Mixing different amplifiers power with ExaktBox ?

[Guillaume Jamet]

Dear all,

With adequate configuration in Konfig, is it possible to have, for instance, an Akubarik Passive driven by an EB10 and 6100+4200 or AV5125+6100 or some other non-Linn 10ch setup.

Or, on the opposite, all amplifiers channels need to be identical ? need to be all referenced Linn models ?

I couldn't find an answer in the Linn docs nor in this forum. And as I do not yet have an ExaktBox, I can't explore the software.

Thanks in advance.

 

[MickC]

It’s easy if you use only Linn amps as they all have the same gain. I’ve used different amps in the past in Aktiv setups, although I’ve never used Exakt.

Mick

 

[Guillaume Jamet]

Thanks MickC for pointing this out!

I went checking in Linn docs :

AV5125 : 28.6dB

For Majiks and Akurates : The range depends on RCA/XLR versions apparently :



So, it would mean that my AV5125 would'nt match with the XLRs.

It was very helpful. Thanks

 

[MickC]

Most Linn amps (presuming we’re limited to that for the time being) with XLR connections have unbalanced too, if I remember correctly, so it could be possible to simply use phono leads rather than XLR.

Mick

 

[arm]

For a short period I drove M140s through anAB10 with a m6100 on mid and bass ,A4200 on tweeters. Sounded unbalanced even after trimming the Akurate channels to -4 using the trim dials on the back

once I added another A4200 everything was right as rain. 

 

[Guillaume Jamet]

@arm Thanks. I see you have the sort setup I'm targeting ;-)   

As you have access to Konfig for AEB10, could you confirm that there is no option to trim the line output level  to account for different amp's gains ?

Thanks

 

[arm]

I only have access of my ADSM through Konfig. Didnt know access to the AEB10 was avaible, so can't confirm that amps are trimmable this way. Not sure why Linn would give both options except that the trim dials on their Amps are legacy issues?

 

[DavidHB]

I only have access of my ADSM through Konfig. Didn't know access to the AEB10 was available, so can't confirm that amps are trimmable this way. Not sure why Linn would give both options except that the trim dials on their Amps are legacy issues?

That is correct. There are no user options for Exakt Boxes (or Exakt speakers) that I am aware of.

Any facilities for output adjustment on the Linn amps are, as you say, legacy provision to support Aktiv installations; for Exakt, these out to be set to zero adjustment, as that is what the software will assume. So far as I know, the Exakt software is unaware of which make/model of amplifier is in use and unable to make adjustments for different amplifier configurations. This means that the more closely matched (in terms both of tonal balance and output gain) the channels are, the better. That said, I have heard several Exakt setups with a mix of Linn Chakra amps (typically Mx100 and Ax200 models) which produced very satisfying results. Which amp channels you put which speakers on will, I guess, vary between speaker models. There is a case for putting the bass units on x200 channels, as bass drivers require the most power; otherwise the predominant recommendation is to put either the tweeters or the midrange units on the better amp channels. Trial and error experimentation is likely to be needed; my dealer (Chris of Hidden Systems) does it all the time.

David

 

[BB1]

So, it would mean that my AV5125 would'nt match with the XLRs.

It would match, because the XLR output voltage of the Exaktbox is twice as high as its RCA output voltage. A factor of 2 equals 6 dB, which matches exactly the gain difference between the amps.

In other words, an amp with XLR inputs and a voltage gain of 22.6 dB plays as loud as an amp with RCA inputs and a voltage gain of 28.6 dB.

Most Linn amps (presuming we’re limited to that for the time being) with XLR connections have unbalanced too, if I remember correctly

Ax200s are either balanced or unbalanced.

 

[MickC]

Ak200s are either balanced or unbalanced.

Ah right - cheers. My experience of Linn amps with balanced inputs is limited to 2250s, Twin and Solo, all of which offer both types of connection.

Mick

 

[BB1]

So far as I know, the Exakt software is unaware of which make/model of amplifier is in use and unable to make adjustments for different amplifier configurations.

One exception are 350s driven by KEBs. They don’t have unbalanced outputs and if using their balanced outputs with unbalanced amps, the output valume (same volume setting on the DSM provided) is 6 dB higher than in an all-balanced setup. In general that’s not a problem at all, but as the bass of the 350 is driven directly by one balanced channel of the Exaktbox, it would be 6 dB to quiet. This is handled in the speaker filters, i.e. there are two variants of the filter ("Klimax 350 with Single-ended Amplifiers Filter" and "Klimax 350 with Balanced Amplifiers Filter").

 

[Guillaume Jamet]

It would match, because the XLR output voltage of the Exaktbox is twice as high as its RCA output voltage. A factor of 2 equals 6 dB, which matches exactly the gain difference between the amps.

In other words, an amp with XLR inputs and a voltage gain of 22.6 dB plays as loud as an amp with RCA inputs and a voltage gain of 28.6 dB.

Ax200s are either balanced or unbalanced.

Thanks for pointing this but for me the gain in dB for doubling is

> 10*log(2)/log(10)
[1] 3.0103

Is it because you also have to 2x voltage because of the balanced line ?

 

[DavidHB]

One exception are 350s driven by KEBs. They don’t have unbalanced outputs and if using their balanced outputs with unbalanced amps, the output valume (same volume setting on the DSM provided) is 6 dB higher than in an all-balanced setup. In general that’s not a problem at all, but as the bass of the 350 is driven directly by one balanced channel of the Exaktbox, it would be 6 dB to quiet. This is handled in the speaker filters, i.e. there are two variants of the filter ("Klimax 350 with Single-ended Amplifiers Filter" and "Klimax 350 with Balanced Amplifiers Filter").

