sound

[-=GST=- Nemisis (cs/cz)]

how can i add volume controll to this circuit? someone told me i could use a variable resistor(pentometer) after the 220uF cap, but i wasnt sure. what do u guys think?

**broken link removed**


also could any recomend a simple way of making this sereo sound, though an ic or something and a replacement for that audio transistor.

 

[red4925]

Yes, that will work. Chose the value based on the impedance of your speaker or input resistance of next stage. Often logarithmic pot's are used for volume control, from what I've heard. But a linear one will do.

 

[-=GST=- Nemisis (cs/cz)]

Yes, that will work. Chose the value based on the impedance of your speaker or input resistance of next stage. Often logarithmic pot's are used for volume control, from what I've heard. But a linear one will do.

well im using 8ohms so what resistance levels could i use, from silence to full sound?

 

[-=GST=- Nemisis (cs/cz)]

also i can get any headphone socket on this page

**broken link removed**

does one of them have the abilitly where its nomally sound out of speakers but if you plug in headphone is automatically switches to headphones like some do?

 

[audioguru]

You don't need to add a volume control, it already has one. What do you think the 10K pot is for? It should have an "audio taper" (logarithmic).
Lots of luck with this extremely, extremely, extremely, extremely, simple super-regen FM radio!
Forget stereo for it.
If your area has lots of stations then tuning it will be a pain.
It will pickup AM too. Tune it a little above the FM band and it will pickup airplanes and air traffic controllers, if it's near an airport. Its radiation might even interfere with them.

 

[-=GST=- Nemisis (cs/cz)]

You don't need to add a volume control, it already has one. What do you think the 10K pot is for? It should have an "audio taper" (logarithmic).
Lots of luck with this extremely, extremely, extremely, extremely, simple super-regen FM radio!
Forget stereo for it.
If your area has lots of stations then tuning it will be a pain.
It will pickup AM too. Tune it a little above the FM band and it will pickup airplanes and air traffic controllers, if it's near an airport. Its radiation might even interfere with them.

im gunna check out the local stations, if i make it and its too crap i will just disgard it, and mabey make one with a different chip, tda7088 or something like that

 

[-=GST=- Nemisis (cs/cz)]

audioguru(or anyone) i need your opinion, would i be better stiking with this design or going for a tda7000 design?

 

[-=GST=- Nemisis (cs/cz)]

oh yeah check this, put together using the ultimate in scematic technology, ms paint

 

[audioguru]

Yeah, that super regen is a crappy radio. It might be OK for a kid's 1st project. It doesn't even have an FM detector, you just tune it to one side of a station and fiddle with the regen control. Very distorted.

The TDA7000 is also unusual but some people like it. It is no longer made but some shops still have some. Zach is making one on another post.

Someone purchased a key-chain radio for only 2 bucks. It had a TDA7088 (surface-mount version of the TDA7000), which has two-button station scan.

 

[-=GST=- Nemisis (cs/cz)]

and is the LM386 a good audio chip to use? from my supplier it only costs 35p which implies its not very good quality, i then saw the LM1875N for £2:05, that sthe kind of price that i would expect. is there a better audio chip to use and does ne one have a schematic if possible? i am really looking for audio quality not loudness, the same goes for the radio, if there are any superhetrodyne chips i could use that would provide better quality then the TDA7000 i would use it but i would need a schematic.

also about the headphone socket, is there one with a switch on the website i posted above(normally sound, when headphones inserted its becomes headphones)?

 

[audioguru]

Hi Nemisis,
Sure the LM386 is pretty good. Wellington is using it for his "Super Headbanger" headphones amp project in one of these posts here. Try a search to find it.
The LM386 is cheap because it is simple and is mass-produced by the millions. With a 6V battery it can drive an 8 ohm speaker to about 1/4W.

The LM1875 is excellent. With a 60V (yes, that's sixty volts!) battery it can drive a 4 ohm speaker to about 42W. That's enough power to blow your head and headphones off, or destroy most small or even medium size speakers! Just idling without any output, an LM1875 draws so much battery current that it will overheat without a heatsink.

Your choice.
All manufacurers have spec's and schematics in their datasheets that are found on the web with a Google search.

A superheterodyne radio circuit is excellent, but I don't think that you want to make one. They need special parts that are hard to find, and test equipment to align them. You might find a kit that is aligned "for the best sound".

Most web electronic parts suppliers have any kind of socket that you could dream about. Of course switched headphones jacks are available, and you probably need a stereo one.

 

[-=GST=- Nemisis (cs/cz)]

ok i have decided on a final design but i do need to know about the headphone connection thing does anyone know?

 

[Nigel Goodwin]

ok i have decided on a final design but i do need to know about the headphone connection thing does anyone know?

It just requires a switch on the socket, these are commonplace on 3.5mm and 1/4" jack sockets - although you do need to ensure you buy the correct ones.

 

[-=GST=- Nemisis (cs/cz)]

hmm i looked at another desing of this some where and it only had one coil, then i looked at zachtheterribles thread and u said that it wasnt stereo coz it wasnt a stereo headphone socket, does this mean that the extra coil is for the stereo sound on this circuit?

 

[Nigel Goodwin]

hmm i looked at another desing of this some where and it only had one coil, then i looked at zachtheterribles thread and u said that it wasnt stereo coz it wasnt a stereo headphone socket, does this mean that the extra coil is for the stereo sound on this circuit?

The reference to stereo was only with regard to his headphones, if you plug stereo headphones into a mono socket it only works in one ear. You need to use a stereo socket wire to mono for both ear pieces to work.

Neither of the examples above are stereo, you need a stereo decoder for that, which I think is unlikely to work with the super-regen radio?. The TDA7000 may well work with a decoder, with suitable modifications - presumably the Philips datasheet would give details?.

 

[audioguru]

A stereo decoder requires a "real" FM tuner that has an IF of 10.7MHZ with transformers or ceramic filters, because the frequency response at the detector must extend to 53KHz.
The TDA7000 won't work with a stereo decoder because its 70KHz active-filter IF rolls-off frequency response above only 10KHz.
One of the newer TDA70xx ICs (surface mount only) is compatable with a stereo decoder but its channel separation is lousy (maybe OK for headphones).

If you could just simply add a coil to get stereo, will 2 coils make surround sound?

 

[-=GST=- Nemisis (cs/cz)]

so if i use a stereo socket on this mono curcuit it will owrk both headphones even though its still a mono sound?

also in my research of this design i used this calculator

with 45pF(18+27) for capitance, then 78nH for henries and megaherz and got 84, i take it when u move the variable capsitor it becomes 44pF overall so you get 85Mhz and then 43pF=86Mhz all the way up he FM band, is this correct?

also what is the difference between a 70nH coil and a 78nH one? are the coils different thikness or difference lengtths?

 

[audioguru]

Yes, a stereo socket that has both channels connected to a mono amp will play mono to both ears. The sound will appear to come from inside your head.

You can't calculate the frequency of VHF LC combinations very well because you don't know and don't allow for stray capacitance that could be 5pF or more.
Why not just use the PCB and component values that are shown in the circuit that is in the datasheet?

A longer coil (more turns) has more "hennies".