Film-Tech Forum ARCHIVE: Vacuum Tubes

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Posted by Edward Jurich (Member # 1787) on 08-02-2003, 01:47 PM:

Anyone else out there like vacuum tubes for audio besides me. I just restored a 1939 E.H. Scott console radio and it has a wonderful sound on AM. It uses 2 - 2A3's in push-pull for about 10 watts output driving a 12" electromagnet speaker.
Besides restoring this radio, I've built new audio equipment with tubes.

Posted by Bobby Henderson (Member # 840) on 08-02-2003, 01:59 PM:

I like the Groove Tube brand 6L6GC power tubes and 12AX7 pre-amp tubes in my Carvin stack. Transistors suck much ass for providing a good sounding "crunch."

Posted by Dan Lyons (Member # 1454) on 08-02-2003, 05:38 PM:

Me too!! Here is my Jolida 102b integrated amp from my hi-fi system. Got it about a year and a half ago. The tubes are EI brand 12ax7s and EL84s. It does keep the room warm when it's on.
On the right is my Creek OBH-8 phono pre amp.

Danny

Posted by David Stambaugh (Member # 1102) on 08-02-2003, 06:24 PM:

The best-sounding audio electronics I ever had was all-tube. The preamp was a conrad-johnson, the power amp Audio Research. That system sounded so good! [Cool]

Posted by Lindsay Morris (Member # 1430) on 08-02-2003, 08:33 PM:

I much prefer Valves with the warmer richer sound and failures when trouble shooting are much less dramatic with valves compared to solid state devices. Sometimes just the simple slip of the multimeter probe sends a packet of expensive Mosfets to the bin but had that been a valve amp in most cases would have just been a big SPLAT.
Am currently constructing a valve amp rack to cover the conversion to Stereo & Surround sound at the outdoor which over the past 7 seasons has run on mono sound from a Westrex valve amp type AE 307 with EL34's in the output and from the soundheads the signal was being collected by the original VERY OLD Photo Cells which have never missed a beat. Tested response was still quite good to 8khz but by 9k the signal had all but gone.
The "newer" line up is a pair of the Westrex AE 307 amps (EL34's) at 35 watts RMS for Left & Right and a pair of RCA (National Theater Supplies) A161 with KT66's at around 50 watts RMS for Centre & Surround. Just quick and rough tests on the bench taking the signal from an Eprad Starlet processor has produced quite good results in the workshop which I am sure will translate to equally good sound outdoors for this coming summer season. I will have to resist the urge to wind it up a bit as it sounds so good right now.
Don't have a drawing of the A161's but am in the process of sketching that out to work out just how it all hangs together and for future reference.
Valves... I love 'em and no problems getting replacements either.
Just repairing a friends Westrex Drive In amp (type AE 293)which has 4 X KT66's in output with 4 X 6SJ7's driving those. When fixed the final test I give these brutes is 24 hours on the bench delivering 70 watts RMS of steady tone into a dummy load which gets rather warm but the amp just cruises!. Only down side is the voltages that some of these units use... the raw HT in the Drive In amp is just over 700 volts so quite lethal and much care is needed.
Lindsay

Posted by Jon Miller (Member # 163) on 08-02-2003, 10:02 PM:

Here's a workhorse Dynakit Stereo-70 I rebuilt and modded in 1993...

About the only things left stock are the transformers, tube cage, and the basic EL-34-based output section. The amp received a Curcio mod featuring a regulated power supply section and a driver card with two 6922 triodes per channel and bias balancing for the output tubes. I replaced the cheap-o original connectors with gold-plated binding posts and RCA jacks, and built a capacitor farm to replace and improve upon the old quad-section filter capacitor.

It may not be a single-ended amp with 2A3s, but that modded Dyna sure does sing! Gotta love those firebottles! [Big Grin]

Posted by Phil Hill (Member # 371) on 08-03-2003, 12:44 AM:

I love tube stuff... I have tons of it... Radios, Ham radio receivers and transmitters, etc. I built my stereo system so I can select between FET & vacuum tube power amps. (McIntosh 240) Depending on what I'm listening to.

In my workshop, I have a Heathkit FM-3A with a A-9C Amp that I built as a kid...both still work great!

