Is this circuit acceptable for this forums use?

[ppcblaster]

Please advise, I found it surfing the net. Thanks

 

[anatech]

Hi ppcblaster,
Be nice if it had an output buffer of some kind. Simple and inexpensive. It probably sounds okay. You could just add another NE5532 to handle both channels after the volume control.

Think about a thump eliminator for turning it on and off. Better power supply really wouldn't hurt either.

-Chris

 

[phn]

Better PSU, indeed.

Personally I would place the tone control before the circuit. It might not make a difference, but I like it that way.

Chris knows more about buffers than I. But wouldn't a high-pass network be in place (after the volume pot has been moved)? I'm not much for caps in the signal path. I'm not much for tone controls either, so it evens things out. (I do like tone controls, in a sense. But since it takes effort to use a Pultec-type tone control properly, I think it's better to just drop the thing.)

 

[anatech]

Hi phn,
LOL!

You crack me up sometimes! Love your avatar!

-Chris

 

[phn]

Hi phn,
LOL!

You crack me up sometimes! Love your avatar!

-Chris

I enjoy cracking people up sometimes.

Maybe an explanation is in place. I don't think tone controls are inherently bad as many people do. But if I'm to have one I want one of those swank Pultec thingies used in pro audio. The problem is that you have to tweak the settings for every album you play. Who the you-know-what has the time and energy to do that?

I just don't know what a buffer would do in this case. But that's not uncommon. This electronics crack me up more often than not. My skull, that is.

 

[anatech]

Hi phn,
I don't mind tone controls, although I seldom use them. On occasion they are useful. Just don't make them part of the feedback network for the power amplifier!

In this case, a buffer would go between the volume control wiper and the outside world. If your amp circuit is but a few inches away in the same box you may not need it. There are some amp circuits that need a low impedance in to be driven with low distortion.

If you intend on squirting your signal down a cable, you really ought to have a buffer in there. It helps to maintain a low signal to noise ratio and avoid other effects and interactions.

-Chris

 

[phn]

I'm with you on the buffer and impedance. But wouldn't moving the volume pot and adding, say, a 2.2uF coupling cap and a 100k grounded resistor take care of it?

As a side note, I don't like the idea of coupling caps. I even started a coupling cap thread. I still don't fully understand its purpose. And I definitely do not like the idea of a cap in the signal path. But in the overall scheme of things, it's probably not that bad.

Edit: DOH! In my first post I wrote "Personally I would place the tone control before the circuit." I mean VOLUME pot. Now it should make sense.

 

[ppcblaster]

Thanks but I have lost parts of my hearing

I am treble deaf, along with almost no hearing in my left ear.

If I boost the treble I can enjoy what I am hearing, otherwise it

is muffled.

Also where can I post a request for a Rev C amp addon?

"The optical digital out is a digital output on the back of your tv

is toslink"

I don't have the skills to build a digital "toslink" input from my TV

to an Amp I want to build.

Any help would be greately appreciated. Thank You...Gary

 

[anatech]

Hi phn,
The problem with putting the volume control first is noise. Having it last means that any noise is attenuated along with the signal. I'm thinking a buffer with a gain of 0 dB, or close to it.

Hi Gary,
I don't follow your request, but you've asked for it here and it's your thread.

-Chris

 

[ppcblaster]

Thanks

I will search, and if I find nothing, I'll start a new thread.

Thank you again

 

[forr]

Warning :
the 100 kOhm balance pot must have a resistor (say 10 kOhm) at its left otherwise the circuit may have a huge gain when the cursor is at full left position, gain which would only depend on the output resistance of the preceding circuit.
The two 1.2 kOhm at the output draw a lot of current.

Basically, this kind of circuit is true hi-fi c and has very low distorsion. however this precise one has been poorly designed by somebody with very low experience.

As said, the tone control should be placed before the volume control to minimise its noise when listening at low levels.

I think it was a stupid idea to remove tone controls from integrated amplifiers because a single touch could be provided to by-pass them. Tone control had bad press because their frequency response were unadequaltely chosen. Curves similar to those of Tom Holman's APT preamp should be aimed at.

Is an input buffer really needed ? Most sources are now of low output impedance.

