'The Music Room'
Music Room - Current System
Transcryptor Skeleton, Mayware Formula IV & Grace F9
OPPO 105 BlueRay
Dyna PAS3X Preamplifier
SANGEAN HD FM Receiver
TEAC X20R Reel to Reel
Denon HDCD Changer
SONY Stereo VHS
Njoe Tjoeb CD Player
Mullard 5-20 Monoblock Amplifiers
ShermanAudio KT88 Monoblocks (display)
Zu Druid MKIV Speakers
TECHNICAL DIARY - 2016
Tonight the clock striked 12pm and we celebrate New Years.
This is a day of medidation and healing.
Time passes and we age and pass along with it.
Our lives enter yet another part of our Universe.
My plans for 2017 are to build the two kits I have ready and complete the rest of my equipment.
Capital Audio Festival is in my sights.
PAST DIARY 2012
D.I.Y. PROJECT DYNACO ST-35 STEREO AMPLIFIER
2012 IS HERE AND A NEW AMP IS BORN IN THE MUSIC ROOM
DYNAKIT ST-35 BIAS BOARD KIT ASSEMBLY
ASSEMBLED PC BOARD
AMPLIFIER COMING TOGETHER NICELY
HAMMOND 1650F WITH A COAT OF GLOSS BLACK RUST-OLEUM PAINT
ASSEMBLED AND NOW READY TO BE WIRED UP WITH A FEW MORE PIECES LEFT TO INSTALL
VIEW OF REAR OF AMPLIFIER AS THE PROJECT PICKS UP SPEED
INSTALLED POWER SWITCH AND PILOT LAMP
FIRST SOUND CHECK IN LIVING ROOM - LEFT CHANNEL DISTORTS WHEN VOLUME IS INCREASED
REPLACED LED PILOT LAMP WITH 120VAC LAMP
CABLES ARE VAMPIRE FROM LUTZ, FL.
PROBLEM FIXED - A FAULTY 6P14EB RUSSIAN TUBE ON THE LEFT CHANNEL PC BOARD.
BOUGHT A QUAD OF GOLD LION CURRENT PRODUCTION
AMPLIFIER NOW 100% OPERATIONAL
NOTE THE GROUND TIP JACK - MAKES BIASING EASY
BOTTOM VIEW OF AMPLIFIER WITH THE COVER REMOVED
AMPLIFIER SOUND - CLEAR VOICE, SUBLIME MIDRANGE, SMOOTH LOWS AND CRISP HIGH'S
KUDOS TO ED LAURENT; THE DESIGNER OF THE ST-35 CIRCUIT.
WISH ED WAS HERE TO ENJOY THIS TRIBUTE AMPLIFIER
This is the latest iteration. Illinois Capacitor 0.22uF. The original WIMA are re-installed.
The 0.22uF made a dramatic difference from the Orange Poly. Here I could attest that the
part change made a dramatic upgrade.
NEXT 2012 PROJECT IS A CONVERGENT AUDIO TECHNOLOGY
CAT-1 BASED PREAMPLIFIER DIY CLONE
STAY TUNED !
TECHNICAL DIARY 2011
2011 is a year that has me in a life/career transition. Having moved away from the Caribbean in late 2010 after 15 years the roots are still not in place. My shop area is still in a transition and projects have been delayed.
But I can share thought's and ideas......
SUBJECT: VINTAGE AMPLIFIER AC VOLTAGE CORRECTION
Voltage correcting transformers are a must to effectively manage the tube life and performance of Vintage Amps.
Not many people understand how un-regulated power supplies work. This is a key understanding in owning Vintage Tube amps.
It is a fact that any odorous and dusty old tube amp will work best when connected to a 115 to 118 VAC mains. Power Transformers of 40-50 years ago were manufactured based on a 117 VAC primary voltage, so the turns ratio was in fact making the correct secondary voltages when connected to 117 VAC.
If you want to compare your voltage readings on that old ST-70, ST-30, A500, A700, Fisher 400 or Marantz 7 you needs to have a Variac and set the primary voltage to the one that is published on the schematic.
The problem we face today is that Primary AC voltages in the range of 115 to 118 VAC are not very common today. Unless one happens to live very far from the power station, in the styx, you will probably measure 125 VAC with your VOM.
Now connect that old Dynaco ST-70 to 125 VAC and you will immediately exceed the DC voltage rating of the stock Quad Electrolytic capacitor, not to mention AC and DC voltages sometimes 20 to 25 % above nominal, I have seen 30% in some old Stromberg Carlson amps I own.
In order to appreciate what I am saying here one must understand that Power Companies always prefers to err on the high side when delivering commercial power. Meaning that less I squared x R losses means less power lost on the electrical lines, more profit, less loss as heat when we buy juice from them for our homes.
