New Sunn Owner (240-C-60) shares pics, open to advice..

[maxbus]

Greetings,
I just picked up an old sunn amp with cab, and I posted pics and such on a different sunn forum, but LOUDTHUD recomended that this site has many sunn owners with lots of knowlege. Any insight you may have as to the orignality of the amp is welcome. I have posted nearly ten pics on the other site. You can see them here.
http://music-electronics-forum.com/t15260-post121719/
Thanks.

[maxbus]

Yup, I can hardly find any info at all on this amp head. Not the exact model number, watts, year, or anything really. I need some advice about the speakers too. They are ribbed. No markings, I'm am starting to think they are original. I will be fixing the head, and possibly reconing the speakers, but after I educate myself more about the history, and how it came stock. I play bass, but would like to possibly have the option to play guitar through it as well.

[rmr84]

If you do some searching on here, you will find a thread with the same head in question. I believe Conrad said it was one of the earlier Sunn head, with the old "smiley" logo and that crazy printed vinyl.

[mckinnon audio]

  Hi there,that's the real McCoy,just about everyone on this forum would die to get a Sunn from that era !! I think they're the coolest looking amps,love the large toggle sw.'s for the Hi and Lo boost.Good luck getting it up and running,you won't be sorry,Mel.

[loudthud]

Your amp is a 40W model. Two EL34 output tubes, GZ34 rectifier, 7199 phase inverter and two 12AX7s (7025) in the preamp. The speaker cabinet appears to be a Spectrum II or Sentura II from 67 or 68. The speakers aren't original and the ports appear to have been modified. Sunn made several models where the amp was the same but it was sold with a different speaker configuration. In the year your amp was made, there was no model name or number on the amp itself. All the 40 watt models were sold with single 15 speaker cabinets in 66.

On the back of your amp there are 4 phone jacks. The two near the center are speaker connections, the two to one side are the inputs. The internal connections to the preamp and power amp are made with phono jacks/plugs. On the control panel there is a switch marked "Standby". It should be in the "On" position for the amp to play. If the amp does not produce sound, take it to a tech for repair.

Your amp, if not modified, does not have a ground switch or a three wire power cord. You may get a mild shock if you touch your guitar strings and a microphone or another guitar player. A tech can modify your amp to fix this.

[EdBass]

Hi there,that's the real McCoy,just about everyone on this forum would die to get a Sunn from that era !! I think they're the coolest looking amps,love the large toggle sw.'s for the Hi and Lo boost.Good luck getting it up and running,you won't be sorry,Mel.

Absolutely! I've got the same amp. I believe the split chassis EL34 amps are more rare than the split chassis KT88 amps are, I suspect they made less of them, Conrad would be the one to ask about that. I'm pretty sure those drivers are 60's-70's vintage CTS, they were very common in all kinds of applications (bass, guitar, PA, organ, etc.), and are a pretty good driver IMO.
I bought my amp a few years back from a guy who bought it used in 1968, and he called it a "Sonic". Internally everything appeared original, a few of the caps in the preamp were bad, as well as the filter caps, but suprisingly the power amp was in excellent shape and very robust; the amp put out north of 50 watts on the bench. The outputs were wired to the 8 ohm tap. I cleaned the pots and switches, put in a 3 prong AC cord and that was that.
The only flaws are that the handle was replaced and... the biggie; it has an early non trademarked Sunn O))) logo plate instead of the smiley face logo, the seller said that was how he bought it in '68.  If anybody has one let me know, for a couple of reasons; First, I'd really like to buy one for my split chassis amp, and secondly if I can get a logo plate or a good clean scan of a smiley logo I'd like to maybe get some T-shirts printed with the old logo on the chest.

[loudthud]

Closer examination of the speaker cabinet reveals that the baffle board, the piece that the speakers mount to has been replaced. All the Sunn cabinets from that time used plywood, probably Douglas Fir, with 1/4-20 T nuts to hold the speakers. Your baffle board appears to be some type of composition board.

[maxbus]

