I'm not talking the little Tigers I'm talking the 200 watt mono block amplifiers.
Both started as kits.
Both started as kits.
Mono block
The southwest tech..my opinion had a better output stage. The Ampzilla supposedly had hand picked outputs at least that is what Bongiorno told me when I spoke to him one time in St Louis.
The southwest tech..my opinion had a better output stage. The Ampzilla supposedly had hand picked outputs at least that is what Bongiorno told me when I spoke to him one time in St Louis.
Attachments
Last edited:
Some early Ampzilla info can be found here on the Popular Electronics Sept 1974 edition. Tried to post it but the file was too large.
The southwest tech Tigersarious can be found in the Dec issue of Radio Electronics.
The southwest tech Tigersarious can be found in the Dec issue of Radio Electronics.
Last edited:
I'd like to mention that I have owned both the Ampzilla (early kit version) and the Tigersarious 200 Watt Mono block amplifiers in the past. In Addition I have owned the 121 G and 121 F Ampzilla model and if memory is correct the "F" I believe was supposed to be the model that had all the instabilities resolved. They still however managed to blow up.
The Ampzilla was prone to blowing up while I never blew up the Tigersarious amplifiers. I did purchase both the Ampzilla and the Tigersarious amplifiers in a non-working condition and repaired them.
I could never get the Ampzilla to drive a 4 ohm pair of speakers without letting out a puff of magic smoke while the Tigersarious would drive them without a problem all day long.
The Ampzilla was prone to blowing up while I never blew up the Tigersarious amplifiers. I did purchase both the Ampzilla and the Tigersarious amplifiers in a non-working condition and repaired them.
I could never get the Ampzilla to drive a 4 ohm pair of speakers without letting out a puff of magic smoke while the Tigersarious would drive them without a problem all day long.
Last edited:
The info in Post #5 is the original layout of the original Ampzilla. The second version had the same circuitry but different layout. The unpopulated 121B circuit boards I have are completely different. Gone is the single floating regulator and in it's place are two CCS similar to the later "E" thru "G" boards. The front end coupling caps on the 121B are also similar to the later boards.
The rumor I've heard about Ampzilla driving low impedance loads is that the output transistors suffered from Beta droop and the drivers couldn't keep up and poof.
The Tigersaurus had twice as many outputs as the Ampzilla and were actual 30A devices, MJ802/4502. The original Ampzilla supposedly had 30A devices but were just "selected" 2N5631/2N6031 which are 16A devices.
I think the Dynaco ST416 was designed to overcome the same problem the ST400 and Ampzilla had with low impedance loads, again twice as many output devices.
I have one Tigersaurs that I've never heard because it had oscillated itself to death which seems to the common problem with them. But this problem seems to be due to crappily built kits. Maybe some day I'll get mine going.
Unfortunately both Dan and James are gone so we'll never know.🙁
Craig
The rumor I've heard about Ampzilla driving low impedance loads is that the output transistors suffered from Beta droop and the drivers couldn't keep up and poof.
The Tigersaurus had twice as many outputs as the Ampzilla and were actual 30A devices, MJ802/4502. The original Ampzilla supposedly had 30A devices but were just "selected" 2N5631/2N6031 which are 16A devices.
I think the Dynaco ST416 was designed to overcome the same problem the ST400 and Ampzilla had with low impedance loads, again twice as many output devices.
I have one Tigersaurs that I've never heard because it had oscillated itself to death which seems to the common problem with them. But this problem seems to be due to crappily built kits. Maybe some day I'll get mine going.
Unfortunately both Dan and James are gone so we'll never know.🙁
Craig
The beta droop is the problem here. It what happens is if the base current of the driver is too high, it UPSETS THE VOLTAGE DIViSION from the resistor stack that biases the upper “slave” transistors. The unequal voltage division results in one transistor being run outside its SOA with more than half the voltage on it, while delivering high current.
Doubling up on outputs helps, but does not completely overcome root cause. The Leach superamp solved this problem by using an output triple to reduce loading on the divider. That works, even driving 2 ohm loads.
Doubling up on outputs helps, but does not completely overcome root cause. The Leach superamp solved this problem by using an output triple to reduce loading on the divider. That works, even driving 2 ohm loads.
That was one of the goals of Ampzilla II(a) a more robust driver stage that used a triple EF driver/output stages. It took a few revisions before they got it stable, well more stable, with the final "G" version.
Craig
Craig
https://worldradiohistory.com/Archive-Poptronics/70s/1974/Poptronics-1974-09.pdf
That is Dec 1973.
https://worldradiohistory.com/Archive-Radio-Electronics/70s/1973/Radio-Electronics-1973-12.pdf
Fig 3 is drawn wrong. Schematic point G is wrong.
Last edited: