Connecting to a computer speaker - UK Vintage Radio Repair and Restoration Discussion Forum

Pete_kaye · 5th Jan 2009, 7:02 pm

I have a simple crystal type set or two,which I use plugged into a pair of Trust 60W computer speakers which can give plenty of volume.
However there is always a loud buzz to overcome which only occurs when the speakers are plugged into the jack plug previously occupied by headphones.My question is whether there is a better way of connecting up .Via a condensor?Series?
The speakers are mains only with a 2 ply lead and no earth.I am using the mains as a separate earth to the receiver.

Nickthedentist · 5th Jan 2009, 7:04 pm

Hi Peter,

Have you tried reversing the connections to the headphone socket?

Nick.

peter_sol · 7th Jan 2009, 10:21 am

I would imagine that the speakers need 5oo mv and the crystal set only gives out a few mv if that so you will have your speakers turned up much higher than normal hence the hum
also the crystal set will be all unscreened you could try screening it

Regards

Peter.

Pete_kaye · 7th Jan 2009, 4:43 pm

Thanks guys. I tried reversing leads. No change. I realised this only occurs when connected to my home made SW coil which gives little output; I will try some kind of screening. I was originally wondering about how to link up these type of speakers. Is it good enough to just connect them where the headphones were? No trx used as phones very high IMP.

Lee de Forest · 7th Jan 2009, 6:09 pm

I run a home made crystal set through some PC speakers. The output was low due to the weak signal strength. I then run the crystal set through the phono input on a HI-FI amp with much better results. I assume this was because the HI-FI amp would have a pre-amp for the stylus.

Framer Dave · 7th Jan 2009, 9:27 pm

Quote:

Originally Posted by Lee de Forest

I then run the crystal set through the phono input on a HI-FI amp with much better results. I assume this was because the HI-FI amp would have a pre-amp for the stylus.

The phono input of a Hi-Fi amp will certainly provide much more gain than the line-level input of a computer speaker, however the amp's phono input is passed through an RIAA equalisation filter, which will result in bass boost and treble cut if used with any signal other than that from a record player cartridge. This is due to the use of the RIAA recording characteristic when making discs.

Sorry if this is a bit OT.

Dave

Pete_kaye · 12th Jan 2009, 4:22 pm

My question is then:can I fit something simple between the radio and the speakers that will boost the input.I have tried a simple 1 transistor amp using a BC108,which gave a boost.I will try inputting via my Leak 1970 amp which has switchable gain and 3 inputs.

5th Jan 2009, 7:02 pm	#1
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Connecting to a computer speaker I have a simple crystal type set or two,which I use plugged into a pair of Trust 60W computer speakers which can give plenty of volume. However there is always a loud buzz to overcome which only occurs when the speakers are plugged into the jack plug previously occupied by headphones.My question is whether there is a better way of connecting up .Via a condensor?Series? The speakers are mains only with a 2 ply lead and no earth.I am using the mains as a separate earth to the receiver.

5th Jan 2009, 7:04 pm	#2
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,844	Re: Connecting to a computer speaker Hi Peter, Have you tried reversing the connections to the headphone socket? Nick.

7th Jan 2009, 10:21 am	#3
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Connecting to a computer speaker I would imagine that the speakers need 5oo mv and the crystal set only gives out a few mv if that so you will have your speakers turned up much higher than normal hence the hum also the crystal set will be all unscreened you could try screening it Regards Peter.

7th Jan 2009, 4:43 pm	#4
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Connecting to a computer speaker Thanks guys. I tried reversing leads. No change. I realised this only occurs when connected to my home made SW coil which gives little output; I will try some kind of screening. I was originally wondering about how to link up these type of speakers. Is it good enough to just connect them where the headphones were? No trx used as phones very high IMP.

7th Jan 2009, 6:09 pm	#5
Lee de Forest Retired Dormant Member Join Date: Sep 2008 Location: Harrogate, North Yorkshire, UK. Posts: 352	Re: Connecting to a computer speaker I run a home made crystal set through some PC speakers. The output was low due to the weak signal strength. I then run the crystal set through the phono input on a HI-FI amp with much better results. I assume this was because the HI-FI amp would have a pre-amp for the stylus.

12th Jan 2009, 4:22 pm	#7
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Connecting to a computer speaker My question is then:can I fit something simple between the radio and the speakers that will boost the input.I have tried a simple 1 transistor amp using a BC108,which gave a boost.I will try inputting via my Leak 1970 amp which has switchable gain and 3 inputs.