Reproduction Retro 40`S Radiogram questions.

[Lignum]

Im making a retro 40`s style stereogram and want to include a valve amp mainly for the “visuals” I want the valves to be visible, so looks are more important than pure sound quality. :)


Geeze Liggie, I bet you are glad you asked. :D
I don't know how far your budget will stretch but have a look at some of this stuff.
Beware, it ain't cheap.

http://www.audiophile.com.au/product_almarro.html
http://www.audiophile.com.au/product_cad-exciter.html
http://www.audiophile.com.au/product_cary.html
http://www.audiophile.com.au/product_slp-05.html



Thanks Cliffie…. :D

Your links are great, way out of my price range but the configuration of the vales is of real interest as I will go with great advice from Zaphod of using valves in a fake way with separate power, as I already have the choice of an older NAD or Cambridge Audio amp. Also will have a Rotel tuner, and looking at an old Duel TT that plays 78`s and I want to add blue tooth and internet radio. Below is the full scale drawing of the cabinet and will be made from Walnut, Macassar Ebony and Black bean. Will be a fun project and I might do a WIP


Nice. As for valves, WES Components is a good choice, if you're in Sydney. EVATCO in Melbourne has a HUGE range. Of course, you can always scrounge second hand valves from all sorts of places. There's a guy in Melbourne who I sourced some valves from a few years back. They were very inexpensive (because no one else wanted them), but, since they were for a similar purpose to yours, they worked just fine. A couple of things to be aware of:

* Big valves look cool (if you know what I mean), but they can consume large heater currents. Some Russian valves consume several Amps. This can mean a large, dedicated heater supply. Small valves (stuff like 12AX7, 12AU7, et al) don't require much in the way of heater current.

* WES supply some very attractive ceramic valve bases for reasonable prices. Again, in Melbourne EVATCO would be the people to see. They all do mail order wherever you happen to be.

* A big valve (6550, KT88, 6CA7 et al) will dissipate around 10 Watts in heater power, so will not get excessively hot, but you will need to arrange for that heat to escape, if damage is not to be caused to surrounding (usually above) timber. Small valves (12AX7, et al) will dissipate around 2 Watts.

Should be a fun project. Ask around for valves which have poor 'emission' but a working heater. You may find that someone has saved some nice looking ones (for whatever reasons) and is willing to part with them for not too much cash.

Thanks Zaph, some great advice there. Ill do a google on EVACTO and see what they have. Im assuming someone with basic electronics expertise can hook them up?

[Zaphod]

Thanks Zaph, some great advice there. Ill do a google on EVACTO and see what they have. Im assuming someone with basic electronics expertise can hook them up?

Very simple stuff. Once you've found the valves (stick to 12.6 Volt and 6.3 Volt types only) you need only find the appropriate pins to connect to your heater supply. 12.6 Volt types can be easily configured to work on 6.3 Volts. Valve data is easy to come by. I have a shelf full of data right behind me.

You could 'phone EVATCO and explain what you want to do. They may have some valves lying around that no one wants that they'll sell you cheap(er). Tell them it's for retro-styling only. They may have some good suggestions.

[Lignum]

Zaph, how much heat will the 12.6v Valves generate? They will be inset into the red area with the amp just above (blue) then Radio (Yellow) Will the top, bottom, sides and back of the valve inset need to have some insulation and vent holes at the top? It will have Macassar ebony veneer in it (with quality heat resistant lacquer)


Also would anyone have a good suggestion for the speakers? I want that big warm old fashioned sound . My Cambridge Audio p70x gives that, so would the Jordan 4" metal cone (http://www.decibelhifi.com.au/prod145.htm) be suitable? I have heard them and love it, but is their a cheaper alternative:?

[Zaphod]

Zaph, how much heat will the 12.6v Valves generate? They will be inset into the red area with the amp just above (blue) then Radio (Yellow) Will the top, bottom, sides and back of the valve inset need to have some insulation and vent holes at the top? It will have Macassar ebony veneer in it (with quality heat resistant lacquer)


Small 12.6 Volt types (12AX7, 12AU7, et al) will disspate around 2 Watts. I realise that you probably need to know what the bulb temp is. I can't tell you with any precision, but my (VERY) wild guesstimate would be that the bulb temp would be around 60oC. I will locate a suitable valve, hook it up to 12 Volts and enclose it in about 1/2 Litre container and measure the temperature rise. I'll let you know after lunch.



Also would anyone have a good suggestion for the speakers? I want that big warm old fashioned sound . My Cambridge Audio p70x gives that, so would the Jordan 4" metal cone (http://www.decibelhifi.com.au/prod145.htm) be suitable? I have heard them and love it, but is their a cheaper alternative:?

If you thought the discussion about valves vs. transistors got weird, don't even THINK about discussing speakers. Here's my thoughts:

The Jordan drivers are very impressive units. They're also Hellishly expensive and a little inneficient. Personally, I prefer a small bass driver + tweeter, since the sound can be tailored somewhat, the efficiency higher and the cost can be considerably lower, for similar performance. I would not call the sound of Jordans "old fashioned". That's just my opinion though. Speakers are all about opinions.

