[TheChairGuy]

I've found preference more often than not to tube preamps in front of my SS amps.  Perhaps it's a change of lsitening habits and musical taste, or I'm listening for different cues in my music now...but tube pre's sound better most often.  I haven't played heavy metal in a couple years - maybe I'm mellowing a bit at 43.

Vintage for me is anything born before me  

I've wanted to just try tube amps.....I have never been impressed with them at shows, dealers, etc, but I figured if tube pre's now work for me, maybe a tube amp will.  Or, at least I can understand it's allure to many better now.

I went thru the gamut of possibilities and settled on monoblocks as my choice.  One talk with Klaus Bunge/Odyssey throughly convinces you of ultimate merit onf monoblocking, so I won't buy anything but now.

But, buying newly manufactured tube mono's were out of my budget...I didn't want to plunk down big money to listen to tube amps as a tube newb.

I did a little research and figured I could get by for under $500 for vintage tube amps and set my sights on attaining a set.  

The vintage Dukane's (made in 1960) I bought on ebay met that price requirement (with room to spare), were guaranteed to work by a guy in WI with great feedback (selling tubes).

My god, they are hideously ugly, required  wiring of the AC, IC and speaker wire to screw posts (no rca, or IECs for these industrial babies), and didn't come with front covers.  But, crap-damn- no foolin', they sound great after re-tubing the output tubes.

Each mono side is a weird compliment of two 6CD6 tubes (cheap at $5.00 a pop!), a couple 12au7's and an OD3 voltage regulator and 5U4 rectifier.  Talk about weird, but absolutely preemo sound quality. I'm just stunned how decent they sound for 45 years old.

Here's one of the world's ugliest tube mono's - that just happen to be excellent performers.  When price is factored in - it's brings a HUGE smile to me pursed lips. Now I just need to learn how to bias and retube these guys (maybe another $90 to do that - all but the 12au7's are dirt cheap) to get the most from them.

Enjoy all - I am....did I just cross over from the dark side, Tube-oholics?  

[chadh]

I'm glad you're enjoying the sound.  But there's even more good news.  Housing these things for just a short while will suddenly raise the WAF of ANY other piece of equipment that could possibly pass through the door.  In fact, I could imagine a wife begging for greater sums of money to be spent on equipment simply to get those suckers out of the house.  They practically raise ugly to an artform!

Chad

[TheChairGuy]

Hey Chad, you've never seen her husband, tho  

He may have already raised ugly to new status  

[lonewolfny42]

As the saying goes...."she's ugly, but she sure can cook !!!"......

Good luck with those John ! They look like a nice challenge....experiment with the tubes.[/list:u]
Any truth to the rumour that your moving to St. Louis ?   [/list:u]
Chris[/list:u]

[Dmason]

"Aren't they lovely? Aren't they GLORIOUS!!"  -- John Hammond, owner, Jurassic Park, in reference to the "monoblock" Toyotas, just before the tour...

John -- but seriously dude, those quite possibly are sacred relics from the Golden Age of Cinema. Dukane made alot of cinematic equipment. You should see some of their GIGANTIC sectoral horns, I mean 60 inches wide and 30 high. ...The output tube complement is beyond anything I have seen in years of playing around with tubes, overall, a tube-rectified push pul tetrode using typical 12UA7 miniature triodes as input/driver, is fairly typical, but generally any of the old tetrodes with top caps are forgotten heroes in the audio end. They are very likely built to withstand the business of showing films all day. Its brother, the 1625, is one of the very sweetest tubes I personally have ever heard, and so I would imagine your amp may well have in it the potential to be A Monster Amplifier set.... What I see is a barge-load of good, vintage iron; no mistaking the fact that bigger is better, and in those days they made damn serious transformers, not like the garbage that is out there nowadays, forcing people to pay top dollar for Magnequest and ElectraPrint. Often the old laminations are sought after to cannibalize into other transformers, at any rate I would say this is a very good reason for the great sound: a tube amp is only as good as its output iron.

