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SOURCES

Turntable

Thorens TD150 from 1971. Clay/lead shot damping on plinth and clay on sub chassis, tar damping on outer platter only.

Sits on or self –seals itself to, a larger marble slab, (ditched little rubberfeet and thin floppy hardboard undershield). The slab is on three adjustable cones - gold on brass. The front two rest on their little matching inset feet; metal and rubber sandwiched with rubber on to the main concrete ‘shelf’ below. The third rear cone is at the stable balance point and its tip is hard to the ‘shelf’.

Mat is a Nagaoka Disk SE22 mineral loaded rubber dished job.

GB Clamp, IMO the best aftermarket clamp ever. Spindle extension for clamp, made by good toolmaker friend!

Nylok nuts on suspension bolts.

SME 3009/ with STAX 2-pin head-shell/ SME FD200 fluid damper (STP).

Cartridge is my second in a row of the Denon DL103D, this one has a VdH type 1 tip new cantilever, and a new coil? The Garrott brothers looked after the other one, thrice.

Very carefully set up.

CD

Rotel RCD 965BX Ltd Edition and Discrete mods. VDH 102 II I/C cable

ferrite clamps on power cable.

RADIO

Tuner? is a rebuilt Kenwood tube receiver (a W8) - with power amps usually off. Hi-Fi AM (?) plus an internal Studio 12 decoder for FM Stereo. There is a saga about this tuner. Brown VdH interconnect!

TAPE?

Cassette deck is an upgraded Nakamichi BX300.

Long play tape is a Panasonic (Technics?) F55V with mods to the audio record and output stages. 4 hrs SP and 8 on Long play. Timer recording.

ANTENNAS - are a source? You betcha?

One 25 ft tall DIY * galv’d pipe mast, 2 long wall mounting brackets and 1 shorter fascia board mount. Sections joined with long ‘inner’ tube sections of scrap pipe.

 

Not guyed yet, bought everything to do it, but it survived a 20 year storm in 2001.

From the top:

FM - one long-boom log-periodic cum Yagi hybrid – horizontal.

UHF TV – 24 element band IV Yagi. The arrow head reflectors have rectangular mesh panels riveted to them.-horizontal

VHF TV – an old band I / II / 111 double H or ‘phased array’. The elements are made of extruded tubing. Cleaned the terminals and sealed the balun connections on.

AM? - yes, the mast also carries ropes and ring bolts for the house end of a long wire feeding an antenna tuner (Variable L and C).

Down leads to diplexer by FUBA are RG6, down lead to house and distribution is RG11 mostly, with some RG6.

Mast and antennas are properly earthed and main down leads are spike / lightning protected. No thin little wires anywhere.

 

PRE-AMP

A ‘four valve’ pre-amp, in a gutted Quad 22 box, Alps 50K pot. Separate grunty PSU, O volt ground plane, bias and heater voltages are regulated. DC heaters.

Ceramic tube sockets, heaps of good RCA's - in round holes on back – and one good replacement strip too. One 5-pin DIN tape in/out socket.

Line stage is two 12AU7’s (Philips ECG NoS JAN 6189), last triode is a CF.

Phono is 2 Sovtek 12AX7WXT and passive RIAA fed by an AT 650 Tx, uses Allen Wright’s 50kh ideas and TdP’s bass alignment and 3rd order rumble filter..

Zero feed back, except for the CF triodes.

Alps ‘blue’ pot in front of the CF’s.

I love the Quad’s switching - ground and signal, no background feed through. No thumps. Gornicht!

Tandy - 3 tape recorder - switching box., real value.

POWER (?) AMPLIFIERS

Two (2) rebuilt / modified Leak Stereo 20's, as a WIP they are now at Stage V. One is in pentode (not UL) and one in triode mode. So the originality types hate me!

Swapped for a Leak Stereo 60 which I was given and did not like. Zero cost to that point!

 

 

Power Supply

Cost can be the only reason why HJ LEAK p/l dropped a choke from the TL12 Plus / Stereo 20 chassis, the value of using a tube rectifier is pretty low without one IMO, and they could have used metal diodes instead. This would have been in the same vein being cheaper still! Maybe not.