I love designing and restoring it. Favorite Power tubes are 6L6GC (of course!), 6550 (KT-88), 6146, 811, 813, 833A...& more.

I still have my original Novice transmitter kit I built in Jr H.S. many moons ago. Johnson "Adventurer" and my receiver National NC-98.

Yeah, I'm a tube junkie...BIG time! HAhahahah

BTW: It always amazes me that the music amp manufacturers design special "distortion" circuits to make their transistor amps sound like tube amps. Seems like an oxymoron.

>>> Phil

Posted by Ken Layton (Member # 133) on 08-03-2003, 12:57 AM:

Tubes are the only way to go! [Cool]

I keep a couple of old Bogen C60 public address amplifiers around for occasional use.

Posted by Bruce McGee (Member # 131) on 08-03-2003, 08:51 AM:

I, too, have a Dynaco Stereo 70. Mine is all original with new electrolytics, and new tubes. It sounds great! (Still looking for that big surround system amp!)

In my travels, I look for things with tubes. I have many clock-radios that work, and some that dont, but look good. I have several 35mm projector amps, and one real oddity from Simplex that uses 2A3's that works like a dream. For 16mm equipment, of the 20+ machines that I own, only 5 of them are not tube amps.

I have a 1956 Zenith B/W TV with a working remote control, and a 1961 RCA color TV that needs caps, but runs decently.

I thought that tube lovers were a minority until I got on the internet. Tubes rule!

BIGGEST TUBE MISTAKE: I once owned 2 (TWO) McIntosh MI-200 power amps. I was 12-13 years old, and a friend of a friend of my dad gave them to me. The thing I remember most about them is the weight! I couldn't find the 8005 tubes anywhere, so they sat in the shed until we did a dump run. Recently, I found out how valuable these units are today.

I know nobody here (in western NC) that has tube equipment anymore.

Posted by Mark Gulbrandsen (Member # 72) on 08-03-2003, 02:43 PM:

I love tubes as well, but they are no longer necessary in the audio amplifier world, unless of course its for the collectability aspect, or if you plain just happen to love them. There are still some very good pieces of vacuum tube based test gear out there though.

For those that may be interested there are several modern solid state designs that are single ended and operate class "A" that will easily beat the socks of any tube amp I know of. These can be easily constructed at home and for little cost. These do require alot of static heatsinking, or built as a water cooled amplifier. I'm in the beginning stages of constructing a second pair of these that will be built with water cooled, solid copper heat sinks. Note that the audio path sees a mere two semiconductors!!

Here is a link to one of the best of these amplifiers.....
http://www.passlabs.com/pdf/aleph/a2srv0.pdf

Please note that although this design is patented, the designer Nelson Pass, encourages people to build them as long as its a not for profit venture.

Also check out www.diyaudio.com

Mark

Posted by Jack Ondracek (Member # 1466) on 08-03-2003, 03:27 PM:

We've always preferred today's modern tube equipment, here at our drive-in. This time-tested technology performs at an efficiency and quality-of-signal level which transistors can not hope to attain.

Shown below is Transmitter Room "Abel", one of the three state-of-the-art, self-contained FM stereo broadcast systems we use to send our audio signal the 300-400 feet from our booth to our customers.

We're very excited about these installations, as they are barely half the size of our original systems. Reclaiming that square footage has allowed us to add an additional 16 toilets to our restrooms!

__________________________________________________

Shown below is a new final amplifier tube, undergoing performance and integrity verification measurements in our maintenance shop. We run through 3 or 4 of these tubes a year. However, the cost is well justified by the looks of satifaction we see on our customers' faces when we fire these babys up. Not shown is our new John Deere lawn tractor, just to the left of this view.

____________________________________________

We're especially grateful to our local power company for the new substation and bug zapper they installed for us last year. Centrally located in Field 1's playground (just in front of the swingsets), it's a sight to behold for young and old alike. On a practical level, it totally eliminated the voltage drops we experienced when turning on the filament, and eventually the high-voltage supplies to our transmitters. Thanks to this new equipment, we've taken out all of our oil lanterns.

As shown, the new plant makes for a friendly and scenic attraction for our customers as they travel the well-worn driveway to the snack bar.

