A suggestion for the PT-100

[jj2106]

I would like to make a suggestion regarding the TA-100. How about separating the preamp from the amp?

Personally, looking at the rear panel, I would trade the summed outputs for an input to the power amp.

This would make it possible to design a multi-way loudpseaker system, and use the on-board amplifier for the tweeters only.

For example, a two-way active system could be designed using the TA -100, an external DSP (www.minidsp.com for example), and an A-100, A-150 or A-300 amplifier depending on woofer efficiency.

The line-level output and input could be linked by a set of external jumpers for ordinary stereo amplification.

This is common on many receivers.

Hope this raises some interest.

Jean-Jacques

PS: I know a PT-100 and an A-500 (or A-700 for three-way speakers) will do more or less the same, but with identical power an all channels, and limitations on total power.

[jj2106]

Nobody interested at all?

[leonski]

EMO is built to a strict price point. Every feature and espeically extra wiring / connectors / features can cost money to make. Few users would ever use preout / main in plugs.

But I DO think it's a good idea. And not just for biamp duties but so simply replace the amp with something more powerful for less sensitive speakers or use in larger spaces.

My Pioneer SX-727 stereo receiver had such jumpers. I'd remove them when going away for weekends to keep the idiot room mates buddies from destroying the system.


Too much to go into about biamping, but a low-powered amp is of limited utility in such a setup.  This 'depends', of course, on many other factors.   You might be able to get away
with it if you crossed fairly high to limit the amount of power needed.    You can, of course, use the MiniDSP as your 'splitter' and apportion power as you see fit with new amps.
My setup is a PAIR of same stereo amps feeding 2-way speakers.   But the crossover is fairly low @600hz.      
And if you check around, you'll see that most of the new generaton of stereo preamps also have built-in DACs and Bass Managment.     Very useful stuff.  

[jj2106]

Thanks for this input and your moral support.
I agree that any product must be built to a strict price point.
This is why I was suggesting to get rid of the summed subwoofer ouputs, and reassign the two existing RCA sockets to amp-in.
This would simplify the circuitry, not complicate it.
Forgetting about my personal problem, many high-quality subwoofers have built-in filtering, and could be used in association with the PT -100 configured as proposed  (don't know about Emo, though; I'm only interested in their excellent electronics)..
And I don't believe the power of the PT-100 is inadequate; if it were, why would Emo make it?
For example, I'm looking at no more than 102dB SPL per channel, wich means 10W RMS for a speaker sensitvity of 92dB SPL.
Finally, I know there are other receivers at a reasonable price point, but none of them offers separate amp/preamp, Linkwitz Transform, filters with different Qs and slopes, PEQ etc...
I'd like to use Emo, please don't discourage me...
Kind regards,
J -J

[leonski]

MOST speakers are much more sensitive than my panels. And for 'intended use', the power is adequate, though I'm not a fan of rating 1% distortion, which is IT for an amp, IMO.

If you want all those filters, you are probably going to end up with MiniDSP or similar.

As for your power calculation? Keep in mind what is generally called 'crest factor'. You might (might) cruise along at your 10watts, but add a 10db PEAK and you are at the 100 watt level AND redline for the amp.
+10db is roughlly 10x the output power. More realistically, you may cruise @2 watts, and it'll be louder in-room. Don't forget the speakers add (+3db?) and you have 'room gain' since the room reflects sound BACK to the listener.
This all tends to work in your favor. 92db speakers are fairly sensitive. (NOT efficient)

sound.whsites.net/bi-amp.htm

This is part 1 of what I think is a 3-parter. In it, quite a few questions are addressed, as well as Power Requirements of bi or tri amped speaker systems, based on crossover points.


I think the point of the 'summed' sub outputs is to relieve some of the stress on the amp. I keep coming back to 'intended' use. The smaller box speakers most will buy for this amp won't have much bass output. So the sub is a good idea. And as music is mixed these days, it is probably
almost always a MONO output below maybe 80hz. The harmonics from L and R speakers give the stage width and you'll never localize the sub, by ear. Ideally, the receiver should low-cut the main speakers, to allow the sub to do its job without creating mush in the crossover region.

Sure, you CAN stay in the EMO family of gear for your purposes, just maybe NOT with the TA-100 as a centerpiece. That might end up in the bedroom doing TV sound duties and low-level bedtime music. Or even sent to school with the Eldest, as he needs a 'dorm system'.