I tried to stay original - Anyway, three out of 6 replacement original type caps (NoS) were no better than the crappiest I had (leaky after a few hours) ; all good GZ34’s are NoS and were very expensive and ‘no serious guarantee’.

Back then I wanted all the power I could = max HT, so I didn’t put in a choke and stay with a tube psu. Instead I went the ‘big cap SS’ route. Hate me if you must.

The PSU uses an array of fast soft recovery diodes (a TPC rec’dn) then big 470 uf 400 volt Ni(ppon)ch(emi)con filter capacitors, at least they fit the can and recifier holes, there are some coupling and bleed resistors in there too!

3 of these caps in the triode amp, and just lately 4 in the pentode. HT is 320 volts orB+, giving > 20 joules in both amps, and there is good decoupling. Ripple is > 20 db down on Leaks spec!

Each amp has one cap where the GZ 34 rectifier tube usually sits, just for a laugh! The next two are in the usual can pos'ns, and the 4th goes underneath.

Each is bypassed with 1 or more WIMA MKP and MKS. There is also an NTC thermistor on the AC in on both chassis.

The AC leads are hard wired.

They are not tweaky, hmmmm here comes a DIY braided lead experiment?

 

The audio circuits

For each stereo chassis – 1 X 6DJ8 (shared) – 2 of 6CG7 (LTP and a fet CCS) - 2 of 2 X EL84M.

The input twin triode (with DC heaters and new ceramic sockets - NoS Mullard. It is flexible enough that I can use a few other tubes straight in. Driver triodes are AWA and AWV Australian made NoS, and very good too, they’ve been in there >2 years now. I know this is probably overkill, but all three tubes are just idling, which is nice.

I wanted to keep 6BQ5's have replaced them with Sovtek EL84M's. I did use up a set of eight 7189's JAN NoS (I think they may have been made in Japan though, National brand?).

I was lucky to get these for the price I did, they are not cheap now, the M's are, and are OK in this role. My memory says that the Sovtek EL84 M’s are not quite as nice as NoS 7189’s!

All the coupling caps are Wima MKP's or styros (feed back), the main circuit resistors are 1% MFs, Beyschlag and Philips and the cathode/bias resistors are 270 ohm non inductive power resistors (dark blue), I forget the brand.

The front end and driver stages now need so little feedback that we were able to increase it a bit around the output stage and still have less ‘total feedback’ (?) than original. The pentode one does 20 watts 20 to 20,000! The output impedance is down to < 1 ohm below 1,000khz, it gets above 1.5 by the top end.

I replaced the RCA's with good ones (Teflon ins'n) and new 5-way binding posts at 3/4 inch banana / pomona centres, but I still use bare wires which I dip in cleaning fluid every few months.

"It isn’t a Leak anymore." Or also "It doesn't sound like a Leak St20! Well, maybe not, but it does sound good. Quiet too.

 

Spare AMP

is a rebuilt STAX DA80 45wpc true class-A transistor amp, remember STAX headphones!

It’s different and very good but not ‘better’. Livability is lower as it usually ends up right in the middle of the entrance way with its wires there to catch at peoples heels. Please don’t tell ‘Trish but it chews more power too, all the time if on.

We checked its AC mains draw – with zero signal – to see if it would draw enough for full power at that state and it did! True Class-A. It’s not quite a Krell though, it gives 50 into 8 and just 90 into 4, and it shuts down into 2. It weighs more than a 200w.p.c. sand-amp I had here recently.

 

 

SPEAKERS.

Spherical concrete enclosures cast in off-white mortar. 20 plus inch diameter, baffle dia. is 15 inch approx. Local guys ‘Audiosphere’ made them in 1979! Volume is 23 liters as spec’d. An 18 inch sphere (volume) is about >40 liters - less the baffle slice, and less the driver / port volumes.

Drivers are by Foster (now Fostex) –

paper cone 8 inch (FW202) with a shallow curvilinear (bowl shaped) cone, faintly stippled, from the original mesh I’d bet, the back of the cone is damped with 1-3mm thick spackled (like fish scales) black stuff – papier mache? The dust cap is a stiffly woven but transparent black cloth. The VC is 38mm, just a tiny bit bigger than the tweeter’s. The magnet is huge for an 8 inch almost as big around as the frame. IE it is a lot heavier than contemporary Kef 8 incher's.

