Help needed with Linn LK2 schematic - 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 16th December 2008, 11:06 PM   #1
lce is offline lce  France
diyAudio Member
 
Join Date: Dec 2008
Question Help needed with Linn LK2 schematic

As an owner of a Linn Lk2, I try to understand how it works.
Thanks to this very informative thread :
tweaking classic Linn LK1 & LK2 / LK280

I got the schematic, put it under LTSpice and now try to understand it ....
As it is not really simple and as I'm not really an expert, I need some help to understand the design choices ...

1) The input stage is a classical differential pair , with constant current source and current mirror.
I just wonder why they use 2 transistors (Q5,Q6) linked by R3 for CCS instead a more classic one transistor one..

2) VAS stage is another differential pair, cascoded input, CCS and current mirror.
Don't really understand the bias scheme (zener D1//(D2,D3,D4)) and why they don't link Q2 collector output
to Q8 base input in a more symmetrical scheme...

3) I must say, that I just don't understand at all the third stage (Q15-Q17). Seems to be a complex Vbe multiplier ,
but why so complex and why it is linked to amp output ?

4) Output stage seems to be a CFP with 2 current mirrors, but why the 2 output diodes D12,D13 ?

All this (26 transistors !) feed by a fully regulated power supply ! (when I say not really simple ...)

So lots of questions and some more :

I plan to recap it because of its venerable age.
Any idea about which cap for each function ?
Without changing all the topology, is there some gain to change some components (better output transistor,etc ... ?)
Attached Images
File Type: gif lk2.gif (24.4 KB, 404 views)
  Reply With Quote
Old 11th February 2009, 09:26 AM   #2
lce is offline lce  France
diyAudio Member
 
Join Date: Dec 2008
Really nobody to discuss about this very "interesting" schematic. ?
  Reply With Quote
Old 19th September 2011, 03:52 PM   #3
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Do you have the sim result of open loop gain curve for this amp?
  Reply With Quote
Old 18th October 2013, 02:53 AM   #4
diyAudio Member
 
ticktock's Avatar
 
Join Date: Dec 2006
Location: Old Anglia
Some time ago - I'm interested though.

Did you read the service manual including "reliability mods" and compare
the LK2 schematic to the one of the LK280?

The front end seems silimar and I guess these mods also apply to the
older LK2 amps:

The unlikely star-candidate - Linn LK-100 - pink fish media

Another worthwhile read about tweaking an old LK2:

Linn LK2 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

Old vs New linn sound

tweaking classic Linn LK1 & LK2 / LK280
__________________
thank you papa !!
Blaue Leuchtdioden machen blöd. (hb)
quod licet iovi, non licet bovi
  Reply With Quote
Old 19th October 2013, 04:52 PM   #5
diyAudio Member
 
ticktock's Avatar
 
Join Date: Dec 2006
Location: Old Anglia
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.


Any comments highly apprecciated.
__________________
thank you papa !!
Blaue Leuchtdioden machen blöd. (hb)
quod licet iovi, non licet bovi

Last edited by ticktock; 19th October 2013 at 05:07 PM.
  Reply With Quote
Old 19th October 2013, 08:28 PM   #6
sbrads is offline sbrads  United Kingdom
diyAudio Member
 
Join Date: Jun 2005
Location: Kent, UK
Off the top of my head with no simulations done........

Q15-Q17 purpose I think is to be precise with o/p stage bias so no adjustment pot is needed. Notice the same transistor is used, ZTX653 for Vbe matching plus a small voltage from R20/R23 to give the required voltage across the o/p stage emitter resistors, which is also why it's linked to the o/p.

The VAS stage Q2/Q8 issue I guess is that Linn wanted a particular distortion relationship between harmonics. e.g. less cancellation of 2nd harmonics. 2nd harmonics sound nice and all that.

D8/D9 might compensate for drop off of Hfe at high currents perhaps?

Last edited by sbrads; 19th October 2013 at 08:46 PM.
  Reply With Quote
Old 19th October 2013, 08:51 PM   #7
diyAudio Member
 
ticktock's Avatar
 
Join Date: Dec 2006
Location: Old Anglia
What do you think about decreasing value of C1 and increasing C2/22?

