Celestion T2 pair

[Paul Barker]

Celestion A2 150 Watt 4 Ohm 90dB bi-wire if desired, I use them linked.

Offers invited.

I play them on a Cambridge Audio CX A60, you can offer for that also if you want, but no need. Its for family room anyway.

I fogot what they are call but Im auditioning some TL’s that the up to date version sell new for 2g’s The owner wants 500 but my mate runs the shop and he’ll charge me 450 using half his sellers fee. They are made for recording studios as monitors. The story is the brand was started by a soundman who didnt like the monitors the bbc were using so he made his own and sells them to the bbc now for a couple of g’s at a time. They also cost a fortune to the public brand new. Theyre 87 db 8 ohm don't recall the tolerance of power or the name.

They are coming here for a shoot out on top floor with my 57’s. Since the 57s are used and horribly old and not sent for reconditioning they are possibly 81dB , Just on my recently souped up EL38 SE amp. Souped up means employing the screen dissipation aswell.

I will know by that audition if they sound good to my ears compared with 57’s. They should be louder and distortion free. It struck me in the shop they were comparable to the 57 sound.

If they do they will fill the void the celestians leave behind them.

The mystery speakers have been updated to the latest crossover, but tweeter not updated. Obvs I’ll look into the tweeter later.

They knocked my sox off in the shop on an ss amp. But I need to know how in my world as it is now ie 6 watts se triode. Though the future plan is now a ppGM70 0.2% 3rd at 25 watts. When I can afford Tango phase splitter they will mutate to that. But firstly valve phase splitter. I’ll have to re-read what Morgan recommends.

So I have studio monitors from this afternoon at about 3 until next week.

First they must pass the upstairs 6 watt se test against the 57’s. In the shop they sounded quite 57 ish. Very fast and light. So fast they shock. I dont know the watts of Chris’s amp but he was being careful about the volume, not wanting to have to buy broken drivers himself, which probably cost much more than £400 he would owe the owner….

[Paul Barker]

These aren’t going back.

[Morgan Jones]

PMC = Professional Monitor Company. I bought a pair of PMC MB1 for work in about 1996. At the time, I had a pair of HFN McDonald transmission lines with their metal dome tweeters replaced by Morel silk dome and driven actively; transistor bass, valve treble. I was seriously worried that I would have to buy a pair of MB1 for myself (about £5k at the time). After a day of listening, I decided that I preferred my own loudspeakers, but it was a very close thing.

[Paul Barker]

Thanks Morgan These GB1’s have the upgraded crossover which is in the GB1i.

£1500 new.

Their soundstage is very good. Bass is articulate which Island Pink would appreciate. The beauty is they sound about the same as Quad 57’s but with a better soundstage. Its clear my 57’s need reconditioning, but I don’t think I’ll bother, because these sound very similar but better.

The roll off is at 30 hz but so is the Sowter pp transformers at 32hz. So bass will dissapear at 30hz.

Ive looked at what to build for more power and less distortion, which looks like its the gk71 UL. Im limiting the anode volts so that the b+ can stay just below 500v at that UL I get 20W 1% 3rd h. The GK 71 is better than most valves at low anode 440 volts. -52 bias.

I have two 400v power transformers so dual mono two hexfred bridges I have two black Gates 100+100 so one per channel 100 :10h choke :100 on each channel. Should all fit in same chassis . I only had two gk71’s but they remain as cheap as they ever were two delivered $77!

The GM70 cant get power from a 500v b+

So the gk71 is a secret sleeper. The reason for limiting to 500v b+ ; to employ Black Gates.

As this amp will fit one box I can bring it downstairs to use it on the Celestions instead of the solid state amp and upstairs on the GB1’s.

And portable enough to take to meetings.

Ive never been any good at making speakers. These are better than anything I ever failed to make.

[Paul Barker]

Anyway, just to reveal Im not quite right in the head yet. By the way I had two victories yeasterday. Found the 22mm press jaws a week after I needed them, and found the bahco comprehensive 1/4” drive socket set the day after I needed it. But still cant found the only car keys. But its no wonder there are two of us in the house losing things. I blame Diana but find it where I put it in the end. Strokes wipe out memories. Diana is still worse though.

Oh yes I found the new rasor I bought, lost it so bought another. Obvs yesterday found the one I lost and saw it was me a culpa not Diana.

Anyway I have to build a 20 watt amp to drive the PMC GB1’s which also have the updated crossover of the GP1i. I have two black Gates left and the power supply is dual mono, so I had to study GM70, and GK71 doing a shootout on paper. Because the Black Gates are 500v I’ve limited the b+ to 495v in my plans. There is allowed 450 at start up. For a long time now I have been certain I only had one pair of GK 71’s.

Anyway, communing about my mind through recovery I wrote this below to gas fitters.