 They seem to be almost hermetically well preserved, and that is a great sign. Like a used car, if the interior sucks, forget about bothering to open the hood. If you poke around on the web long enough, I would bet five bucks you will find at least a feeder page or two that will get you somewhere with respect to schematics a/o biasing issues. I would post a message on Tube DIY over on Audio Salem. This is a witch-hunt free forum. Good luck with those marvellous treasures. Find a local tube-wrangler to take them to for an opinion. With alittle TLC they just might become the best amps you have ever heard.

[TheChairGuy]

Yeo Good Doctor,

The fella' on ebay got them from a local school - 12 of 'em.  He's owned lots of tube amps in his life and said (I don't think he's pumping me either) that he's heard most of the 'name' vintage stuff out there and these compare.  I found an old thread from AudioAsylum where a very experienced tuber said the Dukane's are 'really something'.

So, I bought 'em  

I changed out the 6CD6's..man, the old RCA's it came with were tired.  It snapped everything to attention - bass, treble, imaging and more definition...pretty much textbook old tube ailments, I think. I'll swap out the 12au7, OD3 and 5U4's soon, too.  It's not even $100 to do all this...good for another few years.

The 6CD6 is truly weird, my limited reading on the subject indicate that it was a TV tube.

These amps are NOT at all tubey soft...right now you'd think they were a good, clean sounding $1000 SS amp (as I own the Odyssey Khartago now, I think that's accurate).  I'm hoping some new tubes, a little biasing and removing oxidation from the pins (via DeOxit) might kick it up a notch or two more. Might swap out the 18ga computer cord for...Volex or some decent 14ga just to carry the 15a current from the wall more effectively.  Nuthin' fancy, just a little fatter.  

These are 50 watters...and I bought the service manual on ebay too, from another seller.

[Dmason]

I would change the rectifier first to see things tighten up and this tube usually adds something to the overall sonic. Then the input/drivers. Those might be the best tubes to keep, because they last forever, run fairly conservative, well below their rating, and the NOS 12AU7 are quite pricey. Do those only when you have replaced the voltage tube, and rectifier.

[TheChairGuy]

I would change the rectifier first to see things tighten up and this tube usually adds something to the overall sonic. Then the input/drivers. Those might be the best tubes to keep, because they last forever, run fairly conservative, well below their rating, and the NOS 12AU7 are quite pricey. Do those only when you have replaced the voltage tube, and rectifier.

Dan,

I found Sylvania 4 x 12au7's for $12.50 ea from the same lady on ebay about 20 miles north of me I bought the fine 6GB6's from...so I bought 'em.

I also bought 2 x 5U4 (new E-H's, reported to be very good at $10.50 ea. - as good as NOS) and 2 x OD3 ($4.95 NOS) from Triode Electronics just now - I've been very, very happy with their guidance and pricing in the past.  

$120 later and the monoblocks are retubed.  Total cost into it is still under $500   (I dig this new emoticon)

[Scott F.]

....did I just cross over from the dark side, Tube-oholics?...

ummmm ....yep  



Repeat after me .......   Oh Lord of Thermonics I worship thee Oh Lord of Thermonics I worship thee Oh Lord of Thermonics I worship thee

....Any truth to the rumour that your moving to St. Louis ?...

We've got a place for all you lost souls out there.  


Hey Chairguy, listen and enjoy for a while, then just when you thought it can't get any better, swap out your coupling caps, change the B+ resistor(s) and replace and upgrade your power supply caps. If you think your in heavan now, just wait, cuz you're only in Iowa.
Send me a couple of close ups and I'll point out which ones to go after.

Oh and BTW, those aren't hideously ulgy, they're beautious

[Dmason]

I like them better and better. Interesting to see how far all this creative input, and new bottles, can make them sound.