The main driver originally had just a wire damping resistor, and no Low Pass at all. I think this is unusual for the time, cf say Epos’ much later spkrs. It now has an RC Z rise E-Q circuit but that’s it.

This means that there is no baffle diffraction shelf dip compensation. Want numbers? a –3db point of 215 app. hz anechoic, shelving to –6db maximum at ELF.

Note that the 38mm voice coil is just a tiny bit larger than the dome tweeter. This can only help!

Foster’s claimed to the ‘sphere guys that the bowl shape, damping and dust cap help achieve good performance up to roll out and then assist the roll out!

Foster’s only plot on-axis for each driver showed –3db by 3.3 khz and the slope is amazingly clean, baring a small blip at about 3.6 that doesn’t get above – 5db. There are a few more woodles way down which vary on each, then its gone. No, it doesn’t take off another octave up! There were some good engineers at Foster.

 

The tweeter is Foster’s 35mm soft dome: it has resistive padding, a trap on its FS (at 1100hz?) and a 3rd order High Pass @ 3.5 khz.

Overall response is –3db 38-12,5000hz. Sensitivity is 91db/w and a benign 8 ohm load.

They were mostly voiced and auditioned on shallow dishes right near the floor. Baffle dip compensation would lose 3db or even 6db of sensitivity and lose a lot of transparency too, I wean.

 

 

BI-AMPING

System is bi-amped with the two baby Leak stereo amps.

SPKRS are all but hardwired to the amps *, and the x-overs are out in plastic Jiffy boxes on the floor. * There are two expensive DPDT relays in each x-over to allow polarity switching from my seat.

The most recent tweak was to put 1st order filters on the inputs to the power amps. A high pass @ 175 hz on the tweeter amp,

which was more noticeable than an LP >5khz on the mid/bass amp.

Highs got sweeter and more detailed, cymbals especially - you can hear the little grommets ringing, and ‘hear’ a brush circle around.

Headroom? Possibly, theory says 3 or more db, but it does sound less nasty the few times I have pushed it. I don’t. My wife thinks I do but I have an SPLM meter and its never near clipping. I figure I have about 15dbw at most.

 

CABLES?!

Spkr Cable was Lucas Cable - remember that stuff guys? Want some?

It is now short 6-7 ft lengths of Supra 1.6, hardwired to x-overs also now on floor in separate boxes.

Pre-power Ic’s are 4 long pcs of 'BRAND-REX LTD DIGITAL 1701248 20AWG SHIELDED TYPE 60degC (UL)’. That’s what it says. Ha ha ha.

Interconnects are VdH102II (CD) and IV (LP - Tx to MM) and a VDH brown cable (Tuner) - plus various home made stuff based on DIY/tweaks ideas over two decades, for everything else.

 

RACK/S and Stands

All sources and the Pre are mounted well away around the corner of the L-shaped room, the TT is positioned at a low pressure point for LF.

Main rack is bolted with heavy forged angle brackets to an exterior wall. It is a slab of cream concrete, ie it is a big step, what you climb up into houses on. TT, CD player and Pre-amp are on it

The rest is an old ex-Gov’t plywood suspension file cabinet turned on its side. The original frame is glued and screwed to what used to be one side . The frame is filled with sand and sealed with expanding foam. This is spiked to the floor with the big spikes - stubs from the original casters turned down. The top bottom and sides are reinforced and damped. My radio, rear ambience delay amp, and tape decks sit on its top. The open section is for tapes and audio accessories, discwasher fluid etc.

Spkr stands;

a column and circular (24inch) base are also cast in off-white concrete. The column, [10 inch dished disks glued together and covered by formwork tube] is filled with clean dry rough sand. Six axle caps glued to the circular base allow sliding on the carpeted floor. Each spkr has 9 spikes and collars, in three sets of 3, for each - spkr to column to base to floor. This was reached in stages over > 20 years.

 

AC MAINS

We are fortunate in Australia (240 volts 50 hz), that all our standard wall sockets and plugs have most of the features of the vaunted tweeky ones. Some of them are better still.

