dlb945

Dynaco Mark IV & Mac 250 thoughts .... The Mark IV design is identical to the ST70 with one key exception; each Mark IV has its own power supply resulting in 100% isolation between a pair. Some say that this gives maximum separation and others claim that the Mark IV power transformer lacks the ability to provide the punch compared to the ST70. One friend in the Atlanta Audio Society uses a pair of ST70 amps, each with driver and output tubes removed from one of the channels with claims of more power punch along with 100% isolation/separation. If the user is fortunate enough to have any Klipsch horn design, none of the above matters because it takes so little power/punch to drive these wooden beauties. Al has an interesting insight regarding big Mac SS amps and it is true that the output transformers used with the best Mac SS units impart a sound similar to a better tube amp. Even Roger-Russell, a retired Mac engineering manager, agrees with Al on the advantage of big Mac SS amps. Roger has a great web site with complete Mac history of all products. Take a spin. My discovery for achieving the floating 3D image we all wish for is two-fold. The discovery relates to both ends of the system, source and speakers. Late one evening after one-too-many Martinis, I got up the nerve to straighten the stylus of a high-end cartridge that came with a used turntable from an eBay auction. A pair of pliers with balsa wood glued to the jaws removed the bend. I went though the alignment procedure, grabbed an old scratched up LP, and let things rip. Pow! I got the first really deep and wide floating image. The location of the instruments was smeared and voices sometimes appeared wide instead of concentrated at a point but I concluded that I was just too cheap to spend money on the right things. Hey I said, I think Ill do the ALK project to see if the image improves. I did so and sure enough, the smears were reduced and voices became more focused. I spent several months installing and comparing tube and SS preamps and amplifiers and eventually concluded that the best combo for my ears was a SS preamp driving a tube amplifier. My personal quest here has seen me update caps/resistors in the SS preamps to improve focus. The tube amps I own include the Conrad Johnson MV75A1, Dynaco ST70 and a pair of Dynaco Mark IIIs. I replaced only the driver caps in the CJ unit but am completely balancing the L/R channels in the ST70. My best SS amp is a Hafler DH500 with extensive mods and it also gives a spectacular 3D image but, I still like the warmth of a good tube amp and I can roll (change) output tubes to change the character of the amp for certain types of music. Im sure the tube sound results from the iron laminations between the output tubes (or transistors) and speakers. More recently, I purchased a used Cambridge D500SE CD Player that is a near high-end unit. It also produces a superior 3D image. Again, my recommendations are, buy and install ALK upgrades and get yourself the best source component you can afford. Then try an amplifier with output transformers. There is nothing like the POW and warmth! >>>From too many words Dan

Purchase a Dynaco ST70. Take the time or find someone to update the caps/resistors on the driver board or alternately, puchase a 100% equivilent original design driver board from the Dynaco Doctor fully stuffed and ready to insert into amp. The latter comes with instructions similar to original Dynaco kits and is easy to do. Go a little futher, and update the power supply section, a kit is also available from the Dynaco Doctor. You will end up with the identical sound of the original Dynaco ST70 and the frequency response and distortion will be that of the "Golden Age of Stereo". Everyone should own an updated ST70 for a reality check of today's gear. How will the ST70 compare to an 8B you might ask. The sound of an 8B whether original or updated, will produce an excellent to spectacular sound stage with the image disconnected from your speakers and floating in space. The sound of the Dynaco ST70 rebuild, will have a very good to excellent sound stage again with the image disconnected from your speakers. The depth of the ST70 will be less than that of the 8B but ... quite close. Today, a good 8B will put you back $1,500 or more while a good ST70 suitable for updating is more in the $350 range. The ST70 is a lower cost way to hear what David Hafler & Co. did to "voice" this popular amplifier. If you do have the bucks, don't hesitate to purchase the 8B. Sol Marantz and Sid Smith spent considerable time to "voice" the 8B and it is at the peak of the golden age mountain. By the way, either the ST70 or 8B sounds spectacular with Klipschorns! And, if you own K-horns, puchase the ALK crossover upgrade (see the ALK forum). The sweetspot for either amp with the K-horns is about 4 feet wide and 4 feet deep and when one moves beyond the sweetspot, the 3D image remains but some of the pinpoint resolution begins to smear. >>>Dan

Marvel & Listeners ... I kept the tube rectification for the ST70 rebuilds. The SDS power board, available from Uncle Ned, allows for either SS rectifier or the tube rectification. I tried both but the tube rectifier gives what appears to be a more mellow tone and ... it is much more gentle to the other tubes during startup i.e. no startup DC surge before the tubes warm up. >>>Dan

