a few practical 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

 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
 29th August 2002, 03:45 PM #11 hugobross   diyAudio Member   Join Date: Jun 2001 Location: Flanders, Belgium well that's C4 you mean, it's value is 220 pF. So this value is rather high? I've asked this before, do you think I can leave C4 away? HB.
 29th August 2002, 04:14 PM #12 jan.didden   diyAudio Member     Join Date: May 2002 Location: The great city of Turnhout, BE practical questions Ok, now I get it. The 220pF with the 10k gives a 3dB point of the closed loop gain of something like 65kHz (f=1/(2.pie.R.C)) so that cannot be the problem. 220pF is high here though, normally you see here small values up to 50pF to correct the phase shift, but if it works with 220pF it's OK. What's the Ccb on that Vas stage below the diode string? Jan Didden
 30th August 2002, 12:32 PM #13 hugobross   diyAudio Member   Join Date: Jun 2001 Location: Flanders, Belgium what do you mean with Ccb? I guess the cap between the collector and the base of T6 => 100pF. Other cap values: bootstrap-capacitor: 220 µF cap parallel over the bias diode string: 1µF cap below R10 = 470µF input cap = 10µF (in combination with 10K resistor), maybe I can solve the problem with lowering this cap, but this wouldn't solve the main problem. (sorry for the unclear picture) thanks, HB.
 4th September 2002, 12:15 PM #14 hugobross   diyAudio Member   Join Date: Jun 2001 Location: Flanders, Belgium problem solved Hi all, I've just did another test; this time without C4. The sound is perfect now . Thanks again for all your input!! HB.
 4th September 2002, 10:50 PM #15 traderbam   diyAudio Member     Join Date: Jan 2002 Location: Earth Hugo, a few more tips for your consideration: Put a 470pF polystyrene cap from T4 base to 0V (for stability) Replace R1 R2 C11 D6 with a CCS (for better CMRR) Increase C12 to 100uF (to reduce impedance of the diode chain) Add bias resistors between T8 emitter and T11/T12 emitters. Repeat for the neg half. Use 100 ohms. (for linearity) Remove C9 and replace R5 and R6 with a CCS. (for linearity) Remove C4 altogether - but make sure the amp is stable. (for linearity) BAM
 5th September 2002, 10:49 AM #16 hugobross   diyAudio Member   Join Date: Jun 2001 Location: Flanders, Belgium BAM, you've just described what my new design looks like. I didn't like bootstrapping at all; so the solution was to add a current source instead of the two resistors. I've increased the cap C12 to 100µF, but there was no difference in sound... Can you explane the thing about the 'bias resistors'?? I've also read about a resistor between the emittor of T8 and the emittor of T7 (and a cap placed in parallel). It's said to improve the sound, but I've never read why. thanks, HB.
 5th September 2002, 04:30 PM #17 traderbam   diyAudio Member     Join Date: Jan 2002 Location: Earth The idea is to run the drivers in a reasonably linear region most of the time...to reduce distortion. It will be less important if the output devices are run at high standing current, but bear in mind that unless the betas of the output devices are the same then the drivers will be biased differently from one another at 0V output. Using resistors between driver emitters and output emitters is one way. Another is to run a single resistor between driver emitters. The effects on distortion depend on the deviced you are using and how you match your output devices and drivers. Measure the distortion in each case if you have the equipment. In any case I would not introduce a capacitor across the bias resistor. This is because the Vbe of the two drivers will not always be required to be the same - because the output devices are non-linear. If you use a capacitor to force the voltage to be the same then the drivers will be pumping non-linear current to charge the cap up and down with a non-linear voltage. The impact is frequency-dependent too. I suppose if the output devices are not matched well then it might make a bad job better, but normally I wouldn't do it. Tip: think hard about the effects of capacitance in non-linear circuits. Where in the circuit is it ok and where not? BAM
 6th September 2002, 11:26 AM #18 hugobross   diyAudio Member   Join Date: Jun 2001 Location: Flanders, Belgium Thanks for the explanation! Unfortunately, I don't have all the necessary testing equipment; but in two weeks I return to school where I can test anything I want... Thanks for helping me, HB.

 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         Aussie Amplifiers         CSS         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 Salas Tubes / Valves 10 8th December 2007 05:21 PM tenderland Tubes / Valves 10 1st April 2006 02:56 AM borges Analogue Source 2 20th February 2004 01:59 PM dorkus Solid State 13 24th April 2002 02:34 AM

 New To Site? Need Help?

All times are GMT. The time now is 01:39 PM.

 Home - Contact Us - Advertise - Rules - diyAudio Store - Sponsors - Privacy Statement - Terms of Service - Top - Opt-out policy

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.