Separate AC supply lines - 2 of @ 15 amps. They had to have safety switch relay / circuit-breakers on them, ‘the rules’ before I put them in 1994. Our house has them ‘everywhere’.

Two AC Tx type filters before pre-amp and TT AC leads.

Ferrite clamps on AC leads to CD and VHS tape recorder.

 

ROOM

Is L-shaped, allowing sources to be a long way away around the corner.

But, it is otherwise a bugger acoustically, the outer corner is glass windows from ceiling down to three ft. glass on both sides of the corner. Heavy-ish curtains, yes.

 

 

 

Treatments (?!)

Began in 1981 on this. Wife (and I) chose oriental print fabrics together, and a Marimekko wall hanging.

Have 5 scrounger tweak panels.

Four were made from picture frame stretcher bar with pegboard / reclaimed wool shag carpet invisible on the back / inside. They are covered in Marimekko / Oriental printed decorator fabrics.

All hang off their wall or door - offset by 2-3 inches on 3 or 4 soft bouncy door stops. Two narrow / tall matching ones on each sliding door behind the spkrs, and two larger ones over the side-walls’ first reflection points, each is big enough to damp slap echoes.

5th is a rear ‘diffuser’ - made from two old louvred doors cut up and reassembled using peg board backing. Covered with a Belgian tapestry front and shag carpet (rear). Our heads are about 15 inches in front of it. And it stands off the wall by about 6 inches. NB I used kids bike trainer wheels and roller channels for this and it slides as well.(?)

It covers a floor to ceiling glass door flush to wall cabinet, where my LP’s, model cars and miniature knick-nacks are stored. This is a DIY built-in, it was where the oil heater used to be. So, there is a breast in the exterior brick wall and a sub floor as well. The cabinet is insulated on all sides and top, and rain-water proofed too.

The ceiling has modified 24 inch square acoustic tiles at the first reflection points.

Each spkr has a large throw type / floor cushion resting under it against the support columns.

above photo: GGG III.  Gorgeous George Greypuss, the Third.  Steel grey, all sorts of individual hair colors.  He is either part blue Burmese or Russian blue.  Yellow eyes.  Fur is silky, almost oily, like a Burm's is.  His da was a FERAL tom.  IE a real wild cat, not just a 'drain puss' or 'stray' but a really BIG several generations 'from outta da bush'.

 

SYSTEM STRENGTHS

3D imaging ie some records have a bit of depth others have lots and it is rectangular -mostly. Some recordings image in front of the speakers and behind, and some to the sides as well.

Fast and revealing, fingers on strings, tongues on reeds, glottal stops – listen to Ella working.

Interplay and ensemble very strongly revealed.

Very good microdynamics, and good macrodynamics.

Imaging doesn’t fall apart with crescendoes or at FFF.

 

It passes the 'Audionote test' ??????

Nearly all recordings sound very different from each other – ie Note that this is easiest to listen for on compilation disks.

Usual downside is that is very unkind to ‘obvious’ or any other-wise poor recordings.

Room gain at 30 to 40 hz is strong. Organ pedals are good, and I should know.

 

SYSTEM WEAKNESSES

Several upper bass and mid bass dips – due to the L-shaped room. Also affecting this area is that there is no baffle diffraction shelf dip compensation. See above under speakers.

 

PLANS / TO DO LIST

Bass

The mid bass driver is run as is with only parallel RC for Z rise Eq and damping. ie there is No High pass filter / eq, therefore there is no built-in baffle dip shelf compensation. And, I don’t listen loud most of the time.

Even though I do listen in the near to mid field I think I need to fix this, with a circuit right after my CFers in the preamp ie last out.

Distributed/delayed ambience / surround may also help here too.

OR - DSP room EQ, when it is affordable.

Deep Bass

Thinking still. Have bought 93db/w 12 inch sub drivers. And big 24 inch cardboard formwork tubes 1cm walls.

NB may 2002 - going off this more and more, and thinking about 6th order assisted reflex on the 3’s. two paths from here.

1. face 3’s to floor and EQ, place a pr of Model 2 spheres above them.

