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Audioguru Please See My Simple PreAmp Circuit

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Gayan Soyza

Active Member
Hi!

This very old pre amp circuit I use for my transistor amp. With my transistor power amp (300W) this circuit works well. No more trouble gave me. I tried making different kind of modern pre amps. But finally I thought my old circuit is quite ok. Output gain no need to adjust unlike other pre amps, can directly connect to the power amp input.



Now I want to use this circuit with my STK amp (STK 4191). But I’m not satisfied with the sound quality (may be the cheapy STK IC have poor quality).

The headache is to adjust the BASS. Even though I change the filter capacitors near the BASS control. The BASS is starting to increase (at a feeling level) in the end of the BASS volume level. (In original systems the BASS is working in it’s fully range)

What do you think about this preamp? Can you suggest me a quality preamp (with tone control) for the STK 4191(41XX) series?

(I hope my speaker system & input signal is quite ok. STK 4191 circuit is the original circuit as SANYO specifies in the data sheet)

Thanks a lot
 

audioguru

Well-Known Member
Most Helpful Member
Hi Gayan,
Your opamp has its inverting pin without a DC voltage. It floats at any DC voltage.
It should be DC-coupled.

The 741 opamp is very old and is very noisy. Its max full output frequency is only 9Khz. A TL071 single, TL072 dual or TL074 quad opamp is low noise and has a full output frequency of 100kHz. I think a dual TL072 costs the same as a single 741 opamp.
 

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Nigel Goodwin

Super Moderator
Most Helpful Member
audioguru said:
Hi Gayan,
Your opamp has its inverting pin without a DC voltage. It floats at any DC voltage.
It should be DC-coupled.

The 741 opamp is very old and is very noisy. Its max full output frequency is only 9Khz. A TL071 single, TL072 dual or TL074 quad opamp is low noise and has a full output frequency of 100kHz. I think a dual TL072 costs the same as a single 741 opamp.
I agree, it's a really crap circuit - and not suitable ever to be used, it's essential that there's a DC path to all inputs of the opamp.

A 741 is very old and poor, but in this circuit (assuming it was wired correctly?), it's doing nothing anyway.
 

Gayan Soyza

Active Member
Oh thanks a lot audioguru for your circuit diagram.My current circuit I have to DC coupled as you said.I'm going to make that TL07X series for my STK amps from now onwards.But the supply voltage is little bit high.Never mind.

Thanks a lot
 

audioguru

Well-Known Member
Most Helpful Member
The TL07x series of opamps work fine if the supply voltage is single, like in our examples, or if the supply has dual polarities.
The total supply voltage for the opamps can be as low as 7V or as high as 36V.
 

Gayan Soyza

Active Member
Thats really cool.I was wondering how to give supply to your pre amp 33V.It is better I can give supply from a 12V transformer(single supply).Other wise I have to add another transformer to the amp enclosure.Then the noninverting pin voltage will be going down for a 12V supply.
 

audioguru

Well-Known Member
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A 12V transformer makes unregulated 15.5VDC. Use two resistors in series to make half of it and with a filter capacitor like in your circuit for the non-inverting input.
 

hipanni

New Member
Tone control

hi
i am new bee
i need best tone control circuit for stk4142 . I am also used vellman8084 circuit,yamaha DS62 circuit,TDA1524,KA22233,KA2107 am i not like that. i need depth and punchy bass smooth and clear voice, crystal clear treble anybody send me yours best tone control circuit
 

audioguru

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Most Helpful Member
My stereo has its bass and treble tone controls set to half-way so there is no affect. My speakers have good tweeters so their frequency response is flat up to higher than anybody can hear. They sound extremely clear. My woofers are only 8" in sealed enclosures with a flat response down to 60Hz but are high quality so I added a bass boost circuit for extended bass down to 35Hz.
Of course my Yamaha receiver has enough power for the bass boost and the woofers survive it.

If you have cheap little woofers then a tone control will not give you "punchy bass".
But your cheap old Sanyo STK4142 module has an output of only 25W per channel if it is the "II" version. That is not much power. The distortion is awfully high (not high fidelity) so you will not have "crystal clear highs".

Maybe you need this 3-band tone controls circuit:
 

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hipanni

New Member
thank you friend
plz send any best power amp circuit using 24-0-24 ,3amps transformer supply.
i used tower speaker box it have 8" woofer 6" mid dainty dome tweeters(not piezo).
 
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audioguru

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A 24V-0-24V transformer at 3A is 144VA. When rectified and filtered it makes plus and minus 32VDC. It can power a stereo amplifier that makes about 49W per channel at clipping into 8 ohms.
An LM3886 amplifier IC is excellent.
Your link doesn't work but it lists the LM1036 tone controls IC. It is pretty good.
 

hipanni

New Member
hi this is kannaa, I have TDA7294 Amp give me any driver or tone control circuit. Now i have using TDA1524 tone control
 

audioguru

Well-Known Member
Most Helpful Member
The datasheet for the power amp IC shows its output power with various supply voltages and at different output levels.
The datasheet for the tone controls IC shows that it works fairly well.
 

hipanni

New Member
Hi
Now I have mosfet power amplifier (irfp250n) . I am using harmankardon hk6900 preamp with little modification , McIntosh tone control with little modification and active volume control, what u think about it. Please give me better preamp and tone control circuit with tone defeat. Transformer is 24 -0-24 5 amps two transformers in parallel.
Floor stand speaker box 8" dainty woofer, 4" dainty mid and 3" dainty tweeter three way bolten crossover.
By
Kanna
 

large_ghostman

Well-Known Member
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skeleton.gif WARNING DRIVE BY POSTER AND OLD THREAD!! LG DO NOT POST!!

NECRO POST ALERT :D

kitten.gif
 
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JimB

Super Moderator
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LG you really do have a knack of shooting your mouth off and making embarrassing statements without engaging your brain.

Try reading the name of the supposed drive-by poster, look at his Joined Date, and then look up through the older posts in this thread.
Do any of the posters names look familiar?

JimB
 

large_ghostman

Well-Known Member
Most Helpful Member
Wow so five years go by and he posts in the original thread!! Ok not a drive by but even so................. How long will the project take? One of the few times I would say just buy one.

Oh and sorry you were embarrassed! ;)
 
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