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The Christiansen "DG" 300B Amplifier Build Thread - Page 6

post #76 of 630
Quote:
Originally Posted by sceleratus View Post

Cool to build... get to do some SMD.

 

Love your enthusiasm for shown for SMD soldering rolleyes.gif

 

That said, I don't have much experience with SMD soldering (done a few one off repairs on mobile phones but we also had a reflow/re-work station) and I don't have a very steady hand nor a fine sized soldering tip.

post #77 of 630
Thread Starter 
Quote:
Originally Posted by DefQon View Post

Love your enthusiasm for shown for SMD soldering rolleyes.gif

 

That said, I don't have much experience with SMD soldering (done a few one off repairs on mobile phones but we also had a reflow/re-work station) and I don't have a very steady hand nor a fine sized soldering tip.

This was the first time I've ever done SMD.  Heck, very little soldering of any kind at all.

And I have the shakes due to my meds.

 

Just watch the 3 part soldering tutorial on Dave Jones EEVBLOG.  Follow his instructions.... piece of cake.

All the SMD components are re-flow using an iron.  1) small solder pillow 2)Next, hold the component in place with tweezers 3) Heat component and pad....the tricky part... 4)Let go of the component.  5) solder the other end...6 ) go back to clean up the first.

The components are so cheap get 4-5 extras.   One more thing.  Don't Sneeze.

 

The one thing that made it possible for an old guy like me is a big round magnifier on an arm that lights up.

Get that and you are banked.

post #78 of 630

For SMD, I have a magnifying glass that I can wear like a visor, and it works pretty well.  You need some kind of magnification to work with SMD stuff.

 

But, as SMD goes, these boards don't look too bad, might be a good intro to SMD.  Fine pitch IC's is where it can get challenging.

 

Pretty sure I am going to end up building a 300B amp too, although mine may have a different configuration, I started looking at the different parts of the circuit, to try to decide what to do for each.

 

Randy

post #79 of 630
Thread Starter 

Modifications necessary to support ECC88 are finished.

Upgrade to Jupiter Beeswax caps is complete.

Starting to work on longer cables.

 

 

post #80 of 630

I have heard good things about Jupiter caps so hopefully they sound good.

 

One comment on wiring, when you run two wires together, where one wire is either a voltage or a signal, and the other wire is ground (or return for that voltage/signal), you should twist the two wires together for as much of the run as possible.

 

For example, the wires from the regulators to the driver board should be "twisted pairs".

 

Randy

post #81 of 630

Thanks for the update and the link.  I'm trying not to build up too much interest, though it may be too late for that. :)  Your thread brought me out of a 2 year hiatus from Head-Fi.  I'm enjoying my current amps and don't have a need to build a 300B as I don't have planars, although it would be nice to have "moar power!".  I would probably design and build my own circuit, if I were going to do a 300B build, or at least something on the market with different input tubes.  Maybe something along the lines of a WA-5 with 6SN7 and 300B, or a 6SL7 and 300B variation.

 

Since you did the mod for 6DJ8, are you able to "toggle" back easily?  Also, if you did 6DJ8, you should be able to tweak it to support 6H30 as well.  One of my amps is a Bijou, and I'm using that with 6H30 input and 6N6P drivers.  I like the 6H30 over 6DJ8/6922/ECC88 variants I've tried in the past.  You don't have to, just that I would. :)  It's less "tuby" than others I've tried.  My 6H30 are Sovteks.  Not the most "hifi", but I like em, so that's what I use.

 

I don't know if you put a fuse on the AC side, but please do, use a real tight tolerance while you're building.  This way it'll trip if anything shorts.  Be wary around caps, very wary.  Drain them properly with a power resister, before you touch them.

 

What layout are you planning on, and hopefully you won't get any magnetic coupling of the transformers.  It looks like you have it oriented properly, if you're not aware.  You may still get interference though, try it with some sensitive headphones and see if you get hum and how far apart you need to move them.  Hopefully you'll be hum free when all is said and done.  Also, if you've never built an amp, look into a star ground scheme.  I also like to separate chassis ground (earth) and signal ground with a ground loop breaker.  Personally, I use a ground bus for signal (heavy gauge copper wire, I think I use 8ga), then tie it to earth via the ground loop breaker.

