• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Autobias install questions

Not worried about the ripple, it will be well filtered. I always go overkill in that regard.
An aside I worked on a Primaluna autobias module and noted slight ripple on the bias voltage... Increased the filter supply caps from 100uf to 220uf and it disappeared. It appears that they used the absolute minimum value and once the caps had some hours on them the ripple snuck through (I've tested other units that were ok as delivered).
 
I don't have any plans to redesign the input stage for a simple reason: it sounds SPECTACULAR as is. Seriously, without exaggeration it's the best tube amp I've heard in my system, and I've heard a lot (I run an audio repair biz). Is it perfect? Probably not! But whatever distortion it's got going on is creating incredible depth and width to the imaging with sweet and detailed tone that is exactly what I was looking for. That being said nothing I build is set in stone so someday I might get bored and rework (hence why I'm doing the AB idea).

Tube compliment is Amperex 6SJ7, US Tung Sol 6SL7GT, Gold Lion KT77. I have some RCA 5693s coming in I'll try out.
 
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OK try a 10KHz sinewave into the amp and see what comes out. I thought the world of the K4040 until I did this. Then it had a redesign. There is the concept of a blameless amp - one that does not add coloration to the sound. The problem with the high plate resistors in the LTP is that you may get slew rate limiting here. This leads to a warm fuzzy sound - (valve amp sound).

However ultimately its your listening experience that matters not the amount of distortion.
 
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It's got very good high frequency response to my ear - I have a Cary V12R and that is far more tube-y in comparison, and the V12 is on the brighter side of the spectrum. Now I don't have a distortion analyzer (yet) so can't say exactly what it is doing but it certainly isn't rolled off, warm or fuzzy.
 
Super then the driver stage is just fine as it is. Valve amps can sound brighter as their damping factor tends to fall off with frequency. This can result in more power being delivered into the inductive load of the tweeter than a dummy load.
 
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