audio-talk

And if you are not attached to the TS input stage with 12AU7 (why would you?) you could use the 6SN7 input stage as shown in the 6C33C OTL project and simply connect it to the better sounding but more complex JB 300B output version (each 300B has its own regulator/output cap and the Ip is individual...

Why don't you build the much better sounding SE DC version? Not the AC version from the book (hum) and not the TS DC version but the version which Ray and myself have build with the JB output stage. And its 1W into 8ohms unless you decrease NFB if you have the right speakers for this.

What about a video distribution amp for splitting the SPDIF? It will give you identical 75R impedance outputs for feeding two DACs.
It could work and would be cheap.

I wanted to correct this for a long time but never got to it: The 30k/1,5W resistor needs to be 3W.

Here is the B+ psu that works with a standard Avel Lindberg toroid and voltage doubler. B+ should not be less than 132V.

I don’t want to sound like a party pooper….but this seems to be a different amp with a different sound. The original idea was to match an amp design with a speaker impedance/sensitivity (15ohm Lowther DX/EX4) which included the specific CDF of the speaker. From there the amp was set/tuned to sound b...

Thanks for the detailed answers, Marc. Some time back I was considering to use a “tube only” active x-over for my Klipsch La Scalas but I couldn’t find any satisfying (simple) practical solution. So I am still driving them with 3 fullrange OTLs and a Behringer Ultradrive Pro which is not such a bad ...

I use a polarity tester to find the correct position for the power plug with less hum if nothing helps and everything else has already been done/checked. Even without disturbing audible hum it can improve sometimes dramatically the SQ.

IslandPink, I was wondering what could have been the reasons for some of the choices you have made in this circuit. For example the ECC40 gets a CCS but the 45 doesn’t. I would have expected it to be equally important there (constant current sink). How do you calculate the AC load line with a CCS, a...

True but very hard to imagine from where I am sitting (sweet spot).

I think I should upload a recording so that everyone on this forum can get a picture what I am talking about.

And to change the sound of this amp as it is now would be such a loss as it exudes reality of music. Incredible dynamics, lightning fast transients against a pitch dark noise free background. It doesn’t get better and it seems to have limitless power. If I needed it to drive 8 ohm speakers I would s...

Maybe it's easier to find the right answers, Ray, if we reformulate the question a little? What goal(s) do you want to achieve using two regulators for the 6C33? Is it rather an aesthetic issue that you don't like to work with clumsy chokes and big caps or are you concerned about how mains voltage f...

I finally could listen for the first time with the finished amp in my main system. After 20+ years of wasting a ton of money in the Highe-End scene and building my own equipment for more than 10 years I am still speechless and wondering what to say about this experience. What I can say is that this ...

I simply try to follow the better argument, Nick. Especially your last explanation has helped me better understand your point of view. Funny, that it was a misunderstanding of what I wanted to say that brought it up. Why I mentioned the voltage regulator was to point out that it doesn’t help to disc...

I thought we were talking about grid current that cannot sufficiently flow between grid and the cathode because of Rg (grid leakage resistor) being too high? Every valve passes this grid current, positive and negative, which evens out at some point and then the positive grid current is dominating. T...

I think we need to be more specific if we have this interesting discussion. The only problem I can think of with Rg being too high is that the grid voltage can become positive (bias plus signal) and grid blocking would occur. The grid voltage would run away to positive and stay positive under these ...