In the last 48 hours I've learned a lot about Sunn, its history, and legacy. Even more than that, it all was conceived a mere 2 or 3 miles from my house here in Portland. I know my amp was built in 1966, and is generally knicknamed a "Smiley" because of the Early Badge/Nameplate. The facts I'm still mildly fuzzy about is the specific model number, being told its a 40watt amp, and not the 60watt, I'm not sure how to properly designate my amp. But the main question I have now, and finally, is about the issue with which tubes it had, or is to have in it. It came to me with a 12au7, and two Peavey "super 6's", and a hmmm, well the tube only says "rca FY".
The difference between the 12ax7 and the 12au7 I'm not too sure of, but I had assumed the "super 6's" were 6L6's, and now I continue to read that (possibly) they should be EL34's? This is where my amp/tube knowlege ends. What about the KT88's? Does changing this tube increase or decrease the watt output of the amp? I doubt it, but wanted to be sure. I want to assume that the exact chassis that I have requires a certain tube only. But I have no clue, and I want to be very sure about what tubes a tech wants to put in it. I know different tubes give it a different sound, but I want to keep it mostly stock, and on the smoother side, soundwise.
So, which is the more desirable, and proper tubes I should use? 12ax7 or 12au7? 6L6 or EL34 or KT88 or even 6550.
I think this is a great amp, and I only want to make the right choices about tube replacement. I have seven other tube amp heads from the fifties and such, and I know nothing about them, other than which ones work and which ones I need to have looked at.

[EdBass]

The facts I'm still mildly fuzzy about is the specific model number, being told its a 40watt amp, and not the 60watt, I'm not sure how to properly designate my amp.

Can’t help with the actual model designation, I have no literature from the spit chassis days and the people I know who were using them in those days simply referred to them as “Sunn Amps”. I think I can shed some light on the 40 vs. 60 watt issue.
In the early days, the Sunn amps were essentially Dynaco (or rather “Dynakit”) amplifiers bolted into a box. They came with either the Dynaco Mk lV (40 watt) or Mk lll (60 watt) amplifier, and the same modified Dynaco pre-amp.

But the main question I have now, and finally, is about the issue with which tubes it had, or is to have in it. It came to me with a 12au7, and two Peavey "super 6's", and a hmmm, well the tube only says "rca FY".

Here’s schematics showing the tube the amps were designed around;





As far as output tubes go, IMO you should stick with the “family” that the amp was designed for (in your case EL34, KT77, 6CA7) if your goal is maximum clean output. You can’t just plug in KT88’s and make it a 60 watt amp; in fact you may well defeat your purpose.
As far as tonally, do whatever you want.  I spend a lot of time with guitarists who change tube type like underwear in search of the “holy grail” of tone, including mismatched output types. You should probably do some research on the web to find out more about the out of spec output tube thing, it’s kind of a black magic zone; many conflicting opinions and no “right” answer. Tone is a subjective thing. It’s like arguing that your favorite color is the “best” color.

The difference between the 12ax7 and the 12au7 I'm not too sure of

The difference (besides the “tone” thing I touched on above) is gain factor. Again, I’m not about to open up that can of “tone” worms, but here’s a gain chart for you to reference;

http://thetubestore.com/gainfactor.html

Have fun, and Good Luck!

[Soundmasterg]

I'm in the Portland area and can help you with that amp. In addition, Conrad Sundholm, the co-founder of Sunn lives in the area still and could possibly help you, though I don't want to speak for him. If you're interested, then send me a PM and we can go from there.

Greg

[biltmore]

Wow maxbus, that is one amazing amp you have there. Enjoy!!!!

[maxbus]

Thank you all that have replied, and for your advice. I plan to meet with Greg, and have my amp looked at very soon, and I'll try to add an update in the near future. Thanks. max.

[maxbus]

Well, its been some time, but things are up and running. I can't speak much for describing the sound just yet, as the baffle is hurting, and needing to be recut, and the speakers that are in it are of a low quality, but... I patched the ports for now to achieve a deep tone, and took it to a gig. It did well, for 50 watts or so, I wasn't expecting much, but it sounded decent, and everything on stage was mic'ed, so the stage volume was on the low side, and it did good. I had to keep it under 4, so I wouldn't get break up.
I have SoundMasterG to thank for all his time, work, and recomendations on just what needed to be replced, and what may need attention in the future,
but it definatly plays good. It had a good tone through one of his hand built cabs, so at this point, my attention needs to be turned to my cab to get that up to "snuff". But my cash flow is getting low, so I may just have to enjoy it as is for now. But I'm happy as a clam to be able to play through this. As it stands, its too loud for the house, so I think thats a good thing.
Time for pictures. Thank you all again for your advice, and general interest.
Max.

[sundhy]

You know, I look at the construction of the very first Sunn amps and I shudder to think how crude it was.  Don't get me wrong, they were great sounding amps, but yikes!

See the brown perforated heat vent inside the amp box.  That is also Dyna.  Each amp we order from Dynaco came with a perforated cover to protect the tubes and provide ventilation.  I would cut a section out of that cover with a saber saw and screw to the inside top of the amp head cabinet.

See those round chrome thingy's.  Those are sliding door finger pulls purchased from Crown Hardware in Portland, OR.  I drilled them out and used them to mount the Switchcraft jacks.

Oh yes, the paisley vinyl.  That is seat cover material used on the Pullman passenger railroad cars.

Hey, whatever it takes.

Conrad