Posted by Aaron Sisemore (Member # 145) on 08-03-2003, 03:46 PM:

I too am a huge tube fiend... [evil]

Some of what I have includes the following:

Dynaco ST70: I have two of these, this one has Tesla EL34s, Sylvania 7199s and yes, that's a 5u4G filling in for the Sylvania 5AR4 that shorted out on me [Frown]

My other ST70 has GE Owensboro 6CA7s and a GE Owensboro 5AR4, and Sylvania 7199s.

TruTest Stereo/5: This little baby is what powers my computer speakers!! [Cool]

From left to right: Telefunken smooth-plate 12AX7, 2 Fujitsu 35C5's, RCA 35W4 rectifier.

Stuff not pictured, but fully functional:

Altec 1570B: A pair of RCA 811A's, the other tubes are a mix of RCA's GE's and Sylvanias. I am looking for a second one of these, cheap (yeah, right!) [Wink]

Kenwood KW-55 Receiver: 2 GE 7189A's per channel on the outputs

Precision (Grommes) PA amp: The only thing I have thats operational that uses 6L6's (RCA Blackplates, of course) [Cool]

Akai 1710W reel-to-reel tape deck

1969 GE Porta-Color 11" Color TV: Still works like a charm! [Smile]

I have a lot of stuff that is not operational (much of it probably never will be- I will probably use some of it for the trannies...

-Several RCA theatre amps and preamps (including a pair of 2A3 PP power amps that I plan on restoring one of these days)

-Several Japanese integrated amps (EL84 and 6GW8 power tubes mainly)

-A Hewlett-Packard signal generator

-Several small 'All-American Five' radio chassis

I also have hundreds of tubes, both NOS/NIB and tested good used ones. Some of my favorites include:

Preamp Tubes:
Telefunken 12AX7/ECC83 Smooth plate
RCA 12AU7/ECC82 Clear top
Mullard 12A*7/ECC**
Sylvania 7199
Telefunken 6267/EF86
RCA and GE 6C4

Power Amp Tubes:

Any US-made 6L6GC, with a special fondness for RCA blackplates
Tung-Sol 6550
GE 6550A
Mullard/Philips/Amperex/Valvo EL34
Tesla EL34
GE Owensboro 6CA7
Sylvania/PhilipsECG (US made) 6CA7
GEC (Genelex) KT66 and KT88
Any US or Western European 6BQ5/EL84
Any US made 807
Any US made 6146
Any US made 7591A

Rectifiers

Mullard/Philips/Amperex/Valvo 5AR4/GZ34
GE Owensboro 5AR4
All US made 5U4G and GB
All US made 5R4 varieties

Tubes that SUCK:

Most Russian (except Svetlana) and Chinese garbage

-Aaron

Posted by Paul G. Thompson (Member # 655) on 08-03-2003, 03:55 PM:

Vacuum tubes are great! [Smile]

Posted by Gerard S. Cohen (Member # 994) on 08-03-2003, 08:16 PM:

Bravo, Jack!

I loved your drive-in transmitter spoof which amplified my mirth from shot to shot!

Thanks, Gerard

Posted by Jack Ondracek (Member # 1466) on 08-04-2003, 12:19 AM:

Thanks, Gerard. Guess it proves I have too much time on my hands!

The drive-in I grew up working at has FM now. However, they've maintained their original 1953 speaker system at a level very close to when it was originally installed.

This is the theatre's sound rack. The only changes made to it since it was originally installed have been the removal of the original "S. F. Burns & Co." photocell preamps and the addition of an FM stereo system (the white unit at top). This box also houses preamps and switching for two projectors (which the drive-in had when I installed it), switching for music, film and microphone inputs and voltage-controlled amplifiers for level control. It also has a summing amplifier to drive the speaker systems.

________________________________________________________

This is one of the two amplifiers the drive-in uses to power its original speaker field. It was a common model that RCA used in its turnkey installations. The outputs are 807s. If I remembmber right, it uses a 6SJ7 (6SL7?) for phase inversion, two OD3 (VR150) voltage regulator tubes and a 5R4 (5Y3?, 5U4?) rectifier tube. Sorry about being a bit hazy on tube types. Been a while since I checked it out.

