Is there a way to amplify an audio signal (1 V peack to peack) to 180 - 200 V?
Some distorsion is acceptable but I'd like to preserve the bandwith and harmonics.
can anyone suggest a simple circuit?

The load of this amplifier will have high impedance.
Thank you I hope that the description is clear.. Thanks!

 

Is there a way to amplify an audio signal (1 V peack to peack) to 180 - 200 V?
Some distorsion is acceptable but I'd like to preserve the bandwith and harmonics.
can anyone suggest a simple circuit?

The load of this amplifier will have high impedance.
Thank you I hope that the description is clear.. Thanks!

100V line amplifier will give you 100V rms output from 0.775V rms input.
https://cpc.farnell.com/adastra/dm4...5769&s_kwcid=AL!5616!3!689656657163!!!network}!1677605611826!&gad_source=1

 

Certainly it is possible, BUT how much power is required?? That matters a whole lot.
Audio amplifiers with the output specified in volts only deliver that voltage at their rated power output, and so if the application only requires one watt of power you will not get that voltage.
Otherwise, if you can locate an audio output transformer rated for the required power level that was intended to be used with a tube type output stage, that could be operated in reverse to provide the higher voltage. A transformer intended for "High Fidelity" amplifier should be able to deliver an adequate spectrum response.
It may also be possible to use what was called a "Modulation Transformer", depending very much on what sort of amplifier you intend to use.

 

See

 

100V line amplifier will give you 100V rms output from 0.775V rms input.
https://cpc.farnell.com/adastra/dm4...5769&s_kwcid=AL!5616!3!689656657163!!!network}!1677605611826!&gad_source=1

Thank you very much. Unfortunately I may need a circuit, not an extenral device. But Thank you!

 

Certainly it is possible, BUT how much power is required?? That matters a whole lot.
Audio amplifiers with the output specified in volts only deliver that voltage at their rated power output, and so if the application only requires one watt of power you will not get that voltage.
Otherwise, if you can locate an audio output transformer rated for the required power level that was intended to be used with a tube type output stage, that could be operated in reverse to provide the higher voltage. A transformer intended for "High Fidelity" amplifier should be able to deliver an adequate spectrum response.
It may also be possible to use what was called a "Modulation Transformer", depending very much on what sort of amplifier you intend to use.

Thank you MisterBill!
It's a sort of research project so I have to apply the 200 v pp audio to a crystal wich is electically inert. It does not have impedance so no current drained and no power absorbed.
The idea of a tube tranformer used in reverse is great. The audio signal comes out form a bc 457 NPN transistor. Do you think it can drive a tranformer diretcly?

 

See
View attachment 334428

Thank you Sir!. I only need 200 V in output but I'll carefully review. Thanks!

 

apply the 200 v pp audio to a crystal wich is electically inert. It does not have impedance so no current drained and no power absorbed.

No, it does have an impedance, which is mainly capacitance, and that will require current to drive an AC signal.
What is its capacitance?

 

Thank you very much. Unfortunately I may need a circuit, not an extenral device. But Thank you!

Based on the "technical description" of that amplifier, whoever wrote it has less technical insight than my friend's cat! That is to say, not much.

 

No, it does have an impedance, which is mainly capacitance, and that will require current to drive an AC signal.
What is its capacitance?

OK, the crystal has an extremely high impedance, and a bit of capacitance, probably not much. So it will be voltage driven. This means that most of the power will be absorbed by the losses in the system, because none of it is 100% efficient.
So the amplifier is a BC457 NPN transistor. I have not looked to see what amount of power that transistor can provide.
I am guessing that a transformer rated for five watts will be adequate, in that it can be driven harder to produce the 200 volt output without saturation causing distortion. Unfortunately audio output transformers are mostly rated to match tube output impedance rather than by ratio. So at that point I will need to do some research, unless somebody else has all of that in their head.

 

The

. Unfortunately audio output transformers are mostly rated to match tube output impedance rather than by ratio. So at that point I will need to do some research, unless somebody else has all of that in their head.

Usually they are rated for the impedance of the load (8Ω or 16Ω) and the anode impedance (between 2k and 10k) and the turns ratio is the square root of the impedance ratio; but some are designed to have a standing DC current.
If I were to use a transformer, I'd use a 100V line transformer.
However, I can't imagine that a crystal is going to be much other than a small capacitor in the audio range, as the lowest crystal resonant frequency I can think of is 32768Hz, and the analysis is going to be horribly muddled by the impedance of the transformer, so I'd go with @Bordodynov SRPP circuit. I might even make it with the two halves of a ECC83 which is where it originally came from, because it is likely to be more robust than any transistor circuit.

 

Consider the physical size of that transformer, which would be adequate for over 100 watts of audio.
AND, consider that at that power level the 100 volt winding will be a rather low impedance. I recently worked on a 100 watt PA amplifier and the 70.7 volt line impedance was about 14 ohms, as I recall.
That voltage is present at the rated power level.

 

100V line transformers are available as low as 3W.

 

100V line transformers are available as low as 3W.

INDEED THEY ARE!!Also 70.7 volt transformers. The plan is to select the primary tap to provide the wattage desired to the speaker connected. THAT is how the 100 volt and 70.7 volt systems work.
I had not thought about using a speaker matching transformer in reverse. That cold be a working scheme.

 

INDEED THEY ARE!!Also 70.7 volt transformers. The plan is to select the primary tap to provide the wattage desired to the speaker connected. THAT is how the 100 volt and 70.7 volt systems work.
I had not thought about using a speaker matching transformer in reverse. That cold be a working scheme.

They are normally tapped on the high voltage side not the 8Ω side. A 70.7V system would give exactly half the power if the transformer were designed for 100V line.

 

Audio impedance is the electrical load placed on the amplifier.
Speakers that are (4 Ohm, 6 Ohm, 8 Ohm ) 8 Ohms and less are high impedance.
A very large 8 ohm speaker can be relaced with an 8 Ohm resistor when it is large enough to not smoke.

If I understand correctly, When the load is applied, He prefers that low load harmonics remain and the bandwidth be preserved.
I think he is describing a condition viewed in the frequency domain He wants to set a limit on the number of harmonics.
For example maybe the 9th or 15th harmonic has some useful meaning to this adventure. ???
Depending on what result is expected or estimated as a starting point on the SA, The initial THD might be very low.
As you increase the power there might be a point where there is too much noise from the set up and cables.

The transistor BC457? The BC4000 series is uncommon. The BC547 simulates well, is a nice transistor.
An adjustable audio signal generator possibly has 0.02% THD is applied to the NPN BC547 possibly this where the initial 1Vpp Amplitude is measured.

 

Really, a more common description would be that the TS is asking for a HiFi signal with good frequency response and low distortion. By that I mean no harmonics in the output that are not present in the input signal. Those requirements are demanding but also very reasonable.

 

I would like to tank everyone for the incredible knowledge and contribution.
I will keep you updated on the developements!