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Dynaco 120A ... worth upgrading?

Kevin K7ZS

Kevin K7ZS

New Member
Just received a Dynaco 120A 2 channel amplifier from a brother that is moving, forgot he had it and gave it to me rather than move it.

looks unmolested, nice physical shape, powers up but haven't tested it yet.

Just curious if this is worth updating, (and what preamp anybody suggests for it, if it is ... would be fun to have the PAT-5 to make it a Dynaco system). The Update My Dynaco store has virtually everything to make these better than new - saving only the chassis and transformer! Initial thoughts would be to start with power supply kit and perhaps the larger output coupling capacitors?

Good money going down the drain, or can these be made into a respectable amp?

Thanks -Kevin
 
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You could go either way, refurb or upgrade. If the internals are in good condition and the boards are not heat damaged, replacing all the electrolytic caps should put it back in working order. Fantasia audio on Ebay sells a cap kit for all the smaller on-board caps.

Otherwise the Update my Dynaco parts are well designed and a worthwhile upgrade.

The more important question is do you want seperate components and what preamp will you use. A Pat4 or Pat5 will work, but chances are that will be another refurb or upgrade project.
 
Good morning and thanks for the sage advice!

It's as much a source of a project as is the end result ... this would replace my Marantz 2245 in the shop so it can return to a proper place for that fine receiver that I bought new in 1972! I fired up the Dynaco today, feeding it from a tablet and it is functional with a good sound (well, free from funky artifacts anyway). Turns out, my brother already took the preamp to Goodwill, not thinking I would want the whole system ... he just thought of me because of the sizeable transformer in the stereo! We are going to visit the store to see if we can buy it back! I think this will be a refurbish project, and have been made aware of Fantasia on eBay offering P/S and amp module capacitor kits plus replacement coupling caps with coils. I would probably go for the full size 10000mfd caps on Update My Dynaco and rewind the coils if that is deemed necessary. Just gonna listen to it for a while....

Sort of a landmark amplifier, intriguing to me and it will be a fun project plus perfect candidate for a shop amp!

Thanks for the reply.

-Kevin
 
I am a great proponent of UpdateMyDynaco kits and goodies. I worked on Dynaco SS pieces for a few years, upgrading 120s, Pat 4, Pat 5, SE-10.....everyone was fun to work on and the result was very nice! As I finished each piece, I sold it, sometimes to repeat buyers who appreciated what these pieces could do after some updating of the 40 year old parts!
Rather than try to explain further, check the feedback forum, do a search for CT Jim, and read what a bunch of Dynaco buyers liked about those 'old pieces' that now kick a..

Fun projects!
 
CT Jim said:
I am a great proponent of UpdateMyDynaco kits and goodies. I worked on Dynaco SS pieces for a few years, upgrading 120s, Pat 4, Pat 5, SE-10.....everyone was fun to work on and the result was very nice! As I finished each piece, I sold it, sometimes to repeat buyers who appreciated what these pieces could do after some updating of the 40 year old parts!
Rather than try to explain further, check the feedback forum, do a search for CT Jim, and read what a bunch of Dynaco buyers liked about those 'old pieces' that now kick a..

Fun projects!
Click to expand...
Great testimonial to UpdateMyDynaco! just ordered the P/S replacement caps (C9 and C11) and the C12 replacement kit with cap, as I am seeing a little bit of Cap Crud coming out of the vent on C12. Figure the P/S first - the heart of any amp, then listen to it for a while. Very cool, straightforward and SERVICEABLE piece of audio gear ... In my Ham Radio hobby I prefer the little older gear too, with discreet components that you can replace. Many newer and very spendy 'black box' radios are no longer being serviced, even by the manufacturer, since it's a 'board replacement' approach - and most boards are long gone. A shame to see that magic box being relegated to a parts unit or a paperweight. Not so with my 1980's Kenwood transceivers - they just soldier on. Thanks, this will be fun! Kevin
 
The good thing about almost all Dynaco equiment is there is much documentation and support available. You can refurbished all stock to upgrades for stability to going wild with mods. I have a Dynaco FM3 tube tuner, a ST-35 clone tube amp, and a modified ST-70 tube amp clone. There is a kit for the PAT4 SS preamp that fixes a few issues along with a correction in the phono stage that's worth looking into if you get it the PAT4 back. The cool thing is several of the Dynaco tube amps never went out of production. Even when the company disappeared. Bod Latino, Dynakit and a few others just kept making clones, and still do.
 
