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 16 Dec 2018, 04:33

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: help with schematic
PostPosted: 08 Apr 2018, 19:18 
Offline

Joined: 08 Apr 2018, 18:59
Posts: 2
hello Im new here but have been trying to teach myself as much as possible. I'm still not great reading schematics, so i was hoping someone would look at this schematic for an amp i own and tell me what kind of biasing scheme it has. It's an obscure little amp from Shell Electronics model 2020P Manhasset. I would like to specifically know if its cathode biased.

Manhasset Schematic

thanks for any help!


Top
 Profile  
 
 Post subject: Re: help with schematic
PostPosted: 09 Apr 2018, 05:44 
Offline
User avatar

Joined: 02 Mar 2009, 12:41
Posts: 1070
Location: Vänersborg, Sweden
Yes it is - both channels 200Ohms//100uF. You could split the cathode R and C and use 400Ohms and 47uF (or preferable 100uF) per channel.

_________________
Magnus

“If you don't know where you are going, any road will get you there.”
―Lewis Carroll


Top
 Profile  
 
 Post subject: Re: help with schematic
PostPosted: 12 Apr 2018, 13:14 
Offline

Joined: 08 Apr 2018, 18:59
Posts: 2
Soundbrigade wrote:
Yes it is - both channels 200Ohms//100uF. You could split the cathode R and C and use 400Ohms and 47uF (or preferable 100uF) per channel.


Hmm...yes but it looks like the same resister is used for the 12ax7 heater voltage not sure if it can be changed.


Top
 Profile  
 
 Post subject: Re: help with schematic
PostPosted: 13 Apr 2018, 15:33 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 3858
Location: Arizona, USA
Hi, I have seen that it older amps. The cathode current is used to provide a DC source for the preamp heaters. Usually a rather large filter cap to keep the signal component from modulating the heater of the preamp tube. I have replaced a number of the resistors in that sort of circuit. When they fail nothing works right and usually the fuse does not blow. The amp will not work if the preamp tube is removed either. It can really mess your mind if you have not seen this type of circuit before. Common in Eico amps.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 48 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