A radio from 1920 goes to 2017 !

[flea07]

Hi everyone !

I'm Aymeric, i try to restore a very hold radio :

My idea is to convert this radio into a modern bluetooh speaker by adding bluetooth technologie, modern speaker and battery for a mobil use. I will took off all existent intern element and switch theme by moderne one.

I find this guy who work on smaller radios in similar project, but my radio is a little more huge and the speaker most powerfull (40-60W)

I think i could use this bluetooth card : http://ebay.eu/2qUt2Dm

I think i can use this electronic shemas (in french but comprehensible i think):

My interogation is : What kind of battery can i use in order to make my device mobile and not to wach it burn?^^
Have you some bateries to advice to me ? what kind of chargers ?

Thant you for help

 

[davenn]

I'm Aymeric, i try to restore a very hold radio :

your very old radio pix didn't show up

 

[Audioguru]

Is it a muffled-sounding AM radio that plays lots of AM static sounds?
Will it pickup and play a few stations at the same time?

 

[flea07]

Hi, Thank tou for your reply.

This is a px of the radio : http://hpics.li/8e09571

I only want to make a bluetooth speaker, not a AM radio. I just want to make it playing songs from my phone.
My problem is to have the good battery for this system... I'm a little lost

 

[73's de Edd]

That very old radio is not a 1920 . . . . . instead a 1940-1950'ish . . .trust me . . .I was there.

 

[flea07]

Yes you probably right I hope that someone could help me to give it a second life.

This is my electric shemas : http://hpics.li/cbde796

 

[Audioguru]

The old radio was designed for AM and shortwave stations that had horrible poor sound quality.
Its amplifier and speaker will sound awful. Does it have an auxiliary input for you to connect your phone?

Oh, I think you want to use the old radio case but put a modern high quality amplifier and speaker in it. A 12V battery can power a bridged car radio amplifier IC to produce 15W into a 4 ohm car speaker. If you want 60W then the battery must be about 24V and it can power a bridged class-D amplifier driving a 4 ohm speaker. 60W into an 8 ohm speaker needs a bridged class-D amplifier powered from a 33V battery.
It will be mono, not stereo.

 

[flea07]

Thank you Audioguru.
I will put a new speaker into this radio, there is a 16,5 cm place for it. (look at this pix : http://hpics.li/1d668b7 it is the back plate of the radio face, the place for the new speaker)

I think i will buy this blutetooth amplifier (50w) : http://hpics.li/d20438e
With this speaker maybe ? : http://ebay.eu/2sDimu5

I dont know if it will be optimal, have you others components to advice me ?

I want to make this radio mobile so i would like to have a battry easy to charge (usb would be great but maybe not so strong to recharge a battery).

 

[Audioguru]

Some people say that ebay Chinese amplifiers and power supplies are designed wrong and produce noises and fairly low power. The datasheet for the TDA7492 IC shows 30W per channel into 8 ohms with fairly low distortion when designed properly and powered from 24V, but it is a stereo amplifier so will you just not use the second channel?

The ebay speaker might be a Ground Zero (German) one or a cheap Chinese copy of an old one. It is not listed on the Ground Zero website. Similar Ground Zero speakers have no detailed spec's. The ebay ad says when you buy the cheap speaker you get a pair of them. It says it is 4 ohms which will blow up the amplifier.

USB is only 5V at a low current. It can power a voltage boost circuit but the low current will take many days to charge a suitable battery.

 

[flea07]

Thank you for this informations, have you any pieces (like others kind of amplifiers, speaker or battery) to advice me for making my project go forward ?

 

[Audioguru]

I think cheap ebay things are poor quality. I do not know what high quality audio products are available or made in France.

 

[flea07]

hmm... I'm a little lost, maybe i could buy some pieces on internet, but i do not know what components are better for my project...

 

[Audioguru]

Do not buy pieces on the internet at random without knowing the specifications the project needs.
It seems that this project needs experience about how to do it that you do not have.

 

[73's de Edd]

Confucius say . . . . . . .

 

[Audioguru]

The bluetooth speaker uses a cheap single midrange speaker that produces no bass and no sizzling highs but has a normal peak in its response at a shrieking 5kHz. The cheap Chinese amplifier has its TDA7492 stereo IC with a supply of 9V if the battery is brand new and only one channel drives the original radio's 8 ohm speaker. The datasheet for the amplifier IC shows that its minimum supply is 8V which will occur very soon as the battery voltage runs down and a graph of output power vs supply voltage stops at 15V so the power with a 9V supply and an 8 ohm speaker is only about 4W. (Because it is bridged and is class D then its amplifiers produce about 8V p-p and two bridged amps produce 16V p-p which is 5.7V RMS, squared divided by 8 ohms= 4.0W.)

About 38 years ago my portable sound system was better than all the ghetto blasters on the beach. I used two small stereo speakers with woofers, tweeters and crossover networks and a sub-woofer. The 3 amplifiers I built were bridged and the sub-woofer speaker was 4 ohms for almost double the power that an 8 ohm speaker would produce.

 

[73's de Edd]

Considering the derived chosen cramped space limitations of that radio housing, I feel that he would probably be tickled pink with the results that are seen being attained there . . . .avec . . . .stereo.

A.G. . . . .
Just had the neighbor kid come in to help me compute, and I pulled off my shoes and we figured out that that your construction period time of your DEE-VICE would have been circa1979. Pulled out my olde 1979 Allied Radio Industrial and Engineering Supply catalog to see what would have been availablle in any power AUDIO chips but found nothing in the ECG automotive power audio chips. Then loooked at the probable power source of a Gel cell and they were certainly being quite pricey in those 1979 dollars.

http://www.alliedcatalogs.com/html/1979-790/hr151.html

73's de Edd

 

[Audioguru]

My good sounding 2.1 stereo DEE-VICE for the beach used National Semi LM2896 bridged amplifier ICs with bootstrapping. They were powered by six C size Ni-Cad battery cells producing about 7.5VDC.

I have never used a lead-acid battery for anything except in my car.

 

[flea07]

For avoiding cheap components have yo some links of product i could use that seems better to you?

 

[Audioguru]

You are in France, I am not. I buy good quality products that are available here. I avoid buying cheap Chinese no-name-brand junk from ebay or Amazon. There are other cheap Chinese auction sites I also avoid (Alixxxx).

 

[flea07]

Yes, i understand, but there is not only cheap good on ebay or amazon