 

[Nordic]

Generaly I would say forget about the tone controls...
I would suggest looking at Rod Elliot's project 88.
It uses one more opamp though, but will give you, fixed input and output impedances regardles of pot position, as it is also stuck between 2 buffers.
And it also has a balance contol. I think balance and volume is more than sufficient.

I have mine powered of a 2 x 2.5VA PCB mount transformer if you can believe that, and it sounds sweet.

 

[phn]

Generaly I would say forget about the tone controls...

If you'd read the thread you'd know that this is not about general. The original poster needs the treble boost.

 

[Nico Ras]

Warning :
the 100 kOhm balance pot must have a resistor (say 10 kOhm) at its left otherwise the circuit may have a huge gain when the cursor is at full left position, gain which would only depend on the output resistance of the preceding circuit.
The two 1.2 kOhm at the output draw a lot of current.

Basically, this kind of circuit is true hi-fi c and has very low distorsion. however this precise one has been poorly designed by somebody with very low experience.

As said, the tone control should be placed before the volume control to minimise its noise when listening at low levels.

I think it was a stupid idea to remove tone controls from integrated amplifiers because a single touch could be provided to by-pass them. Tone control had bad press because their frequency response were unadequaltely chosen. Curves similar to those of Tom Holman's APT preamp should be aimed at.

Is an input buffer really needed ? Most sources are now of low output impedance.

Dear phn,

The circuit you present is fine, I agree with the balance circuit metioned above. But not with the tone controls before the volume pot.

A filter needs low inpedance in and high impedance from the following circuit. This is exactly what our designer has done, he followed correct design principles.

I agree that the bass turn-over frequency is a little on the high side, rather play with capacitors in the 470 nF range. Change the values and listen if it is what you want. The range of bass is about 10 dB lift and cut.

The treble lift and cut is also a bit much almost 40:1 and the frequency is too high. Try playing with the resistor values on either side of the pot untill you like what you hear.

Kind regards

Nico

 

[phn]

Dear phn,

The circuit you present is fine, I agree with the balance circuit metioned above. But not with the tone controls before the volume pot.

Nor do I. It was a TYPO. That's why I wrote:

DOH! In my first post I wrote "Personally I would place the tone control before the circuit." I mean VOLUME pot. Now it should make sense.

I latter learned that the volume pot should indeed be placed after the circuit.

Please read the thread before posting.

 

[Nico Ras]

Generaly I would say forget about the tone controls...
I would suggest looking at Rod Elliot's project 88.
It uses one more opamp though, but will give you, fixed input and output impedances regardles of pot position, as it is also stuck between 2 buffers.
And it also has a balance contol. I think balance and volume is more than sufficient.

I have mine powered of a 2 x 2.5VA PCB mount transformer if you can believe that, and it sounds sweet.

I get the destinct feeling that diyaudio sometimes touch the minimalist approach that you read about in magazines. I honestly don't think it is about this at all.

DIY is the ability to tweak something until you are satisfied with what you hear and that is why it is not available off the shelf.

It is a little pointless to have the system that sounds crappy just because you think minimalist is the way to go.

If your speaker is a little inadequate on a song was recorded poorly and does not give you the foot tapping urge, the DIY guy can twiddle a knob and start enjoying it.

The minimalist eaither live with it arguaing that it is what it is supposed to sound like.

Kind regards

Nico

 

[Nico Ras]

Nor do I. It was a TYPO. That's why I wrote:



I latter learned that the volume pot should indeed be placed after the circuit.

Please read the thread before posting.

Sorry PHP.

 

[Nico Ras]

Sorry again PHN, I should put my glasses on

 

[ppcblaster]

Help on this one

What do you think of this

 

[Fenris]

Ick. Please don't use a variable pot in the feedback loop of an opamp. Only bad things can come of this. The original Baxanall tone control is a well established and proven circuit and incorporating it into the feedback loop of an opamp is a good use. Buffering before the tone control is a good way to make the impedance more predictable, and personally I like to add gain first and volume control last to reduce noise. I just did it for a bass guitar preamp and it worked very well. Also, most of the stuff on Rod Elliot's site is pretty good in theory too, although personally I think his PCB layouts could be better designed.