Over the years, I've found two spare amplifiers of the same model for the place. One is fully tubed and ready to go. The other is fully functional, just needing a set of tubes to put it into operation.

Each of these amplifiers could easily run a drive-in twice the size of the one that they're installed at. Still, the theatre runs both of them each night, splitting the field between them. It has the normal ramp switching matrix, including switching to put either amplifier to the full field, and monitoring for each amplifier individually.

The theatre presently runs a Century DA, powered by a Motiograph sound head. A Century R3 is on-hand, upgraded with a Component Engineering reader for the onslaught of cyan tracks we all know is just around the corner!

For anyone interested, here's a mini-tour of the place.

Wheel-In Motor Movie, Port Townsend, Washington

Posted by William Hooper (Member # 71) on 08-04-2003, 02:25 AM:

Ed may remember that I assisted in a radio station project that utilized tubes to route smoke into a newsroom board to entertain the news guy while his mike was open. Those are the best kind of tubes. We had to get a consultant who had understanding of bong technology to modify a dishwasher detergent bottle to incorporate a cigar as a smoke generator. INCREDIBLE output.

Posted by John Pytlak (Member # 331) on 08-04-2003, 09:19 AM:

When I worked at the Grandview Drive-In in the late 1960's, we still used one of those ~1953 "turnkey" RCA sound systems to power the field speakers. I still remember some of those really hot summer nights when the plate leads to the 807 tubes in the final would catch fire (due to the deteriorating insulation). Our CO2 fire extinguisher "saved the day" on more than a few occasions. [Eek!]

Posted by Edward Jurich (Member # 1787) on 08-04-2003, 12:22 PM:

William Hooper said...
Ed may remember that I assisted in a radio station project that utilized tubes to route smoke into a newsroom board to entertain the news guy while his mike was open.

That Hooper is quite the gagster, I remember when he put his best foot forward to stop a showing of "The King and I" [Razz]

Posted by Andrew Duggan (Member # 1302) on 08-04-2003, 01:14 PM:

My guitar setup is also tube driven, a 77 Music Man amp head, using 12ax7s/Preamp and EL34s/Power. It sounds somewhere between 1 and 2 million times better than my old solid state amp. Good times.

(It's also heavy enough that if my stack ever feel on me during a show that I would pretty much die instantly. Nothing like living dangerously....)

Posted by Aaron Sisemore (Member # 145) on 08-04-2003, 05:53 PM:

quote:
BIGGEST TUBE MISTAKE: I once owned 2 (TWO) McIntosh MI-200 power amps. I was 12-13 years old, and a friend of a friend of my dad gave them to me. The thing I remember most about them is the weight! I couldn't find the 8005 tubes anywhere, so they sat in the shed until we did a dump run. Recently, I found out how valuable these units are today.

I have a couple of BIG tube mistakes as well (If I only known then what I know now!): [Roll Eyes]

-I had an EICO ST70 integrated amp (7591A outputs) that caught fire on me in 1987. Rather than repair it, I just sent it off to Goodwill. Didn't even pull the tubes [Eek!]

-Around 1985 I had a beautiful near-mint Dynaco ST35 power amp that I traded in 1986 for a pair of 6550's (!!) and a large HAM rack that I wanted the trannies and chokes out of. ST35's are one of the most sought-after, rare Dynacos out there nowadays [Eek!]

Sometimes I still smack my head when I think about what I had done [Mad]

-Aaron

Posted by William Hooper (Member # 71) on 08-05-2003, 02:32 AM:

Ed:
[scream]

Posted by Lindsay Morris (Member # 1430) on 08-05-2003, 06:08 AM:

807's...a nasty surprise for the unwary are those fellas.
Usual quick test was "finger on the grid" trick for a rough estimate of where the problem lay in valve amps except if they used 807's as the grid cap was not one of those but the anode instead.
Can still remember the look of horror/surprise on a "smarty pants" looking over my shoulder once when I was pondering what was driving an RCA amp with 807's absolutely crackers. (noise was out of this world).
Comment from smarty pants "easy things to fix these, just bung your finger on the grid and listen for the noise".. He did just that but no noise from the amp it all came from him when he hit the 807 anode cap first up seconds before I could say anything. He slunk off with my peels of laughter ringing in his ears and then the boss wanted to know what all the noise was about.
The real noise was a sliver of hookup wire stuck in the socket shorting out a few pins... took me a while to find that.