[jj2106]

All that makes a lot of sense.
But I don't see as many potential problems as you do, in my application of course.
First of all, I will definitely use a miniDSP, with four channels of amplification in total.
The loudspeakers shall be my old faithful JBL-L122A woofer and either a Markaudio Alpair -12P, or a Fostex FE168ESigma full-range driver (crossover frequency between 100 and 140Hz).
For both of these, I need about 12V RMS of amplification  (without EQ) to achieve my magic 102dB.
I am very much in favour of drivers with similar sensitivity, because they give similar dynamics (see www.tnt-audio.com/clinica/driver_air_volume_acceleration_e.html)
I do agree that there will be 10dB peaks, but on classical music, they will remain...well, peaks.
So, I maintain that the PT-100 amplifiers can do the job for the full-range speakers.
The woofers, conversely, will need equalization at the bottom end of the spectrum, because they will be used in a sealed enclosure, and their Qts is very low  (0.231).
Therefore, the miniDSP will provide a Linkwitz transform with a target Q of 1 and a first order filter at the same target frequency (32Hz).
I will therefore end up with a third order Butterworth alignment, which will protect my woofer against overexcursion.
And this is where I hit the power problem, because the combination of the LT and the 6dB filter will generate a 5.3 dB gain.
So, I need about 23V RMS of amplification, excluding peaks.
And that's where I think a nice BasX A-300 would give the required headroom. Out of interest, 20*LOG(sqrt(175/50)= 5.44 dB. Bingo!
To be honest with you, I could buy a TA-100 and a BasX-A100 to do what a PT-100 does, but I may as well buy a PT- 100 and have it converted locally by the addition of 2 RCA sockets on the rear panel, and a simple cabling mod inside.
The warranty will be void, but I don't care.
Your comments are obviously more than welcome.
J-J

[leonski]

Years ago I had a Kenwood integrated amp. Model KA-7100 was sold in the mid-late 70s. It is still in service with my nephew. Amazing.

But the point? Amp was clearly built in sections. I identified the 'jumper' from pre to main and ran some RCA cables out from the pre section to my new power amp, a Carver at that time.

Easy.

But today? I'd have to look inside and see if the pre / main sections were easily disconnected or you risk fatal damage to the unit.

Me? I'd go all separates and at least Double the amount of power I thought I needed. At Least. Calculations are all well and good UNTIL they meet a real room. Crossover point is VERY important in the apportioning of power per 'way'.
Your near-6db bump is 2 'doublings' and represents a LOT more power.

You are going to change the woofer from a ported to sealed enclosure? I wish I could remember the TS parameters to determine 'correct' use of a woofer. Some ratio? Can't remember off hand and I'm not about to look it up, but just make sure
your woofer will run properly in a sealed enclosure. You're going to add a sub below the woofer cutoff? It's not clear.

[jj2106]

Hi Leonski,
Many thanks for this very interesting discussion.
You are right, modding a TA-100 maybe a risky exercise; moreover, we don't know the respective impedances of the preamp and poweramp sections.
Chances are I'll go for separates  (PT -100, miniDSP, A -100 and A -300).
With regard to power, 102dBSPL per speaker means 108dB for two; deafening in my relatively small room (albeit with a very high ceiling : 21'L x 19'W x14'H).
I forgot to mention that I already considered 102dB as a peak value, but without distortion.
Regarding my drivers, you shouldn't worry either. I use my own Excel models, which give me all the required details, including EQing, power and voltage, impedance (useless with active filters) and so on.
In case you wonder, I'm 68 years old and not exctly a newbie.
I have the T/S parameters of all JBL drivers (available on the web), and I want to reassure you: any driver models well in a sealed enclosure with the help of a Linkwitz Transform.
The penalty to pay comes under the form of additional power requirements; in my case, I need a 1.85 voltage ratio (or 5.3dB).
That' s virtually exactly the difference between 50W and 175W; hence the choice of an A100 and and an A-300. The output level of the miniDSP on the woofer channels will be reduced by 5dB in order to avoid digital clipping and allow the power amps to use their nominal gain.
To anwer your last question, I will not use a separate subwoofer; with the chosen alignment, my 12" woofers will give me -3dB@32HZ, and -6dB@26Hz, which satisfies me.
Thanks again,
Jean-Jacques

[garbulky]

Mar 18, 2018 5:01:05 GMT -5 jj2106 said:

I would like to make a suggestion regarding the TA-100. How about separating the preamp from the amp?

Personally, looking at the rear panel, I would trade the summed outputs for an input to the power amp.

