Any kits for high quality simple preamp

[thyristor44]

Hello
Can anyone recommend a kit for a simple high quality preamp to amplify the output of my dac. Say with gain of two or three.
Thanks
thyristor44

 

[Mooly]

Does it have to be a kit ? OK, that was the question so here are a couple,

K8084 - VELLEMAN KIT - VOLUME & TONE CONTROL PRE-AMPLIFIER | CPC

PM-1 - CEBEK - PRE-AMPLIFIER | CPC

(click further details... would want PM4, and two of them)

And another,
Browse for Products | CPC

If you fancy making your own preamp then its as simple as one opamp and around six resistors for a stereo unit.

 

[Lazy Cat]

I have something like that, very simple, measures only 25 x 40 mm, but it is not a kit, it's ready made module.

 

[thyristor44]

Thanks for replies.
Never thought of cpc Mooly, bit if they did a PM-1 in stereo it would be ideal.
Alternatevely I could make one on veroboard, single ic, gain of about 2-3, preferably single 12v rail.Dont have schematic though.

 

[Mooly]

Its easy to make a simple single rail preamp. I'll draw you one.

 

[Mooly]

This has a gain of 3. The opamp can be something like a TL072 or NE5532.

Rin defines the input impedance.

Rg sets the gain which is (Rf+Rg)/Rg

The zener sets a stable midpoint voltage to bias it all.

 

[Lazy Cat]

Thanks for replies.
Never thought of cpc Mooly, bit if they did a PM-1 in stereo it would be ideal.
Alternatevely I could make one on veroboard, single ic, gain of about 2-3, preferably single 12v rail.Dont have schematic though.

I thought I read in the first post that you need a quality one

 

[thyristor44]

Thats brilliant Mooly, I could use one ne5532 and make dual amp. Where would be the best place for a trimmer pot to vary gain from 1 to 3, preferably twin gang if they exist. Things have moved on alot since I made anything.

 

[Lazy Cat]

Thats brilliant Mooly, I could use one ne5532 and make dual amp.

Far from brilliant, not even quality.

 

[KatieandDad]

You don't want to make an amplifier with variable gain, it's not good engineering practice. All you need is an attenuator at the pre-amp output - aka a volume control.

 

[thyristor44]

Far from brilliant, not even quality.

Lazy Cat mate both your designs seem to be quite complex and also power amps. I actualy want a simple preamp with gain of 1 to 3.

 

[thyristor44]

Point taken KatieandDad

 

[Mooly]

Thats brilliant Mooly, I could use one ne5532 and make dual amp. Where would be the best place for a trimmer pot to vary gain from 1 to 3, preferably twin gang if they exist. Things have moved on alot since I made anything.

The NE5532 and the LM4562 are probably the best of the standard "bjt" or normal transistor ones, other options would be the OPA2134, the OPA2604 or even the old TL072 (don't discount it until you have tried it)

Far from brilliant, not even quality.

Its easy to criticise basic circuits... perhaps you could submit one of your own that meets the requirements.

You don't want to make an amplifier with variable gain, it's not good engineering practice. All you need is an attenuator at the pre-amp output - aka a volume control.

I'd tend to agree with that, however if you really want adjustable gain then making Rg variable (a dual 10k pot) is the way to do it. You would also need to add a series 470ohm or thereabouts to ensure the gain has a maximum absolute level when the pot is at minimum resistance.

Further refinements to the circuit would be the addition of an input RF filter. That would consist of a series input resistor and cap to ground.

This shows these parts added and also the combined response of the circuit. Depending on what the circuit feeds, a low value resistor in series with the output might be considered a good option. That would isolate the opamp output from capacitive loading and help ensure totally unconditional stability. 47 or 100 ohm is a suitable value. A small electrolytic cap of around 10uf across the supply pins of the opamp would take care of decoupling.

 

[thyristor44]

Thanks again Mooly, Ill give it a try when I get the bits together.

 

[Mooly]

OK. If you get stuck, just ask