But ..... today's 125 VAC mains does not work well with most old tube amps, unless some method of voltage control is used, or the design itself provides a 120 VAC tap. Most vintage tube amp designers happened to make their quiescent points in the lower third of the input AC voltage range, making some headroom for the rise in AC mains voltages. But not all did and we shorten the life of our tubes when we connect old equipment directly to the power grid.
If you don't believe me, you need to measure the voltages and currents on your vintage tube amp and compare them to the original values shown on the schematic to understand what "High Mains" AC does to your precious tubes.
AC Filament voltages will often rise above the 10% maximum allowed and dramatically shorten tube life.
Most current production tube amps do not have this problem, as their transformer primaries are wound for 120 VAC and the voltages settle down quite nicely.
But amps built from the late 40's up to the mid 70's have some issues as their Power Transformers primaries were using the 115 VAC standard, obsolete in today's un-regulated power supply designs but still commonly used.
Regulated power supplies correct for this, but 99.99% of Vacuum Tube amps do not implement regulation. Some Tube Preamps do and in fact benefit from this. But regulating 485 VDC is not an economical thing to do, and would probably double the list price of any Tube Power amplifier. Also the complexity and size of a regulated 500 VDC power supply is $$.
High AC Mains will make filaments wear out sooner. You know when this is happening, the tubes act like lightbulbs and actually provide illumination is a dark room. When tube filaments are lighting up your room, they are actually screaming for help !
Remember that 6.3V and 12.6 V (DC or AC RMS) are the nominal voltages that the tube filaments require. The specifications will allow 10% over, meaning 6.3 VAC + 0.63 = 6.93 VAC.
But..... operate your tubes at 6.93 VAC and you shorten tube life.
This is a well known and scientifically proven fact that has been common knowledge since the late 50's. Wise designers operate tube filaments at the nominal value or 3% under.
There are a class of tubes that will suffer dramatically from high filament voltages, DHT Triodes.
These tubes have filaments that do not work well with high filament voltages.
The filaments on these tubes will draw proportionally more current as the voltage rises unlike a resistor whose behavior is defined by Ohms Law. In old radio's (I meas 1930's) 2A3 tubes actually had a rheostat in series with the tube filaments that allowed filament voltage adjustment over a specified range to adjust gain.
Build a "home brew" - Balanced Power Toroid - in a box, with a fuse and switch. Use a toroid that has 55-0-55 VAC on the secondary and the common but outdated 115 VAC on the primary. This solution will shave off those extra volts and dramatically extend tube and amp life. Parts Express sells some toroids 800 VA that will work to power a tube amp.
Or you can use a 60-0-60 VAC toroid and 125 VAC primary. In any case the goal is to produce no more than 120 VAC to your amplifier, preferably 117 VAC.
In my modded Transcendent Balanced Power unit I replaced the 60-0-60 VAC Toroid with a 55-0-55 VAC keeping the same 115 VAC primary.
Un-loaded and connected to 125 VAC, the voltage I measure is 121 VAC-122 VAC.
As you load the transformer with equipment, the voltage will drop a few %.
The more you load the transformer secondary, the lower the settled voltage.
For instance, if you have a Dynaco Stereo 70 that will draw about 1.5 amps when powered up, this means about 180 VA of AC Power.
You can use a 500 VA Model so that it will load at less than 50% of it's total capacity, I would go with an 800 VA for extra headroom in case you want to connect a PAS3 Preamp as well.
The trick with voltage correcting transformers is not to load then past 50%.
1000 VA load at 500 VA (4 amps AC RMS continuous)
800 VA load at 400 VA (3 amps AC RMS continuous)
The 500 VA model is far more practical as you can also connect a Tube Preamp.
There are 625 VA, 800 VA and finally the 1000 VA models to choose from.
The benefits of Balanced Power operation are also realized here.
Any vintage tube amp will run cooler with lower AC Mains, the amp will sound better and you will be happier knowing that your vintage amp and precious tubes will last longer.
The side benefits of Balanced Power are lower radiated electrical fields from the AC Secondary cabling and quieter performance.
The link below will provide Toroids for your project:
Here is the schematic of my modded Balanced Power unit:
Order any one of the Toroids in the 500VA to 1000VA range, depending on your application and build this into a small project box.
You will need to machine a mounting for a 120 VAC mono receptacle, usually a Greenlee Hole Punch, or your local machine shop can punch a correct diameter hole.
If you want to power a complete vintage tube amp/preamp/etc. system with an 8 Amp fuse, you need to order the 1000 VA Avel Lindberg Model [Y236954].
Maybe you can request that Transcendent Sound sell you the Balanced Power kit without the Toroid and you simply order the model that I show on the schematic. I haven't tried this yet, and my suggestions to Transcendent Sound were not welle received. The suggestion was to use a bucking transformer on the primary. I don't see this as a solution but a fix to a problem with their design.
