Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Headphone Systems Everything to do with Headphones

"Estudiante" Hybrid (7370 + MOSFET)
"Estudiante" Hybrid (7370 + MOSFET)
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 7th February 2018, 02:08 PM   #31
Antoinel is offline Antoinel  United States
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
"Estudiante" Hybrid (7370 + MOSFET)
Quote:
Originally Posted by xrk971 View Post
Nice work JP. What DC-DC step up are you using? Note that you need to use the LM317HV for the CCS of the SE Class A output stage. I tried regular LM317 and it did not work. Very finished design.
Hello xrk971. A constant current source [CCS] which uses LM317 can oscillate unexpectedly. Consider adding a Zobel [10 Ohm resistor in series with 0.1uF] like that found in power amps between the output of LM317 and ground to remedy!

Best
Anton.
  Reply With Quote
Old 10th February 2018, 10:55 PM   #32
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
"Estudiante" Hybrid (7370 + MOSFET)
I think the issue was the 48v supply - LM317 is not rated that high and it probably latched into a safe mode.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 14th February 2018, 04:26 PM   #33
Obe1 is offline Obe1  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Stumptown
Default Cathode Resistor Clarification

Thank you SodaMod for presenting this project and all your nice tutorials on the wtfamps.com web site.

I'm a tube noob, so please help me understand this: Since the target quiescent operating point is -1 volt DC on the grid, to created 2.5mA of plate current, it seems like the cathode resistor should be something closer to 400 Ohms instead of the 750 Ohms shown on the schematic? Please set me straight.
  Reply With Quote
Old 14th February 2018, 05:02 PM   #34
Obe1 is offline Obe1  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Stumptown
Default Correction

My apologizes to Sodacose for misspelling you name in my earlier post.
  Reply With Quote
Old 14th February 2018, 05:24 PM   #35
Sodacose is offline Sodacose  United States
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Your observation is not flawed, Obe1! The plate curve calc suggests that 400 ohms would put us where we want to be (1V/2.5ma).

Our goal is to get the anode to sit around half the supply voltage so that the output stage can swing up and down with signal. In practice, I found that a 750 ohm resistor put my anode at 24V. I didn't explain this anywhere on the page though. I'll revisit my write up and maybe add some additional voltage check measurements (probably helpful for others, too).

Here is a detail of the different cathode resistors:

Click the image to open in full size.

You can see that although the difference in value appears to be large, the anode voltage (found on the green dashed line) varies less than you might expect (between dashed red and dashed blue).
__________________
WTF Amps || /r/diytubes/
  Reply With Quote
Old 14th February 2018, 10:24 PM   #36
Obe1 is offline Obe1  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Stumptown
Thank you Sodacos for your prompt and comprehensive responce to my inquiry.

It all makes much more sense now.

My lesson of the day: Creating a design using vacuum tubes is like working with any other component. When you wish to push it close to it's specified boundaries, science & logic must accept some assistance from a strong dose of thaumaturgy, a pinch of good luck, and possibly a bigger hammer.

Salud!
  Reply With Quote

Reply


"Estudiante" Hybrid (7370 + MOSFET)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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
lGl-2, continuing "hybrid madness" - no GNFB class A vzaichenko Solid State 225 18th February 2015 05:22 AM
"Hybrid A-1000" - Very Old MOSFET amp duane2012 Solid State 3 10th September 2012 05:59 PM
A "Vintage" Integrated Amp Inspired Hybrid regal Headphone Systems 1 29th December 2011 07:12 PM
Jfet/opamp "hybrid" phono stage 00940 Analogue Source 8 11th March 2011 06:29 PM
Hybrid amp Aloia GY-50 "a step beyond of" Stee Solid State 12 27th January 2011 07:19 AM


New To Site? Need Help?

All times are GMT. The time now is 06:23 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki