Re: Monoblock Finished
Great to hear your enthusiasm for the sound, Lissitzky. Did you not try toroids O/P trafos before? Well done on the build - I've been hovering around completion of mine for some time now. I'm hoping to finish before summer
lissitzky said:
Great to hear your enthusiasm for the sound, Lissitzky. Did you not try toroids O/P trafos before? Well done on the build - I've been hovering around completion of mine for some time now. I'm hoping to finish before summer
TimA said:
Hi Tim, how are you !
I have heard both but I suspect my JLH was not quite as refined as yours.
Susan's amp sounded lovely - very emotionally involving but a bit less detailed than I am used to.
best for single full range drivers rather than crossover speakers.
cheers
mike
Miklem, what do you think underlies the detail smoothing in the Zeus compared to the JLH? Is there any clue in the distortion spectrum differences between these amps?
My description of JLH amp is now from memory so I can only speak generally but think the main difference is that the JHL has negative feed back. If optimised with very low noise power supply and high quality resistors etc it could sound very nice indeed ( although I never had enough available current on mine to give the dynamics I would have liked ).
So if you work at a JLH, it could have very low noise & quite a lot of detail because of the feed back.
The Zeus naturally already has very low noise - you don't have to work at it - it's part of the fundamental design but the Zeus has no feed back so the sound is more fluid and perhaps more graceful. A good level of detail is there because of the low noise but it is a little less defined - hehe - less detailed details.
With a perfect source I think I would prefer the extra detail - but what source is perfect ?
With an imperfect source I guess it's just a matter of preference - that's the best I can say.
I still clearly remember hearing Susan's system and it still remains one of the most pleasant sounding system I have heard.
cheers
mike
So if you work at a JLH, it could have very low noise & quite a lot of detail because of the feed back.
The Zeus naturally already has very low noise - you don't have to work at it - it's part of the fundamental design but the Zeus has no feed back so the sound is more fluid and perhaps more graceful. A good level of detail is there because of the low noise but it is a little less defined - hehe - less detailed details.
With a perfect source I think I would prefer the extra detail - but what source is perfect ?
With an imperfect source I guess it's just a matter of preference - that's the best I can say.
I still clearly remember hearing Susan's system and it still remains one of the most pleasant sounding system I have heard.
cheers
mike
Hi Mike,
Thanks for the reply. I recall that you had a JLH and had heard the Zeus. In fact I thought you had built one.
Interesting!
Hope all goes well with you.
Tim.
Thanks for the reply. I recall that you had a JLH and had heard the Zeus. In fact I thought you had built one.
Interesting!
Hope all goes well with you.
Tim.
Thanks Mikelm,
Great reply - I appreciate your description of the amp differences although I'm also aware that memory of sound is notoriously untrustworthy. I, like TimA, had thought you had built a Zeus. Also, like Lissitzky I'm hoping for an amp for life so I can direct my efforts on improving the source.
Great reply - I appreciate your description of the amp differences although I'm also aware that memory of sound is notoriously untrustworthy. I, like TimA, had thought you had built a Zeus. Also, like Lissitzky I'm hoping for an amp for life so I can direct my efforts on improving the source.
jkeny said:
Tim / jkeny,
I did build a zeus, but with the speakers I was using at the time, which had a crossover without constant impedance, the sound was unbalanced because of the zeus high o/p impedance.
That was in the UK and I think it is still there - but I still have most of the parts for another one here and now as I am using Jordan full range drivers I am quite tempted to build another one.
Ah, Mikelm, so you had a more intimate listening experience and longer time to evaluate the amp - that's good/better/excellent.
My speakers are Jordan JX92S in a 3D folded spiral box not much bigger than the Rogers LS3/5As, my other speakers. Both very different but I'm happy with them and have great hopes for their synergy with the Zeus. Indeed, Susan said the LS3s sounded better with the amp than with other amps.
