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I'd like to preface by reminding you folks that I was born in the late 70's and was raised on cheap transistor equipment. Prior to this hobby, the only exposure I'd had to tube audio (except guitar amps) was a few brief yet memorable moments with my grandfather's Fisher 500C as a young kid. That said --
I've been fiddling with EL34 and EL84 circuits for well over a year now and have been pretty pleased with the results. I've tried several variations of push-pull designs with these tubes - run as triodes and pentodes, with and without feedback, different driver types, etc.
What I've achieved with these tubes so far is what I would describe in simple terms as a very good "hi-fi" sound (I assume we all know what that means 'round here) with more natural tone and timbre than that of any of the SS gear I've heard. It is also important to note that the tube circuits are quite PHYSICALLY pleasing to the ear and brain - I've experienced little to no listener fatigue with the circuits I've tried, which alone makes this hobby worth the effort in my opinion.Enter the Zenith C845 AM/FM tube radio.
I purchased this radio on eBay. I bought it for a good friend who listens to a lot of radio but had always used whatever cheap little boom box was readily and cheaply available. This was an exciting event for both of us. After a long, hasty unpacking, we both grabbed a bottle of Schneider-Weiss Eidelweiss and plugged in the radio (caps had already been reformed) and tuned in to what just happened to be one of the finest NPR jazz line ups I've ever heard - or was it the finest SOUNDING line up? What I was hearing amazed even me - this big, glorious, colorful sound came effortlessly rolling out of the single 8" speaker with a sort of rich, tonal warmth and presence that I've not heard since...well, those early memories of Grandpa's Fisher. THIS WAS SO FREAKING COOL! My friends and I were in complete awe and ecstasy over the gorgeous sound we were experiencing - and this did not fade as we continued to listen. Were we experiencing what is refered to as "euphonia?" Sure, the top was rolled off pretty low and the bass was a little loose on the ends, but the midrange tone, detail and space were nothing short of supremely musical. The detail and depth were also much better than I would have expected.
The radio's output tube is a single 35C5 pentode -- http://www.tdsl.duncanamps.com/show.php?des=35C5 -- which has some interesting characteristics and high distortion figures. It looks like the thing was made to run its filament directly from wall current in some sort of series circuit. I am aware that what I was hearing, in measurable terms, is what a ferocious gaggle of scope jockeys might deem unacceptable - but DAMN it sounded good!
I'm collecting parts to start experimenting with SET's. I hope that I can achieve some of the magic that I experienced with the Zenith.
Thanks for reading. I'm open to your thoughts.
Follow Ups:
It of course sounds better than any radio you can buy today. You have to pay a lot for a modern radio that has an air dielectric tuning capacitor (most are now varactor tuned in a big chip, the high distortion type), and they aren't tubed and they don't have as big a speaker, and the speakers aren't that nice paper cone full-ranger with a whizzer cone. Seriously, a good simple table radio today costs as much as $150 and while they pick up stations better, it doesn't sound better.My radio also uses the 35C5 pentode (same Zenith make, so it's likely). I bought it at an antique dealer for $25 and all it needed was a new 12AT7. It's been going good ever since.
So yes, I understand your excitement. I really like mine and it's playing music in the background as I type.
Hi.As a sorta kinda collector of antique radios, the one often keeps my ears occupied while I am on my workbench, is the Northern Electric
AM table radio in painted white bakelite housing, cica 1930s, which I picked up humming like hell for 10 bucks from a garage sale, so unexpectedly.This AC/DC operated radio got a 30L6GT power tube, which I triode-strapped as I dislike any non-triode sounds. It sounds pretty OK let alone its antique old-timer look.
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Part of the glory might have been the single full-range driver. It probably has an alnico magnet and a very light paper cone. Of course it doesn't really cover the 'full range,' but some of those old speakers in open back cabinets present a deliciously satisfying sound that you just don't find anywhere else. They mate so well with simple little SE amps.It's tempting (and easy) to suppose that it's just a lot of 2nd order harmonic distortion giving a rich sweet flavor, but I don't buy it. 2nd HD is easy to produce. Adding it to a 'clean' system does not bring back the magic.
> Part of the glory might have been the single full-range driver.Another part might be the single full-range driver. :) Seriously, most of those old brittle paper cones couldn't reproduce 12K with a kilowatt. Removing the upper passband takes a lot of distortion products with it. I've heard many, many others through the years refer to restricted bandwidth consoles and table radios as having "sweet tube sound."
Do you suppose that if LowRedMoon rolled off a couple of octaves on each end of his EL84 or EL34 systems that he would be rewarded with the captivating midrange beauty that took him by surprise in the table radio?
