14, 2011 at 08:13 AM

wow thanks for the additional knowledge...

just to confirm... does this mean i remove my cathode resistor and bypass cap and replace it with the YHLMCCS? nothing more nothing less?

Sir Edrel was trying to adjust cathode resistor and bypass and we were able to make around 36mA. tube specs is 40mA...

so if I introduce a 32ohm resistor on the YHLMCCS we would then get 39mA on the pentode...

hehe... tama ba mga sinabi ko?

Yes, though I find that you still need to bypass the lm317 with capacitor, it sounds much better with the caps.

ATJr. · « **Reply #46 on:** Sep 14, 2011 at 01:40 PM »

^you do not need bypass caps with LED's...

stick · « **Reply #47 on:** Sep 15, 2011 at 08:12 AM »

now I'm really learning... thank you...

we're gonna try these informations on the second build... we call it now "The Twin"...

will post pictures soon...

ATJr. · « **Reply #48 on:** Sep 15, 2011 at 03:33 PM »

i use forward biased silicon diodes on my preamp builds......

resistor/capacitor combo on the cathodes present varying impedance with frequency and so is a source of distortions.....

one of my design philosophies is to avoid capacitors where i can and use the smallest value needed...... capacitors are evil.....

stick · « **Reply #49 on:** Sep 21, 2011 at 08:17 AM »

made some more tweaks on the triode side, changing values here and there... now the amp sounded more lively than before, details are so much better, I tought it already sounded excellent before... clipping is almost gone... this 6BM8 tube is tricky!...

ATJr. · « **Reply #50 on:** Sep 21, 2011 at 12:43 PM »

rules of thumb with triodes, gain increases as you increase the plate load resistor, but output swing decreases...

removing the cathode bypass caps decreases gain but increases output impedance.....

nice to remember these rules of thumbs....

efren_ · « **Reply #51 on:** Sep 21, 2011 at 12:48 PM »

Quote from: stick on Sep 21, 2011 at 08:17 AM

made some more tweaks on the triode side, changing values here and there... now the amp sounded more lively than before, details are so much better, I tought it already sounded excellent before... clipping is almost gone... this 6BM8 tube is tricky!...

congrats sir & happy listening, 6BM8 has a good reputation even among foreign builders.
I use the same opt(world class

) from sir Edrel in my EL84M SE, now the amp is in the hands of my brother

Presently i'm using 13FM7 compactrons for my SET, tubes & opt build by sir Tony, Z11 irons from sir Edrel

stick · « **Reply #52 on:** Sep 22, 2011 at 07:51 AM »

Quote from: TonyT on Sep 21, 2011 at 12:43 PM

rules of thumb with triodes, gain increases as you increase the plate load resistor, but output swing decreases...

removing the cathode bypass caps decreases gain but increases output impedance.....

nice to remember these rules of thumbs....

Thank you... this are very good information for us to remember...

Quote from: efren noble on Sep 21, 2011 at 12:48 PM

congrats sir & happy listening, 6BM8 has a good reputation even among foreign builders.
I use the same opt(world class ) from sir Edrel in my EL84M SE, now the amp is in the hands of my brother
Presently i'm using 13FM7 compactrons for my SET, tubes & opt build by sir Tony, Z11 irons from sir Edrel

Thanks... do you have links for the schematic of 13FM7? I'm currently studying differnt tubes and their behavior in circuits...

ATJr. · « **Reply #53 on:** Sep 22, 2011 at 12:16 PM »

^yes, tubes do not have a sound on their own, it is what you do with those tubes that brings out the magic......ergo, the magic is really in your hands......

efren_ · « **Reply #54 on:** Sep 23, 2011 at 09:53 PM »

Quote from: stick on Sep 22, 2011 at 07:51 AM

Thanks... do you have links for the schematic of 13FM7? I'm currently studying differnt tubes and their behavior in circuits...

here's a 6EM7 SE (6em7 loctal i think, & 6V heater, 13FM7 is a doudecar 12 pin compactron & 13V heater) I use the schematic for 13FM7.

for the power tranny i use a C4242

the final outcome

LEDs provide the blue glow

stick · « **Reply #55 on:** Oct 20, 2011 at 07:29 AM »

^Really nice blue light...

Updates on my 6BM8 Amp... Clipping is now gone... at last!....

now to start another project... a pre-amp using 12AU7 or 12AX7 or the 5842... and the EL84/6BQ5 zen amp...

dana · « **Reply #56 on:** Oct 28, 2011 at 04:46 PM »

hi james, nice meeting you earlier together with some friends/officemate I brought along Edrel's skunk work area.

edrel, thanks rin...first time to hear those humungous bookshelf speakers, WOW

: 15in Celestion mated with 8in full range (Phillips? alnico driver...with a simple 2.7uF crossover)...

stick · « **Reply #57 on:** Nov 04, 2011 at 07:23 AM »

Thanks dana... if you have time you can drop by today and take a listen to the 6BM8 driving those humungous bookshelf speakers

....

parasound · « **Reply #58 on:** Jan 11, 2012 at 04:14 PM »

posting for james.

SET EL84 (Decware Zen)

stick · « **Reply #59 on:** Jan 11, 2012 at 05:18 PM »

^^ Thanks for posting... was not able to take pictures before you left the country...

I have now completed seven (7) amps... 3 sets SE 6BM8, 2 sets SE EL34 (Decware), 1 set SE KT88 (Alex G.) and lastly SE 6V6GT... will post pictures soon...