audio-talk

OK been away for a week but back now. Repeated the above with the same measurements. Triode mode, cathode bias resistor unbypassed, into 100K load and I get a gain of just over 80. Before I proceeded I want to experiment with wiring the D3a as a pentode and I've not done that before. If I understand...

Looking good

izzy wizzy wrote: ↑Sun Jul 04, 2021 12:50 pm If you need help with the sim to choose EQ values, happy to help. Will be interested to see what direction you take.

Many thanks

Question for my own curiosity - wouldn't heat rise through the heatsink or is that a misconception caused by confusing conduction with convection ?

I ask because if the higher part of the heatsink takes more of the heat it would seem natural to place the active device lower down ?

Oh and I already have the key components : LL1660PP, D3a, chocie of output valves

Thanks. I'm definitely working up to building something similar. For me the joy of this hobby, quite aside from getting to listen to some pretty damned good music and revel in the fact that I built some of them, is that I can try changes for myself instead of having to read between the lines others ...

When the RIAA output goes positive both the grids will go positive Sorry, I ignored this as I thought you meant DC. No at AC the second grid is tied to 0v, so the AC signal is only on the first grid, the transformer will force it into balance acting like an AC only CCS. Oh I see . Long tailed pair ...

Its sort or a cathode coupled phase splitter also relying on the transformer to improve balance. Interestingly, as drawn the grids have no path to ground. I guess it will find a place between the d3a anode voltage and the cathode voltage across the shared cathode resistor. Would ac ground through t...

Following in the path of Izzy of this parish I'm working on a phono stage using some of design for inspiration. The signal path is D3a (pentode) into passive RIAA , then a pair of valves in push pull across an LL1660PP for balanced output. I'm struggling to see how the phase is split? SE D3a into RI...

OK set up and measuring/recording properly. First config is : PSU is 350v mains TX -> Bridge Rectifier -> LCLC : output from LCLC under load measured and recorded D3a triode wired (g2-A, g3-k) 47k g1-GND Anode load is 2K + LL1667-20mA (200H) Bias : cathode 78R + 1000uF bypass Output load = 100K Vak...

OK set up and measuring/recording properly. First config is : PSU is 350v mains TX -> Bridge Rectifier -> LCLC : output from LCLC under load measured and recorded D3a triode wired (g2-A, g3-k) 47k g1-GND Anode load is 2K + LL1667-20mA (200H) Bias : cathode 78R + 1000uF bypass Output load = 100K Vak ...

Nick wrote: ↑Thu Jul 01, 2021 11:25 pm Noise should be fine. I used it as a pentode with 40db gain and it was almost quiet enough to use without a step up.

impressive thanks

Thats a lot of step up for a 400uv cart. I would have thought 10:1 would be better. Also remember all things being equal 20kHz is 20db Up on the 1kHz signal (not that there is that much signal at 20kHz, but pops and clicks are to be considered. And now fully reading Nick's post, always a good idea ...

Christ on a bike that's a big mofo heatsink !

IslandPink wrote: ↑Thu Jul 01, 2021 10:32 pm