TGM Amplifier ? - Page 2 - 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 15th March 2009, 04:11 PM   #11
Banned
 
Join Date: Apr 2005
Location: Stockholm
Very nice, ostripper. I would omit C1.
  Reply With Quote
Old 15th March 2009, 04:25 PM   #12
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
Very nice, ostripper. I would omit C1
That would create 100's of MV's offset at output. For those who
like no caps in signal path , an op-amp with adjustable
null point would do nicely.
OS
  Reply With Quote
Old 15th March 2009, 04:41 PM   #13
Banned
 
Join Date: Apr 2005
Location: Stockholm
ostripper,
I did mean C1 in post #9.
  Reply With Quote
Old 15th March 2009, 05:15 PM   #14
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
You mean the 68p?
tried that , It seems to work good (no ringing),
loop response stays the same. IF you did use
a faster VAS device (KSC 3503..etc) Cdom might be needed.
But the slower 340 seems to do just dandy without..
OS
  Reply With Quote
Old 15th March 2009, 05:57 PM   #15
Banned
 
Join Date: Apr 2005
Location: Stockholm
ostripper,
all right.
  Reply With Quote
Old 15th March 2009, 06:40 PM   #16
fjr is offline fjr
diyAudio Member
 
Join Date: Feb 2009
Default RE: schematic in post #1

Looks OK, but I think some mods are needed.

First, add an RC filter to the negative rail too, anyway you'll get high PSRR.
I'm not sure D1 is needed.
Then R1 must be = R9.
C4B would blow. Omit that.
A 100n...1u foil cap in paralel with R15 would be a good idea. R15's value is too low.
Add resistors is serier with C11 and C13 (1r...10r).
Use some lag compensation as OStripper suggested is his schema.
Omit L1 if the amp is stable driving capacitive load without the inductor. Or add a low value resistor in paralel with the inductor.
Use CFP Vbe multiplier or the bias will vary with rail variation.

I cannot agree with OStripper related to emmiter degeneration. I don't think they are needed in this circuit.
Current source and current sink for the LTP are not needed. Keep it simple.
An RC is needed in the input for lowing TIM (series R, paralel C).

Good luck!
  Reply With Quote
Old 15th March 2009, 07:07 PM   #17
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
by fjr -Current source and current sink for the LTP are not needed. Keep it simple.
I suppose you could ditch the CCS if you were using
independant power supplies for each amp. But BG said
these would be part of a HT system (3-6 amps).

the current source I added does -60db /1k, with none
PSRR turns to CRAP. So, maybe even a better one
(LED, cap, 2 resistors) would be in order.

The sound of this topology would remain the same.
ASKA himself improved this design in later amps,
(aska100) by adding the CCS AND current mirrors.
OS
  Reply With Quote
Old 15th March 2009, 07:40 PM   #18
Banned
 
Join Date: Apr 2005
Location: Stockholm
fjr,
did you mean something like this?
Attached Images
File Type: jpg input stage.jpg (25.4 KB, 2286 views)
  Reply With Quote
Old 15th March 2009, 08:14 PM   #19
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Default Re: RE: schematic in post #1

Quote:
Originally posted by fjr
Looks OK, but I think some mods are needed.

First, add an RC filter to the negative rail too, anyway you'll get high PSRR.
An RC is needed in the input for lowing TIM (series R, paralel C).


Quote:
Originally posted by ostripper


the current source I added does -60db /1k, with none
PSRR turns to CRAP.

As mentioned, an RC filter will improve PSRR dramatically. That 100 ohm R (on one rail!) is a wee bit too big though, more like 10-22 ohm plus a 100uF or more cap.
  Reply With Quote
Old 16th March 2009, 11:12 PM   #20
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
sorry guys, this is probably snails pace for you. But first time ever using MacSpice this weekend - I have managed (after finishing the floor tiling) to get the LTP set up and obtain a dc analysis (see attached).

I am starting to understand how the LTP is the 'heart' of the amplifier, it determines many of it's properties as well as being a very elegant design element.

I can see that the total current through the LTP is 0.75mA but the imbalance is still a bit high (0.45mA T1 and 0.3mA T2).

I still plan to use AKSA as my 'guiding principle' so no constant current source. However, I read a posting in a forum that it uses 68k as the default load for the LTP. Looking at the limited data I have for 2N5401 I don't see why the lower current (0.5mA) would be a problem (does it hurt linearity or frequency response ?)

I understand that including two separate load resistors for each T1/2 aids performance by 'swamping the emitter resistance variations with current' (paraphrased from Rod Elliot).

I haven't figured out how to get spice to do an AC analysis (yet)
Attached Images
File Type: gif ltp1.gif (45.8 KB, 2187 views)
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  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
Wanted: DIY amplifier builder with experience. I need a 0.7 ohm stable amplifier Audiophilenoob Swap Meet 34 16th May 2005 11:58 PM
Questions about how to decrease the PASS A-40 amplifier into a class AB amplifier. novtango Pass Labs 2 21st October 2002 01:50 AM


New To Site? Need Help?

All times are GMT. The time now is 09:16 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