#26 pre amp - Page 162 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th February 2012, 07:55 PM   #1611
diyAudio Member
 
Join Date: Nov 2002
My B+ supply ONE CHANNEL
Attached Images
File Type: jpg #26 schematic with VR and regulators 2112012.jpg (50.8 KB, 451 views)
  Reply With Quote
Old 11th February 2012, 10:37 PM   #1612
diyAudio Member
 
Join Date: Jan 2007
Location: The 1st State
Gents,
Quick grounding methodology check....
On my turret board (See post 1557) I have a ground connection on the board which I will use as my central ground connection. Im assuming that:

1 - The filaments will be grounded here (through a 1 ohm 2w resistor) only (the CT on the heater transformer will float)
2 - This will be the only ground connection to the signal chassis
3 - This is where I will connect a single wire to the umbilical cord ground

If the above is correct - excellent. If not, please let me know where I've strayed.

Additionally, the ground for the input/output....I assume that the input grounds will join the output ground, which only gets connected to the output transformer ? Or do these then join the central grounding point as well ?

In the power supply, I am going to ground the center tap of the HV transformer at the first cap, and have the entire PSU drain back to the plug. I will also connect the umbilical ground at this point (plug). The safety ground will connect to the PSU chassis at one point at the plug (3rd prong).

Thanks,
Steve

Last edited by Steven-H; 11th February 2012 at 10:44 PM.
  Reply With Quote
Old 11th February 2012, 10:57 PM   #1613
Magz is offline Magz  United States
diyAudio Member
 
Join Date: Oct 2009
Location: New Jersey, USA
Quote:
Originally Posted by Original Burnedfingers View Post
My B+ supply ONE CHANNEL
Similar to my plan, but I'm thinking I'll use a cascode CCS in place of R1 (set to 26mA), no SSHV reg and a parafeed type output with a Lundahl LL1676 amorphous cobalt core x-former wired 2:1 and a 1uF cap from the x-former back to the cathode, to get an output impedance of ~1875ohms.

That's the plan today, anyway...
  Reply With Quote
Old 12th February 2012, 07:53 PM   #1614
diyAudio Member
 
Join Date: Jan 2007
Location: The 1st State
More grounding thoughts....

I've started to layout my umbilical. It is a standard 8-pin screw-in molex affair. My thoughts are:

Pin 1 - Left Fil +
Pin 2 - Left Fil -
Pin 3 - Right Fil +
Pin 4 - Right Fil -
Pin 5 - B+
Pin 6 - Bias
Pin 7 - Ground
Pin 8 - Ground

Now after reading this forum and searching elsewhere, it seems that I maybe best served to ground the input jacks, output jacks, and volume control at a single point, and carry this back to the main ground in the PSU..So that could be Pin 7.
Pin 8 would ground the last bias filter, and the cathode resistors, and take that back to the PSU.

Does that make sense, or am I best served grounding everything at one central point, then use a single ground back to the PSU ?

Thanks !
  Reply With Quote
Old 12th February 2012, 08:23 PM   #1615
diyAudio Member
 
Join Date: Nov 2002
I'm thinking about an XLR for the filament feed and a Speakon NL4FC for my high voltage. I'm going to float the RCA ground from the chassis both input and output and run the ground either back on the unused #1 terminal of the XLR or an unused terminal on the Speakon connector. I have had good luck taking the ground (signal) and putting a resistor 10-40 ohm in series and then running it to the star ground.

Last edited by Original Burnedfingers; 12th February 2012 at 08:25 PM.
  Reply With Quote
Old 13th February 2012, 02:02 PM   #1616
diyAudio Member
 
Join Date: Jan 2007
Location: The 1st State
Well....I got one of the chassis done last night....Kinda

Its all glued up and sanded; however I don't think Im going to apply the finish yet. I'll build the amplifier, test it - then if all goes well I'll be able to just remove the top and side plates and apply the finish (too clumsy on my workbench...hot soldering irons do a number on natural shellac...).

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

Sorry for the poor photo quality....I'll get better ones once the finish is applied.
  Reply With Quote
Old 13th February 2012, 02:04 PM   #1617
diyAudio Member
 
Join Date: Sep 2009
Location: Vietnam
Blog Entries: 2
Send a message via Yahoo to quanghao Send a message via Skype™ to quanghao
[QUOTE=Steven-H;

Nice!
__________________
Group buy DAC-END R (ES9018) full assembled board
update 06/14/2013 :http://www.audiodesignguide.com/DAC32/index2.html
  Reply With Quote
Old 13th February 2012, 02:13 PM   #1618
Magz is offline Magz  United States
diyAudio Member
 
Join Date: Oct 2009
Location: New Jersey, USA
Quote:
Originally Posted by Steven-H View Post
Well....I got one of the chassis done last night....Kinda

Its all glued up and sanded; however I don't think Im going to apply the finish yet. I'll build the amplifier, test it - then if all goes well I'll be able to just remove the top and side plates and apply the finish (too clumsy on my workbench...hot soldering irons do a number on natural shellac...).
Nice! What TVCs are you using, and how many steps does it have? I have a Khozmo 48-step ladder attenuator for my build, but am contemplating TVC because of the step-up ability.


.

Last edited by Magz; 13th February 2012 at 02:15 PM.
  Reply With Quote
Old 13th February 2012, 02:18 PM   #1619
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
Hi Steven,

Quote:
Originally Posted by Steven-H View Post
Does that make sense....
I do it exactly as you have planned. Ground all signal grounds in the preamp to one point. carry all grounds of separate supplies like B+ and bias separately from PSU to preamp and connect them to your cetntal ground or ground buss there.

Nice build BTW!

Thomas
__________________
http://vinylsavor.blogspot.com/
  Reply With Quote
Old 13th February 2012, 02:18 PM   #1620
diyAudio Member
 
Join Date: Jan 2007
Location: The 1st State
Thanks !

I picked up the SILK autoformers:
Silk Audio 23 Step Supermalloy TVC (Pair) | Diy HiFi Supply

They are 23 step. As you can see in my one photo, I am going to wire up that step-up ability to a switch in the front for some lower powered sources.

Click the image to open in full size.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 09:51 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2