A country DI had a similar RCA amp setup and the owner wanted radio sound so he bought an "elcheapo" mini FM transmitter and got his young projectionist to hook it up.
The instructions from the supplier were to connect it to the "grid cap" and it will work a treat!!! Guess which grid cap they tried.. YUP the 807!
When I went there later on there were 2 rather charred looking FM transmitters sitting on base of the rack... loved to have been there when they went up.
Lindsay

Posted by Jeff Stricker (Member # 224) on 08-05-2003, 06:57 AM:

Not to mention a bunch of amateur radio receivers and transmitters around here, I use a pair of McIntosh MC-40's (PP 6L6's) in my screening roon. Great sound [thumbsup]

Posted by Jeff Stricker (Member # 224) on 08-05-2003, 06:58 AM:

Not to mention a bunch of amateur radio receivers and transmitters around here, I use a pair of McIntosh MC-40's (PP 6L6's) in my screening roon. Great sound [thumbsup]

Posted by Edward Jurich (Member # 1787) on 08-05-2003, 08:40 AM:

I'm going to attempt (my first try at this) to attach a couple pictures of that 1939 E.H. Scott radio. It's got 2 chassis and they are all chrome plated.

Here's what it looks like in the cabinet after refinishing. The top lifts up (original) so the radio chassis can be viewed.

[ 08-05-2003, 02:28 PM: Message edited by: Edward Jurich ]

Posted by Jack Ondracek (Member # 1466) on 08-05-2003, 12:52 PM:

quote:
A country DI had a similar RCA amp setup and the owner wanted radio sound so he bought an "elcheapo" mini FM transmitter... 2 rather charred looking FM transmitters sitting on base of the rack.

Yup. Too often, I've run into drive-ins that have hooked their transmitters up to the outputs of their main amplifiers... then wondered why their old speakers sounded better. [Roll Eyes]

ED... nice looking load of chrome you have there! All that metal around the tubes reminds me of the McIntosh amps the phone company used to put in their central offices for distributing background music for Muzak, etc.

Posted by Jeff Taylor (Member # 443) on 08-05-2003, 01:50 PM:

Although I grew up in the vacuum tube age, I use a QSC 800 in my home screening room (mono) driving a Yamaha 12" and horn PA cabinet for the "stage" channel, and a Yamaha 18" subwoofer in bi-amped configuration. I also use a subharmonic synthesizer for a bit more punch. I'm very happy with the QSC, but my engineer son who builds knock off Fender tweed amps for a hobby/side business is trying to talk me into going back to tubes. One thought I had was an Altec 1570 (811's) for the sub, and a 1569 (EL-34's) for the stage channel. Any of you guys have any thoughts on the subject--other than the fact that I'd be trading a nice cool compact setup for one hot rack? My other thought was to "upgrade"? to an Altec horn for the stage channel in lieu of the Yamaha cab, but then I've got the issue of most of the drivers you see kicking around being 24 ohm or so. No problem for a tube amp, I agree, but for the QSC it could be. All thoughts appreciated.

Posted by Jeff Stricker (Member # 224) on 08-05-2003, 07:28 PM:

Ed, the Scott looks terrific! What excellent radio gear. [thumbsup]

I have a Scott RBO (military version - that I'm currently selling)--- what excellent fidelity off the AM broadcast band! There used to be a station in Chicago that was particularly broad banded that played music from the 40's and 50's -- it sounded great.

I have a friend who lives near here who is a big collector of Scotts.

Posted by Aaron Sisemore (Member # 145) on 08-06-2003, 02:50 AM:

quote:
One thought I had was an Altec 1570 (811's) for the sub

While it is one of the most powerful tube amplifiers around, the 1570, in my opinion does not do very well with bass frequencies below 150 Hz. (extreme distortion and a definite lack of 'balls' in the bass)

I would go with a solid state amp for the sub, and tubes for the other channels, or if you absolutely INSIST on driving the sub with a tube amp, try building something using a 'bass-friendly' beam-tetrode based (6550's or 6146's) output a la Ampeg SVT.

