Old radio to stereo amplifier

[GlowBlue]

Can i take 2 the same tube ampliefier-radio's and make 1 propher stereo tube amp out of it?And if so,What Philips radio i should look for?In my area those radio's are given away for free.

[Refugee]

If you can find two the same model with gram settings you can just restore them.
Most have at least two AM bands that would be an added bonus and some even have FM.

[GlowBlue]

But if i leave the radio,can i make a nice stereo amplifier out of it to drive my things?

[Refugee]

The sets with gram inputs work fine.
They used to have a turn table that just plugged in like a modern stereo one does.
A modern turn table will need a preamp if it has a magnetic pick up as it would with most valve amplifiers.
Old tape recorders can also work as amplifiers too and with just a socket added are not far from a modern gram amplifier and may be adjustable enough with the tone control too.
It might be worth building an amplifier from scratch with valves that are still made.

[Ed_Dinning]

Hi GB, some nice Philips/ Mullard circuits that use radio valves (5-10, 3-3 etc) if you want to try that route.

Ed

[Robstan234]

If you are asking whether you can use two separate amps side by side as effectively two mono amps to produce stereo from a pre-amp then there will be a few problems. I am not knowledgeable in valves to ensure safety in the design as I would imagine that you would need a couple of good quality audio transformers to prevent any earth problems between the three parts, but I will leave that to better people than me. Rob

[Radio Wrangler]

Through the nineteen fifties radio designs changed from having isolating transformers in their power supplies to simply using DC created by rectifying the incoming AC power directly. Consequently a great many radios have no isolation between their circuitry and the incoming mains. This makes them very dangerous if anyone modifies them and brings connections in or out of their cases.

Many record players also use this system and so are not safe without major modifications for use as an amplifier to be connected to external things.

On the other hand, tape recorders tended to stay with isolated power supplies, so they may be better donors than radios.

However, it may be a lot easier and yield a neater result to find an amplifier and restore it, alternatively to build an amplifier from scratch.

David

[trickie_dickie]

Just connect to the mains supply via an isolating transformer. Simples.

[crackle]

What you will end up with, if in fact you are able to achieve it at all, will not be Hi-Fi without serious modifications to the circuit and the purchase of expensive audio output transformers.
Why not buy yourself a nice stereo hi-fi amplifier from the 80's or 90's there are plenty around.

Mike

[stuarth]

You don’t just need “an” isolating transformer, you need an isolating transformer for each live chassis unit you use. You should not connect more than one unit to each isolating transformer.

Stuart

[mark2collection]

I once had a bit of fun with two Bush DAC90A's and a pair of signal generators with external modulation capabilities.

Sig-gens on different frequencies, modulated left & right accordingly, from the same audio source.

Far from HiFi, but it was true stereo

Mark

[ValvoStef]

Originally Posted by GlowBlue

But if i leave the radio,can i make a nice stereo amplifier out of it to drive my things?

Sure you can build a stereo amp out of two radios, however, as said above, the result will be far away from HiFi quality. The used output transformers are not good enough.

[boxdoctor]

Hi Glowblue,
As ValvoStef has stated above, The result will probably be disappointing to say the least.
With few exceptions, table radios were built down to a price, and the circuits were thus very "economical" in the sense that the transformers, smoothing arragements, speakers, and general specifications would be as low priced as the maker thought they could "get away" with.
You are therefore starting with a big handicap if you want really good HiFi results.
This is before we start considering things like non-isolated chassis and other safety and practical considerations.
I'm sorry to have to be so negative, but you would be better off starting from the beginning with a proper HiFi design.
The result would be so much more rewarding. Tony.

[Tractorfan]

Hi,
If you're lucky enough to find a valve radio similar to this one, which a Blaupunkt, and is stereo with four speakers, everything you need is already there. It has two ECL86 output valves and a mains isolating transformer.
I'm sure Philips made ones like it. It's got a DIN socket input and connections for external speakers plus the usual bands. For FM stereo, a decoder was available. Even on the internal speakers it sounds good in my opinion .
Hope this helps.
Cheers, Pete.