 

Do you know what the overall gain is going to be?

 

Oh, SMD soldering.  Solder reflows on to the pads "automagically", just dab and go, and inspect with a loupe.  Use flux, when in doubt use some more, and swipe it over the pins, and it's all golden from there.  For most things, I like a wider flat tip, and swipe away from the body, in parallel with the pins.  I've tried smearing across the pins and that never really worked well for me.  I've done lots of SMD projects and they are all more or less the same technique.  An easier way is to use solder paste and bake it.  I think that's the way Twisted Pear builds their boards.  I've never done that, though, as I've never had problems with SMD work.

 

http://www.freetronics.com/pages/surface-mount-soldering-with-a-toaster-oven#.UcTrn-tVuKA


Edited by holland - 6/21/13 at 8:40pm
post #82 of 630
Thread Starter 

Made all the cables.

Checked the 300B bias.

Ran a check with some crappy GE 6BQ7A's that came with my Lyr.

 

A huge improvement over the 6N6P's

 

I now have real-glass plugged in.

 

1958 Amprex "tiny" Bugle Boys.  "D" getter.

Outrageous.

 

I still have the damn snow problem….. for now I'm just kick'n it and enjoying some incredible tunes.

 

Thanks for the tips.....  I need to read your post and digest.   Right now I'm toast.... soldering all day....  It was worth it.  I have the ECC88 / 7308 / 6922 sound that I wanted so badly.

post #83 of 630
Congrats, my friend. Well done! Enjoy. smily_headphones1.gif
post #84 of 630
Thread Starter 

It's starting to settle in.

Does anyone have an opinion about Genalex Gold Lion 300B's versus the JJ 300B's ?

 

Photos.

First is the sketch of the enclosure.

 

Second  is the final Top and Rear panel cutouts.

I noticed the other day that my silicon bronze panel is warped.  This probably won't work for the water cutter.

If that's the case, I may switch to copper

 

Last is another shot of Frankenamp with cleaned up wiring and 1965 E188CC's.  Very sweet glass.

Ok.  Since it's my thread, I can post redundant photos. smile.gif

 

 

 

 

post #85 of 630
Thread Starter 

Schematics:

 

 

 

 

 

 

 

post #86 of 630

I was taking a closer look at his site, he's got some cool stuff, including an amp that I was thinking of (no PCB though).

 

Thanks for the schematics, put it in the OP too (?).  Are you able to list the 6DJ8 mod in detail?

post #87 of 630

In one of the early threads after it started working, you said there was "slight static", like vinyl.

 

It is still there?  Is it like low level noise?

 

Curious.

 

Otherwise, sounds like a winner, can't wait for the meet to hear it.

 

Randy

post #88 of 630
Thread Starter 

Quote:
Originally Posted by holland View Post

I was taking a closer look at his site, he's got some cool stuff, including an amp that I was thinking of (no PCB though).

 

Thanks for the schematics, put it in the OP too (?).  Are you able to list the 6DJ8 mod in detail?

 

A bit of a disclaimer.
I asked Tom how many 300Bs are working in the field (NPI).  He said most folks don't let him know when they are working.  I was the first.
Tom has two units, that makes mine serial  #3.  Add to that that this is the first HP implementation mine would now be serial #1.  This is not a Bottlehead build, Tom has no intention of kiting it out.  He does however provide a complete BOM that includes DigiKey part numbers.  That the guesswork out of ordering the components.
Remember, I'm an idiot with a soldering iron… "OP" is that operating points? 
 
 If's so I don't have a clue but Tom talked about it them for the conversion to ECC88. ...
"Modifying the circuit to try out the two different operating points identified from the data sheet, selecting the best one, and taking a few quick THD measurements took a bit over an hour. At 1 kHz, the THD comes in at about 0.2~0.3 % for 1 W out. 1 % THD happens at 9.5 W. Max output power is just shy of 11 W."
 
