6B4G - The Resurrection Shuffle

[Cressy Snr]

Glad it was not a terminal problem with your amplifier and was probably down to a bad tube.
I enjoyed the listening session this morning. Glad you liked the sound of the "Groovy Pink SET" (good name for a 60s easy listening group that)
Appreciated the comments about the bass performance of the speakers. Those JJs do seem to have very deep bass, I didn't think myself that the OmniMets were capable of going that low with that degree of control until I fired up the SET earlier this week. That was a pleasant surprise and nice to have it confirmed by someone else.

So now we have had three SETs play through these speakers: Steve's PX25, your 2A3 and my 2A3-40 and all have worked beautifully with them. The OmniMets appear to really get on with SET amps

Personally I love The Groovy Pink SET's tonal colour saturation and musicality. Probably lots of second harmonic love in the mix, but I've now given up chasing hi-fi presentation so I'm not bothered. Both it's visual and tonal colour bring a smile to the old fizzog whenever the Groovy Pink SET is lit up and playing.

I'm gonna have a name plate made up bearing that moniker next week

[Cressy Snr]

Have done away with the delay relay. Got sick of odd behaviour at startup. Two flashovers taking out the hybrid bridge in as many days. My remaining valve rectifiers are far too old and decrepit to put up with 45 seconds of ion bombardment from the 450V of AC.

Am now using my well tried and tested, rock solid, SS 1000V Schottky bridge rectifier, followed by a hairy arsed TV damper diode as a slow start for the HT and 75 Ohms of series resistance to back the HT down to the design level
Used a Valvo EY500A as the soft start element, with a short length of double insulated lawnmower engine HT lead to the top cap cover....sooooo butch!
No more drama, just a nice, slow smooth ramp up.

[Ant]

No large bang and magic smoke release then

[IslandPink]

I shall now look at the TV damper diodes in my main power supply in a new light, Steve !

[Cressy Snr]

6 hours of work rebuilding the rectification, working out where to put the bridge rectifier, shifting transformer wires, moving the main earth star to make room, fitting the bridge, wiring the bridge, removing the octal, replacing with a Novar, wiring the Novar, drilling the chassis for a hole and grommet for the HT lead, doubling up part the HT feeder bar to provide a secure mount for the bottom of the HT lead from the damper diode, checking, testing and finally firing the lot up and hoping for the best.
What a bloody game!

Contrast this with the NVA A20/P20: plug in, turn on, play music.

Ah but where's the adventure in that, I hear you say?

[Cressy Snr]

I shall now look at the TV damper diodes in my main power supply in a new light, Steve !

I'm always ready to shine a new light on the mundane.

[Cressy Snr]

Had a very enjoyable day out in Hull, with Steve, Ed, Scott, a few CDs, Steve's speakers, Ed's F4, a brace of A20s and the Groovy Pink SET.
Thanks for the bacon butties and copious quantities of tea Steve.

[ed]

not to forget the scones....

awesome, as always,

thanks Steve

[Cressy Snr]

Ah yes, the scones, how could I have forgotten those.

[steve s]

Cheers gents, what a good day ...

Steve's new amp sounded really good
I would say it his best one so far
It was detailed clean and a natural tone. And on top of that it looks fantastic
Ed's f4 sounded great, a slightly different flavour but equally impressive
Steve brought along his a20 as I wanted to monoblock mine. Just using one channel on each amp
At first there seemed to be quite a difference but it turned out Steve's amp was a tad smoother and cleaner than mine
We put it down to Steve's being more run in, time will tell, but the a20 nicely improves on a chip amp I was using in the lounge, although not quite up to Steve's new pink job, it's similar presentation and a bargain for the price.
I've been playing them both all night after sorting the left speaker which it turned out, had a slight fault on it and only uncovered today.
I've still not made my mind up if monoblocking them is an improvement, there is not much in it.

And again thanks to you all today for bringing both some great gear and your valued opinions
Cheers..

[ed]

just have to agree with thoughts on Steve(C)' amp. I don't recall hearing anything better. Those special 2a3s really are special, and I agree, it may be your best one yet Steve....

for my money it really reinforces the simple is best philosophy, as going back to basics with no frills certainly works in this case....but not to forget the magic of partnership with Steve's speakers may have had something to do with presentation.

we found a really good revealing track in Tracy Chapman's fast car...it does seem to expose whether an amp can resolve finer detail....YMMV(maybe for discussion)

[Cressy Snr]

Thanks chaps

For anyone interested, here is the schematic:

[Cressy Snr]

Power supply:

[Ray P]

we found a really good revealing track in Tracy Chapman's fast car...it does seem to expose whether an amp can resolve finer detail....YMMV(maybe for discussion)

Agreed, it's one of my stock tracks when I have something new to listen too. Excellent album as well (and rather like her later stuff too).

[Cressy Snr]

Had an interesting 48 hours since the visit to Steve's on Thursday.

I think I can now safely stick my head above the parapet and say that the pink amp performed very well on Steve's speakers, in fact it sounds so right, that I won't be investigating DC filaments, fancy PSU caps, better output transformers or anything else that might "improve" the sound. There is definitely some kind of synergy going on, and I'm not about to do anything to the amp, that potentially could jeopardise the sound quality. Been there before; not going there again.

I really do love the sound of Steve's speakers. In his room, they completely do the biz and put the performance right there in the socket. I want that kind of immediacy and presence at home, and wasn't getting it from my omnis, even with the multiple tweeter array. So I've removed all the multiple tweeters, turned the cabs back the right way around and returned to the configuration as seen in this old pic below, which means that the tweeter again fires on a shallow upward slope towards the listener:


I've reduced the sensitivity of the 96dB bass/mid driver by 3dB by using a fixed value LPad, with 2R7 of series resistance and 18R across the voice coil to maintain the 8 Ohm impedance.

Basically I have engineered an overall reduction in the effective sensitivity of the bass/mid unit down to 91dB, if the LPad effect and the natural couple of dB reduction caused by the up firing driver configuration are added together and subtracted from the "real" 96dB. So with the 94dB sensitivity of the SB acoustics neodymium magnet ring radiator, I have tipped up the frequency response and got a better subjectively balanced sound out of the speakers.

I don't suppose that attenuating a bass/mid driver is ideal, but it has worked very well. The Faital Pro 6PR110 driver has such a wonderful tone through the midrange...it really is beautiful; so good, that I was not prepared to change it for a less sensitive unit. A solution had to be found that did not involve losing that driver. The Faital now marries up very well, to the SB ring radiator tweeter.

The 2A3 amp and the tweaked up OmniMets are producing some cracking sounds together; a clean, clear and detailed presentation, that is also highly musical, without becoming hard or aggressive. I could have used the cones, if I had reduced the main driver sensitivity a bit more, but I was wary of going too far with the attenuation; -3dB is about right. The SBs are giving out some nice treble.

Once I have had a few days with the new omni crossover configuration and am confident I have the tweeter level right, then I'll get some higher quality Mills power resistors for the mid/bass LPad.