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Posts by Zaubertuba

Working to tame the gain a bit....   Assuming my math is right, differential gain without feedback is around 30.  This version with the feedback resistance set at 240K reduces that to 22.  If I increase the input impedance a hair I can shave another 2 off each triode for a gain of 18.
 LOL and here I went and simplified the CCS before you posted that!   It's all good though...I actually learned a bit in redoing it, so maybe when I put the Cascode version back in I can calculate the values better.  Is it useful to have more voltage swing across the CCS?  If it doesn't really matter I'll rework it tomorrow swinging just ground--->-15V. Also added some NFB.  A little scared how the numbers will work out because the input impedance is so low (picked the...
You're right--I was trying to fully utilize my stereo pots but the legitimate shunt would probably work better anyway.  Fixed.   I also redid the CCS.     I was just thinking, perhaps I could add some local NFB to tame the gain a bit?
 Thanks-I'm looking forward to looking through that pass article. I really appreciate you wanting to keep me from going down the wrong dark path (I do that with my son sometimes   ).  Here's my dilemma with changing the topology this late in the game: -I've already invested in a balanced setup and the bulk of the components for this balanced build (including some of the casework which would involve scrapping some expensive copper I won't be able to use in an SE...
  LOL I was just going through all sorts of the mental gyrations you'd expect when you have two experts giving you conflicting information, when I realized I have to use a different CCS to do what dsavitsk is suggesting, anyway.   By the way thanks for posting Kevin, and I love the title on your calling card--my Dad used to use that phrase from time to time, and I've found myself using it as well.
I drew up the schematic in a format that should be a little easier to read.      Another question...Q1 is actually a darlington pair.  I thought I had a grasp of calculating the current for the CCS but well, now I'm not so sure...   ...can anyone recommend a good reference on the topic?       EDIT: Forgot the tube label!  
Cat5e is actually pretty good quality stuff--check out what Chris VenHaus has done with it: http://www.venhaus1.com/diycatfivecables.html   I use it all the time for projects for my low-voltage stuff.  It's cheap to find and easy to work with.  Maybe some litz-braided interconnects would be fun.   Do spend some time and pour over these threads, the first might already have answers to some of your...
You're not likely to get a factor of 10 in perceived improvement from doing your own mods.  Most of the mods I've done (and seen) have been noticable, but incremental in nature.  That said, if you dig a little you can find things that work (and avoid those that don't).  Way back when the HD555/595's came out, it was as easy as removing a foam pad to turn the former into the latter, since we found out they use the same drivers.  That was an easy and tangible mod that could...
Boy that's a lot more elegant solution. So from what I read, it sounds like putting the series resistors at 90% of the value of the shunt pots preserves the pot curve the most and provides the least attenuation at full volume.  Closest value is 4.7k, so, a balanced shunt using my faders before the ltp might look something like...   Am I on the right track?  Seems like getting the pot out from between the ltp and the JISBOS as you suggest would cover a multude of sins...
...and I'm sure the electronics bench tube-lesson will continue. Meanwhile, in the garage, I've made some advancements in the case-work...     Lubrication and a bi-metal hole saw works surprisingly well when you can't afford a $45 step-bit:         Drilled and marked-up sheet ready for bending in my home-made metal brake:       I had to cut a pocket in the brake to fit the compound bend:       Completed tube bracket.  I'll polish the visible parts to...
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