The Christiansen "DG" 300B Amplifier Build Thread

[sceleratus]

me too.
the probe skated
 
i had to use the stupid, huge. 0.22uF Mundorf caps and it covered the 9 pin socket points.
pin one is under the cap, close to Q3 and the heat sink.  I had to guide the probe straight down. i couldn't see it but im pretty sure i shorted Q3 and it incinerated everything around it.
for good measure i replaced Q1-4, U1&2 and 8 surrounding resistors.
 
i just this minute finished putting humpty back together again.  i will light the mains in a few minutes.

 

[sceleratus]

I am happy beyond belief.  It's been an ordeal, but I now have MUSIC.
 
I have yet to hook up the resistive circuit necessary for HP's  The amp is dead bang quiet.  Zero as in zero noise.
I started with Zu Audio Soul's.  They aren't as efficient as I expected.  You need to peg the POT and it's loud but at times I think I'd like another 10%
 
BTW.  I am using the SE board with a pair of large Mundorf 0.22 uF in place of the input transformers.
 
I thought there was no way this amp could drive my Thiel CS 1.5's.  Spec says they need 50W.
Guess what, they sound amazing.
So amazing in fact that the Zu Audio Soul's are going back,   Just a much more complete voice.'
 
Tomorrow.... get the HP's working.
I can't wait to hear if they are as quiet as I think they will be.

 

[sceleratus]

My speaker / headphone switch works great.
The Audeze LCD2 R2's sound amazing !
Zero static / fuzz / snow / hum.
Stop the music and they're as quiet as a dead church mouse.

 

[sceleratus]

Now that Humpty Dumpty is rock'n again, I'll take him to the San Diego Meet on Sat Nov 2nd

 

[tomchr]

"Minimum power needed: 50 W"
 
Most of the time for casual listening you're probably driving them with 10~100 mW. Yes 0.01~0.1 W. Maybe even less. 
 
Marketing is a funny discipline. 
 
~Tom

 

[sceleratus]

Here are photos of the current guts.
The  input trans have been switched to the driver board build option that uses 22 mF caps.  I'm back to the 100 ohm Alps Blue pot instead of the stepped attenuator.  RCA jacks replaced the XLR's  (different from photo)  The headphone / Speaker rotary switch works great.
 
It is still quieter than a dead church mouse and my 15 year old Thiel CS 1.5's sound great.  The Audeze LCD2's are amazing  esp. with some old vinyl that I ripped.  I love to hear the needle drop.
 
I'm going to enjoy the music for a few months.  After that, if I get antsy I might implement a differential configuration using the Jensen JT-11P4-1 input trans that Tom drew up.  The recording level of the vinyl rips is lower than digital sources.  It is my understanding that differential will give me a 4V input instead of 2V on the RCA's  A boost to speaker volume would be nice.  Since I made a new assembly for single ended, I can easily switch them.
 
I also came up with matching furniture for the music room.  I'll have to see if it's in the budget.
Other items on the wish list are KR 300B's, Goertz speaker wire, and LCD3's.   I listened to them at the San Diego meet and they are smooth as silk.  It defies logic.
 

 

 

 

 

[tomchr]

Dude!! Suggestion: You really aught to pull the speakers away from the wall. Due to the Haas effect, reflections from the wall will be largely ignored by the ear/brain combo if they arrive after 5~10 ms. Hence, the total round-trip time from the front of the speaker to the wall and back to the front of the speaker should be at least 5~10 ms. This means your speakers should be 340*0.005/2 ~ 340*0.01/2 = 0.85 ~ 1.7 m away from the walls. That's 3~6 feet in 'Merican units.
 
~Tom

 

[sceleratus]

Since that photo the speakers have been moved forward.

With your information I will experiment further.
Many thanks

 

[Tjj226 Angel]

Will you quantify that?

Sorry, I have been extremely busy with school. 
 
What do you mean by this? 

 

[sceleratus]

  Sorry, I have been extremely busy with school. 
 
What do you mean by this? 

Below is the definition:
I was asking if you would empirically backup a subjective opinion with something that can be measured.
 
Empirical evidence is information that justifies a belief in the truth.
 
quan·ti·fy
ˈkwäntəˌfī/
verb
 

• 1.
  express or measure the quantity of.
   
  "it's very hard to quantify the cost"
  
  
• 2.
  LOGIC
  define the application of (a term or proposition) by the use of all, some, etc., e.g., “for all x if x is A then x is B.”.
   
   
  
  

 

[sceleratus]

  Dude!! Suggestion: You really aught to pull the speakers away from the wall. Due to the Haas effect, reflections from the wall will be largely ignored by the ear/brain combo if they arrive after 5~10 ms. Hence, the total round-trip time from the front of the speaker to the wall and back to the front of the speaker should be at least 5~10 ms. This means your speakers should be 340*0.005/2 ~ 340*0.01/2 = 0.85 ~ 1.7 m away from the walls. That's 3~6 feet in 'Merican units.
 
~Tom

Yo! Professor Dude,
If I move the speakers forward, away from the front wall, and closer to the listener and the back wall, won't it take less time for the sound to get back to the front of the speaker?
 
EDIT:
THE RT60 of my room is 0.50
2700 cu. ft.

 

[sceleratus]

Do I have this right?
If my normal listening volume is  > ~45 dB, I won't have a reverb problem
with the source 10ft from the listener.
 
I take it this is w/o RT60 factor being applied.
 

 

[Tjj226 Angel]

  Below is the definition:
I was asking if you would empirically backup a subjective opinion with something that can be measured.
 
Empirical evidence is information that justifies a belief in the truth.
 
quan·ti·fy
ˈkwäntəˌfī/
verb
 

• 1.
  express or measure the quantity of.
   
  "it's very hard to quantify the cost"
  
  
• 2.
  LOGIC
  define the application of (a term or proposition) by the use of all, some, etc., e.g., “for all x if x is A then x is B.”.
   
   
  
  

 
 
1 : The driver is very old. They did not have testing equipment for speakers in the 1950s
 
2: Experience > data Don't believe me? How are the highs on the LCD2 (or 3?)? Pretty good right? A little roll off, but they still sound really smooth and clear. Now go look at a frequency response graph and ask yourself if the graph really reflects your personal experience. 

 

[sceleratus]

  Dude!! Suggestion: You really aught to pull the speakers away from the wall. Due to the Haas effect, reflections from the wall will be largely ignored by the ear/brain combo if they arrive after 5~10 ms. Hence, the total round-trip time from the front of the speaker to the wall and back to the front of the speaker should be at least 5~10 ms. This means your speakers should be 340*0.005/2 ~ 340*0.01/2 = 0.85 ~ 1.7 m away from the walls. That's 3~6 feet in 'Merican units.
 
~Tom

This like it would help the situation.
48" x 48" Sound Panels 
 

 

[tomchr]

Moving the speakers out from the wall beats wall treatment on price every day of the week. The same is true for the reflection off the back wall. If the couch (listening position, I assume) is up against a wall, you may benefit from moving it away from the wall a bit. Just so your ears receive the wall reflection at least 5~10 ms after the incident sound.
 
Rather than adding fancy wall treatments, I'd stick a ficus in the corner for diffusion. It looks prettier than the acoustic foam too.
 
~Tom