Some tardy holiday earnings were installed today for run-in:



I'd been after a set of these GT jobs for some time, and luckily the find coincided with the ability to purchase. These are NOS eighties-vintage Sylvania-made 7027A's, the first new OPT's in Bertha since the mid-nineties.

The set they are replacing (straight Sylvanias) goes out with over 600 hours, and they are still good, but I could tell the difference on instruments right away. 150 ma total plate drain with the old set coincided with roughly 180 ma with the new set. I biased them down to 150 ma total to conserve them as I did the old set.

Listening: Leos Janacek, Sinfonietta and Taras Bulba, Rafael Kubelik with the Bavarian Radio Symphony, Deutsche Grammophon 2530075.

Czech composer Leos Janacek was rooted in the context of two other great Czech romantic composers (Smetana and Dvorak). Being younger, however, he reached well into the 20th century, and his late music such as the Sinfonietta (1926) shows it. This is a demanding work for any orchestra, the winds in particular. It will also stretch any reproduction system. The layering of the brass parts in particular will tell you what your speakers are made of.

Taras Bulba, a tone poem depicting the career of the great Cossack hero, is an earlier work, but it is no less colorful and demanding. The orchestration includes bells and organ in a full-bore finale that again will drive the weaknesses of any sound system into the open.

Cold 807 time again for a 4-hour run-in.

Cheers!

Larry

Finally got an onstage date!

If I am not forced to alter my plans, Bertha is going to the RARSfest this year to help me entertain for the RARSfest Social on the evening of setup day (Good Friday, with the fest on Saturday). I was able to arrange the help I need to get the unit and its speaker cabinet to the fest and get them back.

The club always provides a sit-down dinner at the Social, and I have provided the dinner music since the 2000 edition. I keep the volume at background level during dinner, but there will be plenty of time during setup to open BB up and see what it will do with a pair of DX7's driving it at full bore .

For an amp like this, an onstage test as a music production unit is the ultimate litmus test.

Cheers and a mug of the finest!

Larry

Congrats, Larry! It'll be the hit of the show!

Many thanks, Clay. I hope you're right. Even with help, it will be the devil of a job to get that unit out and back, and I hope the effort is justified. I'm hunting lurking Achilles heels with this test, problems that I can't turn up in testing at home, since I have no way to drive that unit hard enough and still keep my lease . A full-bore onstage test will turn up any problem that unit may have.

The old-timers at the fest will remember her. She is a past prize-winner in the Homebrew contest (1998, if I remember correctly).

Incidentally, you should have seen some of the other homebrew productions that have turned up in that competition over the past 10 years. The sophistication and workmanship on some of those jobs was absolutely out of this world. I expect this year to be just as good, if not better .

Best regards ,

Larry

Speaking of "Achilles' heels", watch your back humping that sucker around. Living on Ibuprofen for a month is never fun.

I know, Clay. I've had back issues for some years now.

You should step out to Raleigh and join the fun on Easter weekend .

Larry

You know, if I didn't have a class on Monday, I'd think about it.

Great news Larry. Too bad that there just a few of us here in the world that can really appreciate what will be displayed and playing there.

Speaking of heavy lifting, I have a friend that takes his Hammond B3 and both Leslie speakers to his rock-and-roll gigs in Delaware. I can only imagine lugging that thing around. He has a GMC van and those pavers that look like ornamental concrete blocks that go from the driveway to the basement sliding doors. Grass grows up through the openings and you can't see them. That is where his studio/night club is located. Called "Club Phred".

Enjoy yourself!

Thank you, Don. Wish you could be there (and maybe you can be ?). It's always a fun fest, and it's growing, too. We'll be in the Graham Pavilion at the fairgrounds this year because we ran out of space in our prior venue.

I'm sure there'll be a number of club friends on hand who'll understand and appreciate BB. A lot of the old-timers who'd built a lot of their own gear looked her over closely in 1998, when she was in the Homebrew Contest, and there are several newer people in the club who aren't strangers to BB's breed of tube tech. I simply have to make sure that Mr. Murphy doesn't step in and foul up this gig.

I know what you mean about the Hammond B3 with the Leslie. A late musician friend of mine used that same combination for many years. It may be hard to believe, but he did not quit dragging that B3 with its Leslie around until he was in his nineties . I only hope I can manage some kind of longevity to approach that.

All the best ,

Larry

Aw shux, Clay, classes are made to be cut.....

Larry

For my 3000th post, I am saving this exposition from another thread. It's the sort of exposition that isn't out of place anywhere, and I expect to have need of it again....



Thanks for understanding, one and all .

Larry

Change of plan (blast it!).

There won't be room in the staging area for BB and her speaker cabinet. There'll barely be room for my ordinary keyboard rig.

So, doggone it, I'll have to postpone that planned stage outing for BB, and make do with my regular gear.

The best-laid plans of mice and men .......

But it'll happen yet! In the meantime, I'll simply have to catch a time when nobody is at home in neighboring apartments, and then send the studio KB's through Bertha at normal stage volume.

Best regards to one and all ,

Larry

Bummer...

Yes, Don, it is, but it's probably my own fault. I should have made sure of staging arrangements before I decided to drag that unit out there . God knows I've been on stage long enough, and in enough different places, to have made a habit of that kind of foresight. I guess I just got enthusiastic and slipped up.

Meanwhile, I decided to make this the first "cold 807" night in awhile . I think I've earned it.

LISTENING: Hindemith, Symphony in E-Flat (1940), Sir Adrian Boult conducting the London Philharmonic Orchestra (Everest LPBR-6008).

