• explore ···

Last Modified: 21 Jul 2012


Compiled from Audio Talk forum topic


arly 2011 I got involved in a short e-mail correspondence with a chap in Canada, he asked is the circuit and info on my web page for a slightly modified Danielak phono pre-amp up to date, I replied yes it is, and then I thought actually I'd better double-check, and found actually not quite, what I'm using is a bit different, so I told him that, and in what way(s) ...

For reference, Bob Danielak's original pre-amp is here: https://www.abcelectronique.com/annuaire/montages/cache/1009/preampli-phono.html


I applied sort of mods as per Jeremy Epstein, then quickly dumped the cathode battery idea, mainly 'cause of the sonic properties of modern rechargeable batteries rather than the idea. To (try) get more gain out of it I effectively doubled the anode resistor value of the 2nd stage and cap bypassed the cathodes. I thought it was the best phono pre I'd ever made and I e-mailed Bob to tell him so. I think he was pleased. (See Phono Preamplifier #1).


Conversation with the Canadian chap continued, as he was looking for more gain, and could it be done simpler, e.g. is it absolutely necessary to have paralleled triodes for the 1st stage. Danielak's DC coupled pre-amp came up (the Canadian chap found it) but apparently this has not gone down well on the DiyAudio forum.

So I started looking at my one again, and eventually figured out that if one of the 6SL7's was moved to 2nd stage, we'd get something approaching more like CD player output level, which it does. Not only that, but one less double-triode required to boot. Which suited the Canadian fellah I think as space available for valve sockets was at a premium apparently.

Also, the Miller capacitance of the input stage is reduced by half, which, it turns out, plus allowing for the arm rewiring (see Rega Arm Rewire), suits my Nagoaka MP10 cartridge better than hitherto actually. Anyway so it all works just fine thank you. Another pinnacle of excellence reached...


Photos follow then circuit.

Note #1 ~ second octal socket from the front has become "not used".

Note #2 ~ it uses Panasonic 'FC' electrolytics for the cathode bypass, as was recommended by Nick Gorham.

'{Cx}' is any extra capacitance for cartridge matching. In my case this was not needed, as the total input capacitance is: Miller effect, approx. 150pF, plus strays, cables etc.

Components list:



Power supply
Is as per phono preamplifier #1, except the CLCLC filter was simplified to CLC, 100 µF, 15H, 200 µF by virtue of the last choke being bypassed (omitted) and the last two 100 µF caps combined in parallel. The primary reason for this was to obviate power supply resonances due to the equal values caps and chokes forming a resonant tuned circuit.

Again the filament supply is 12.6VDC regulated, simply by a TIP120 Darlington basically biased from a 13V Zener. There is a 2.5Ω inrush limiter (power thermistor) on the output side of the TIP120 to give it an easier time on initial start-up.

I then had a bit of bother because since the original set-up was 2 x 6SL7 & 2 x 6SN7, the heaters of each pair could be in series, total 900 mA. But one 6SN7 was taken out, so what to do?

A 22Ω resistor in series with the remaining 6SN7 filament wasn't going to work, as the filament wouldn't go past 3V.

Ah yeah but no but it just so happens that there is 6.3VAC coming up the umbilical from the transformer box, but hitherto never used.

So it was simply a case of adding a twisted pair of wires and pins to the two spare chassis socket positions and voila. It do am worketh....





Final schematic:

---