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TUBE RADIO TO TUBE AMPLIFIERS

Wharfedale EVO4.4 Speaker

ashar

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Sep 2, 2018
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amravati
In this post i ll share my works with tube radios and their coversion to mono or stereo amps as we dont have any sw mw bands existing and the radios are useless and just showpieces so why not good tube amps from them

Local flea market score

IMG-20180905-WA0043.jpg

curious me..
chasis is out for inspection.

It contains BEL tubes all working fine IMG-20180905-WA0044.jpg

Radio removed,
Chasis modified to allow the tubes IMG-20180905-WA0045.jpg put to view from front panel.

Mono amp also added a inside lamp IMG-20180905-WA0049.jpg

 

ketanpote69

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Mar 28, 2015
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Hi Ashar ,

Great Job ! I have been thinking on same lines for a very long time .
Got a tube radio but could not gather support for conversion .
Also thought of making a new box after modification .
My question can we make .
1. Make it more compact and
2. Output on 8 ohms speaker thru transformer .
Ur comments pls.

Rgrds ketan
 

pksnathan

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Jun 13, 2008
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Quite a thoughtful idea and really interesting.Is the amp a mono or stereo?Please let me know.Thank you.
 

ashar

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Sep 2, 2018
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Location
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Thankyou for all your interest in the amp.

Its a mono amp thats how all radios are.
The plan is to have two mono amps and have the stereo effect. Like u can two monoblocks.

Yes it can be made compact like the mcintosh or even stingray just need to throw the old radio cabinet and make a good looking chasis.

Most tube radios do have a output transformer and dont need an extra to be added what looks like a big capacitor in my tube radio is a output transformer.
 

kbhuvi

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It might be a stupid question but what cleaning agent did you use. It will be mighty kind of you if you could mention the cleaning process along with some pointers (in brief or detail), as per your convenience.
 

yogibear

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Great job !

Many vintage consoles in US are being converted to some super sounding mono blocks and stereo ones are stripped of tone controls and converted to stereo tube amps.

It would be interesting to get hold of two identical radios but the possibility is remote.
 

ashar

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@kbhuvi I m a biker. And petrol works everywhere for me. A good soft brush, then petrol in a squirt bottle and cotton rags.
You can also use thinner (paint reducer) , medical spirits (not recreational) .

@yogibear you are right thats the way to go. and the only hurdle is finding two identical. once u get that its just a good build away
 

reubensm

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Alternately, you can replicate the existing mono channel leveraging common resources within, and covert the rig into a 2-channel piece. You'd already have the chassis and valve sockets (spare ones after removing the RF valves), you can leverage the same power supply (rectifier, usually EZ80, filter capacitors, choke and power (auto) transformer. You'd need an additional set of valves (possibly EL84 and EF86), some components and an output transformer which you can salvage from any other valve radio in this range (model does not matter), hence you technically don't need to find 2 absolutely identical models after all :)
 

ashar

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Sep 2, 2018
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Alternately, you can replicate the existing mono channel leveraging common resources within, and covert the rig into a 2-channel piece. You'd already have the chassis and valve sockets (spare ones after removing the RF valves), you can leverage the same power supply (rectifier, usually EZ80, filter capacitors, choke and power (auto) transformer. You'd need an additional set of valves (possibly EL84 and EF86), some components and an output transformer which you can salvage from any other valve radio in this range (model does not matter), hence you technically don't need to find 2 absolutely identical models after all :)
very well thought.
I ll try to do the same
 

yogibear

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Replicating is hard as you will be always stuck with output transformers. You can take advantage of the schematic and then start with all new parts.

Two similar specs OT will not sound same unless they are identical. Even two same specs resistors if not identical and are in the audio path, will not have same tone. It will be really awkward to have two channels with different tones. Two tube amp mono blocks, must have identical components to sound same for a stereo set.

I have given up on some amazing deals just because of this reason. Even different cores of otherwise identical OTs, will always sound different.
 

reubensm

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if one is game, there are loads of lovely output tranny pairs, from the likes of telefunken and others, that come up quite often on ebay.de

These are usually of the 3-10 watt types.

Also from experiences shared by my father during long electronics discussions, the output transformers and power transformers used in most Indian brand valve radios of those days were usually made in Delhi or Punjab and were of very basic quality, to keep costs to a minimum. These were kind of similar and interchangeable.

Personally i have found the output trannies in old guitar amps to be very good, but they are impossible to get.
Edit:
Also wanted to add, at times I have found the output transformers on Indian Philips tube radios to be slightly different from those in Murphy, Nelco, Bush, etc. The very designs of Indian Philips tube radios used to be slightly different.
 
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analogadikt

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Feb 19, 2009
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No need to pull out the oscillator and tuning circuit section. All these radios have PU input that takes a line level signal directly to the amp section when selected. What is necessary and critical is to renew all power supply caps, modify the rectifier section if it uses selenium rectifier and clean the volume/tone control pots with a good contact cleaner.

And for stereo, an easier option is to look for old R2Rs in the bazzar. Akai 1710 and Grundig TK46 come up quite regularly.


Regards
 
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