It's an older mono recording, but it's a good one. The orchestra is not "right up in your face," and the resultant depth of the recording makes up a lot for it being a mono recording.

And above all, it has Sir Adrian Boult, who was a contemporary of the great 20th-century composers like Paul Hindemith, Gustav Holst and Ralph Vaughan Williams, and thus had first-hand knowledge and insight into how their works should be rendered. I have heard a lot of Hindemith over the years, but nothing to top this.

The Symphony in E-flat is a grim, relentless, and virile work, most appropriate for its brutal World War II context. It captures the atmosphere of those days as well as any written text or video documentary could. In fact, it might have been a soundtrack for a docu-drama to end them all.

A mug of the finest to one and all .

Larry

I was fortunate enough recently to pick up three bright 6AF6G eye tube spares for Bertha, which uses a pair. They might be worth a word here, since the type isn't nearly so well known as the 6E5 and 6U5, or even the 6AB5/6N5, 6T5 and the 1629.

The 6AF6G is a dual-shadow tube with independent control elements, allowing you to monitor two controlling voltages simultaneously. It has no control tubes built in. Therefore, the shadows read between zero volts (90 degree) and 160 volts (zero degrees).

You may add any control tubes you choose, sharp-cutoff, remote-cutoff, or a combination of dissimilar types (such as the 6AE6G, if you can find one).

With Bertha, I run one of the 6AF6's across a voltage divider to monitor the regulated B+ voltage off the #2 supply (power amp front ends). It is set so that 300 volts off the supply closes the shadow exactly.

The other 6AF6G is used as a bias balance indicator on the output stage, with two 6BN4 triodes as controllers. It is set for very nearly closed shadows at optimum bias for type 7027A's in Class AB1 service.

If the bias in the push-pull output stage tilts out of balance, the appropriate shadow on the 6AF6G will open somewhat (and the other will overlay to a much brighter green than the target).

Thus:



The tube is shown with the bias tweaked enough out of balance to show how the shadows appear if there is any significant balance drift. The shadow to the upper right shows underbias, and the one to the lower left shows overbias.

This kind of service calls for close attention to the 6BN4's, which must always be equal, or at least very near equal, in performance. My experience with them, however, is that if they start equal, it's typically quite some time before they begin to drift apart.

These 6AF6 eyes can be useful in many other services where standard eye tubes won't serve, or would only serve with difficulty in circuit arrangement.

Listening: Famous British Marches, Central Band of the RAF, conducted by Wing Commander J.L. Wallace O.B.E., L.R.A.M, A.R.C.M., R.A.F. EMI/Odeon CSD-3658.

This is a splendid (and exhilarating) example of a wind band that is balanced and drilled as such a band should be, sounding like one player instead of fifty or sixty. The parts are balanced as they should be, and no one falls flat or pulls sharp.

Above all, the percussion instruments are treated as instruments, and not as mere noisemakers.

The album includes a medley of famous marches by Kenneth Alford (Fred Ricketts) of Colonel Bogey (River Kwai) fame, but no complete Alford marches (a number of those were recorded on a companion album).

The rest of the selections are drawn from other British march composers, Ord Hume among them. Perhaps the selection most familiar to old bandsmen here is Our Director, by Bigelow, a tune that was a staple for bands at the intermediate and high school levels for years (and is still a fine tune! ).

I played it MANY times in those days, and I still like to pick up my old trombone sometimes and play along with the records (you don't forget your parts, once you've memorized them).

You can spot the album in a minute. It has a Vulcan of RAF Bomber Command in the foreground on the album sleeve.

Cheers and a mug of the best !

Larry

Cheers to you as well my friend! Unfortunately I don't have any suds so a couple of Single Malts had to suffice

I do like the eye tube. I recently bought five from a bloke on eBay. Four were just fine. But one of them had some kind of strange pattern on the green, I forget what it was. But when I buy stuff, I try to average the price and not get too upset if one out of five is not up to par. I looked up the tube just now. I thought it was one of those little stubby guys. But it appears to be about the size of a 6SN7GT?

BTW, when we were cleaning out mom's home for sale after she moved in with my sister, I found in a dresser drawer a Zenith 6T5. I knew what it was but don't know where it came from. Had my fingers crossed but when I tested it, you have to turn the lights off in the room to see the green.

Darn, Zenith and 6T5? I see that two sold on the auction site (don't know the brand) for $46 and $76.

Sounds like a 6AL7GT. It should have a pair of rectangular patterns side by side. One of them is "full length" and monitors one voltage. The other one is a pair of "half length" patterns and monitors two voltages. It was brought out for use as a tuning indicator in some early FM receivers.

Since it was the only readily-available short-bodied octal "eye tube" with a built-in signal amplifier like a 6E5 or 6U5, I ran a 6AL7GT in Bertha's Mark I and Mark II versions, when a couple of big pilot light assemblies were installed where the 6BN4's are now. They were "backlight" shielded assemblies, meant to light up the front of the output transformer and the logo silkscreened onto it (the big "K").

I still have those assemblies. Haven't seen any for sale in God knows how long.

Cheers to you and hope everything's going well .

Larry

I think Sylvania made the 6T5 for Zenith. I have seen one Sylvania 6T5 new in the box, but that was back in the late 70's. Otherwise, the only 6T5's I have ever seen were Zeniths (and not many of those).

A bright one goes for BIG bucks these days.

Larry

One other possibility, Don. It could have been one of several older Euro types. I'd be curious to learn what it actually is .

Larry