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 18 Sep 2019, 23:16

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 97 posts ]  Go to page Previous  1 ... 5, 6, 7, 8, 9, 10  Next
Author Message
 Post subject: Re: Baxandall circuit
PostPosted: 28 May 2018, 01:48 
Offline

Joined: 13 May 2016, 02:02
Posts: 131
Location: Javea, Spain
I have a problem. As I said, the above setup sounds great. From the start, I've been listening to Robben Ford and the Blue Line..... good loud raunchy blues. Now, I've listened to some quieter music and discovered that I have crackling and popping sounds. Turn off the music altogether and there it is, a continuous crackling and popping. Switching the tone stack in and out with the defeat switch makes no difference. Using the earth lift switch makes no difference. Take out the preamp and just use the 6EM7, no crackle and pop. When I built the preamp I followed Suncalcs' schematic but left out the 33uF bypass caps because I didn't have any. I assumed this would give me less gain but no other problems. Could this be because I have a wooden chassis and therefore no shielding against radiated EMI/RFI noise?


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 28 May 2018, 02:14 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5134
Location: Australia
Try different tubes in the preamp

_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 29 May 2018, 10:51 
Offline

Joined: 13 May 2016, 02:02
Posts: 131
Location: Javea, Spain
Okay, tried different tubes and the problem is still there. Switching out the tone stack doesn't make any difference so that should rule out that part of the circuit causing problems. The noise is in one channel only. The noise has no pattern just random crackling with occasional loud pops.
I've been prodding around with a plastic stick on solder joints and components without any luck. I could just exchange each component in the problem channel with the good channel until the noise changes channel, but was hoping for a more scientific approach.


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 29 May 2018, 12:50 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4023
Location: Arizona, USA
Hi, Check to see that the tube pins and tube socket are clean. Use something like DeOxit on a pipe cleaner to do the socket pins. Crocus cloth or other fine grit stuff can do the pins.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 30 May 2018, 09:39 
Offline

Joined: 13 May 2016, 02:02
Posts: 131
Location: Javea, Spain
Hi Bruce, Thanks for your input. I tried your cleaning tips and even soldered in a new tube socket for the 12AU7. No change, still have the problem. I will change the 12A*7 tube socket to be sure but I'm not hopeful. I have only one 12AU7 but I have another on order. I put the one I have in another preamp and it worked fine. This was my only way of testing it, but I guess it's not a real test as it's in a different environment. Could I try a 12AY7 in place of the 12AU7 to see if the fault is still there? I know I couldn't leave it there, but for a short test to rule out the tube?


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 30 May 2018, 12:21 
Offline

Joined: 13 May 2016, 02:02
Posts: 131
Location: Javea, Spain
After all the tube pin and socket cleaning I was pretty sure it wasn't a tube or socket problem. Switching the tone stack in and out made no difference so it wasn't that. The tone stack did make a difference to the sound of the crackling and popping, so I assumed the problem must be before the tone stack. Began changing components between channels from the beginning of the signal chain and on the fourth component change (100k resistor to ground after 5k resister on cathode) the noise changed channels. Put in a new 100k and problem solved. I've metered the resistor and it shows 100k exactly. It just breaks down under load. There must have been an easier way. Still, happy now, just have to tidy up.


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 30 May 2018, 17:47 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1591
Location: US Pacific Northwest
john55 wrote:
I've metered the resistor and it shows 100k exactly. It just breaks down under load.
So just as a point of curiosity, what was the resistor technology (metal film, metal oxide, wire wound, carbon film, carbon composition, etc.) and what was the source and country of origin?

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 30 May 2018, 18:14 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5134
Location: Australia
john55 wrote:
After all the tube pin and socket cleaning I was pretty sure it wasn't a tube or socket problem. Switching the tone stack in and out made no difference so it wasn't that. The tone stack did make a difference to the sound of the crackling and popping, so I assumed the problem must be before the tone stack. Began changing components between channels from the beginning of the signal chain and on the fourth component change (100k resistor to ground after 5k resister on cathode) the noise changed channels. Put in a new 100k and problem solved. I've metered the resistor and it shows 100k exactly. It just breaks down under load. There must have been an easier way. Still, happy now, just have to tidy up.

I hate fault finding but love building from scratch. Good work, persistence paid off.

_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 30 May 2018, 21:31 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4023
Location: Arizona, USA
Hi, Not a common problem, but it is the kind that will drive you nuts.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 31 May 2018, 01:13 
Offline

Joined: 13 May 2016, 02:02
Posts: 131
Location: Javea, Spain
Suncalc wrote:
john55 wrote:
I've metered the resistor and it shows 100k exactly. It just breaks down under load.
So just as a point of curiosity, what was the resistor technology (metal film, metal oxide, wire wound, carbon film, carbon composition, etc.) and what was the source and country of origin?


PR9372 series, Metal Film, 0.5W, Audio Resistors manufactured in Mediapolis, Iowa USA by Precision Resistive Products Inc.
This is the first time I've used non color coded resistors. I wouldn't do it again. It's too difficult to see what is where.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 97 posts ]  Go to page Previous  1 ... 5, 6, 7, 8, 9, 10  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 15 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