To Marvel & other watchers ... I rebuilt a pair of ST70's for a friend in the Atlanta Audio Society. I started with cleaning and replating the chassis(chrome not nickel), rust removal and repaint of transformers, original driver circuit board (Dynaco Doctor), high quality caps/resistors (matched on a bridge), new power supply capacitor board (SDS Labs), specially crafted test jacks and output terminals, and military spec hook-up wire (high-purity copper, silver plated and Teflon insulated). A picture of one of the completed ST70 units can be seen on my personal website at: http://home.bellsouth.net/p/PWP-dlblabs If any of you are futher interested, you can find rebuild pictures at: http://pg.photos.yahoo.com/ph/dlb945/my_photos How did they sound? Each amp was inserted between a Marantz 7T Preamp and a pair of Klipschorns. They sounded wonderful and created a very nice image that floated somewhat in back of the speaker plane with good (not excellent) depth and very good dynamics. I then strapped each unit for mono operation, one for the left Klipschorn and one for the right Klipschorn. The image was still back of the speaker plane but the depth increased and the dynamics were increased considerably. The power output of the strapped units must have been in the 50 watt range. Today ... I am rebuilding a ST70 for myself and should have it completed in a few weeks. I'm using the same rebuild philosophy as above. >>>Dan

To Dylanl See attached photo showing special wire to both crossover and speakers. The answer is yes, I used this wire throughout. Some history and thoughts follow. I used this Mil-spec Belden hook-up wire (MIL-W-16878/4) in several colors to update a pair of Dynaco ST-70 amps for a friend with outstanding results. I decided to use this same wire in my ALK designed crossovers. I used double-spun wire throughout the crossover itself (can see in photo). Used double-spun for tweeter & squawker and triple-spun (green and white in foreground of photo) for the run to the woofer. The cable between speakers and amp shown is 10 ga high purity copper. After a few months, I got further improvement by replacing the 10 ga with Nordost Solor Winds (12 length). I originally saw this wire used in applications at a nuclear fuel production facility several years ago. The custom-built measurement and control devices used this hook-up wire throughout. The engineer for the lab (an audio friend as well) suggested that it made solid state amplifiers sing. Ive never tried it in a solid state rebuild but I can tell you it makes a considerable difference in golden age tube gear. I am working on my own ST70 rebuild with the same wire. Before I rebuilt the ST70 driver board, I purchased 10 each of every resistor/capacitor and did a match of L/R channels using an antique bridge. I think they may be matched to 1% and can hardly wait to complete this project. I wont argue with AL that this upscale wire does not make a difference. I can tell you that I have heard one other pair of K-horns with ALK upgrades being driven by McIntosh Amp and Preamp and the image generated from my rebuild produces a better 3D image with good to excellent recordings. Im talking pinpoint accuracy in width, depth and even height! But, this is an evaluation with my ears and there could be some bias. >>>Dan

Decided to try ALK design with 100% DIY. Result ... breathtaking 3D image floating in space completely disconnected from K-horns. Don't just wish, buy either completed or kit and install in your speakers. PS ... I used 20 ga silver plated high-purity copper w/teflon for both x-over and runs to tweeter, squawker and woofer (multiple strands). No, it is not a hot sound, just faster on transients. Wow! File attached shows mirrored left/right under construction. Enjoy.

Thanks to all! Great forum. It must have been a vintage year. I happened to have both K=horns out from the corners as I replaced the Type AA Crossovers with an ALK Engineering Type A design. As I took pictures of the installed crossovers (see attachment), I decided to snap a picture of the label to see if someone knew the What Year answer. This evening, I'm driving the horns with favorite components: slightly updated Marantz (SS) 7T Preamp, Conrad Johnson (Tube) MV75A1 Amplifier, Harmon Kardon T65C Turntable with Orotofon OM-30 Cartridge, Sony ES CD Player, and some dusty old vinyl. Nice change to the sonic character of the system with deeper sound stage and smaller-locked instrument and voice locations. Highly recommend the crossover design. >>>Dan

Does anyone have an idea on the year my pair of Klipschorns were manufactured. Picture of Left Horn cabinet label is attached. It appears that the serial numbers are: Left ... 135168 ... or 13 S168 Right .. 135169 ... or 13 S169 Thanks >>>Dan

The rebuild of an ST-70 is today, very straightforward. If you can use a soldering gun, the recommeded steps follow with approx prices. 1) Remove all parts from chassis - transformers, sockets, boards etc. 2) Get local auto replate shop to recondition chassis - $130.00 3) Order new driver board kit with parts - $100.00 4) Order new power supply board with parts - $60.00 5) Order new sockets, silver coated wire, pots etc. - $160.00 6) Order/buy new S.S. Pan Head screws/nuts/washers/Lwashers - $40.00 7) Remove end-bells and refinish - $5.00 8) Using ST-70 kit guide and board guides, mount and solder all in place. 9) Purchase and install all NEW tubes - $90.00 to 200.00 Checkout an example at >>> http://home.bellsouth.net/p/PWP-dlblabs