Is my Dynaco Stereo 400 worth repairing for resale?

This will give you an idea of listing prices. As far as repair/update costs, I am ignorant.

https://www.hifishark.com/search?q=Dynaco+Stereo+400

Designed by James Bongiorno who worked for SAE, Southwest Technical Products, GAS, Sumo and Rectilinear.

@jasonbourne71 Southwest Technical Products is certainly a blast from the past. I was 16 years old and upgraded from a Dynaco SC35 to a pair Mk III’s. I built a STP preamp kit that had push buttons. Did they have a connection Texas Instruments? 

@curiousjim if you want to sell it, and it works now as-is, maybe a simple check-over would suffice. If you look at the hifishark link above, click on the "sold" tab. Gives an idea of what they sold for. Maybe the right buyer will invest in it when ready to upgrade it is my thought.  

My Dynaco 400 sold for less than I had hoped for years ago and it was nice and minty.  

@decooney 

Thanks for the great suggestion.  I’ll check USAudiomart.

@jasonbourne71 

I’m sad to say James Bongiorno is no longer with us. I never realized how many of the products he designed, I bought over the years.

@buellrider97 : I have an original owner pair of 60 watt mono SS amps from South West Technical Products. Designed by James Bongiorno - full complimentary symmetrical circuit using the then-new PNP output transistors. Before that SS amps were limited to using only NPN output stages. JB went on to design the high-power Tigersaurus amp for SWTP which became the Ampzilla kit. 

@curiousjim : Little known fact is that James Bongiorno joined Rectilinear to work on the model X  speaker. Later he joined Spread Spectrum Technologies.

Interesting you mention the Rectalinear X. I tried to find a pair unsuccessfully in the late 1960s. I found it a fascinating speaker, sort of an augmented full range speaker with a whizzer cone mid range used from 100 Hz to 8kHz, a 10 " acoustic suspension woofer and a simple 2" cone tweeter. Add it used a series crossover  and it was a pretty unique design(even today). 

@curiousjim did you see the seller on the big e auction site selling the upgrade/restore kit for the ST 400?  Has main caps too, two sets left and 9 sold.  

I was wondering if you still listen to the amp at all any more or just storing it and thinning the collection?

Option-B:  People do look for the amp and if you were using it once in a while, and lets say if you were still listening to it once in a while, you could buy the kit, keep it for a future buyer or find someone local to install it as another option.  I liked my old Dynaco amps and when the right person comes along looking for one, decide then. Sometimes I'd like to have mine back to rotate in for fun once in a while. I liked the soft nature sound of that amp. Worked nicely with my electrostatics at the time, and I tried it with several different speakers, never a problem to drive many of them.  

A room mate of mine built an Ampzilla kit in 1975 that I got to live with for a time.  Very fondly remembered driving Cizek 1s.  Was JB also designer of the classic JBL integrated amp model SA660?  I know he did the SAE IIICM and Dyna ST400 around the same time as the Ampzilla.  I was smitten by Rectlinear IIIs when I first heard them, but not by their other models. The X was a very low efficiency largeish bookshelf model, IIRC, and sounded pretty dark to me, more like an AR3 than the III, which had more in the way of transparency to my then-young ears.

@dynacohum Wrote:

Was JB also designer of the classic JBL integrated amp model SA660? 

I don't think so. Bart Locanthi designed the T Circuit in that amp see here.

Mike

@ditusa,

Thanks for the documentation.  I really wanted one of those back then!

@dynacohum: See here.

Mike

Will Vincent or Tubes for hifi both rebuild but they basically use the case and transformer.  Those are 1700-2000.  They sell kits as well.  

We used to have Magnapans.   We used Ampzilla and Quattre.  Both blew up. There were some reliability improvements that can be made. Bonjoirno and Leach put solid state on the right path.  Much more pleasant sounding than many of the day.

How much do you like it? How much would it cost to replace? How long do you plan on keeping it?

If you get all the electrolytic caps replaced, along with any other out of spec part, the amp should last another 20 or so years with out issues, other then cleaning. 

If you love it, fix it, if not sell it for something you will love. 

In the last 6 months have referbed 3 of my amps, and 2 of my pre-amps. All sounded so much better after, it was way more sweat equity over cost as I DIY'ed it. Cost was about $80 per piece, sans the amps big power caps. 