My speakers are Jordan JX92S in a 3D folded spiral box not much bigger than the Rogers LS3/5As, my other speakers. Both very different but I'm happy with them and have great hopes for their synergy with the Zeus. Indeed, Susan said the LS3s sounded better with the amp than with other amps.
optimal load
Sheldon!
What is the optimal load for a power mosfet (for example IRFP240) ?
Is the Rds mean the same like by the tubes the Ri?
Tyimo
Sheldon!
What is the optimal load for a power mosfet (for example IRFP240) ?
Is the Rds mean the same like by the tubes the Ri?
Tyimo
Bias calculation question
O.K. I already know the answer for my last question.🙂
But I have a new:
How do you callculate the bias current for the Zeus amp??
I read on the web page in the "Building instructions" of the 35W version that:
But I learnt ( for example a zeus style amp with power supply’s 15Vdc+) so:
With this calculation I need 2 times more bias current!
I am affraid that the first suggestion would give current limiting in the output power.
Which calculation is true????
Greets:
Tyimo
O.K. I already know the answer for my last question.🙂
But I have a new:
How do you callculate the bias current for the Zeus amp??
I read on the web page in the "Building instructions" of the 35W version that:
But I learnt ( for example a zeus style amp with power supply’s 15Vdc+) so:
With this calculation I need 2 times more bias current!
I am affraid that the first suggestion would give current limiting in the output power.
Which calculation is true????
Greets:
Tyimo
I suggest you have the bias current as high as the size of your heat sink allows. This will give you minimum distortion.
If you adopt this idea first you have to decide how hot you will allow ur heat sink to be - let's say 60 deg C is ok.
If you assume ambient temperature of 25 degrees then that gives you a temperature rise of 35 degrees.
Then you need to know how many degrees ur heatsink rises per watt.
If we assume 0.5 degrees per watt that means you can have 70 watts of dissipation in ur output stage.
If you now divide ur voltage into 70 ( watts ) this will give you the current that can be shared between the two output devices.
Then you divide this by 2 for the current in each device.
Is this clear ? . . . or am I teaching my granny to suck eggs ?
hehe
mike
If you adopt this idea first you have to decide how hot you will allow ur heat sink to be - let's say 60 deg C is ok.
If you assume ambient temperature of 25 degrees then that gives you a temperature rise of 35 degrees.
Then you need to know how many degrees ur heatsink rises per watt.
If we assume 0.5 degrees per watt that means you can have 70 watts of dissipation in ur output stage.
If you now divide ur voltage into 70 ( watts ) this will give you the current that can be shared between the two output devices.
Then you divide this by 2 for the current in each device.
Is this clear ? . . . or am I teaching my granny to suck eggs ?
hehe
mike
Hi Mike!
Thanks!
Yes, but I am afraid that your calculation method is not the right one. 🙂
You approach this current-bias question from the heat dissipation and heat sinks side and not from the amplifier biasing and loading side. What you say it is true and works, but still not give me the correct answer.
I would like to understand how to set the bias current for the optimum without any hetasink question. Most important for me that the amp would get as many currents as needs. Than I would give it the suitable heatsinks for it.😉 It is not a problem in the 35-70W region. (for me.....😀 )
Greets:
Tyimo
Thanks!
It is not a problem for me. I am from the Pass Labs forum.....😀
Yes, but I am afraid that your calculation method is not the right one. 🙂
You approach this current-bias question from the heat dissipation and heat sinks side and not from the amplifier biasing and loading side. What you say it is true and works, but still not give me the correct answer.
I would like to understand how to set the bias current for the optimum without any hetasink question. Most important for me that the amp would get as many currents as needs. Than I would give it the suitable heatsinks for it.😉 It is not a problem in the 35-70W region. (for me.....😀 )
Greets:
Tyimo
The current the amps need depends on what you think it needs it for.
Your definition of this seems to be to obtain an elegant combination of voltage & current to get the maximum power from the amp with minimum power dissipation - but to really achieve this you will need to consider the impedance of your speakers and then adjust both the voltage and current to get an optimum match.