If you wished to ditch the vintage flavour abit for a more "elegant" look, you could scrap those stout port n starboard bulwarks, now that she's in drydock for good, and go to a good lumber yard, find some nice chair rail equal to the height of the chassis, sand, finish and cut the rail up to make a nice finished hardwood band around that US Navy looking hull of a chassis. Point is they could easily be dolled up to look quite the business, if greater aesthetics were desired.

Finally: in the last while I have been seeing eBay as the new repository of old tubes, and a never ending stream of vintage tube stuff. Some of it really special.

[TheChairGuy]

Scott,

I think I'll let a local tube expert take care of those solder savvy upgrades...I just haven't invested the time to be proficient in it.  

Oh Lord of Thermionics, I see your higher power, your purpose and feel your warmth


Dr. Dan

I'm kinda' in love with their compactness - they are only 4" high and  two stacked in my rack leaves room for everything else but my balanced power unit.  I think I may just fashion fronts from fireplace mesh or window screen (painted silver or deep blue maybe) and leave it be at that.  

The backside faces nuthin' but wall and the sides 4" high / 7" deep sides ain't nuthin' worse to look at than any other component.

[TheChairGuy]

Indeed ebay is a vast repository of nice tubes...I bagged the Sylvania 12au7's last night and scoured thru ebay today.  I ended up buying 4 clear top 12au7 made by RCA matched quad.  The deal was sweet - $35.00  

I critically listened to these amps for the first time today.  I've heard my Ellis Marsalis Trio / Twelve's It a hundred times, at least, and never heard it like that today.  There was nothing I found partcularly bothersome (nitpick things only, but easy to listen to and commendably dynamic)  about it's performance; and many things to like.  I put my little Mortite/Dennis rope caulk dime sized hat on the 12au7, OD3 regulator and 5U4 rectifier - and as it has in every other instance, bass is firmed up considerably; the entire performance becomes more settled.

Once hatted, and the bass deficiency typical to tube amps relative to SS amps, become quite small...allowing tube virtues to become more fully expressed.  At least, in my small-ish room with easy-to-drive, small floorstanders(without much output below 50hz - and nearly nuthin' by 40hz)

[skrivis]

We've got a place for all you lost souls out there.  


Hey Chairguy, listen and enjoy for a while, then just when you thought it can't get any better, swap out your coupling caps, change the B+ resistor(s) and replace and upgrade your power supply caps. If you think your in heavan now, just wait, cuz you're only in Iowa.
Send me a couple of close ups and I'll point out which ones to go after.

Oh and BTW, those aren't hideously ulgy, they're beautious

Yeah, there are a lot of grotty old parts in there that could be replaced with new ones.

However, it could well be that part of the amps' "magic" for you is because of old out-of-spec parts.

[TheChairGuy]

Retubed with NOS Hewlett-packard 6CD6G's today all around (2 in each amp), cleaned those pins and Caig'ed 'em, and the sound improved a lot.  

A slight hum from one amp now...hopefully, just a tube change needed. The 12au7, 5U4 and OD3's are arriving later this week. Hope it's not a cap change needed - out it will go to repair then as I am ill-equipped to handle such a task.

One amp went dead today.  Checked the fuse first and, sure enough, it was blown.  The reason it blew was that someone along the past 45 years put a 2 amp fuse fast blo where a 3 amp fast blo is supposed to be.  A trip to the hardware store solved that.  But beware if you're buying vintage, you are buying vintage scew-ups, too  

Saxophone and piano just sound great...and stand up or electric bass does not sound too rounded or soft like many tube amps I've heard. I am clearly no engineer, but I strongly suspect that part of the admirable bass performance is due to the (tube) voltage regulation.  Again, it's small-ish 12 x 15' room, and kinda' lively with lots of windows and a large sliding glass mirror, so excessive bass can't be handled nor wanted at almost any volume in here.

But, I'm noticing any pronounced deficiency in the bass region....and the mids (vocals) and highs (hi hats, cymbols, etc) are just very pleasant to hear for hours on end.