__________________
thank you papa !!
Blaue Leuchtdioden machen blöd. (hb)
quod licet iovi, non licet bovi
  Reply With Quote
Old 20th October 2013, 09:21 AM   #8
sbrads is offline sbrads  United Kingdom
diyAudio Member
 
Join Date: Jun 2005
Location: Kent, UK
Quick rough calculation shows the bass -3dB is 8Hz which I would leave alone, but the top end roll-off is a worry. Fed from a low say <200R impedance you'll get something like 35kHz -3dB but this falls alarmingly if fed from a few kohm, so 2n2 might be worth trying.
  Reply With Quote
Old 20th October 2013, 03:16 PM   #9
diyAudio Member
 
ticktock's Avatar
 
Join Date: Dec 2006
Location: Old Anglia
THX!
Guess I will go for C1 2.2 nF mica and C2/20 220 µF Silmic II parallel with 47 nF KP
as I have some 220 µF Silmics in the parts box, no less.
__________________
thank you papa !!
Blaue Leuchtdioden machen blöd. (hb)
quod licet iovi, non licet bovi
  Reply With Quote
Old 29th October 2013, 08:14 PM   #10
diyAudio Member
 
ticktock's Avatar
 
Join Date: Dec 2006
Location: Old Anglia
Sadly there are very few doing mods to scottish amps. Linniacs fear modding,
many DIYer don't like Linn gear. Several sites covering Naim mods show the
way though.

This has beeen one of the starting points to think about decreasing value of
C1 and increase C2/C20 - measurements of the der LK260 on the Vintage-
Radio-Forum:

Quote:
Left Channel:

Frequency response, -3 dB points: < 10 Hz and 37 kHz
Frequency response, -1 dB points: 18 Hz and 17.8 kHz
Frequency response, -0.5 dB points: 25.0 Hz and 12.0 kHz
Distortion: 0.012%
100 Hz spikes visible on output with no signal

Right Channel:

Frequency response, -3 dB points: < 10 Hz and 38 kHz
Frequency response, -1 dB points: 17.5 Hz and 19.0 kHz
Frequency response, -0.5 dB points: 24.0 Hz and 13.0 kHz
Distortion: 0.04%
100 Hz spikes visible on output with no signal
... and on Stereophile of the LK280, slightly better:

Quote:
At a 1V output level, the '280 was ostensibly flat throughout most of the audio band, though
there was a slight droop at the edges, the response being 0.75dB down at 21Hz and 20kHz.

Measurements will probably better after mod.


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.

Linn LK2 Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

LK260:

Linn LK2 power amplifier - UK Vintage Radio Repair and Restoration Discussion Forum

LK100:

The unlikely star-candidate - Linn LK-100 - pink fish media

The later LK100 is a cheaper and simpler variant of the same of the almost
same circuit.

tweaking classic Linn LK1 & LK2 / LK280



I'd strongly recommend to do these mods to any owner of a LK2/60:

- do the Reliability Mods (R33 und R49 > 2 W, C6 & C19, see below)
- heatsinks for Q10, Q11 und Q14 (the still get hot)
- evtl. heatsinks for LM317/337
- add the two 100 µF, the LK2/75 comes with
- renew several lytics, e.g. Pana FC, Silmic or Nichicon Muse
- consider to renew the big lytics, go for 10.000 µF
- if you remove the transformers and put them in an external case, you'd gain spce for additional capacitance
- swap C5, C6 & C19 for Micas
- decrease C1 to 2.2 nF, C2/20 > 330 µF + MKP (e.g. 150 nF)

Hope I didn't miss anything.



Does it sound better?

It does.


The modded LK260 play more authoritively, quicker and more dynamicly. The
former "british Sounding" has gone. If you like the old british day, don't do it.
If you like music and realism - do it !!
Probably there are more modifcations you could do, but there's already more
air and a deeper basement. I can listen to Marcus Millers Bass lines better.

I have to say I already have put the transformers into an external case
(similar to "Spark").
Hard to understand why Linn chose C1 so big and C2/20 that small. I cannot
understand als why there are no heatsinks on Q10/11/14. Even with some
Copper HS they still are 55° - 60° C hot. No wonder the melt the styrenes.
R49 also still gets hot. This one is prone to burn as it's just two 1/4 W types
from factory.


ps:
The later Klout and LK100 etc. have similar circuits. The Klout is a LK280 in a
more beautiful chassis, the LK100 has a simple PSU and no dual mono design.
Likely LK240 monos are similar. The later LK85/140 are not though.
__________________
thank you papa !!
Blaue Leuchtdioden machen blöd. (hb)
quod licet iovi, non licet bovi
  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
Linn Intek Schematic required burbeck Solid State 48 18th August 2014 10:57 AM
Linn Axis Schematic beamish Analogue Source 5 25th May 2008 02:03 PM
Linn LP12 Plinth measurement needed Mikewong Analogue Source 10 24th October 2006 03:17 PM
Linn Sizmik sub amp repair - need schematic len_scanlan Solid State 0 13th January 2006 01:31 PM
Anyone have the Linn LK-2(60) Power Amp Schematic? dtm1962 Solid State 1 2nd April 2004 12:27 AM


New To Site? Need Help?

All times are GMT. The time now is 01:13 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