OT: Dynaco SCA35 stereo amplifier

[Gil]

I finally came across one in a mint condition (first hand user !). The amp is from about 1964 and looks just like new. The guy asks about 300$ for it. It is an integrated 17W per channel amp (class A), which uses EL84's if I'm not wrong. Any input on this amp will be appreciated.

[R.G.]

Beautiful amp. That's a little stiff on the price, but if it's worth it for the beauty factor, get it. I have two of them, although not in such mint condition. They make an absolutely beautiful tweeter amp in a bi- or triamp setup.

A personal request - please don't carve up one of these amps for guitar use. There are lots of other places to get the transformer iron from.

[Andy]

whats a transformer iron rg?

[petemoore59]

I it's anything like my Dynaco Stereo 70, [I believe it is] it's one killer clean amp.
 These reproductions of Dynaco experiments proved very successful, have won fans worldwide of the amp listening 'Elite'. I too have seen many fine amps like McCintosh in use, Dynaco tube amps are the Bees Knees in butter.
 I've been using the 70 since the 70's. Had many amps come and go. My buddies had great reverence for the amp. I was getting this great sound on the guitar with 12'' speakers, the organ sounded fantastic through the 12's, Vocals through the Dyna...and 12's...oh rich complex mids, bass definition we tested amps...talkin bout a super sparker. Like beyond...I know this band I used to love to listen through that used McCintosh for PA power [stage amps for stringed instruments] ...here I am talkin tube trash again!
 As long as you're not expecting a gainy class A/B type sound, and love warm, rich sounds, expanded dynamic range etc etc etc [makes the boxes all sound way different than my MkII for instance] I would say you'ld be loving to having a Dynaco amp product around. 35w is a big round sound!
 I went through something to rebias it for 120v. Some of the older amps like this were designed for the lower voltage available at the time from any wall outlet 110v.
 Running it at the higher voltage [after reads on the subject] caused the 7199 tubes [in the pcb] to fry the pcb. I rewired the entire front end, then had extensive re-bias work done to it, and added a cooling fan [plent o room]......However I understand all this [except maybe the fan] was completely unecessary, the way to do it is reduce the voltaqe coming in at the ac line that goes to the wall outlet...I understand resistors will do this but [AFAIK] using more than one somehow to increase heat dissipation...
 Could be 64's were running cool enough...I saw a place where you can get aftermarket PCB's. Upon glance inspection my PCB was buckled, discolored, etc.
 They are not hard to work on, especially if the manual w/schem is there. Actually the amp, and amp literature helped me with early electronics diagnosis learning.
  I don't want to scare you off...these things need work FTTT. I've changed tubes once since the late 70's, and I don't think it was even necessary at that time..80's

[petemoore59]

The transfermer in these Dyna's are sought after...I guess some ppl retro-engineer the amp with mods, or use the transformers to build something else...they're doing just fine right where they are, I too would recommend not messing about with trying to turn it something else...it's like a work of art, and you're probably best off not doing anything radical as far as changing the ckt...sticking to the guidlines of the manual.

[petemoore59]

These transformers 440A's [Stereo 70] and other Dyna's are known for being overrated and 'indestructible'.
 I would put a beat output tube in one side, turn the bias up on it to 'medium fry' cause it to glow orange, and get melting tube tones..harmonic feedback pitch shifts, octave's?' down etc...ultra cream...'till the tube innards became so malleable that they warped and melted to death...awesome!!! Once the tube got to Med fry temp.,  it would last only about 20 min max though.
  Neat way to get the last big kick out of an otherwise diminished output tube. I had the cooling fan in there...the output tubes sockets are  in  frame holes...proceed at your own risk...probably not recommended for maximim amp life...lol

[Gil]

Thanks !

I wonder how it is gonna sound with my Mission 702... The reviews says it's bass is not very strong, how will it sound with these 25W-to-125W speakers ? It also needs a new set of EL84 anyway as the ones it uses currently are of different manufacturers causing the left channel to sound VERY weak but the right channel like cream !

[Gil]

There's also that one at a much cheaper price.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=39783&item=3042713644

[Regan]

Those are a pretty cool amp, they do have a flabby bass though. Depending on how efficient your speakers are makes a big difference with these, I doubt if you get 10W per side. The price is a little high though, you may be able to find a stereo 70 for that.
Regan

[Gil]

Thanks,

but than I'll have to get a preamp as well won't I ?

[petemoore59]

Actually the 70 has those 7199's in pentode config [like AC 30 I read], this boosts the preamp input even more than 'normal' and lets the amp work at about 30% vol with the guitar plugged straight in.
 I wasn't going to mention this [it's in contradiction to an earlier post about not amp hacking on Dyna's]...the bottom end [I read] is easy to tighten up...I would be guessing [try ampage 'they rock amps' there..] and is a fairly common mod for using these as musical instrument amps.
 Getting one of these going is not always plug 'N play...however a 'right' working one is well worth the trouble...IMO. Finding a tube amp that is exactly what you want it oto be can be this way or pricey...I had to fit a side ways cap 'in the basement [over the bottom under the pcb]...I couldnn't find the original' replacement for the big double cap. When ' I had dude' work on it he found the part to mount in the original way though.
  One of the big differences between Dyna's/Mac's and other amps is the transformers. being highest quality hand wound...they have very even response to a wide band of freq's and don't tend to cancel any of them like an Iron with overlaps or gaps in the windings. That and the fact that these Dyna experiments [ckt] turned out to be very well liked.
  Can be 'some messing' to get one working properly and the way you want...but once you do you'll be going uuoohhh Yeahhh...that or...Find a Matchless for cheap [lol].
 I read a review in guitar player "Big amp shootout" and they did a part on the new Vox amps [nothing Vox was available for the fifteen year period of contracted Thomas distribution][yerx] anyway the old ones had better Iron according to the review...louder and more responsive.