Resistor recommendations

[Roscoe Primrose]

Walt,

While searching for shunt attenuators, I found this from GoldPoint. They say, source sees variable impedance with shunt regulators.
https://goldpt.com/attenuator_types.html

If that matters to your source, get a better source...

Roscoe

[Roscoe Primrose]

In another thread I talked about a shunt attenuator where there is no pot or stepped attenuator in the signal path -- just a high quality resistor such as that noted above.

BAT 3Ki Shunt Attenuator.pdf

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Half of the pot is still in the signal path....

Roscoe

[tomp]

Walt,

While searching for shunt attenuators, I found this from GoldPoint. They say, source sees variable impedance with shunt regulators.
https://goldpt.com/attenuator_types.html

If that matters to your source, get a better source...

Roscoe

Amen to that.

[Cogito]

If that matters to your source, get a better source...

Roscoe

That’s not the point they were conveying.

Although behaving just like a ladder attenuator for each switch position, shunt attenuators vary the impedance as seen by the signal source. To minimize this, one wants to choose a large value input-to-output resistor. This can conflict with the need to have a small input-to-output resistor so that the attenuator will pass the maximum signal level at high volume settings (and have less effect on high frequency signals).

This type of attenuator is best used with low impedance signal sources, thereby minimizing the effects of the attenuator’s own varying input impedance and allowing a smaller value for the input-to-output resistor.

Shunts can do strange things to the sound with impedance changes when turning them up/down.

These things as volume controls in a preamp stage is ok, as the shunt regulator is followed by amplification stage which also reduces the output impedance of the preamp.

With high input and output impedance how do you implement it between amp and speaker or between preamp and amp?

[SoundMods]

Walt,

While searching for shunt attenuators, I found this from GoldPoint. They say, source sees variable impedance with shunt regulators.
https://goldpt.com/attenuator_types.html

I would not find bobbin type WW resistors. However, I found .3W Riedons on digikey.

The source seeing a variable impedance has never been an issue with my BAT 3Ki. But getting the pot out of the signal path rocks!

You might find what you need here:
https://www.ebay.com/sch/i.html?_from=R ... &_osacat=0

Vishay bulk-film resistors are a great second choice -- or even a first choice for that matter. Dale resistors are a good compromise when you can't find the primary goodies. I have inventory -- tell me what your needs are.

[SoundMods]

Walt,

While searching for shunt attenuators, I found this from GoldPoint. They say, source sees variable impedance with shunt regulators.
https://goldpt.com/attenuator_types.html

It just dawned on me. The nice thing about a shunt attenuator it is that it is not something you buy -- you can create one with any pot of choice and value of choice with the signal resistors of choice.

As long as the pot has a logarithmic taper otherwise known as an audio taper you are good to go. If you look at the schematic of the BAT the shunt attenuator has three parts per channel. The pot and two resistors.

Perfect for DIY.

Attachments

BAT 3Ki Shunt Attenuator.pdf

(546.85 KiB) Downloaded 306 times

[Roscoe Primrose]

If that matters to your source, get a better source...

Roscoe

That’s not the point they were conveying.

Although behaving just like a ladder attenuator for each switch position, shunt attenuators vary the impedance as seen by the signal source. To minimize this, one wants to choose a large value input-to-output resistor. This can conflict with the need to have a small input-to-output resistor so that the attenuator will pass the maximum signal level at high volume settings (and have less effect on high frequency signals).

Yes, that's EXACTLY the point they're conveying.....

This type of attenuator is best used with low impedance signal sources, thereby minimizing the effects of the attenuator’s own varying input impedance and allowing a smaller value for the input-to-output resistor.

Shunts can do strange things to the sound with impedance changes when turning them up/down.

These things as volume controls in a preamp stage is ok, as the shunt regulator is followed by amplification stage which also reduces the output impedance of the preamp.

With high input and output impedance how do you implement it between amp and speaker or between preamp and amp?

You completely lost me on that last part.... The amplification stage after the shunt volume control has ZERO affect on the fact that the input impedance seen by the source changes as you change volume.... Not sure why you'd want to use a shunt volume control between the amp and the speakers or between the preamp and amp, why would you want to put a volume control between your preamp and amp, isn't that what the preamp is supposed to do anyway?

Roscoe

[Cogito]

You completely lost me on that last part.... The amplification stage after the shunt volume control has ZERO affect on the fact that the input impedance seen by the source changes as you change volume.... Not sure why you'd want to use a shunt volume control between the amp and the speakers or between the preamp and amp, why would you want to put a volume control between your preamp and amp, isn't that what the preamp is supposed to do anyway?

Roscoe

I am not an expert but this is what I think…..

Typical speaker impedance is 8ohms. Output impedance of the amp has to be 8 oks or lower for proper operation. If you place the shunt regulator with high output impedance, say 1kOhms, between the amp and speaker, would it work properly?

I am using 5-way active system. Preamp does only the volume control. Each speaker’s level needs to be matched still.
For level matching, I have two options:
1. Attenuation network at the speaker
2. Attenuation network between the preamp and the amp along with passive line level crossover network.

It’s my turn for head banging.

[Roscoe Primrose]

You completely lost me on that last part.... The amplification stage after the shunt volume control has ZERO affect on the fact that the input impedance seen by the source changes as you change volume.... Not sure why you'd want to use a shunt volume control between the amp and the speakers or between the preamp and amp, why would you want to put a volume control between your preamp and amp, isn't that what the preamp is supposed to do anyway?

Roscoe

I am not an expert but this is what I think…..

Typical speaker impedance is 8ohms. Output impedance of the amp has to be 8 oks or lower for proper operation. If you place the shunt regulator with high output impedance, say 1kOhms, between the amp and speaker, would it work properly?/quote]

It's not a regulator, it's an attenuator.... And, no, it wouldn't work worth a damn in that configuration.

I am using 5-way active system. Preamp does only the volume control. Each speaker’s level needs to be matched still.
For level matching, I have two options:
1. Attenuation network at the speaker
2. Attenuation network between the preamp and the amp along with passive line level crossover network.

It’s my turn for head banging.

If you want to do it between the amp and the speakers, you're pretty much out of luck using shunt attenuators. For a passive resistive attenuator to work properly, it needs to have an impedance that's at least as high as the source impedance, and lower than the load impedance, preferably much higher and much lower... How do you meet both of those criteria between an amp and a speaker? That's what L-Pads are for....

Between the crossover and the amps, it's easy.....

[Stuart Polansky]

With regards to the assertion that only the series portion of a shunt/series volume control affects sound or "is in the signal path". Not true. In addition to what Roscoe mentioned regarding a variable load being applied to the preamp, the shunt element has current flowing through it. Noise is developed as a result of that current. In my personal experience, the "sound " of that shunt element is audible and not insignificant.

As to Roscoe's question about attenuation a load after a preamp, the purpose would be level matching in a line-level crossover, if I understand the questions asked.

Now the really cool approach would be multiple and identical line stages, each with its own gain control, each filtered to serve the drivers its related amplifier is powering. The challenge is then changing levels without changing relative levels during daily operation, once the balance is determined.

Of course a linear balance pot could be used (or stepped-type control built). The advantage of that approach would be shortening the signal path, always a worthwhile goal.

Stuart