ECC88 Driver Board BOM Modifications:
Switch the LEDs D1, D3, D6, D8 for high-efficiency Vishay TLHG6400.
R2 = 47 ohm
R16 = 47 ohm
D5 = Wire jumper (short circuit)
D10 = Wire jumper (short circuit)
TU1 = E88CC
TU3 = E88CC
Reworking the board was not too difficult.  A Soldapullt is mandatory.  I ordered the parts to have on hand if I wanted to take it back to 6N6P.
Also there is a set of Driver board schematics on Tom's site for the ECC99 / 12BH7A.
 

 

 

 

Quote:
Originally Posted by randytsuch View Post

In one of the early threads after it started working, you said there was "slight static", like vinyl.

 

It is still there?  Is it like low level noise?

 

Curious.

 

Otherwise, sounds like a winner, can't wait for the meet to hear it.

 

Randy

 

Randy,
The snow is still there, It's a bit north of "slight", but fades into the music.
Tom is working on it.  As you know anything shows up in a HP amp and this, as I said, is serial #1
 
Here is how the snow starts: 
Turn the power switch on.
5 seconds of slight hum..builds a bit, then
A sound like a needle across vinyl.
A slight pop…then the snow.  Like it passed gas.
It does not matter where the volume pot is set, the snow volume is constant.
 
I thought it was the 300B's.  Tom's reply:
When the tube is cold, its cathode (= filament for a directly heated triode like the 300B) doesn't emit any electrons. So no current flows. The hum you hear is probably just some induction into the output transformers or something. The needle across vinyl, I'm guessing is the output tube starting up. Its filament/cathode is now warm enough that it starts emitting electrons. The slight pop (probably occurs about 20~30 seconds after power-on) is likely the input stage starting up. That brings the hiss.
I don't recall a needle across vinyl sound in mine. But if my hypothesis is correct, that sound would really depend on how exactly the filament warms up and how the voltages stabilize. That probably varies considerably from tube to tube.
Good news is that I've found a way to reduce the hiss by almost 25 %. You'll need a 10 uF electrolytic capacitor rated for at least 25 V. Connect the capacitor at the footprint for D2. The (+) pin goes to the square pad (what would have been the cathode of D2). Short out D4 with a wire. Connect a similar 10 uF cap at D7 and short out D9. These D2, D4, D7, D9 are the empty footprints by the LEDs. They were intended for zener diodes for use with the 12BH7A, but can be repurposed for these capacitors. I was able to lower the hiss on my amp from 375 uV to 300 uV.
 
It's certainly isn't COTs, it's a work in progress.  (It also lack a UL approved sticker.smile.gif)  Don't get me wrong, I like dead-bang quiet and I hope it can get there.  All in all, I am enjoying my amp a lot. 
 
I'm hoping a set of Balanced HD800's show up at the show so I can audition them.
 

 

 

 


Edited by sceleratus - 6/23/13 at 11:43am
post #89 of 630
Quote:
Originally Posted by sceleratus View Post

 

Remember, I'm an idiot with a soldering iron… "OP" is that operating points? 

 

Opening or original post.  It would be good to have the schematics in the first post of the thread

 

Quote:
If's so I don't have a clue but Tom talked about it them for the conversion to ECC88. ...
"Modifying the circuit to try out the two different operating points identified from the data sheet, selecting the best one, and taking a few quick THD measurements took a bit over an hour. At 1 kHz, the THD comes in at about 0.2~0.3 % for 1 W out. 1 % THD happens at 9.5 W. Max output power is just shy of 11 W."
 
ECC88 Driver Board BOM Modifications:
Switch the LEDs D1, D3, D6, D8 for high-efficiency Vishay TLHG6400.
R2 = 47 ohm
R16 = 47 ohm
D5 = Wire jumper (short circuit)
D10 = Wire jumper (short circuit)
TU1 = E88CC
TU3 = E88CC
Reworking the board was not too difficult.  A Soldapullt is mandatory.  I ordered the parts to have on hand if I wanted to take it back to 6N6P.
Also there is a set of Driver board schematics on Tom's site for the ECC99 / 12BH7A.

 

Thanks for the info!

post #90 of 630
Thread Starter 
Quote:
Originally Posted by holland View Post

 

Opening or original post.  It would be good to have the schematics in the first post of the thread

 

 

Thanks for the info!

DONE

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