This would make it possible to design a multi-way loudpseaker system, and use the on-board amplifier for the tweeters only.

For example, a two-way active system could be designed using the TA -100, an external DSP (www.minidsp.com for example), and an A-100, A-150 or A-300 amplifier depending on woofer efficiency.

The line-level output and input could be linked by a set of external jumpers for ordinary stereo amplification.

This is common on many receivers.

Hope this raises some interest.

Jean-Jacques

PS: I know a PT-100 and an A-500 (or A-700 for three-way speakers) will do more or less the same, but with identical power an all channels, and limitations on total power.

You can use a splitter on the analog outputs of the ta-100. But seriously, if you are looking to do some sort of active amping using a separate amp for the tweeter and then using another amp for the other two is imo a bad idea. Using identical amps would be a better way of doing things.

[leonski]

Mar 29, 2018 9:42:27 GMT -5 garbulky said:

Mar 18, 2018 5:01:05 GMT -5 jj2106 said:

I would like to make a suggestion regarding the TA-100. How about separating the preamp from the amp?

Personally, looking at the rear panel, I would trade the summed outputs for an input to the power amp.

This would make it possible to design a multi-way loudpseaker system, and use the on-board amplifier for the tweeters only.

For example, a two-way active system could be designed using the TA -100, an external DSP (www.minidsp.com for example), and an A-100, A-150 or A-300 amplifier depending on woofer efficiency.

The line-level output and input could be linked by a set of external jumpers for ordinary stereo amplification.

This is common on many receivers.

Hope this raises some interest.

Jean-Jacques

PS: I know a PT-100 and an A-500 (or A-700 for three-way speakers) will do more or less the same, but with identical power an all channels, and limitations on total power.

You can use a splitter on the analog outputs of the ta-100. But seriously, if you are looking to do some sort of active amping using a separate amp for the tweeter and then using another amp for the other two is imo a bad idea. Using identical amps would be a better way of doing things.

Amp power needed REALLY depends on crossover frequency.     Gain, which I was taught was a bigger issue, can easily be addressed using the MiniDSP

[garbulky]

Mar 29, 2018 10:27:41 GMT -5 leonski said:

Mar 29, 2018 9:42:27 GMT -5 garbulky said:

You can use a splitter on the analog outputs of the ta-100. But seriously, if you are looking to do some sort of active amping using a separate amp for the tweeter and then using another amp for the other two is imo a bad idea. Using identical amps would be a better way of doing things.

Amp power needed REALLY depends on crossover frequency.     Gain, which I was taught was a bigger issue, can easily be addressed using the MiniDSP

Yeah but you are then going to be using different amps - likely even different brands and trying to blend those together in to one speaker somehow.

I've tried passive biamping with two different amps - a Yamaha and an Emotiva and they just didn't quite gel. Just more trouble than its worth. Using a A-500 would be a better idea. You can split the analog outputs on the TA-100 to get more outputs.

[leonski]

biamp......With either a passive or active LL crossover.
No way to correct for gain with the speaker crossover still in the circuit.

I have a buddy with biamp Magnepan MG20s. EMO amp on bass and Tubes on top. It doesn't 'prove' anything, but it sure is seamless.

[jj2106]

As far as I 'm concerned, using an A -150 and an A-300 is not an issue. The gain on the respective miniDSP outputs will just be different.
Plus, those two amps belong to the same family.
I 'm even prepared to bet that their schematics are identical, with just a different power supply and different output transistors.
Only Keith Levkoff could confirm or disconfirm, but I doubt he'll be willing to.
J-J

[leonski]

Yes. 'scale' is one way to make a bigger amp. Add more output devices? and a more robust and possibly higher voltage PS. Done.

Pass makes good use of this technique in some of his DIY designs. Check out 'First Watt' among others.

We must be careful not to conflate gain with power. 2 amps with the same gain (most of current EMO family?) can have quite different amounts of power.

And I thought of my answer, above, which isn't quite right. My Parasound amps have gain controls at EACH input of each channel. I could turn the bass or treble down
some if I thought it was 'too hot' or thought I had some kind of gain issue. I don't, and do leave them 'wide open'. A possible way forward would be to swap the potentiometers for
a stepped level control. Nice. repeatabble and very exact.

