Low-Noise Stereo Preamp Kit
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4 of 4 Reviews
Built this as an audio pre-amp to drive some external BBC meters - works fine except that the frequency response of the two channels is widely different - sweeping from 150hz to 1Khz produced output level changes on one channel, but no the other - I guess I need to look at the poor resistors and capacitors to level this out - Changed the 2 1k to 10K, as advised by other post - more stable and much improved, but still pretty poor..and still a channel disparity.
Further mods for improvement
I agree with the previous reviewer; bass roll off at such high frequency is a serious problem for this type of pre-amp. Also with the noise comment but the correct replacement components would be M10k and M100k which are 0.6W rated as opposed to the 2W components in the previous review. Those would be difficult or impossible to fit. Overall an easy kit to assemble and use.
Great little kit , bought this to boost the output from a TosLink to Phono adapter, from TV to House Stereo , needed that little bit more as Stereo was nearly on full to get good volume ...now I can turn it down to half way and get great volume. Agree totally with Marc's review and have swapped the resistors for metal film and changed the input values from 1K to 10K ( R1 and R5 ) , this worked brilliant and only needed this on half boost for both channels to get the volume right , eg : same as Tuner /CD Player. Note however , my kit came with 2 Ceramic Capacitors replacing 2 of the Polyesters , and the paper add in did not make it at all clear as it only mentions C2 and C4 nothing about C1 or C5 , to clarify this I used the DOWNLOAD available and looked at the Circuit Diagram , so to help those less knowledgeable here is the answer C4/C5 are Ceramic (Small brown disc stamped 104) , C1/C2 are Polyester ( Yellow and Rectangular ) , also NOTE the IC chip in the picture shown is fitted the wrong way around , the DOT should be at the other end with the NOTCH on the 8 pin DIL Socket. I also used a 12v 1A ( 500mA would be OK ) wall wart to supply the power to this . One last thing , if you buy the 6 extra resistors at the same time you get free delivery , as it goes just over £10 ,and you save the £2.99 delivery, so you can upgrade this kit for free almost :)
I'd love to report this is a great kit - and the NE5535 is a fairly neat chip so it's a good choice and the use of single-rail biasing is convenient. Things go downhill from there though. I've come to trust designers and when I first built one of these I was disappointed by the performance; particularly at the low end. Turns out this amp - simply down to poor component choice - rolls off at around 160Hz - making it pretty useless for music. Simply increase the 1K resistors to 10K (dropping the gain to x10) and a more respectable 16Hz rolloff is achieved; together with a more respectable 10K input impedance. Worse perhaps, is the choice of carbon film resistors - while these are easier to read than the metal film ones sold by Maplin (the blue body ones) they are noisy! Swap them for the stock Maplin metal film and presto, you have yourself the beginnings of a decent audio amp - for little extra cost. Six off D100K and two of D10K will do nicely! If you need more gain, just chain two together or increase the value of the feedback resistor - but beware that the NE5535 is prone to oscillations; and this board is no exception.
QuestionsAsk a Question
5 of 5 Questions
Hi, could I attach two ECM mics (Order Code: QY62S) to the + and - inputs on this preamp, and a 9v battery or similar?
jell shore said:
can this pre am be used to between my hifi and subwoofer to make the passive subwoofer louder so i can hear the bass ?
Paul Maloney said:
MAP 437 - N47FL Would this pre-amp circuit work to boost the output of an MP3 player (low output impedance)to a level suitable to drive the AUX input of a typical stereo receiver?
Could this preamp (N47FL) be used to amplify the signal from a lapel mic being used in an acoustic guitar?
Lost Ninja said:
Would this be suitable for amplifying an MP3 player prior to playing through Speakers?
|Item code||Item name||Quantity||Price|
|N47FL||Low-Noise Stereo Preamp Kit||(100+)||£6.37|
|N47FL||Low-Noise Stereo Preamp Kit||(25+)||£6.79|
|N47FL||Low-Noise Stereo Preamp Kit||(10+)||£7.22|
|N47FL||Low-Noise Stereo Preamp Kit||(5+)||£7.64|
|N47FL||Low-Noise Stereo Preamp Kit||(1+)||£8.49|
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