A tale of two Hampiflyers

[andrew ivimey]

For the past month, when I’ve been allowed, I’ve been messing with a couple of ideas; not my own but.

I have a feeling that simplicity is the key (for me) so…
On the one hand imagine input stepup transformer into 1626 (indirectly heated transmitter triode from 1942) into interstage into 1626 into output transformer. Two cathode resistors and two bi-pass caps and that’s your lot, plus a not fussy PSU.
So glass and metal and precious little else. The chassis I built the 1626 on is a nasty ‘music angle’ as is the mains trafo that gives me the SS H.T. and a voltage doubler gave me the 12volt heater supply. This amp is one of the well published variants on the ‘Darling’ amp which seems to have diehard following similar to the SExAmp.

I found that using better output trafos improves the sound – not surprising.
I found that using AE interstages improves the sound hugely over the very, very cheap Hongkers I.T.s, which nevertheless are respectable.
I found the stepup input trafos (Hammond nickel 124B) really sound nice, but the 6DN7PP is no more as a consequence)
I found that a smoother HT helps a tad but I’m lazy – laters
I found that a simple voltage doubler for 12volts sounds much better than a switched mode power supply and a tad better than a simple regulated power supply wall wart thingie which prob has a 12volt regulator IC in it. Car battery 12volts was clean of course but strangely, er lifeless. More investigation?

So this little monster puts out about 1watt per channel and I like it. Time will tell.

And the other ….

Well I thought I wanted to try lots of KT types, chuck in anything that is beam tetrodish and of course an old pair of el34s. My feeling about what happened to ‘Rocky’ just got too complicated so I started with one shared dual triode package and rummaging around a 6N6P emerged first, not bad but a 6N1P romped home and that is what I am using now – has anyone got the load lines or indeed any useful data on this valve (abit like a 6922???) This sounds good anyhow and to get things going I started with 5881 (I have a lot spare if anyone wants to ‘speriment) Then it was a matter of plugging in any valve that came to hand; so far, KT88, KT77, 5881, 6W6, 6V6 and of course EL34. Ideally changing cathode resistor is a good idea and I have but not as much as I should (Laters).

The PSU is as simple as can be, choke loaded but then variable HT by using a reservoir cap if I wish so then bog standard PSU. 6 volt heaters to valves and six volts to the 6D22Ss, of which I’m fond. No trouble whatsoever with heater hum.

Using the very heavy Hammond 1628SEA output trafos the sound is enormous and deep purple headbanging sort of way – they are too big for the box I built the amp on. So I’m using a pair of tiny hongker output trafos which cost me about £25ish and they sound very nice, if not quite the same bass!

So they both are going to get a bit of a listening to.

I can't recommend too highly something of the ilk of what was called 'Rocky'. It is so easy and very gratifyingly powerful. We should all have one!