[Dmason]

When all is said and done, a tube amp really is only as good as its power supply, and especially its output transformers. The older stuff was really taken care of in this department, and the state of the art was realized in these type of PP designs, YEARS ago, IMO.

The reason for the shi shi triode tube's popularity is market-driven forces, leave it at that. They are being produced.  Unless someone wants a minimum run made of 10000, no one will make the tube. These beam-tetrodes are available by the thousands, sweep tubes in the millions, for usually around $5-10, and properly implemented, as they are in your amp, absolutely KILL much of what is out there in modern post 1985 conspicu-fi. A big plus is the fact that they often have envelopes made of hardened glass, and fabulously rugged construction, and are biased waaay below what they could be, and still run happily. By the sounds of things, it may be that you have lucked out into some very sweet iron amps indeed. Just as you get very used to the sound, change the caps, and think of something nice like Jensen PIO, Mundorf Supreme would be extremely tasty.  

The ONE amplifier I truly regret ever getting rid of, out of so many over the years, was a Magnavox console unit pulled out of one of those big home units of ~1960 vintage, PP 6BQ5/6EU7/5U4. This was, I would say, the best tube amp I have ever heard, and I have heard plenty. Keep us informed on your Journey To Thermionia..

[TheChairGuy]

Remarkably, I got my NOS RCA Clear Top 12au7's from No. Virginia today....2 days via USPS Priority Mail!  Also remarkably, they made it quite safely - that is, they didn't look like some Italians took them out on Columbus Day, spirited on with vino rossi and sambuca, and played bocce ball with them    

Non-Italians, if much of this doesn't make sense - it'll take too long to explain. (the wife is Sicilian /Napolitano; so I speak from a little experience)

Anyhow, those are sweet tubes.  Or, the GE 12au7's that the amps came with stunk...or were a bit weary after 40 years...or they stunk and were tired, too.  Beats me, but this is a nice, subtle upgrade.  As they are the input tubes, I didn't expect much, but I'm truly happy with the upgrade.

I Have limited experience rolling tubes of the same type - only a few 12ax7's and 6922's.  Tho you'd think all should be pretty much the same as they their electrical parameters are the same - the differences are pretty large, actually.  At least to us snotty audiofools.  I can understand difference between substitutes of different types, like swapping out 6922's for 6n1p's, but I am truly surprised that swaps among the same type of tubes matter as much as they do.  Especially, when all are on an equal plane - that is, new and have been damped to reduce microphony.  

I think the general consensus among tube cognescenti is that the 12au7 ain't too pretty sounding overall, but among the better ones (sanely priced, at least), the RCA Clear Tops rank up there. NOW, I understand. It was one of those three note instances that Frank van Alstine mentioned recently, and others have echoed since here on AC.

Everything is just a bit sweeter now, with a hint of of better detail - as opposed to everything firmed up and stood straighter / tauter after changing out the 6CD6 output tubes the other day.

Andreas Vollenweider's harp sounds just a bit lusher, air-ier and lovelier than yesterday    Layered, delicious and delightful right now.

The slight hum from one amp is still there...hopefully, it will straighten out with a rectifier and regulator changes out.  They are due in on Friday from Triode Electronics.

This is really turning into a nice purchase  

[TheChairGuy]

And on with a little more to my virtual semi-blog today....

Not a full-fledge tube-aholic, my experience rolling tubes is limited.  But, having seated the NOS 12au7's for about 10 hours in total now, they have bloomed a little further. I have found that in my limited 'rolls' in the past the tubes do take some time to settle in...or my brain does to them.  And so today, they are quite nice  

Right now, in the pecking order of things, I'd have to rate these vintage Dukane's right up these with my recently sold Odyssey Khartago...perhaps a smidge higher on the pleasure scale.  I am really not sure if it is tube vs. SS that is at play, or the effect of monoblocking vs. a stereo amp. As of now, I don't think I'd ever purchase anything but monoblock amps again - the separation is astounding  

I have Khartago Extreme Monos coming in shortly from Santa Klaus, so it'll be an interestig comparo all the way around.

