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 21 Jul 2019, 17:22

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 94 posts ]  Go to page Previous  1 ... 6, 7, 8, 9, 10  Next
Author Message
PostPosted: 12 Oct 2008, 13:17 
Offline
User avatar

Joined: 04 Jun 2008, 22:27
Posts: 146
Location: Brazil
RiGuy wrote:
Thats insane and really cool. So, you put it on the output. I wonder if you could use a filter at output instead of the snap on. Not that the snap on is a bad idea to have there. Just wonder if a filter would do the same thing.
So how did you come up with this idea? Just desperation?
Is the output line just straight through the ferrite or did you wind it?
Anyway, really interesting and makes me want to try it on mine just to see if there is any difference. I have cleared up all problems on mine except a humm from my preamp and some HF from the power supply. I think its the fans on the supply but would be neat to try ferrites as I bet they don't mess with the sound as much as caps.

Well, I guess you could call that desperation, yes. I knew my wiring was perfect and still somehow the chips were oscillating. The only thing I hadn't tried so far to fix that was some ferrite chokes, so I thought it was worth a shot. Indeed it worked.
Also the output line is just straight, my wire was too small to wind it around the ferrite. But maybe I'll wind it in the final version.

BUT... there are some bad news. I'm getting a quite dirty top end from the amp. I don't know why really, and I'm 100% sure its not the ferrites (I removed all of them and disconnected both chips, so I had only one working, and still the top end was quite dirty).
What could cause this? All my parts are premium, except for those 68uF caps (cheap no brand). Right now I'm using 26V DC at each 3875.

I would strongly recommend some ferrites in your amp Ri. I never really believed they did help at all, but now I really do.

_________________
http://www.regenceaudio.com
http://valvuladosvintage.blogspot.com.br/


Top
 Profile  
 
PostPosted: 12 Oct 2008, 13:19 
Offline
User avatar

Joined: 04 Jun 2008, 22:27
Posts: 146
Location: Brazil
gmilitano wrote:
Hi Bernardo, I wonder if the problem is your speakers / speaker cable. Are the cables high capacitance? Perhaps the speakers are a very difficult load to drive. Perhaps you can try the amp with another pair of speakers.

I'll try it with another pair. Actually the cables are just cheap ones. But still, the chips without the ferrites and with a dummy 8R load still heat up.
What do you think could be causing the dirty to end?

_________________
http://www.regenceaudio.com
http://valvuladosvintage.blogspot.com.br/


Top
 Profile  
 
PostPosted: 12 Oct 2008, 13:21 
Offline
User avatar

Joined: 04 Jun 2008, 22:27
Posts: 146
Location: Brazil
johnmcquay wrote:
I can't help but think you have a problem with earth loops. :|

Hi John, thanks for your help. I checked and re-checked everything but there are no ground loops. I'm using star ground and all chips have a separate ground wire running to the star bus. I really dont know where is this oscillation coming from. Right now Im even using coax cable everywhere, even for the speaker connection!

_________________
http://www.regenceaudio.com
http://valvuladosvintage.blogspot.com.br/


Top
 Profile  
 
PostPosted: 12 Oct 2008, 13:46 
Offline

Joined: 29 Jul 2008, 08:12
Posts: 182
Location: Wiltshire, UK
You're welcome. It was a shot in the dark for me, I've never built a gainclone amplifier so had to just take a guess.

Kind regards, John.


Top
 Profile  
 
PostPosted: 12 Oct 2008, 22:34 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4577
Location: Winnipeg, CANADA
bsgd wrote:
I'll try it with another pair. Actually the cables are just cheap ones. But still, the chips without the ferrites and with a dummy 8R load still heat up.
What do you think could be causing the dirty to end?

Right, so that rules out the cables and speakers. I'm stumped and out of ideas. Sorry.

_________________
[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


Top
 Profile  
 
PostPosted: 13 Oct 2008, 03:00 
Offline

Joined: 29 Jul 2008, 08:12
Posts: 182
Location: Wiltshire, UK
Have you tried putting a 1n Cap between the supply rail and ground?

Kind regards, John.


Top
 Profile  
 
PostPosted: 13 Oct 2008, 14:48 
Offline

Joined: 29 Jul 2008, 08:12
Posts: 182
Location: Wiltshire, UK
Would it be possible to see a photo of the inside of the build? I work with someone who's built more amps than I've had hot dinners. It's a possibility he may spot something that has been overlooked. I know we all hate a smartass (me especially) but a fresh pair of eyes may be all it takes.

Kindest regards, John.


Top
 Profile  
 
PostPosted: 14 Oct 2008, 12:14 
Offline
User avatar

Joined: 04 Jun 2008, 22:27
Posts: 146
Location: Brazil
johnmcquay wrote:
Would it be possible to see a photo of the inside of the build? I work with someone who's built more amps than I've had hot dinners. It's a possibility he may spot something that has been overlooked. I know we all hate a smartass (me especially) but a fresh pair of eyes may be all it takes.

Here's the pic of the amp built based an BR100 circuit;
download/file.php?id=202&mode=view

Right now the innards is really a mess (cause Im experimenting with everything I can) but I can post a pic anyway. But, aside from small changes, its just the same.

_________________
http://www.regenceaudio.com
http://valvuladosvintage.blogspot.com.br/


Top
 Profile  
 
PostPosted: 14 Oct 2008, 12:15 
Offline
User avatar

Joined: 04 Jun 2008, 22:27
Posts: 146
Location: Brazil
johnmcquay wrote:
Have you tried putting a 1n Cap between the supply rail and ground?

I tried that with 100n and 220n. Didnt help.

_________________
http://www.regenceaudio.com
http://valvuladosvintage.blogspot.com.br/


Top
 Profile  
 
PostPosted: 28 Oct 2008, 15:44 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 20:12
Posts: 972
Location: Houston, TX
Ok. Another suggestion.
Actually you are not following the circuit as shown in 1192. You are using monster caps on your chips. These are supposed to be about 4.7uf and polypropylene. Thats it. The power you need is going to come from your supply. Trust me you can get bass without those monsters on the chip.
Now we may want to ask Gio on this, but the schematic says otherwise. Mike Feurbacher has used this chip with NO caps and claims decent, not fantastic, bass.
Check the datasheet on page 6. It says use of large leaky electrolytics will effect the offset of the ouput voltage.

There seems to be a lot of talk about how hard it is to bridge this chip. Some people are using a DRV134 to help with the problems of differences in input voltage. I need to look into this more and discuss it with Gio.
I am going to post this in the thread so he sees it and comments.
I will work on your boards when I get this figured out because right now I think individual amp boards may not do the trick since these issues and the lack of the DRV134 or some similar circuit may be causing your problems.
Not to worry though :) We will get it done.
Ri

_________________
DIY Lightspeed Passive Attenuator


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 94 posts ]  Go to page Previous  1 ... 6, 7, 8, 9, 10  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 5 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:  
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