“Keep changing my plans for building the next valve amp. Anyway at the moment its push pull GK71 ultra linear, mainly because it can deliver power at relatively low voltage. So without looking in my head only I decided I only had 2 gk71, as they are Russian and the cheapest power valves on earth, but very good sounding and the best at low voltage. When I say low voltage, just under 500v because that is the limit of the capacitors and the reson for the limit.

Anyway I ordered two more $77 US comparable valves UK made are 813 £150. See what I mean?

So I was looking for valve bases enough and only found two, so ordered another two. Then I found a box with 8 gk71’s brand new and two more bases. So my memory and reactive mind a little behind still.

Anyway I bought some new loudspeakers from my mates shop though they are £500 Chris wanting to sell them said he wwould give me half his commission, so they are costing £450. New price is £1,500.

Its for those speakers I have to build this amp.”

[Paul Barker]

So anyway, back to you lot. I love the speakers they out quad 57 the quad 57’s but have a phenomenal stage feeling very real sounding, depth pinpoint placing etc and all the coughing from the live audience. Better controlled bass but only goes to 30hz. Anyway the Sowter pp only inductively satisfactory to 32 hz, so nada bass below 30. I bet thats quite common anyway. I might bust out one of my subs.

So at anode volts and auto bias volts limited to 495v the GM70 is a train wreck, but the gk71 ultralinear delivers 20 w at 1% 3’rd h if goes up in power but so does ‘3rd.

Still have to decide on the phase splitter. My brain hurts so I’ll probably just go Williamson style.

I dont think I need drivers, Im keeping the gk71 well away from A2. By the way triode mode is only 9.5W 3’rd h 0.43% though. So I’ll find out if 9.5 watts is enough and if I can tell the difference between 1% and .43%.

The gm70 is hopeless in the race at 450v anode colts. Cant recall but sub 5 watt.

I like the idea of safer b+. Im still half way round the bend. But all this is aiding my recovery.

By the way the se el38 is probably 4.5 watts and its not quite enough. These speakers are very revealing and are telling me something is wrong! I could pp the el38 but decided its idht and probably not adequately pure for such revealing speakers, and anyway the gk71 has more power at the same voltages. So the shootout on paper says gk71.

[Paul Barker]

Which surprised me, I’d never used the gk71 for higher voltages because of its 600 g2, though we have discussed ways round that, and you have to consider something mentioned in the discussion about gu81m the 600 limit is partly because -200v fixed bias expected. So if auto bias maybe push it a bit.

But no need the limit today is 445v anode and 52 auto bias.

OK so that inspired me to just check if fixed bias with the spare voltage for the anode volts improves the power in triode mode, and yes is the answer. I feel its enough more power for sufficient power at home and better tone expected.

In case you havent seen it of the bias mentioned on the chart 10v of it robs from plate volts. So the maths appears 10v out, but it isn’t; the fixed bias supply required is -50v.

.

[Paul Barker]

I have bids on phase splitting interstage transformers.

[Paul Barker]

I don’t know why I put T2 in the Title. Its A2.

[Paul Barker]

I had bids on two pairs of phase splitting interstage transformers. I won both pairs I had bids on. Electraprint and Schumacher. Paid for two pairs 382 delivered. Electraprint cost most £166, the schumacher £90. They sound better remainder is postage. From USA £126.

Same seller, an audio electronics engineer, who ran testing and both sets of transformers are tested for phase and roll off. Both very satisfactory.

I’m OK with having won both pairs, both auctions ended while I was fast asleep, so I put quite a lot on as I wanted to win at least one pair.

Jack Eliano retired due to materials costs and probably age. So without having bought these it would have had to be Tango or Hashimoto which would have cost very much more. Ive at least paid far less than one pair of either.

I have some 50% Nickel EI Lams for winding my own pair which I would parafeed the primary on. But that will be a long term project. Im not yet ready to wind transformers again.

Well as well as the Sowter PP output transformers I have a pair of LL. So first Im building the low voltage GK71 triode ate 14.4 watts, as earlier in the thread. Secondly something at higher b+ and the 1500v polypropylene caps. Probably the higher voltage supply will be seperate for powering the second PP amplifier and a SE amplifier with the Tribute transformers. Then Im done.

I’m certainly done with speakers these PMC’s are on the money. The A2’s had good bass but nothing near the trebble of the PMC, probably a combination of poorly chosen tweeter and poor design of crossover, But their forte is bass. Midrange is nothing that competes with Quad 57’s even ones that aren’t fettled. The amazing thing is the Limits of the 57’s are exceeded by the pmc’s and the soundstage on the pmc’s is just sit back and hear the musicians around the stage, plus the audience breathing and coughing. I’ve found the soundstage is so well placed I can put the speakers full width with no gaps.

[Paul Barker]

I don’t have to study phase splitting valve stages and I can have a mix of harmonic’s. I liked the PP 6b4g I brought to one Owston with the Danbury phase splitting interstage transformers which I lost after I broke it down. Well, no disrespect to Danbury but I’m going up in the transformer world, so this next amp should come out better and I was perfectly happy with that one.

Why did I break that one down?: Wally!