I realise that this is nit picking, but this point (of which I was unaware, as my budget runs to neither KEBs nor 350s, so thanks for the info) is surely just an aspect of the way in which the software handles the relationship between the Exakt engine and the speakers, in which it, so to speak, takes the intermediate amplification as a given. The servo bass on the 350s, though it obviously involves amplification, is part of the speaker. I think that the OP was looking for Konfig-style settings related to the amplifiers, and there aren't any of those.

David

 

[BB1]

Thanks for pointing this but for me the gain in dB for doubling is

> 10*log(2)/log(10)
[1] 3.0103

Is it because you also have to 2x voltage because of the balanced line ?

If e.g. calculating voltage or current values, you have to multiply by 20, not 10. The factor 10 comes into play when calculating power, i.e. the maximum output power of an Ax200 is 3 dB higher than the output power of an Mx100 (200 W vs. 100 W).

The definition for decibel with respect to power is:
dB = 10 * log (P2 / P1)

Electrical power is defined as
P = U * I
which could be written with Ohm’s law as
P = U2 / R

If assuming that R2 and R1 are identical, the above formula becomes
dB = 10 * log ((U22 / R) / ( U12 / R))

R can be cancelled out and therefore
dB = 10 * log (U22 / U12) = 10 * log ((U2 / U1)2)

Finally
n * log (x2) = 2 * n * log x

and therefore
dB = 20 * log (U2 / U1)

 

[BB1]

Ah right - cheers. My experience of Linn amps with balanced inputs is limited to 2250s, Twin and Solo, all of which offer both types of connection.

Mick

At the time I’ve bought my A4200s they were acting as external amplification for an MEB-I, hence I had to choose the unbalanced variant…

 

[Guillaume Jamet]

If e.g. calculating voltage or current values, you have to multiply by 20, not 10. The factor 10 comes into play when calculating power, i.e. the maximum output power of an Ax200 is 3 dB higher than the output power of an Mx100 (200 W vs. 100 W).

The definition for decibel with respect to power is:
dB = 10 * log (P2 / P1)

Electrical power is defined as
P = U * I
which could be written with Ohm’s law as
P = U2 / R

If assuming that R2 and R1 are identical, the above formula becomes
dB = 10 * log ((U22 / R) / ( U12 / R))

R can be cancelled out and therefore
dB = 10 * log (U22 / U12) = 10 * log ((U2 / U1)2)

Finally
n * log (x2) = 2 * n * log x

and therefore
dB = 20 * log (U2 / U1)

Agreed! Crystal clear! It was me ignoring that the gain of amp was given in power.Thanks!

 

[BB1]

I realise that this is nit picking, but this point (of which I was unaware, as my budget runs to neither KEBs nor 350s, so thanks for the info) is surely just an aspect of the way in which the software handles the relationship between the Exakt engine and the speakers, in which it, so to speak, takes the intermediate amplification as a given. The servo bass on the 350s, though it obviously involves amplification, is part of the speaker. I think that the OP was looking for Konfig-style settings related to the amplifiers, and there aren't any of those.

David

My reply wasn’t meant as nit picking, but to mention were gain factor differences are currently handled. I’m sorry if you’ve perceived this as nit picking. It wasn’t my intention.

Here’s an excerpt of the Akubarik filter:

<xover version="3">
<info>
<design_name>linnakubarik</design_name>
<designer>linn</designer>
<version>4</version>
<variant>Standard</variant>
<compatibility>External</compatibility>
</info>
<design>
<speaker>
<gain>9.5</gain> // overall gain
<drive_unit>
<name>IsoBass</name>
<xover_channel>0</xover_channel>
<output_channel>0</output_channel>
…
<gain>-1.5</gain> // channel specific gain
</drive_unit>
<drive_unit>
<name>UpperBass</name>
<xover_channel>1</xover_channel>
<output_channel>1</output_channel>
…
<gain>2</gain> // channel specific gain
…
</drive_unit>
…


The overall gain is used for providing the same loudness for different speakers at the same volume setting of the DSM. The channel specific gain is part of the crossover design. If different gain factors of the amps in use need to be taken into account, these gain settings needs to be adjusted.

Of cause there is no user setting for doing this, but someone with access to Exakt Design might easily make the required changes (pure speculation, as I don’t know how Exakt Design actually works).

 

[BB1]

It was me ignoring that the gain of amp was given in power.

Actually the gain of an audio power amp is given as voltage gain. Power gain makes no sense at all, since the input impedance of the amp is very much higher than the impedance of the speaker. The ideal input impedance of a power amp is infinity, i.e. no input power needed at all. Thinking further, this would result in a power gain figure of infinity...

Power gain only makes sense for amps providing an input impedance equal to their load impedance. This is usually true for HF amps working in e.g. a 50 Ohm system (input impedance = output impedance = 50 Ohm).

There’s one figure in the Ax200 manual clearly indicating that 22.6 dB and 28.6 dB are voltage gains: "Input level for clipping" (1.1 Vrms for unbalanced models, 2.2 Vrms for balanced ones). Hence the balanced model allows for twice the input voltage (6 dB) before clipping which perfectly matches to the different gain factors.

 

[DavidHB]

My reply wasn’t meant as nit picking, but to mention were gain factor differences are currently handled. I’m sorry if you’ve perceived this as nit picking. It wasn’t my intention.

No, that's not at all what I meant. You made, as I said, a useful point. I was simply acknowledging that there was an element of nit-picking in my (following) response. I hope that explains things; I'm sorry for any confusion.

David