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 23 Sep 2020, 01:31

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 2 posts ] 
Author Message
PostPosted: 15 Jun 2020, 18:17 
Offline

Joined: 15 Jun 2020, 17:13
Posts: 1
Bought a 185 on ebay but it has been partially modified to be a line level ready amp. The preamp section was removed along with the 7025 tube/socket. How do I go about connecting the RCA's to the input tubes. Shouldn't there be some sort of buffer circuit from the rca to ground? I assume it can't be directly wired to the grid of the 12ax7 tubes. Also what is the hum pot's purpose. It looks like they started to take that out as well. Thanks for any help.


Top
 Profile  
 
PostPosted: 15 Jun 2020, 20:40 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4235
Location: Arizona, USA
Hi, As a line level power amp you will need a way to control the volume. I believe I would put a 100K volume control at the input and it should be fine. The output (center tap) of the control can probably go directly to the tube grid. The "Hot" end of the pot going to the RCA and the other end to the signal ground. The hum pot is not usually seen on consumer gear but is quite common on pro (like guitar) gear. It goes between the two sides of the heater circuit. The center tap then goes to the ground. Adjusting it tends to minimize the hum in the amp. There are other variations but that is the most common.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Google Adsense [Bot], ropetrick and 31 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