DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 12 Jul 2020, 04:13

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 1690 posts ]  Go to page Previous  1 ... 39, 40, 41, 42, 43, 44, 45 ... 169  Next
Author Message
PostPosted: 12 Nov 2010, 02:31 
Offline

Joined: 18 Sep 2010, 12:48
Posts: 81
Are you saying that I should remove the earth ground of the scope in order to measure more accurately without the interference of the earth ground, and only the reference ground?

180 degrees out of phase - the wave goes the other way round?


Top
 Profile  
 
PostPosted: 12 Nov 2010, 04:59 
Offline

Joined: 18 Sep 2010, 12:48
Posts: 81
Does anyone has the sound files to do test/observation/benchmarking on a scope?

I hear occasional pops in the music I hear through the amp, what could be the problem? Capacitor internally shorted itself?


Top
 Profile  
 
PostPosted: 12 Nov 2010, 13:14 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
santik wrote:
Are you saying that I should remove the earth ground of the scope in order to measure more accurately without the interference of the earth ground, and only the reference ground?

180 degrees out of phase - the wave goes the other way round?

No lifting the ground will prevent accidentally shorting your amp out. As far as phase shift read Neets Module 6 http://www.tpub.com/content/neets/14178/ specifically "operation of the triode".

As tube gate voltage increases that means current through the tube increase and the voltage is dropped across the anode resistor. Since we are biasing the gate fo the mosfet from below the resistor the perceived voltage decreases as all of this is happening. The audio signal is in the mv range and it is controlling a 12v dc or relative +/- 6volts swing because our bias is set midway. Hence the signal is amplified and 180 out of phase with the input. We are only listening to the output and not a live recording so there is no issue with cancellation.

Think of it this way, if you go to you home stereo and swap the + and - on both speaker you would not notice a difference. If you swapped + and - on only one speaker you would get cancellation, as one speaker is pushing air the other is drawing back. The sound will be hollow and dispersed. Hope this makes sense.


Top
 Profile  
 
PostPosted: 12 Nov 2010, 13:18 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
santik wrote:
Does anyone has the sound files to do test/observation/benchmarking on a scope?

I hear occasional pops in the music I hear through the amp, what could be the problem? Capacitor internally shorted itself?

You may hear an occasional and quick Pssst sound, that's the mosfets. Some fets will do this more than others. You can try heatsinking the Mosfets or try other mosfets.


Top
 Profile  
 
PostPosted: 12 Nov 2010, 13:35 
Offline

Joined: 13 Apr 2010, 10:39
Posts: 37
Location: Dallas, Texas, USA
You know, I've experienced some 'warming up' noises.
The tube heats up and the pins will expand and move around in the tube socket.
Sometimes the audio is quite noisy during a short period in warm-up.

I'm sure a 'top quality' tube socket might help, but I just used some
spares I had on hand, and I think they were old-stock from the 1960s.

I think we've grown up in a period of solid-state and perhaps we're not used to these
characteristics...

Mike Y
Dallas, Texas
roggom wrote:
santik wrote:
Does anyone has the sound files to do test/observation/benchmarking on a scope?
I hear occasional pops in the music I hear through the amp, what could be the problem? Capacitor internally shorted itself?

You may hear an occasional and quick Pssst sound, that's the mosfets. Some fets will do this more than others. You can try heatsinking the Mosfets or try other mosfets.


Top
 Profile  
 
PostPosted: 13 Nov 2010, 11:07 
Offline

Joined: 18 Sep 2010, 12:48
Posts: 81
we know that the tube has Mu of 17...

but is there any components in the amp that will increase or decrease the gain?
and what is the formula?
for different headphones, different impedance. 8-)


Top
 Profile  
 
PostPosted: 13 Nov 2010, 13:22 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
The plate load resistor, generally called RL in most circuits P1 in mine. sets the gain of the tube. Now remember we are limited by the power supply, because too much gain will cause clipping and distortion. Also CK or C2 in the schematic will increase gain ( or in respect prevent decrease in gain) by maintaining the correct cathode voltage, also known as AC bypass.

If your amp is still on the breadboard take out c2 and you will notice a decrease in gain, well enough to notice. This amp is designed for 10db of gain, enough for headphone use.

Now headphone impedance is a whole other animal. The mosfet buffer has a gain of approximately 1, its job is to decrease the amps output impedance to match the impedance of the headphones. You may have seen opamp buffers were the output is tied to the negative input pin. This is used in fa-schmidts yaha amp http://www.fa-schmidt.de/YAHA/

My amp was a combination of the yaha with a Szekers, it was improved by using the plate voltage to bias the buffer and reducing part count.

Gio has an awesome example of the Szekeres mosfet follower amp.


Top
 Profile  
 
PostPosted: 15 Nov 2010, 23:28 
Offline

Joined: 18 Sep 2010, 12:48
Posts: 81
roggom wrote:
santik wrote:
Does anyone has the sound files to do test/observation/benchmarking on a scope?

I hear occasional pops in the music I hear through the amp, what could be the problem? Capacitor internally shorted itself?

You may hear an occasional and quick Pssst sound, that's the mosfets. Some fets will do this more than others. You can try heatsinking the Mosfets or try other mosfets.


so, you are saying that the MOSFETs should be as cool as possible in order not to induce distortion? and some FETs will definitely make this sound?


Top
 Profile  
 
PostPosted: 15 Nov 2010, 23:31 
Offline

Joined: 18 Sep 2010, 12:48
Posts: 81
How to make the ripple go away from my AC-DC power supply? it gives hissing...

I have 4 1000uf 50V electrolytic, 1uf 250V MXP, 0.1 50V ceramic. how can I join them?


Top
 Profile  
 
PostPosted: 16 Nov 2010, 13:51 
Offline

Joined: 16 Nov 2010, 13:03
Posts: 1
Hello Roggom,

I'm looking at the PCB image you provided (http://diyaudioprojects.com/Solid/12AU7 ... -Image.png) .

But seems to me there is an error with the C2 capacitor polarity (at the top).
The positive (+) pin should be connected to the cathode (pin no. 3 of the tube) not the GND trace as the image shows.
Same error is on the component layout image and eagle BRD file.

Am I right?

Please put an update to the project page for everyone using your PCB design to check the polarity.

thanks
--
smiki


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 1690 posts ]  Go to page Previous  1 ... 39, 40, 41, 42, 43, 44, 45 ... 169  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 7 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy