Bi-amping With "Y" Splitter: Any Impedance Problem?

[Ron Resnick]

For our electrical engineer members: Does using a "Y" splitter on an interconnect cable to direct a pre-amp output signal to two different amplifiers for bi-amping cause any impedance problem?

Does having the dual amplifier loads derived from the same interconnect alter the source/load impedance seen by the input of each amplifier?

Thank you!

 

[JohnP]

For our electrical engineer members: Does using a "Y" splitter on an interconnect cable to direct a pre-amp output signal to two different amplifiers for bi-amping cause any impedance problem?

Does having the dual amplifier loads derived from the same interconnect alter the source/load impedance seen by the input of each amplifier?

Thank you!

It may or may not be a problem, but the impedance definitely changes. For example, I have a solid-state amplifier I use to drive my sub. It has an impedance of around 10K ohms. I also have a tube amplifier I use to drive my Quads in my system. It has an impedance of approximately 100K ohms. The 100K load is an easy load to drive but when I add the 10K load of the solid-state amp, the load is more difficult to drive. As a consequence, the pre-amp I use should have a low output impedance. If I only drive the tube amplifier, I don’t need the pre-amp to necessarily have a low output impedance. Hope this helps.

John

 

[Ron Resnick]

Thank you, John.

Yes, that's what I was expecting.

I just checked the input impedance of the transistor amplifier in question, and it's 200,000 ohms, so that should be fine.

Are you using a simple "Y" splitter to split the signal to the solid-state amp for the subwoofer and to the tube amp for the speakers?

 

[JohnP]

Thank you, John.

Yes, that's what I was expecting.

I just checked the output impedance of the transistor amplifier in question, and it's 200,000 ohms, so that should be fine.

Are you using a simple "Y" splitter to split the signal to the solid-state amp for the subwoofer and to the tube amp for the speakers?

Yes

 

[audio.bill]

For our electrical engineer members: Does using a "Y" splitter on an interconnect cable to direct a pre-amp output signal to two different amplifiers for bi-amping cause any impedance problem?

Does having the dual amplifier loads derived from the same interconnect alter the source/load impedance seen by the input of each amplifier?

Thank you!

When using a Y adapter on a preamp output to connect to two power amps, the effective load seen by the preamp is determined by the formula of their impedance PRODUCT/SUM. For example, connecting an amp with a 100,000 ohm input impedance along with another amp of 50,000 ohms, the resultant impedance seen by the preamp is (100K x 50K) divided by (100K + 50K) which equals 33,333.33 ohms. This makes sense since the preamp will see the two loads in parallel, having to provide current for both so the resultant load is lower than either amp on its own.
Hope that helps!

 

[Robh3606]

You are driving two amps from a single source full range. That is not Bi-Amping it's just driving two amps from a single source.

Rob

 

[Holmz]

Thank you, John.

Yes, that's what I was expecting.

I just checked the output impedance of the transistor amplifier in question, and it's 200,000 ohms, so that should be fine.

Are you using a simple "Y" splitter to split the signal to the solid-state amp for the subwoofer and to the tube amp for the speakers?

200k seems like it is a very high output impedance.
I would expect an input impedance more like 200k, not the output impedance.

Ideally the output impedance of the preamp is more like in the 1k ohm range… hundreds of ohms to maybe a few k-ohms.
A very high output impedance makes the cables become more of a load for the preamp, and the cables and preamp should not really be designed to be affecting the load.

 

[DonH50]

For our electrical engineer members: Does using a "Y" splitter on an interconnect cable to direct a pre-amp output signal to two different amplifiers for bi-amping cause any impedance problem?

Does having the dual amplifier loads derived from the same interconnect alter the source/load impedance seen by the input of each amplifier?

Thank you!

Thank you, John.

Yes, that's what I was expecting.

I just checked the output impedance of the transistor amplifier in question, and it's 200,000 ohms, so that should be fine.

Are you using a simple "Y" splitter to split the signal to the solid-state amp for the subwoofer and to the tube amp for the speakers?

