what about a symasym?
~50W into 8r0.
which JLH? if 10W, then efficient speakers are needed.
4ohm will run out of ClassA current at lower level than 8ohm and low efficiency exacerbates the problem.
Single ended ClassA hard limits (distorts badly) at the ClassA limit.
Push Pull goes from ClassA into ClassAB if the power supply can meet the demand.
~50W into 8r0.
which JLH? if 10W, then efficient speakers are needed.
4ohm will run out of ClassA current at lower level than 8ohm and low efficiency exacerbates the problem.
Single ended ClassA hard limits (distorts badly) at the ClassA limit.
Push Pull goes from ClassA into ClassAB if the power supply can meet the demand.
JHL, and almost well designed Class A unit will eat an AB into the breafast
of course operating within the limits of power not to distort.
Class A audio quality is very special.... the problem is the heat, low power, low efficiency....but audio quality is excelent.
Your class AB will sound alike if you operate the unit while it is operating almost alike a class A amplifier... when operating into a very low power.... 1 or 2 watts depending the amplifier.
Of course a bad class A design will be eated by a good class AB design...... but JLH amplifier is very, very, very good one.
You have to build both, and listening you will realise the one is better to your ears, and i suggest you to try both, will learn a lot, and by yourself.
Compare both, using A to B switching mode... same speaker... same power level.... and reality will come to your brain.
regards,
Carlos
of course operating within the limits of power not to distort.
Class A audio quality is very special.... the problem is the heat, low power, low efficiency....but audio quality is excelent.
Your class AB will sound alike if you operate the unit while it is operating almost alike a class A amplifier... when operating into a very low power.... 1 or 2 watts depending the amplifier.
Of course a bad class A design will be eated by a good class AB design...... but JLH amplifier is very, very, very good one.
You have to build both, and listening you will realise the one is better to your ears, and i suggest you to try both, will learn a lot, and by yourself.
Compare both, using A to B switching mode... same speaker... same power level.... and reality will come to your brain.
regards,
Carlos
Sonic experiences are very hard to explain using words
Unfortunattely, the correct way to decide is to listen both units.
Class A distort less....more pure sound.... less dinamic power... a more pleasant listening.
Your question is an extreme of complexity to answer.... well... i have tried, but long time experience about that subject you will have when you have spent long time listening many units... this is personal, we cannot transfer experience into words or produce a file to travel into internet... this depends on yourself, to listen and learn how to evaluate, to perceive those details...no formula available, not the way people use instructions to make a cake.
The real better one is to have both of them, to evaluate by yourself and to decide by yourself... then you will be absolutelly sure.... you may have different opinnions here... you may love both or hate both... this is also a possibility.
Carlos
Unfortunattely, the correct way to decide is to listen both units.
Class A distort less....more pure sound.... less dinamic power... a more pleasant listening.
Your question is an extreme of complexity to answer.... well... i have tried, but long time experience about that subject you will have when you have spent long time listening many units... this is personal, we cannot transfer experience into words or produce a file to travel into internet... this depends on yourself, to listen and learn how to evaluate, to perceive those details...no formula available, not the way people use instructions to make a cake.
The real better one is to have both of them, to evaluate by yourself and to decide by yourself... then you will be absolutelly sure.... you may have different opinnions here... you may love both or hate both... this is also a possibility.
Carlos
well, I've gone back to read my downloaded copy of the 1996 ClassA and it talks us through increasing power from 10W to 15W into 8r0.
It also reminds one that the single ended can only deliver current upto the bias level.
If you use a 15W into 8r0 single ended amp connected to a 4r0 load then the maximum power delivered to the load is just 7.5W.
I ask again
It also reminds one that the single ended can only deliver current upto the bias level.
If you use a 15W into 8r0 single ended amp connected to a 4r0 load then the maximum power delivered to the load is just 7.5W.
I ask again
BTW 90dB/W/m are not efficient speakers. If they are 90dB/2.8V/m they are even worse.
Andrew
I have told you they have been designed by Geoff Moss to run at 30W per channel into a 4 ohm load. He has given me the necessary instructions to achieve this, so please don't ask that question again.
