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Old 30th Aug 2011, 5:11 pm   #81
tri-comp
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Default Re: 2C34 Project taking off...

Last ones for now.

rgds,

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Old 30th Aug 2011, 5:42 pm   #82
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Default Re: 2C34 Project taking off...

Your construction looks very professional.

Good luck with your project.

Lawrence.
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Old 2nd Sep 2011, 8:39 pm   #83
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Default Re: 2C34 Project taking off...

Quote:
Originally Posted by val33vo View Post
I am curious re 2c34, just had a look on the valve museum and its a transmitting VHF double triode
why use this for an audio amp ? ( but I have no doubt it will work )
val33vo, it seems I'm not the first to imagine this valve running audio.
Have a look at this datasheet for the 4074-A which is just another name for the 2C34 / RK34.
No wonder I succeded in pulling 12Watts from the PP-setup

Today I replaced the Sylvania 5687WA with NOS RCA 5687. Bias had to be re-adjusted of course and the general impression is that heights are cleaner. Bass strong and firm as usual but there's a small but definite improvement in treble. Best I can say without an audio-analyzer to back it up.

rgds,

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Old 25th Oct 2011, 9:21 pm   #84
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Default Re: 2C34 Project taking off...

Update:

New NOS Sylvania JAN 6AN8A's (1977 issue) developed the same 'singing' mechanical microphony-problems as the first ones used (Also Sylvania's). After a while it appears; first barely and later on really annoying. Tomorrow NOS Toshiba 6AN8's will arrive and I shall report. If that doesn't solve the problem I have plans to replace them with NOS Telefunken ECF802 which will also be here tomorrow. That, however will require a little experimenting with operating-points besides rewiring as the pin-out is different.

rgds,

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Last edited by tri-comp; 25th Oct 2011 at 9:26 pm.
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Old 26th Oct 2011, 12:06 am   #85
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Default Re: 2C34 Project taking off...

hi,you could also try a 6u8-plenty to be found in old tek scops.
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Old 26th Oct 2011, 6:58 am   #86
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Default Re: 2C34 Project taking off...

Quote:
Originally Posted by love kt3 View Post
hi,you could also try a 6u8-plenty to be found in old tek scops.
Yes, that's also an option.
I just went for the ECF802 (=6JW8) as I found a few NOS TFK's at a reasonable price.
Did anyone here do audio pre-amp/phase-splitter with these in the past?

rgds,

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Old 26th Oct 2011, 9:32 am   #87
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Default Re: 2C34 Project taking off...

NOS Toshiba 6AN8 mounted and oscillation is gone.
For the moment, at least. The Sylvie's behaved the same but after a month or so they all developed the 'singing' problem.
Let's see how it goes with the Toshiba-brand. They're not the 6AN8A-variant but I really don't know the difference.
The box and the tube itself is labelled 'Hi-Fi' so that would indicate minimal microphonics. Time will tell.
The box is also marked ¥1100 which appears to be the price.
Today that would be around €10; pretty expensive for the time.

rgds,

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Old 19th Nov 2011, 4:27 pm   #88
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Default Re: 2C34 Project taking off...

Update on 6AN8A problem.

Using the Toshiba's totally cured the problem.
When you gently tap the tubes the Toshibas also shows microphonics as do all tubes.
However, the microphonics are way lower than with the Sylvania's.
I believe they are made with a very different internal structure.
The filament is clearly also different.
Take a look at this rather low quality proto showing the bright glowing Sylvie front right and the dimmer Toshiba left front.
Sorry about the quality of the photo. This forum dictates a max resolution of 800x600 and my picture lost definition rescaling it. Besides, the light and flash have to be off to actually see the filaments glowing.

rgds,

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Last edited by tri-comp; 19th Nov 2011 at 4:30 pm. Reason: I attached a scan of the original Toshiba valve-data from the box.
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Old 21st Aug 2012, 9:18 am   #89
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Default Re: 2C34 Project taking off...

Hello to everyone, I just came across this site... fascinating. My admiration for this project knows no bounds Tricomp, it is truly a thing of beauty! My jealousy also knows no bounds, having spent many years hammering, filing, cursing, drilling and injuring myself during the construction of many questionable projects (both mechanical and electronic).

I was 'brought here' by Google (looking up 2C34), and have to say I was initially surprised at your choice of this valve for an audio project. I have one which is a treasured posession, still in its 1944 US Army box, though this one has a white ceramic base. I have fired up the heaters (to see what it looked like!), but never found any equipment that used this device, or considered it for any project. I hate to use the word 'obselete', but similar sized octal valves (and even a few B9A's) deliver far more power at low frequencies, and being a radio man I went the QQV07/50 route when it came to low VHF power mischief....