The QSC amps will handle a 24 ohm load with no problems other than maybe a slight loss of power...

-Aaron

Posted by Phil Hill (Member # 371) on 08-06-2003, 03:44 AM:

For driving subs with tube-type amps, and audio amps in general, it is not necessarily all that important to have tubes like the 6L6GC, 807, 6146B, 6550, etc. There are many great triode amps that outperform a lot of those beam power pentodes types.

What is important, is the design and construction of the output transformer. For any size power amp, the $$$ sunk into that xmfr will more than pay for itself in performance...especially at the low freq and high freq ends.

Also just as important, especially for bass reproduction, ya need a big ol' "stiffie" ...A power supply that wont sag when required to supply sustained high current. Not just big filter caps, but BIG efficient low-impedance power transformers (or switchers) as well.

BTW: Ed, that Scott is a honey! It is in fantastic shape! [beer]

>>> Phil

Posted by Jeff Taylor (Member # 443) on 08-06-2003, 09:44 AM:

Phil and Aaron, thanks for the feedback on tube bass amps. Any thoughts on going to an Altec horn (or are there any other recommended horns?) for the main "stage" channel of my setup?

Posted by Edward Jurich (Member # 1787) on 08-06-2003, 04:27 PM:

The Scott radio came from Chicago (LaGrange, Il) and is my wifes grandfathers who bought it new around 1939. Check out the chassis underside, the big wheel in the middle is part of the band switch. It rotates with the band switch, has contacts on the underside for the different coils.

Below is a view of the underside showing the coil contacts.

Below is a view of the chassis contacts that connect with the coil wheel. Note that it is gear driven. There are 2 other switches that switch with the coil wheel and all three have to be in sync.

When I refinished the cabinet I did not strip the original finish. The original finish was still in good shape, it just had a couple bag gouges and several scratches. I filled in the gouges and wiped the cabinet down with stain and all the scratches filled in. Then gave it some coats of new varnish and buffed with very fine steel wool. There are still some minor dents in the cabinet that don't look bad but then it is an antique.

Posted by Will Kutler (Member # 770) on 08-06-2003, 06:41 PM:

I have to agree with Phil Hill about transfer design. Transformer engineering is one of the "Secrets" to sucessful amp design!

For anyone interested, Western Electric 300Bs are now being produced again, and are not cheap for a matched pair! They can easily be found on the "www"

Vacume Tube Logic is one of the vacume tube amp powerhouses in the industry today, and are located in Ontario, CA. Anyone who is interested should view thier books regarding amp design. These books are legendary, but on one hand, they do omit some vital info.

I have to disagree with Mark G. regarding how tubes are outdated. There is nothing that can beat tubes for sure sound quality!

One funny experiment that I recently tried. I went into a local hi-end store to check out some new vacume tube systems that they had. I had a Sinatra c.d. on hand, and the tubes made it sound awesome, while the hi-end transistor amp, played back through the same c.d. player, pre-amp and speakers made it sound ho-hum. The tubes really made the c.d. sound rich and full...and gave a lot of warmth! The funny thing was that the store had a "rap" c.d. on hand, and I thought that it would be funny to listen to it on tubes. The rap recording was crap to begin with, so imagine how the tubes added the same warmth and ambience that it did to the Sinatra recording! [Big Grin]

RAP IS NOTHING BUT TEST TONES WITH VOICE OVERLAYS!

Posted by Bruce McGee (Member # 131) on 08-06-2003, 09:01 PM:

Ed, that Scott radio is fantastic! I sure wish they still had all that detail in modern equipment!

When todays 'stuff' is 60 years old, how much of it will still be running?

Posted by Lindsay Morris (Member # 1430) on 08-07-2003, 03:45 AM:

Ed, That Scott is out of this world... never seen a think like that here in Australia. Have tangled with plenty of bandswitching radios in the past but most of those were of 1950's vintage... but the Scott is something else, an excellent restoration job and I hope it sounds as good as it looks.

