Is my Dynaco Stereo 400 worth repairing for resale?

I built the Ampzilla in 1975. I paid for a rebuild 12 years ago after a 2 hour conversation with Mr. Bongiorno months before he died. I subsequently used it until I finally replaced it with a Spread Spectrum Analysis (SSA) Son of Ampzilla II amplifier, circuitry designed by Jim and finished in partnership with Jim by Wyred for Sound who physically built it and designed the beefy power supply.

A note about his name: I have only seen references to “James” Bongiorno in the last 25 years, with pictures of him usually wearing a wild colored suit with an extravagant shirt. When I met him as an 18 year old in late December 1984, he introduced himself to me as Jim and was wearing a white T shirt with a leather jacket, very biker like.

The original Ampzilla had a “dual-differential input” and had completely complimentary symmetry from input to output. I think the SWTP Tigersaurus had a complentary output stage with differential input. Others may know better, but the lineage of the Ampzilla runs through the Dyna400 to SAE 4 to Marantz 500 chain most directly. I think that the Marantz 500 was the first to use both high powered PNP and NPN transistors in its output stage.

@mswale 

Did you use fancy dancy caps and could you hear a big difference in the sound? If so, was it a good or bad difference?  I’m still trying to decide whether I want to keep the 400 or hopefully sell it.

Likely not very helpful, but I had a few Dyna 400s in my day, with and without meters. I found them to be ok sounding, but that was with analog only sources, different rooms and so on. I cannot speak for today if I would enjoy listening to one. I have a very large amp collection, and I enjoy many of them, as my speakers are very easy to drive. My best, MrD.

@curiousjim 

LOL, fancy caps. Well, I used audio caps (Nichicon Muse ES, Gold) for the signal path, and regular caps for everything else. Also replaced all carbon comp, and fuse resistors with metal film. 

Yes, it made a very noticeable improvement, everywhere! Bigger sound  stage, lower noise floor, cleaner sound, more bass, more high, cleaner mids, more dynamics. Like a vale was lifted. 

Also have a spare pre-power amp set as a backup, switched it back to back with refreshed vs original. The refreshed is just so much better. 

Like I said, cost was nominal, my time was vast. Think my pre-amp took 12 hours over a couple of days. Power amp was like 18 hours over a few days. Replaced over 100 parts (caps, resistors, diodes) in both units. 

IMHO your question really is a subjective one. I have a Dynakit Stereo 70 that my late Dad built in 1961.  My first experiences with audio were with a system that my Dad had in our Family den. The system was composed of a Fairchild 412 turntable with Shure tonearm and mm phono cartridge, Dynakit Pas 2 preamplifier, Dynakit Stereo 70 power amplifier and an Acoustic Research I speaker used as a subwoofer, with a Janzen electrostatic tweeter.  This was a really nice sounding system back in its day and I remember being introduced to many different genres of music through it.  The Holiday season was especially memorable listening to a myriad of different songs celebrating the Christmas Holidays.

So where many younger people might see a groady looking old tube amplifier, I see some wonderful memories from a long time ago.  

And at some point I am fairly certain that I will invest in having this old gem of an amplifier restored. 😊