[jj2106]

I definitely intend to use a quad stepped attenuator between the miniDSP outputs and the A-150/A-300 inputs.
But level pairing will probably be done on the miniDSP, because I don't like the idea of fixed additional attenuation on the analog side, although this is obviously possible.
By the way, talking about gain, I sent a message to Emo, who haven't answered yet.
Unless I'm wrong (quite possible), gain cannot be identical between two amplifiers with the same input sensitivity and different power ratings; this is a contradiction.
What's  your opinion?
J-J
Edit: before you stand a chance of reading this, let me support my question with a few calcs, taking the A-xxx family as an example.
dBgain=29dB (as per the manual)
So V/v gain=10^(29/20)=28.18383
Now input sensitivity=1.2V (as per the manual)
Therefore, output voltage=28.18383*1.2=33.821V
And output power=33.821^2/8=143W
That is quasi exactly the advertised power of the A-300  (150W)
But neither the A-150 (75W) nor the A-500/700 (110W) can share both the same sensitivity and the same gain.
All calculations above are RMS per channel across an 8-Ohm load.

[leonski]

Let me mull this over. Perhaps a good reason to use identical (same) amps when doing an active biamp.

As for the gain situation? I will just note for now that you will never turn an amp up ALL the way.

Also, the way I understand it, an amp is 'fixed' gain. No matter what the input level, it applies the same amount of gain to it.
So, an amp might have ratings of input / output, but it is NOT a 'Variable Gain' device.

Just running that out to see how it fits in.

[jj2106]

Let me try to reply to each point.
Not all muti-amped speakers use identical amplifiers. I that were the case, a setup composed of an 84dB woofer, a 104dB horn tweeter, and a midrange in between would require 20dB (!) of passive attenuation at the input of the tweeter amp (and perhaps 10dB on the midrange amp). A real waste of resources, not to mention the SNR.
Second point: of course, you will not normally turn an amp up all the way; but it is desirable, me thinks, to operate all amplifiers at the same fraction of their possibilities. This being said, we all know that the musical energy is fairly concentrated in the midrange, at least with classical music. But some of us prefer heavy metal (not me)!
Third point, the gain. Of course, an amplifier is fixed gain; i.e. assuming no input attenuator ( which is the case of the A -xxx family, except the A -100, which is very different), a given input voltage will always translate into the same output voltage :Vout/Vin=Vgain , dBgain=20*LOG(Vgain), and of course, Vgain=10^(dBgain/20)
So I estimate the gain of the various models as follows:

A-300:
Vout= (150*8)^0.5=34.64V
Vin=1.2V
Vgain=34.64/1.2=28.87
dBgain=20*LOG (28.87)=29.2dB

A -150:
Vout= (75*8)^0.5=24.49V
Vin=1.2V
Vgain=24.49/1.2=20.41
dBgain=20*LOG (20.41)=26.2dB   No surprise, this is 3dB less than the A-300

A- 500/A- 700:
Vout= (110*8)^0.5=29.66V
Vin=1.2V
Vgain=29.66/1.2=24.72
dBgain=20*LOG (24.72)=27.9dB

I really hope Emo will give us their answer
J-J

[jj2106]

I finally got the information from Emo.
All A-xxx models have the same gain, but different input sensitivities.
Here is what Keith says.

Quote:
Obviously there's a typo in one of the manuals.
I think you'll find that the GAIN on all the amps is 29 dB as specified.
(And the output power ratings are accurate and correct.)
A few models may be MORE sensitive than specified... which is actually not considered to be wrong.
Note that input sensitivity is not an especially important spec...
It essentially tells you the maximum amount of signal you will require to drive the amp top full output.
(So, for example, if an amplifier will reach full power with 600 mV input, it isn't wrong to spec it at 1V - because 1V is
"more than enough to drive it to full output" - which means that it simply "exceeds" the "1V spec" by being more sensitive than specified.)
You will find that any of the BasX amps can be driven by any more or less normal preamp.
(There is no specific reason to "match" output and input levels as long as your preamp can deliver more than the necessary voltage.)
Unquote.

I am dubious, because as far as I'm concerned, published specs should be comprehensive and consistent.
Here is an example: www.qsc.com/live-sound/products/power-amplifiers/gx-series/gx3/
I have done the calcs, and they are OK.
Also, I would prefer to have the same sensitvity and different gains on all models, rather than the opposite.
This will not prevent me from buying Emo gear, but it means that some experimental tweaking will be needed on the MiniDSP. Not ideal.
Anyway, this is where I am.

J-J

[leonski]

Are the 'gain' promblems you see coming anything that can't be fixed with test tones and a calibrated mic?

[jj2106]

They sure can. Not a real issue. Just my reaction to inaccurate specs.
Thank you, Leonski.
J-J