When I built the Balanced Power unit from Transcendent Sound I connected my amps to the unit (I had not even bothered to measure the secondary AC RMS voltage) and noticed that my amps were GLOWING BRIGHT and the plates of the 6550 tubes were cherry red.
I measured the loaded secondary voltage on the stock design and my meter read 131 VAC.... yikes!!!
My plans in 2012 are to build a few "Vintage Tube Amp Savers" in stock for sale with the option to have an Analog or Digital meter on the front panel.
ShermanAudio Q3/Q4 2011 projects
DYNACO ST-35 REPRO in a nice Ebay Chassis... EL84 Yummyyyyyy.
TRANSCENDENT SOUND CATHODE FOLLOWER AMPLIFIER from Bruce's liquidation sale. Class A low power..ummmmm. I got the chassis and toroid from Transcendent Sound.
KISMET III - FIXED BIAS VERSION from a project that needs to evolve. That clear vocal bliss only the 2A3 can provide.....
The order in which these will be built DIY depends on the Sun, the Moon and some free weekend time.
On my Workbench, there will be a few of my restored Vintage Amps. These will get a full checkout before I sell them to make sure that they are all reliable and up to original operating specifications.
TECHNICAL DIARY 2010
The precious few hours of free personal time I have left to work will be documented here. This part hopes to share my direct experiences as my restorations, D.I.Y. activities and repairs take form.
AIKIDO PREAMP OUTPUT CAPACITOR UPGRADE
The Mad Modman is onto a Russian Teflon and Oil capacitor thing, so he suggested that I try some in my DIY gear to see if they made a difference. Well I said "OK" and proceeded to warm up the Weller.
So here is the photo of the 0.47 uF Teflon Russian Military Capacitor upgrade. And wow, these thing put any of the fancies to total and utter shame.
Immediately the music became better. How, well the Bass performance is now up to par. Whenever I swap capacitors I listen for improvements at the frequency extremes first to see how they are behaving.
The midrange is very nice. So for a song, you can try these caps and see if they improve your musical experience.
These part are built like they were made to be installed inside a Missile. They don't have leads but have metal lugs.
Enjoy the photos... a bit blurry but the camera is a Casio and all of the photos it takes are out of focus even though it's an 8 Megapixel.. My SONY Cybershot from 2001 smokes the Casio dead, and it's only a 3.3 Megapixel, but it has Carl Zeiss optics,, ahhhh das ist wunderbar.
I also put 4x 0.22 uF of these in my KT88 Monoblocks and they also made a definite improvement over the Kimber Caps.
MESA BOOGIE .50 CALIBER COMBO AMPLIFIER
The Mesa .50 Caliber amp is but one example of how a PC board failed to age gracefully and how NOT to put together a guitar amplifier if you want it to become a classic design.
Looking at the heat damage, I can see that the heating problems are mostly located right at the point where the 9pin ceramic tube sockets are soldered to the board itself. Also most of the heat from the power tubes aged the board and caused it to degrade.
Also it is obvious that this board was worked on many times as it developed the symptoms of a sick and overheated PC board. Several repairs have lifted PC board traces and ruined the board, requiring jumpers.
The reason why we see this kind of damage is simple. The PC board is mounted inverted, the tubes facing down and the heat from all of the tubes rising up against the component side of the board.
You can clearly see the effects of this heating on the foil side of the board. The component side shows discoloration around the tube bases.
I called Mesa on the phone and they said that the PC board is not available any longer. Granted they were very courteous, helpful and empathetic.
The photos were taken by me during the repair process. You can almost smell the BBQ as you see what heat and moisture can do to a Mesa .50 Caliber PC board. I attempted to jumper all of the burned PC board traces, and the bias of the 6BQ5's continues to jump from -19 to -7.5, switching sides on my last attempt to find a better ground.
I gave-up and concluded that the amp needs a replacement PC board, no longer available. If the owner has the desire, I could re-wire this amp completely point to point by mounting the sockets directly to the chassis and implementing new sockets with covers for the 12AX7/12AT7 and spring loaded retainers for the 6BQ5's.
CLASSIC MARANTZ MODEL 7 PREAMPLIFIER AND MODEL 9 MONO-BLOCK AMPLIFIERS
In for repair a totally retro-classic vintage paired set of Marantz Tube equipment.
On order are a pair of Marantz 9 Main Power Supply capacitors.
(1) 40/40/40 uF/525 VDC CE Manufacturing FP plus (4) JJ 100uF/385VDC capacitors; 7/8" diameter.
I am tempted to spray these caps with some "Heat Resistant" Grey paint to maintain that original Marantz look.
Some people get really nervous about changing Marantz parts but wouldn't think twice about plugging these into the wall blind.... go figure.
Some Variac action is due and once they play, I will break them back into normal operation and finish any leaky cap or drifted resistor.
Once they are working, they will be up for sale.......................... any offers ????????????????????????????????????