Lavane said:
The good thing about almost all Dynaco equipment is there is much documentation and support available.
Click to expand...

And pretty easy to fix if they do fail. I fixed a neighbor's ST-150 and don't recall it being very hard.
 
Easy is good, if they perform, and this seems like one of those nice designs that got the job done without a lot of proprietary or hard to find parts, which is great! UpdateMyDynaco shipped my capacitor kit within 24 hours of placing the order, great service!
As for the preamp, the first look at the Goodwill store where the PAT-4 went didn't turn it up... they probably send things off to a central sorting facility? I'll find one. Stay Tuned, and thanks for the encouragement! Kevin
 
Go for the PAT-5. The ideal feature set. External processing loop, two tape monitors, defeatable tone controls.

I have one in the closet that needs fixed, and I'm thinking about rebuilding it with the updatemydynaco boards. I haven't is that it ends up an expensive build and I don't have a need for another preamp right now. And I'm lazy - er I have other projects.
 
Yes, keeping it all Dynaco and period correct is what I intend to do ... I guess I'll be hitting Goodwill a lot for a week or two and hope the original mate shows p, but I'll look for a PAT-5 as it does appear to have some nice features over the PAT-4
The hunt is on!
 
I've only worked on one pat4 and needed to replace all coupling caps. And PS needed fresh caps.

Like the st120, plenty of options
 
Kevin K7ZS said:
Yes, keeping it all Dynaco and period correct is what I intend to do ... I guess I'll be hitting Goodwill a lot for a week or two and hope the original mate shows p, but I'll look for a PAT-5 as it does appear to have some nice features over the PAT-4
The hunt is on!
Click to expand...
It likely never made it to the floor. GW is notorious as of late for putting anything of value like that on their online sale site.
 
I'd get a hafler, like a 101 or 110.

Then you can get a pat4 or pat5 when one pops up within your budget.

And still enjoy your st120 system.
 
Hey Catmanboo, thanks for the tip, I'm camping on their website now ... for sentimental reasons would like to get it back ... my Bro is sick about it, not thinking I would want it, so a couple of reasons to try and find it ... making a game of it now ... One can only hope!
 
WELL, I found a PAT-4 to match what my brother had, from an eBay seller only TWELVE MILES from my house! Says "VERY clean, powers up but cannot test further". Matters not, as long as it's complete I can deal with it. This will replicate the system as my brother had it and I'll get my feet wet with refurbishing my first Dynaco system. Fun! Stay tuned! (Still checking shopgoodwill.com though, and will check the store occasionally to try and get THE real one! The hunt is more fun than the catch often times!)

-Kevin
 
I think all the options discussed here are good. I have three 120's that work well. One is the fully updated version from Dan Joffe's updatemydynaco.com, one I built from an unopened kit I found a few years ago (box still stapled shut) and one is s stock workhorse that's been around forever.

The original design is sometimes criticized for "crossover distortion" found in many early solid state designs, but I can't hear the "problem".

The update with LM3886 chips is not really a ST120 anymore, but it respects the heritage by using chassis and transformer, and being cap coupled. Even Stereophile likes it.

I vote PAT-5 for the preamp. Consider the FM-5 or AF-6 tuner as well if you have any good local stations.

I could go on about all my Dynaco pieces, but enough.
 
Hi JRhoBurton ... well, circumstances led me to a local, clean PAT-4, but that makes it faithful to my brothers setup, so that's cool... I don't have a phono player any longer so I will rebuild the PAT-4 line boards and P/S, it will serve my needs.

NOW, I am looking for the AF-6 tuner. I do listen to AM a lot while working in the shop, so the FM-5 would not suit my needs. Seems they are pretty available, so I'll put the radar net up to find a nice example

I love getting a piece of gear that leads to discovering a brand and products from an era that I understand, AND can work on!

Thanks, stay tuned!

-Kevin
 
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