I am still awaiting the new tube rectifier and regulators..due in tomorrow.  Due also on Monday will be two 14ga cords I bought from:

http://www.angelfire.com/biz/bizzyb/AGONSALE0206.html

They are $23.99 per 8' cord and they are hospital grade on both ends.  Too bad I'll be snipping off the IEC end, but I still think it's worth he premium over the $5.52 Volex cords (from Carlton-Bates when you buy 5 of 'em at a time).  I've read the pro's and cons on shielding, and no shield makes better sense to me. We'll see - they should be at any rate be a step up from the 18ga computer cords I have now.

fyi - I think this Paul/BizzyBee guy has a great selling gig.  Dealer free, he let's lower cost Asian labor build his product point-to-point and then slightly alters/modifies them for his US audience.  His prices are terrific for the gear - and if you click thru the Audiogon link above, there are pretty significant savings over his listed website pricing. Ie., the cords have free shipping thru that link...saving you $6.00 over the website price.  Not shabby - a 12% savings on 2 cords.  Too bad I only found this link after I had already bought my cords from his website  

Aside from buying his two Iron Lung Jellyfish power cords, I don't know this fella' from Adam (or Eve, or Eve's hottie little sister - hehe - just seeing if anyone got down this far in my blog).  

So, enjoy - I am  

[skrivis]

When all is said and done, a tube amp really is only as good as its power supply, and especially its output transformers. The older stuff was really taken care of in this department, and the state of the art was realized in these type of PP designs, YEARS ago, IMO.

Filter caps were generally quite a bit smaller in the old days, so modern materials have probably helped with power supplies. Silicon rectifiers are superior to tube or selenium, so we're better off there too.

Transformer design depends upon people, and it may have been better in the old days in some cases. But modern materials for transformers may well be better. (And there are some modern transformer designers who equal those in the past too.)

Some of the old stuff is good and some of the new stuff is. I just don't see that the great tube masters of the past wrote the book on things and we can't even dream of equaling them.

[Dmason]

Skrivis,

I think you are electing to twist my words somewhat, so I reply. I was merely stating that tube art hasn't gone far in years and years. Much of what is stated as "new" has also been forgotten, and they don't make steel like they used to. Very generally speaking, you can EXPECT, okay, that the quality of iron from a company like DuKane, of this vintage to be very good. Let us avoid hair-splitting. Very general statements on my part.

[skrivis]

Skrivis,

I think you are electing to twist my words somewhat, so I reply. I was merely stating that tube art hasn't gone far in years and years. Much of what is stated as "new" has also been forgotten, and they don't make steel like they used to. Very generally speaking, you can EXPECT, okay, that the quality of iron from a company like DuKane, of this vintage to be very good. Let us avoid hair-splitting. Very general statements on my part.

The manufacturing of the tubes themselves probably has not progressed much. The topologies of modern tube circuits are mostly the same as those worked out 50 years ago.

I disagree on the transformers. Modern transformers are capable of being better than the old ones because we now have a much wider choice of materials. Look at VTL or Manley. They're using iron that's better than the old stuff. Bobby Carver did some excellent work with transformers. Conrad-Johnson and ARC also have a good handle on how to make transformers. Then there are the transformer manufacturers themselves.

Those Dukane amps could very well be golden oldies. It seems that TCG is very happy with them and happy with the price, so that's good.

I actually feel that modern tube amps have the potential to be better than the old classics of the past. We have better materials available in some cases. We have PCBs, modern plastics for insulators, SS diodes and transistors, ICs, etc. We can also use the computer to model and design circuits and examine a large number of different designs in a short period of time. You can see exactly what the changes you make are doing and observe trends as you do so.

I think that we are actually now in the "Golden Age of Tubes." When we use tubes now, it's because they do something better than other devices, not just because they're all we have.