Balanced Zen, R15, and Gain Questions
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Pass Labs This forum is dedicated to Pass Labs discussion.

 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
 21st February 2009, 06:59 PM #1 dsavitsk   diyAudio Member     Join Date: Jan 2005 Location: Hartford Balanced Zen, R15, and Gain Questions This is an old article, but I am a little slow on the uptake and I am trying to understand what is going on. For reference, here is the article: http://www.passdiy.com/pdf/balzenpre.pdf Can anyone explain R15 to me? How is it that it sets gain? Second, would replacing R1 and R2 with current sources drive the gain super high, regardless of R15's existence? Finally, any modern parts that would be preferable to the IRF610, or is it still a good choice? Thanks __________________ http://www.ecpaudio.com :: http://diy.ecpaudio.com
Zen Mod
Official Court Jester
diyAudio Member

Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
top left , page 3

Quote:
 The gain of the circuit is the ratio of the impedances of the output circuit divided by the impedances of the circuit that couples Q1 and Q2. The summed impedance of the output circuit is essentially R1 plus R2, and is 1500 ohms. The impedance of the coupling circuit is 124 ohms summed with the approximately 12 ohm apparent source resistance of each of the MOSFETs, or about 150 ohms. The gain of 10 (20 dB) reflects the 1500 ohms divided by the 150 ohms. You can adjust the gain of the circuit arbitrarily by adjusting the value of R15 without affecting the quiescent DC values of the circuit. As you decrease the value of R15 to 0 ohms, the gain will approach 50 (34 dB). As you increase the value of R15, the gain decreases, with 430 ohms giving 10 dB of gain. Some of the performance curves presented later will reflect both 10 and 20 dB gain settings.
anyway - Aleph P is still better than balzen

__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM

 21st February 2009, 07:39 PM #3 dsavitsk   diyAudio Member     Join Date: Jan 2005 Location: Hartford Yes, I saw that. It explains what the total gain is, but does not explain why, which is what I am after. It looks to me like some degerative feedback from one source to another, but I could use some additional explanation. __________________ http://www.ecpaudio.com :: http://diy.ecpaudio.com
Zen Mod
Official Court Jester
diyAudio Member

Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
 Originally posted by dsavitsk Yes, I saw that. It explains what the total gain is, but does not explain why, which is what I am after. It looks to me like some degerative feedback from one source to another, but I could use some additional explanation.
yup ...... sources are ( one to each other) sort of virtual ground

edit : it's always funny how Papa finds a way to explain things in simple way ;

I'm sometimes even thinking ( reading his papers ) how electronic is simple .......

naah .........
Attached Images
 balzen.gif (8.8 KB, 153 views)
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM

dsavitsk
diyAudio Member

Join Date: Jan 2005
Location: Hartford
This is what I was thinking about. Basically, it seems like the load (whatever is reflected from the transformer) will replace the drain resistors from the BalZen in the gain calculation, and the gain will change depending upon both R15 and whether this is driving a high (10K - 50K) load, or something like a headphone load (32-300 ohms). Is this right, and will it work?

For a headphone amp, this can work to one's advantage with R15 = 32R, low Z phones will get unity gain and high Z (300R) phones will get a bunch of gain (about 10?). However, for a line stage into a 50K load, this could be an issue.

This begs a final question (two actually), too, which is what is the Zout of the circuit? With triodes, this would be a function of Rp and rp, but I have no idea with sand.

The other final question is what about a choke load for a mosfet? Again, with triodes, picking a choke is a function of rp, so I am stumped how to do it here. Maybe it won't work at all due to the mosfets being CCSes and more like pentodes themselves?
Attached Images
 mosfet_out.gif (5.8 KB, 125 views)

 22nd February 2009, 05:13 PM #6 mjf   diyAudio Member   Join Date: Jan 2009 Location: Austria hello. using a zen amp with an outputtransformer like a tube amp have a glance at zen variations 7. or perhaps you try to connect the outputs of the balzen (straigt way) to a transformer with a practicable inputimpedance. greetings..........
Zen Mod
Official Court Jester
diyAudio Member

Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
 Originally posted by dsavitsk This is what........

basically - neglect biasing and lower 750E resistors, and look at that as two plain triodes ;

with everything included - Ri , cathode degeneration etc. where degeneration resistor is R15

edit : I think that in your quiz example with xformer - reflected impedance is pretty trivial , just because these 3-legged critters have pretty low Ri , at least comparing with da toobz
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM

 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 Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Holton Precision Audio         CSS         Dx Classic Amplifiers         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post nostar Tubes / Valves 2 25th May 2007 07:00 AM MarkL Pass Labs 11 18th January 2006 10:29 PM runeight Tubes / Valves 10 28th August 2004 01:57 PM Solid Snake Solid State 12 17th November 2003 10:02 PM lykkedk Pass Labs 9 19th June 2003 07:24 PM

 New To Site? Need Help?

All times are GMT. The time now is 11:46 PM.