Anyway I appreciate any comments you would like to make between the 2 amps.
Have you actually heard these 2 amps?
Destroyer X
Thanks for the advice, I agree with what you have said, however it would be nice to hear some opinions as I am not sure I have the time or money to build both as I still also have to build a preamp.
I have told you they have been designed by Geoff Moss to run at 30W per channel into a 4 ohm load. He has given me the necessary instructions to achieve this, so please don't ask that question again.
Anyway I appreciate any comments you would like to make between the 2 amps.
Have you actually heard these 2 amps?
Destroyer X
Thanks for the advice, I agree with what you have said, however it would be nice to hear some opinions as I am not sure I have the time or money to build both as I still also have to build a preamp.
Just some more information to assist in giving advice:
I am a bass player, so obviously the quality of bass sound and tone is number 1 priority followed by drums and percussion and then guitar/saxophone and then other instruments.
Also I notice when playing electric bass I find I prefer the tone when playing through a valve preamp into solid state amp (integrated hybrid units) such as Eden or Trace Elliot.
Thanks again for all the advice so far
I am a bass player, so obviously the quality of bass sound and tone is number 1 priority followed by drums and percussion and then guitar/saxophone and then other instruments.
Also I notice when playing electric bass I find I prefer the tone when playing through a valve preamp into solid state amp (integrated hybrid units) such as Eden or Trace Elliot.
Thanks again for all the advice so far
Hi,
Do we assume your speakers are 4 or 8 ohm ?
If 8 then its a 15W amplifier, if 4 then you sure you have enough current ?
FWIW the lowish powered Class A amplifiers I've heard that cannot
do Class B struggle with the bass end, (sugden and kelvin labs).
They are like the JLH, they severely current limit in one direction.
also see the "Death of Zen", similar to the JLH.
If your considering both I'd say you need a proper push pull amplifier
heavily biased into class A rather than the "white cathode follower"
arrangement of the above amplifiers.
In fact by reducing the voltage rails and wacking up the bias current
in a Naim style amplifier that is what you would actually get, assuming
http://www.neilmcbride.co.uk/jknamps.html
Is representative of the NAP 140.
/sreten.
Do we assume your speakers are 4 or 8 ohm ?
If 8 then its a 15W amplifier, if 4 then you sure you have enough current ?
FWIW the lowish powered Class A amplifiers I've heard that cannot
do Class B struggle with the bass end, (sugden and kelvin labs).
They are like the JLH, they severely current limit in one direction.
also see the "Death of Zen", similar to the JLH.
If your considering both I'd say you need a proper push pull amplifier
heavily biased into class A rather than the "white cathode follower"
arrangement of the above amplifiers.
In fact by reducing the voltage rails and wacking up the bias current
in a Naim style amplifier that is what you would actually get, assuming
http://www.neilmcbride.co.uk/jknamps.html
Is representative of the NAP 140.
/sreten.Hi,
I missed the Usher 2.5 way 4 ohm bit.
http://www.zalytron.com/Schematics/usher2w5s3.pdf
One could argue not very class A friendly and in fact only 87dB
or so per real watt (as opposed to 90dB or so for a 4 ohm watt).
/sreten.
I missed the Usher 2.5 way 4 ohm bit.
http://www.zalytron.com/Schematics/usher2w5s3.pdf
One could argue not very class A friendly and in fact only 87dB
or so per real watt (as opposed to 90dB or so for a 4 ohm watt).
/sreten.2.5 Way is great.
One trick I am trying with my 2.5 way Quad 22L2 is passive biamping. Use a stereo amp per speaker, both channels driven full range.
One channel drives the 2 way section, the other channel drives just the 0.5 or bass driver. Since most have a slow roll off on the bass driver the fullrange power is not wasted. The other side is full range to begin with.
Not every setup is the same, but in my mind, this is a perfect application. This also will address the current delivery issues mentioned. The two drivers handing the bass are in parallel from a couple hundred Hz down. So they will be ABOUT 8 ohm if split.
