audio-talk

Just pointing out that the site clock is an hour behind.

Although Rocky is lacking some gain until I get/make a pre-amp, the Apls pot on its own without the shunt mod is something I will do.

Is the 'blue beauty' everyone refers to the same as the Alps RK27 stocked by Rapid, 66-0225? If not, is it the same as the one stocked by WD?

Thanks,

Mike.

Not all of the valves were removed - the GZ34 was left in. I guess if I remove the recifier and there is still a hum then that rules out any of the rectification or HT so any induced hum must be from the heaters, mains wiring or the power TX. Logical? So out comes the GZ34 (other valves fitted) and ...

I noticed tonight that the remaining hum on my amp is there as soon as I switch it on, i,e, before the valves warm up. I then removed the pairs of valves one at a time and I don't know whether this is common but the hum remains with all of the valves removed. I therefore assume that this must be lea...

Hands off the second one. I found them last night after returning.

Isn't it amazing that you can get a guaranteed NOS from Langrex and yet some people are asking €100 for a pair!

All, I'm on the lookout for the options around my Rocky valve set-up. A Sylvania JAN 6SN7GT VT-231. Mullard/Seimens/RFT EL34 or any other well regarded 'classic' option. I'm looking on e-bay for a pair of the Mullard XF2 OO getter variant that seems to be in demand. The Seimens also seems to be well...

Well a big thank you to Toppsy for being the first independant critic to have a listen to my efforts. First up we compared Rocky to Colin's 6EM7. In my view the 6EM7 was a tad more detailed and refined but Rocky carried extra weight. I would suggest 'advantage' to the 6EM7 but there's plent of time ...

I think this calls for a... Maybe should go in the 'jokes' section but the image used by Scott reminds me of one of my favourites, particularly after a few beers, and I hope this is not too smutty for you sensitive souls, (please delete if felt inappropriate). Why do seals have flat willies? Have y...

Turning the TX has resulted in a noticeable reduction in hum as advised. Not gone all together but not audible at normal listening distances. I was in too much of a hurry to try turning the TX that I didn't get round to bonding the TX chassis. Will do this the next time it's open. If there is still ...

Mike, The blue one as you rightly guess is the the left output TX, the small one being a 12VA one to power the DC heaters (and yes with hindsight probably under-rated). The TX is closish to the output TX as you can see from the picture. I was trying to keep the 240V/9V input/output wiring away from ...

ROCKY GOES DC I've been playing around with the amp these last couple of weeks, the first part of which was tinkering with settings of the SRPP input stage. With my initial 1.5k resistors, the current was quite low at 3.6mA and grid bias of 5.6V. My previous notes were at these settings but under th...

I don't have MJ's books to hand but I know in one of them he does suggests the preferred methods for referencing heater supplies including the use of the CT if you've got one as well as the 'fake CT' as discussed on another thread. I am however surprised with your comment regarding "0V" un...

If I do end up testing/using a LM338 regulator circuit for the 300V SRPP supply, should I leave the heater bias circuit on the HT or should I move to the regulated output? My gut feel is to take it from the latter and build it into the design.

All this discussion on the heater power supply but if as me you have a dc bias on the heaters, should this be optimised in order to get the most from the dc supply? In my instance I simply have a potential divider on the HT with a filter cap across the lower resistor/heater bias supply leg. When sca...

Sorted I think. Two 1K0 2W metal films in parallel in the neutral supply leg drop 23V off the primary. Measured voltage across the regulator is now 3.7V and at 1.2A would equate to 4.4W or 35 degrees temp rise with the heatsink I have.