Set xover to ‘avoid’ the floor reflection dip.

Super tweeter - 1st order above the Corals?

 

 

2. 6th order assisted and baffle dip comp’n in pre, replace tweeter with new Philips’ psuedo ribbons, active crossover 2nd order LR just above 2khz. Add DSP eq for dips later.

 

OR - Sensitivity / detail / maximun loudness

Change main pair spkr drivers for greater efficiency and directivity. Deal with baffle dip step at same time. ADIRE HE 10.1 kit answers all this and gives 95.5db/w?

 

Other

Ambience extraction and delay (surround)

using seven small distributed speaker cabinets arranged along the floor against the side and rear walls,
the angled fronts firing at 60 deg. up the walls.
I have the processor and seven FE103’s just waiting, can also use tube power amp sections of the old Kenwood Radio

Improve / enhance the room treatments.

Deeper offsets - fill with fibre and seal sides, for existing side and front-wall panels.

Improve the rear diffuser

with some cardboard tubing off cuts and snakes of slotted corrugated tubingon its rear
improve /strengthen the roller system

Add absorption / diffusion to ceiling directly above speakers.

Make and install triangle cushions ala Green @ ceiling corners.

DIY Bass tube traps.

For the waiting TT

New motor and supply. Thorens wall wart and 18 volt AC motor – OR - a DC motor and supply.

Mount the original damped Mission 774 arm I now have (on a second waiting TD150). It is the one designed by John Bicht, of Versa Dynamics fame!?

 

 

Sealed ‘vacuum’ cabinet (fan motor) and stepper motor to flip arm lever down. ?????????

Ideally with a controller that turns on the vacuum extractor / fan motor briefly, then turns it off and then flips the arm lowerer. To start this from my seat, so I don’t miss the beginnings anymore!

HUM and BUZZ - A story

My hum problems with both my Leak ST20's were first due to the condition they were in when exchanged for a Stereo 60, Good swap eh?

Causes, Poor rectifier tubes serially, including expensive NoS, and Chinese tubes. These died so quickly it was like watching the fuel gauge move on a Ford Falcon GT, just more colour and movement like watching a mini big bang.

This did put me off them. Though I already knew that tubeophiles, like Quortrop et al, had 'issues' with SS PSU's. Second were the filter caps, again a serial experience of leaky and noisy OEM and then NoS originalist replacements, farting buzz and hum.

I was already wary of tube amps that farted like that. ? See last para, - barrup, BurRP baRARR... BARRA... BABOOM!!!

Soooo, out they went, BUT, I did use an array of quiet fast soft recovery diodes with snubbers, an inrush NTC thermistor, and 3 (or 4) big caps, each bypassed with a ladder of Wima MKS and MKP's.

Ahhh .... Quiet. Bass went Bang Bang and decayed and bloomed, when it should. Hard headed timp sticks in HIP perf's very sudden and real. Tube bass guitar heaven, and - quiet - too.

Now I finally could do it - biamp. One stereo amp. chassis per speaker,

and back came the hum, buzz, and hash and loss of grip at loud.

Tried one channel in triode, for each tweeter, less hash, clearer and sweeter, together!

So, thought, asked, and the stopped using vertical, and went to 'horizontal'. DC heaters and silver-ceramic socket for the input twin triode helped. Horizontal biamping = One amp does stereo duty in the mid/bass, now in pentode (4 filter caps) 20wpc, yes, 20 to 20k. The other is in triode mode and does stereo tweeter duty.

Much, much better. Theories? Less recirculation of 'earthy' currents/volts.

NB I did run a single earth reference wire between each amp, use one neg. spkr post on each amp, it helped. Try it.

Next? a proper zero volt reference ground plane, in the PSU for the preamp, was another big help. Properly earthed, they don't hum

NB Any high impedance high gain circuit is prone to hums and buzzes from stray capacitance alone, so a bit of maintenance on leads and earth posts helps.

A real exterior ground system signal earth point is a big help too.

Use thick 'earth wire' and a copper coated (at least) earth post. OZ

'soils' can be very hard so solid copper earth rods are like hen's

teeth. I have three copper coated steel ones banged in.