My amps have limited voltage swing, 35 volt rails, so maybe 30 volts rms. But should be able to dump 20 amps. It still makes a difference in the mids and in the bass.
The damping factor is increased, and maybe moving the low pass filter for the bass driver out improves the mids.
If you have the resources to build two identical steeo amps, and the Ushers are biwireable, this might float your boat.
George
One trick I am trying with my 2.5 way Quad 22L2 is passive biamping. Use a stereo amp per speaker, both channels driven full range.
One channel drives the 2 way section, the other channel drives just the 0.5 or bass driver. Since most have a slow roll off on the bass driver the fullrange power is not wasted. The other side is full range to begin with.
Not every setup is the same, but in my mind, this is a perfect application. This also will address the current delivery issues mentioned. The two drivers handing the bass are in parallel from a couple hundred Hz down. So they will be ABOUT 8 ohm if split.
My amps have limited voltage swing, 35 volt rails, so maybe 30 volts rms. But should be able to dump 20 amps. It still makes a difference in the mids and in the bass.
The damping factor is increased, and maybe moving the low pass filter for the bass driver out improves the mids.
If you have the resources to build two identical steeo amps, and the Ushers are biwireable, this might float your boat.
George
Look at pdf file for speaker sensitivity (ie roughly 90dB).
Yes I agree not very Class A friendly, however with Geoff Moss' help I have been given the necessary information to build a Class A amplifier designed specifically for a 4ohm load at 30W per channel.
Any way I will probably build both but I intend on building the JLH first. I have now received the PCBs and will start ordering the necessary parts.
Yes I agree not very Class A friendly, however with Geoff Moss' help I have been given the necessary information to build a Class A amplifier designed specifically for a 4ohm load at 30W per channel.
Any way I will probably build both but I intend on building the JLH first. I have now received the PCBs and will start ordering the necessary parts.
Hi,
that sensitivity graph says dB/W for 8ohms.
I suspect that is telling you that it is really dB/2.8V for the speaker load.
Since the speaker is rated as a 4ohm load that brings the true sensitivity down to 87dB/W/m.
30W into 4ohms is +15dBw and gives a peak SPL of about 102dB. This is low but OK. Certainly worth pursuing.
that sensitivity graph says dB/W for 8ohms.
I suspect that is telling you that it is really dB/2.8V for the speaker load.
Since the speaker is rated as a 4ohm load that brings the true sensitivity down to 87dB/W/m.
30W into 4ohms is +15dBw and gives a peak SPL of about 102dB. This is low but OK. Certainly worth pursuing.
Hi Andrew T
I still think these speakers are rated at 90dB/W/m. Check out the link below, of some commercially made speakers using the exact same drivers in 2.5 way set up. (look at the specs tab)
http://www.usheraudiousa.com/products/loudspeakers/6-series/cp-6371
For those that are interested, below is an extract from Geoff's site:
"When used with conventional speakers, this circuit can deliver over 40W provided the supply rail voltage and quiescent current are selected to suit a specific load impedance. The supply rail voltage needs to be a couple of volts higher than the peak output voltage swing and the total quiescent current should be about 0.7 times the maximum output current. The power dissipated in each output transistor (supply rail voltage times half the quiescent current) should be limited to about 40 to 45W, assuming decent sized heatsinks are used (0.6 to 0.8degC/W per transistor)."
I still think these speakers are rated at 90dB/W/m. Check out the link below, of some commercially made speakers using the exact same drivers in 2.5 way set up. (look at the specs tab)
http://www.usheraudiousa.com/products/loudspeakers/6-series/cp-6371
For those that are interested, below is an extract from Geoff's site:
"When used with conventional speakers, this circuit can deliver over 40W provided the supply rail voltage and quiescent current are selected to suit a specific load impedance. The supply rail voltage needs to be a couple of volts higher than the peak output voltage swing and the total quiescent current should be about 0.7 times the maximum output current. The power dissipated in each output transistor (supply rail voltage times half the quiescent current) should be limited to about 40 to 45W, assuming decent sized heatsinks are used (0.6 to 0.8degC/W per transistor)."
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