Voltage gain stage for Non-NFB MOSFET current amp - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 19th October 2009, 12:54 AM   #1
Banned
 
Join Date: Mar 2009
Location: Atlanta, GA
Default Voltage gain stage for Non-NFB MOSFET current amp

I have a 2SK1530/2SJ201 class A/AB (adjustable) amplifier, that has unity voltage gain and no negative feedback.

I have attached the circuit for one mono side, power supply included.

What should I drive it with? I would like a discrete voltage gain stage, with as little feedback as possible.

Thanks!
Attached Images
File Type: png A15MK2.png (24.4 KB, 521 views)
  Reply With Quote
Old 19th October 2009, 01:21 AM   #2
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Blog Entries: 1
How about that JFET BOZ?
  Reply With Quote
Old 19th October 2009, 02:16 AM   #3
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally Posted by gripracer View Post
I would like a discrete voltage gain stage, with as little feedback as possible.
How 'bout one with no feedback, highly linear, ultra low noise, outstanding common-mode rejection, can accept balanced and unbalanced sources, and has infinite PSRR?

Click the image to open in full size.



se
  Reply With Quote
Old 19th October 2009, 02:16 AM   #4
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Try a single-ended parallel-feed 6H30 triode with a constant-current anode load. Bias at about -3 V and about 25 mA with about 80 V on the anode. Yes, honestly.
  Reply With Quote
Old 19th October 2009, 02:52 AM   #5
Banned
 
Join Date: Mar 2009
Location: Atlanta, GA
@ Steve: I don't know if you're joking, can I seriously use a transformer as a voltage gain stage?

Quote:
Originally Posted by ra7 View Post
How about that JFET BOZ?
Do I know you?

I do have a BOZ that I could use. I just wasn't sure if it was the right type of thing


Quote:
Originally Posted by Gordy View Post
Try a single-ended parallel-feed 6H30 triode with a constant-current anode load. Bias at about -3 V and about 25 mA with about 80 V on the anode. Yes, honestly.
Could I do the same thing with a 6N6P or 6N2P?

Last edited by gripracer; 19th October 2009 at 02:55 AM.
  Reply With Quote
Old 19th October 2009, 03:06 AM   #6
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by gripracer View Post
Could I do the same thing with a 6N6P or 6N2P?
In theory I would suppose yes, however I've not used those tubes in practice. If I remember correctly the 6N6 is much like the 6H30 but for lower power duties. The main factors to consider are gain, internal resistance (R plate) and (perhaps the most important) the linearity. Check out the anode curves. The 6h30 is very good - notice how parallel the lines are. This leads to good open-loop performance which I guess you are searching for. When it is constant current source loaded the output impedance is roughly equal to the internal plate resistance, which is about 1350-ish Ohms for the 6H30. As long as your power buffer has reasonable input capacitance then they should match up fine. You will get a gain of about 14 from it as a single tube stage.
  Reply With Quote
Old 19th October 2009, 03:16 AM   #7
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally Posted by gripracer View Post
@ Steve: I don't know if you're joking, can I seriously use a transformer as a voltage gain stage?
Oh absolutely.

Of course you can't take just any step-up trannie and drop it into any circuit or any situation. But as long as you provide it with proper loading, drive it from a source which doesn't overload it or have too high an output impedance, absolutely you can use a transformer as a voltage gain stage. And a very nice one at that.

se
  Reply With Quote
Old 19th October 2009, 03:30 AM   #8
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
@ Steve: I don't know if you're joking, can I seriously use a transformer as a voltage gain stage?
Mr. Eddy was NOT jesting. While a trafo can't yield power gain, it most certainly can step a voltage up. Steve has put a considerable amount of resources into making trafo based voltage gain blocks work well.

Gripacer, what is the magnitude of the I/P signal and how much voltage gain do you need? If you are starting with the CDP "standard" of 2 VRMS, your best bet (IMO) is a vacuum triode. Why? Fact, vacuum triodes are the most linear amplifying devices ever made. If the gain structure works out, a 6SN7 section will require (sic) zero NFB.
__________________
Eli D.
  Reply With Quote
Old 19th October 2009, 06:28 AM   #9
Banned
 
Join Date: Mar 2009
Location: Atlanta, GA
Quote:
Originally Posted by Steve Eddy View Post
Oh absolutely.

Of course you can't take just any step-up trannie and drop it into any circuit or any situation. But as long as you provide it with proper loading, drive it from a source which doesn't overload it or have too high an output impedance, absolutely you can use a transformer as a voltage gain stage. And a very nice one at that.

se
Cool! My source is the (+) outputs of a CS4397 DAC chip. It puts out 1.4vpp (avg) according to the data sheet, but I think it puts out a full 2v, as it gets as loud as a regular CD player output, and doesn't require a preamplifier. RL=1k min, CL=100pf max.

What do you think is a suitable transformer under $50 ea?


Quote:
Originally Posted by Eli Duttman View Post
Mr. Eddy was NOT jesting. While a trafo can't yield power gain, it most certainly can step a voltage up. Steve has put a considerable amount of resources into making trafo based voltage gain blocks work well.

Gripacer, what is the magnitude of the I/P signal and how much voltage gain do you need? If you are starting with the CDP "standard" of 2 VRMS, your best bet (IMO) is a vacuum triode. Why? Fact, vacuum triodes are the most linear amplifying devices ever made. If the gain structure works out, a 6SN7 section will require (sic) zero NFB.
Yes, I think that's a great idea too. After reading Lukasz Fikus' pages, I have been quite impressed by the triode as a voltage gain stage.

I'm not actually sure how much voltage I need...
- I am starting with around 2v
- The MOSFET stage is rated at 10w class A, 35w class AB.
- The supply voltage will be 18-0-18VAC

How much would be suitable?

I have 6N6P and 6N2P triodes on hand. Should I follow the Lampizator SRPP design (two triodes, self biasing)?
  Reply With Quote
Old 19th October 2009, 06:49 AM   #10
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally Posted by gripracer View Post
Cool! My source is the (+) outputs of a CS4397 DAC chip. It puts out 1.4vpp (avg) according to the data sheet, but I think it puts out a full 2v, as it gets as loud as a regular CD player output, and doesn't require a preamplifier. RL=1k min, CL=100pf max.

What do you think is a suitable transformer under $50 ea?
How much voltage gain are you wanting?

se
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Maximum Voltage for Mosfet Output Stage? Xoc1 Solid State 12 6th September 2009 02:26 PM
What about FETs for Cellular Base Stations in Audio Cascode Voltage Gain Stage (line tiefbassuebertr Solid State 8 23rd August 2009 02:53 AM
Best MC Load Resistor Type, current gain stage... tubenut Analogue Source 29 4th September 2006 10:43 AM
Heretical Unity Gain line stage PLUS a little gain ? yagas Tubes / Valves 7 24th January 2006 01:30 PM
R21? and Current Source AC Current Gain macka Pass Labs 9 20th May 2002 08:58 PM


New To Site? Need Help?

All times are GMT. The time now is 03:45 PM.


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