On the subject of "subs" and valve amps I must admit that I cheat a bit at the outdoor and run a powered sub parked in the "W" bin with the pair of 15" normal bass units just to add a bit more grunt... The bass disperses rather rapidly outdoors so I took the easy way out and added a Studio Acoustics 12" 100 Watt unit which just cruises and just gives that nice deep "thump" to the very low sounds and effects. On their own the pair of 15" drivers do a really good job but needed a little help.
Certainly the output transf needs to be well designed but many of those cinema type units from the 50's and 60's were well done with plenty of copper and iron and well done windings and most of the cinema amps I have come across have had plenty "of GO" at the bottom end.
When I get a decent snap I will post a picture of the DI amp I have just repaired. Load tested for 24 hours at 108 watts RMS from a sinewave signal (onset of clipping on the scope) and mains trannie just warm and less warm was the output stage.(The hottest thing was the dummy load!!)
Weight of the animal is around 25KG so not the sort of thing you use in the lounge room but really sounds nice when driving a big speaker setup... very clean.
Now I will get back to completing my new amp rack ready for stereo sound conversion.
Lindsay

Posted by Edward Jurich (Member # 1787) on 08-07-2003, 08:57 AM:

I have a friend who thinks I'm nuts when I say tubes sound better for audio. However, here's something I did a few years ago that says otherwise.
I was Chief Engineer at WWMX radio in Baltimore (also known as W-MIX then) from 1988 - 1992. I built new studios for them and had everything running top notch. However, while sitting at home listening to the station, it just seemed to me that something was lacking in the sound. I remembered that years eariler my brother-in-law had a mono HiFi that sounded better with more realism than my stereo radio station. Then it dawned on me that is was all tube. So, after 20 years of not touching a tube, I bought a bunch of 12AX7's, tube sockets and started building a vacuum tube audio leveling amp. I came up with a 12AX7 gain control stage so everything in the audio path is triode.
One night I installed my vacuum tube leveling amp in front of the Orban Optimod ( a modern soild state audio processor ). I backed off on some of the Orban processing and let my vacumm tubes do a lot of the audio leveling. I did this without telling anyone.
And the result was fantastic, the station had realism like I had not heard in years. After a couple weeks one of the other station engineers in town called to let me know how great my station sounded. I had other people tell me how good the station sounded.
The best one though was when a music consultant heard the station while driving through Baltomre and stopped by to see why our station had such a "unique" sound. I opened the back of the rack so he could see all the tubes glowing, his mouth dropped wide open.
That station had an increase in ratings (number of listeners) while that tube processor was in use. I built that tube processor at home with my own parts so it went with me when I left the station. I still have it although it's been collecting dust the past 4 years since I've been out of radio.

Posted by William Hooper (Member # 71) on 08-08-2003, 01:25 AM:

I don't understand, Ed. Tubes? Is this some sort of intravenous music delivery system? Like that special microphone at the CBS news station in Chicago?

Posted by Phil Hill (Member # 371) on 08-08-2003, 10:01 AM:

Bruce said:

quote:
When today's 'stuff' is 60 years old, how much of it will still be running?

Probably most of it...IF it ain't thrown away like this "disposable" generation seems to like to do.

I can see it now: 60 years from now when Josh is 79 and all of us are dead, he will be still posting on the net (or whatever is around then), looking for carts for his machine....he will be a true patriot and carry on history! [beer]

>>> Phil

Posted by Edward Jurich (Member # 1787) on 08-08-2003, 10:37 AM:

William Hooper said
"I don't understand, Ed. Tubes? Is this some sort of intravenous music delivery system? Like that special microphone at the CBS news station in Chicago?"

I can't believe you remember the microphone gag. Back in the early 70's while I worked for WBBM (CBS) in Chicago, the TV guys pulled a gag on a new news person. They brought out one of the highly directional Electro Voice microphones that had a 2 foot long by 3/4 inch dia element. They told him it was one of the "new" rectum microphones. One of the other news guys ran a mic cable down his pants so the connector was hanging out his pants leg and said, "I've got one on now".

On the subject of stuff lasting 60 years. I don't think there will be a lot of what's in use now around in 60 years. For one thing, standards are changing so fast that things become unusable much faster now. And, with surface mount electronic parts, stuff will be just plain unrepairable after a few years.

Posted by Paul Konen (Member # 41) on 08-13-2003, 11:04 AM:

To further justify that people realize that tubes give audio a better sound

Tube SACD CD Player