Depends on the preamp and amplifiers. Usually they play well together, but some combinations such as a tube preamp and some SS amps might not. I assume you mean the input impedance of the amplifiers is 200k-ohms, yes? If so, I can't imagine that's a problem for anything; the parallel combination is still 100k-ohms, acceptable for most tube and all SS preamps I have seen.

If the two amps are identical, then the preamp will see one-half the input of each amplifier as the load. If they are different, then if R1 is the input impedance of one amp and R2 the input impedance of the other, then the load the preamp sees will be:

Rload = R1 * R2 / (R1 + R2)

HTH - Don

 

[Audiohertz2]

For our electrical engineer members: Does using a "Y" splitter on an interconnect cable to direct a pre-amp output signal to two different amplifiers for bi-amping cause any impedance problem?

Does having the dual amplifier loads derived from the same interconnect alter the source/load impedance seen by the input of each amplifier?

Thank you!

If its a Tooby preamp you will hear a tonal balance change due to the lower parallel impedance being driven and cable RLC .

SS preamps are less affect but you may also notice a slight tonal balance change as the same cable RLC effect will come into play..

 

[Ron Resnick]

Yes, I meant 200,000 ohms input impedance. Thank you.

 

[Holmz]

Yes, I meant 200,000 ohms input impedance. Thank you.

You sort of need to also state the output impedance of the preamp to work things out @Ron Resnick .

This is why those passive preamps can be very different sounding.
As the volume goes down the output impedance goes up and up, and then the cables start to become more of a contributor to the load.
Whereas a preamp with an output buffer maintains a constant output impedance, and less of an affect.

Doubling the load with a “Y” should have little to no sonic effect with the average preamp that is a low output impedance.
But it would not surprise me if there are preamps with high output impedance that I am unaware of.

 

[Audiohertz2]

@Holmz ,

Its not double it’s actual half load being seen when paralleling with a Y adapter ..

 

[DonH50]

@Ron Resnick is this a passive preamp? That would greatly change my answer... I have an analysis of that sort of situation over on ASR that takes into account the passive volume control with source and load impedances. A passive control can be (not always "is") high impedance and thus much more sensitive to the load (amp input) impedance.

This is the link to the article: https://www.audiosciencereview.com/forum/index.php?threads/attenuator-bandwidth.34268/

 

[Holmz]

@Holmz ,

Its not double it’s actual half load being seen when paralleling with a Y adapter ..

The impedance is half, so the load is twice… assuming that “load” refers to current.
Semantics… I suppose ?

(With a short would being considered as “an ‘ell of a load.”)

 

[Ron Resnick]

You sort of need to also state the output impedance of the preamp to work things out @Ron Resnick .

This is why those passive preamps can be very different sounding.
As the volume goes down the output impedance goes up and up, and then the cables start to become more of a contributor to the load.
Whereas a preamp with an output buffer maintains a constant output impedance, and less of an affect.

Doubling the load with a “Y” should have little to no sonic effect with the average preamp that is a low output impedance.
But it would not surprise me if there are preamps with high output impedance that I am unaware of.

Let's say the output impedance of the preamp is 1000 ohms.

 

[DonH50]

Let's say the output impedance of the preamp is 1000 ohms.

A 1k source (which is fairly high) into a 100k load (for two identical amps of 200k input impedance) should not be a problem unless you have very long cable runs. A 20-foot run of typical cable (30 pF/ft, on the high side) is a high-frequency corner of about 60 kHz. The low-frequency (DC) loss is less than 0.1 dB.

HTH - Don

 

[Ron Resnick]

One amplifier has an input impedance of 200,000 ohms, and the other amplifier has an input impedance of 100,000 ohms. So I think the calculated input impedance seen by the preamp is 66,000 ohms.

The interconnect run is 50 feet long. I am using low capacitance cable.

 

[Audiohertz2]

Wait not matching amplifiers ...!!!

 

[bonzo75]

Wait not matching amplifiers ...!!!

No he is trying to keep Jadis for midrange and have the Westminster or Hegel for power.

 

[Ron Resnick]

Wait not matching amplifiers ...!!!

Matching amplifiers? What fun is that?