I think the 2C34 (DET19) was used in the (somewhat primitive) VHF RT sets used in battle of Britain Spitfires and Hurricanes, but details of these seem rather scarce? The old 'Dalek bottle' was clearly designed for low VHF, hard driven class C operation (15mA grid current...phew!), probably crystal controlled AM, running at relatively low voltages (300 was low, the T1154 used well over 1kV to get a measly 50 -60W on SW).

That aside, a triode is a triode, and the 2C34 does look fantastic (physically), as does your magnificent amplifier. The very best of luck with it!

Martin
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Old 21st Aug 2012, 3:23 pm   #90
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Default Re: 2C34 Project taking off...

Martin,

Thank you for all the Roses
Having ironed-out all wrinkles I can say that I'm extremely happy with this amp.
I use it daily; it's even connected with my TV and I wouldn't want to watch anything from there on original speakers anymore.
After having built the 2C34-amp I've done more valve/tube-work but NOTHING has sounded as good as the 2C34-PP.
This valve is still available in the US as NOS. Just to stock-up I ordered 10 @ $5/ea. Probably my amp. has upped the price by now, sorry
If you read through my thread you'll see that there ARE problems with valves, even NOS ones. Time takes it's toll and I believe they eventually go gaseous. The pair of 2C34 I've got in now has been there for all 2012 but in the late of 2011 the amp started clipping on strong bass. Something that it NEVER did before; it's extremely dynamic. It turned-out that one 2C34 was gone, more or less. Replacing both restored high-fidelity and I must say it was the valve and not the construction that was the culprit. It must be as the amp has now been running with new valves for 8 months+ and still sounds like with new NOS inserted.

By all means put that 2C34 to LF-work, you'll not regret it

rgds,

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Old 22nd Aug 2012, 5:21 am   #91
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Default Re: 2C34 Project taking off...

Thanks for that tri - you are a true enthusiast, and I have to say, inspirational too. I say that as an aside from technical elctronic details, as you clearly have an 'artistic' flair, and attention to detail, which sadly seems to be going out of fashion when it comes to building anything electronic.

As a 'radio man', I have (as you seem to) a love of structures that not only perform well, but look good. I am all too familiar with the rats nest innards of WWII radio sets, built only to function, and no more. All well and good in wartime I suppose, but anything I have built myself (valved equipment that is) has involved a (some have said) obsessive attention to detail, involving everything from tateseful -ahem - colour matching of wires and components, to polishing the valve screens of my old R1155A and aligning all the nuts and bolts. Irrelevant perhaps, but satisfying... I am glad I'm not alone!

I have to say, nothing I have ever done comes close to the beauty of your construction, I don't think I have ever seen such excellence - congratulations. To me, electronics is truly an art in many ways, and it is heartening to see that there are others who appreciate that the is more to electronics than mere performance!

Cheers
Martin.

PS Where did you get those lovely valve sockets? I am stuck with a few crumbling paxolin ones from 1938....
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Old 22nd Aug 2012, 7:09 pm   #92
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Default Re: 2C34 Project taking off...

It's a nice thing to be able to have your design made-out in 3D before actually cutting any metal.
Just moving valves, transformers actually anything visible from the outside, including the back-side and rotating the construction, watching it from any angle you like is a huge advantage. It's unbelievable how easily you detect flaws in design when you're able to look at it from different angles.
Would you believe all four 9-pin valves are positioned in an arc?
Well, they are because it looks better from a distance, not looking from a straight frontal view.
How the output valves and transformers are positioned had to relate well with the 9-pins AND the terminals at the back-side.
VERY easy to see results of different positioning when rotating a 3D.
Of course this amp isn't perfect; I'm no pro designer!
For example I didn't take into account that the 2C34 anodes are not angled equally in production (...and in specification) because i didn't think it mattered. Well, it matters because the anode-cap's position themselves according to the angled tops thereby NOT requiring the anode-cable holes in the chassis to be centered around the 2C34 axis. They should be skewed, but they aren't in my amp. Details, details and not important details, BUT next time I'll pay attention!
Under the hood I just did what I could to address hum-problems. Tightly wound filament cables dressed as far as possible from signals. Same with mains-cables. Shortest possible signal-routing, star-ground INCLUDING the power-supply section.
PSU & OP-Transformers angled to reduce coupling; PSU far away from input-circuits and signal-routing. Nothing spectacular, just details!
It paid-off; there's NO hum worth mentioning even with open inputs and with the volume-control at max!
Also I didn't want wobbling of parts and made a sturdy design accordingly.
It didn't cost anything much, just needed to pay attention to details

The 7-Pin Medium Ceramic sockets were bought here:
http://www.vacuumtubesinc.com/Produc...beSockets.aspx
I bought several items from this company including the 10 x 2C34 I mentioned before and I was always treated the best. I can only recommend this company!

rgds,

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