I have a couple of these lying around:

http://translate.google.com.au/translate?hl=en&sl=fr&u=http://www.audax.com/&ei=5yVdStP2IJeBkQWEvOTfDA&sa=X&oi=translate&resnum=6&ct=result&prev=/search%3Fq%3Daudax%2Bloudspeakers%26hl%3Den%26sa%3DG

And:

http://translate.google.com.au/translate?hl=en&sl=fr&u=http://www.audax.com/&ei=5yVdStP2IJeBkQWEvOTfDA&sa=X&oi=translate&resnum=6&ct=result&prev=/search%3Fq%3Daudax%2Bloudspeakers%26hl%3Den%26sa%3DG

And:

http://translate.google.com.au/translate?hl=en&sl=fr&u=http://www.audax.com/&ei=5yVdStP2IJeBkQWEvOTfDA&sa=X&oi=translate&resnum=6&ct=result&prev=/search%3Fq%3Daudax%2Bloudspeakers%26hl%3Den%26sa%3DG

These products are high quality and provide excellent results. Alternatively, some of the local suppliers have kits which may suit your requirements.

[Zaphod]

Zaph, how much heat will the 12.6v Valves generate? They will be inset into the red area with the amp just above (blue) then Radio (Yellow) Will the top, bottom, sides and back of the valve inset need to have some insulation and vent holes at the top? It will have Macassar ebony veneer in it (with quality heat resistant lacquer)


I placed a 12AX7 into a small cardboard box (An Australia Post video cassette postal box) and connected a heater supply. I let it run for about an hour and measured the result.

Ambient temperature - 18.5oC
Bulb temperaure - 45oC approximately (It's tricky measuring the temperature of glass)

That should provide some ideas for what you can expect.

In my explorations, I uncovered a half dozen ECC91 valves. They look nice, since the cathode structure is exposed and it glows a nice, dull red. See if you can find some. They should be cheap, since they don't appear to have much use in audio.


[/QUOTE]

[Lignum]

Ambient temperature - 18.5oC


Thanks for doing that. 18.5oC is reasonably hot in a small area, so ventalation would be a must. Good to know now:2tsup:

So what would be some "big and wild" looking valves. I looked at This mob (http://www.lucasmilesaudio.com.au/)
because the are close to me. These seemed ok for the price.
Chinese Valve Arts KT66 @ $48
Genelex Gold Lion KT66 @ $58
Electro-Harmonix 12AX7 @ $18
JJ E88CC GOLD @ $44

And you know the "cages" you see on the valves, are they available commercially or made specific for the Amp makers.:)

[Lignum]

In case anyone’s wondering about the cabinet, it’s based around a 1945 Malvern Star, mainly known for their pushbikes. I didn’t want an exact replica so I am altering bits here and there.:)

[Zaphod]

Thanks for doing that. 18.5oC is reasonably hot in a small area, so ventalation would be a must. Good to know now:2tsup:


18.5oC was the ambient temperature of my workshop. The bulb temperature is the one you need to be concerned about. With the 12AX7, that is around 45oC.



So what would be some "big and wild" looking valves. I looked at This mob (http://www.lucasmilesaudio.com.au/)
because the are close to me. These seemed ok for the price.
Chinese Valve Arts KT66 @ $48
Genelex Gold Lion KT66 @ $58
Electro-Harmonix 12AX7 @ $18
JJ E88CC GOLD @ $44


Considering you will not be using these valves to make any sound, the prices seem too high. You could consider the KT88 on the site you mentioned. They're as low as $44.00. WES sell a cheap KT66 for 37.50. There is no point in using a premium valve for your application. In fact, you should contact Lucas Miles and ask them if they have any faulty valves (but with functioning heaters) they can let you have cheap. Valves have a pretty high DOA figure. Probably in the order of 1 in 20 for Chinese valves. Russian ones are somewhat better. When I first started using Chinese valves, the DOA figure was around 50%. And, by DOA, I mean that the heater worked, but the rest of the valve was stuffed, on arrival, brand new, from the distributor. If Lucas Miles does a fair bit of work, then they'll see plenty of dead valves which you could use.

Don't forget: The KT66/KT88 runs much warmer than the 12AX7 I cited earlier. It will dissipate around 10 Watts of heater power. I'll try to measure the bulb temp later today, if I can find some time.



And you know the "cages" you see on the valves, are they available commercially or made specific for the Amp makers.:)

Usually, they're custom jobs.

[Lignum]

That is hot.:oo: I will have to make a test box with the veneer, top ventilation and actual lacquer and run the valves for a day or two to find out what happens. And the reason I chose those valves (very quick search) was for looks. I want big fat sexy ones plus a couple of nice small delicate ones. :)

[Zaphod]

That is hot.:oo: I will have to make a test box with the veneer, top ventilation and actual lacquer and run the valves for a day or two to find out what happens. And the reason I chose those valves (very quick search) was for looks. I want big fat sexy ones plus a couple of nice small delicate ones. :)

Just to clarify: 45oC = 45 Degrees Celcius. It's not that hot, IMO (the human body operates at 38oC). That is the glass temperature. The surrounding air will be lower in temperature. If you can arrange some convection coooling, the glass temperature will be somewhat lower and the surrounding air temperature will be significantly lower.

[Zaphod]

That is hot.:oo: I will have to make a test box with the veneer, top ventilation and actual lacquer and run the valves for a day or two to find out what happens. And the reason I chose those valves (very quick search) was for looks. I want big fat sexy ones plus a couple of nice small delicate ones. :)

I measured a KT88 in a 2 Litre cardboard box. Bulb temperature was around 55oC (55 Degrees Celcius).

[GraemeCook]

Just to clarify: 45oC = 45 Degrees Celcius. It's not that hot, IMO (the human body operates at 38oC).


Hi Zaphod

Pesky problem when keyboards do not have a degrees sign, but if you write 45oC as 45*C then it is a little less likely to be misread, IMHO.

Cheers

Graeme