This guy, old and in the way, enjoyed this thread.  I've got a dead Superphon in storage. I keep thinking I'll get it fixed some day.

@decooney 

Yeah, it’s been used once in the last couple years and should probably move to a home where it’s going to be used, but….  can you send me a link to Big E?

@puptent 

The Stereo 400 was a kit and it has a ton of parts, but if I can bring it back to spec, or better yet, I might just keep it around. 😁

@mswale 

I built this amp so long ago I barely remember where everything goes. It has VERY little room inside, so I would need the exact power caps, cause there’s no room for anything much larger.  It’s a heavy beast too!

I still have 8 or 9 Dynaco pieces though I tend to grab the tube stuff. Have some solid states like the  PAT-4's & a Stereo 120 but I've never owned a 400. 

There are definitely people that are still interested in Dynaco's. If it's clean & in good working shape you can make a couple bucks on top of the repair costs but not much. With anything it depends on the buyer. What I would do is take your time renovating it for minimal costs but with quality parts. Do it for the enjoyment & keeping old audio alive. 

Then list it for a price you are comfortable with..with the expectations it might not sell right away. Enjoy it in the meantime or box it away. Eventually someone will come around that wants a solid working 400 to add to their collection. And won't mind paying a little extra for one that has been recently brought back up to spec. Fixing one up for a quick sale or needing your small investment money back right away might not end like you would want it to.

I was unable to see the exact one that you have but the 400's with VU meters still fetch a pretty penny. There was a really clean (exterior) 400 without meters on the Bay for like $320 plus shipping. So I'm guessing anywhere from $3 to $500 depending on some things. Although I'm looking at some right now as high as $950 no meters..$1800 with. How long have they been sitting for though. 

If you have the means & time to fix it up I say go for it. Keep your investment as minimal as possible. Or upgrade all the parts & keep it for yourself. 

Your Dynaco 400 might not need any immediate work. Put it on a variac to reform the power supply caps. Then use a multi-meter to check the DC voltage on the two speaker outputs. If those show only a few millivolts of DC try the amp with a pair of speakers. Not all old amps need parts replacement. My 40 year-old Sumo Andromeda - another Bongiorno design - has been in use 24/7 for seven years now without a hiccup! 

Under no circumstances should anyone buy "restoration" parts from Hi-Fi-Audio-Rocks on eBay.  He's notorious for send poor or wrong components and providing weak or nonexistent documentation.  There's a long thread mover at Audiokarma about this seller.

@curiousjim 

I get there is little room inside, however, all new caps of the same value will be much smaller. At times I have had to check the values again, they are less then 1/2 the old caps size for the same value. In fact have gone up in voltage on a lot of caps, they are sill much smaller. 

Point it, there should be a lot more room, after you swap out a few caps. 

Yes, do not purchase any "kits" get the service manual, it should have a parts list, with that, put together an order with mouser or digikey.

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. 😊

I had a Dyna 400 that was a factory build, roughly 1973 as I recall. I got an accommodation since I worked part time in an audio store. I liked the idea of the "Dynaguard" (running from memory here), it performed well. I swapped it out for an original Phase Linear 700 which was a beast and yes, it did flame out, but got fixed promptly by Carver back in the day. (We are talking 1973 still). I used stacked Advents and went through my share of tweeters. Then did an about face, bought a pair of Quad Loudspeakers, built a Stereo 70 as a stop gap and within a few years, ARC preamp and amp. I've been in tube world since then.

I have no idea what it is worth today. Solid state stuff back then was not a smooth, it had a more pronounced "grain" in the mids- not specifically the Dynaco 400 but I remember the Phase Linear 400 sounding better than the 700 at the time. Whether it is worth a recap-- probably depends on how attached you are to it.

I still have my ARC Dual 75a-- which I kept for sentimental reasons. I recapped it in 2003 or so through an authorized facility and it was used intermittently as a rear channel home theater amp with two other ARC tube amps. I eventually got tired of the heat generated by all those tubes running in a home theater application and switched to a big McI solid state multi-channel basic power amp, which I still have. 

I don't know how many Dyna 400s are around or how that cuts in terms of market value should you want to sell it. We've come a long way in solid state since then though I'm still a tube devotee. 

@abnerjack 

I just saw your reply.  Not sure how I missed it,

But Thanks.