For me I would just want the amp so sound as good as possible and for that the solution is simple . . . buy a good sized heat sink and then just try different bias currents and see what you prefer - hehe
It might be that ur experience disagrees with your theories . . . 😉
Your definition of this seems to be to obtain an elegant combination of voltage & current to get the maximum power from the amp with minimum power dissipation - but to really achieve this you will need to consider the impedance of your speakers and then adjust both the voltage and current to get an optimum match.
For me I would just want the amp so sound as good as possible and for that the solution is simple . . . buy a good sized heat sink and then just try different bias currents and see what you prefer - hehe
It might be that ur experience disagrees with your theories . . . 😉
Yes, this is why I would like to knwo the correct formula.🙂
Yes! I will.....😀
Did you build this amp? With what voltages, currents and speaker impedance???
Tyimo
Tyimo,
Let's use the same example as before:
Take your supply voltage and subtract about 5 to account for the bias voltage. That gives you your maximum peak voltage. Multiply that number times 2 for peak to peak voltage across the primary. Divide by 1.4 to get RMS voltage. Divide that number by your transformer ratio, square it, and divide by your load resistance to get power.
Example for 50V power supply, 4:1 transformer and 8 Ohm load: 50-5 = 45Vpeak. 45x2/1.4 = 64vRMS. 64/4 = 16vRMS output. 16x16/8 = 32W output.
For this example, 16V into 8 Ohms will give a peak current of 2 amps at the secondary. But, remember, that to get the current at the primary you have to divide that figure by 4 (winding ratio). So for full class A operation, you need 500mA across the primary and across each FET. Add a little extra for good measure - that's where Susan's figure of 500-750mA comes from. You can operate at lower current, but will be in class AB operation. Try both, and see what you hear. Depending on your listening volume, you may find that you can operate at a lower bias current.
Sheldon
Let's use the same example as before:
Take your supply voltage and subtract about 5 to account for the bias voltage. That gives you your maximum peak voltage. Multiply that number times 2 for peak to peak voltage across the primary. Divide by 1.4 to get RMS voltage. Divide that number by your transformer ratio, square it, and divide by your load resistance to get power.
Example for 50V power supply, 4:1 transformer and 8 Ohm load: 50-5 = 45Vpeak. 45x2/1.4 = 64vRMS. 64/4 = 16vRMS output. 16x16/8 = 32W output.
For this example, 16V into 8 Ohms will give a peak current of 2 amps at the secondary. But, remember, that to get the current at the primary you have to divide that figure by 4 (winding ratio). So for full class A operation, you need 500mA across the primary and across each FET. Add a little extra for good measure - that's where Susan's figure of 500-750mA comes from. You can operate at lower current, but will be in class AB operation. Try both, and see what you hear. Depending on your listening volume, you may find that you can operate at a lower bias current.
Sheldon
Hi Sheldon!
Thank you very much!!
I understand now!
Only one problem:
with 34V PSU and 2:1 transformer and 8 Ohm speaker
I got 1.29 A on the primary.
On the Zeus page I saw for the 35W version: 34Vdc, 2:1 transformer, and 500-750mA bias.
Greets:
Tyimo
Thank you very much!!
I understand now!
Only one problem:
with 34V PSU and 2:1 transformer and 8 Ohm speaker
I got 1.29 A on the primary.
On the Zeus page I saw for the 35W version: 34Vdc, 2:1 transformer, and 500-750mA bias.
Greets:
Tyimo
I haven't had time to go back through Susan's page, but you are in the ballpark. FWIW, I didn't see a much increase in distortion on my mini version, by going below the class A current.
Sheldon
Sheldon
Keep in mind too, that when you go from 4:1 to 2:1, you double the output voltage. Which means the power output quadruples into the same load, assuming you are not current limited.
Sheldon
Sheldon