...
that if you don't have any bass it pays to balance the sound out by not having any treble.Still, those old tube radios sound better on AM too, where max frequency is 5 KHz. At least I think so.
...
I'd like to hear some of the newer Alnio drivers (older ones are hard to come by in my experience). They're pricey, but if what you're saying is valid (and I don't doubt that it is), then I think it would be worth looking into. The Fostex F200 looks affordable.
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Your wife or significant other will love you more for it. Your children will have shoes! You've discovered a TRUTH in the world. There is only one infirmity that can inflict one worse than going to the TUBES; clock making! Ray Hughes
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
I was once captivated by clocks and only started reading about them when I realized that, although the concept of time is an interesting one, it is an idea that I don't think is compatible with my personality. Sure, it'd be fun at first, but I don't think I could handle the growing obsession of objectively measuring something so infinitely measurable. Maybe I'm missing the point. Maybe that's a good thing.Ha det bra!
I never thought of that. Table saw... oak... tiny little precision mechanisms that move...
Here is the way to make a clock the proper way,
http://uk.gizmodo.com/2006/06/27/alltube_digital_clock.html
Wow. Wow...Wow. That is just...amazing.Looks like a sure-fire way to prove to your friends and loved ones that you have surely lost it.
> The radio's output tube is a single 35C5 pentodewhich has some interesting characteristics and high distortion figures. Just so you know, all pentodes show high distortion figures in data sheets. They're meant to be operated with negative feedback, and that cleans up the numbers. If you don't like NFB, triodes are the ticket.
Good point. Thanks for reminding me. I've been using pentodes as triodes for so long, I've forgotten about their native numbers. I've not yet even heard REAL power triodes in action. I look forward to that.I'm trying to find the schematic for this radio. I want to know more about what's going on in the circuit - specifically what is responsible for the warm, rich, inviting sound.
Given that the tube is the only one of its kind in the output section, I assume that it's a single-ended pentode output. I have no idea what type of feedback is applied, if any. I haven't opened it up yet. I'm sure I'll choose to replace the selenium rectifier and electrolytics once I'm in there.
Peas,
There's two minor reasons I started DIY tube gear.One, it looks cool in the dark, and most people are really not very familiar with the equipment, so they are captivated by the sight.
Two, I can sit back and say, "I built that!" Sure, it's easy to go out and buy this or that audio equipment, tube or SS. But so much pleasure comes from the fact that my blood sweat and tears went into the amp (and speakers).
But, of course, if it were only these two motivators, I would have stuck with off the shelf SS. My experience was similar to yours, in that I got my P-P EL34 completed, and it was full of problems (RF, 60Hz pickup, imbalance, poor room size, crappy speakers). Regardless of all these fighting against me, I was hearing things I never heard before.
I'm not talking about the times you install a new $2000 car stereo system, and you hear some bells in the background you never knew were there. NO, NO.
I'm talking about hearing the pick snap off the guitar string. Hearing the transient and follow up decay of a cymbal strike. Hearing the texture of the Jew's Harp in the Who's "Join Together". Hearing the bass harmonica in Simon & Garfunkel's "The Boxer"- it actually forces a smile on your face.
From there, the fixes and tweaks were completed, and things just got better. All this with poor speakers, single electrolytic in the tweeter path.
I can fully relate to what you're saying, Kurt. Hearing more of the music surely paints a better picture so to speak.What I heard in the Zenith though, was a certain bloom, color, presence and lushness that I'd not yet totally heard in any of my tube amps. It is now a goal to gain some of that warmth and presence in one of my home made amps. My EL34's and EL84's hint at it, and do certainly sound good, but this was a new experience all in its own.
Peas,
"Bottlehead!"
Their SET kit amps would be a great next step, though their sound will differ in some ways from your radio (much greater clarity, though of course this also depends on the speaker.)
I've looked at the Bottlehead kits repeatedly and they sure do look tempting. It kind of makes sense to go that route - the circuits are proven good and are well distributed, the parts are sourced for you and you become a part of lovely little cult at the same time. It all sounds very inviting.I can't bring myself to buy a kit, though. I prefer to learn by deeper involvement - to make mistakes, which is really the best way to learn something, as droll as it seems.
I have received several boxes of old tubes, transformers, caps, etc. - all of which come from an audio builder's stock. There are couple of 2A3 in there and several others that look promising. I plan to scrap together some SET circuits over the next month and during stormy summer nights. My goal is to have a good 2A3 circuit built this summer - possibly an all-DHT circuit if I'm able. I like what I hear about them. I think they might be what I'm looking for.
Thanks for the suggestion. It's a sane one. I'll probably one day realize that I should have taken the suggestion, but you know how we kids are - can't tell us anything.
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