I will have to visit some day 🙂
Thanks for the pictures and descriptions, that's extremely helpful!
Congratulations on the beautiful build.
-Klaus
I compared a Cobra s2 to a SMPS1200 on an existing class AB amplifier I ripped the (noisy AF) linear supply out of. The Hypex was slightly quieter, 0 to 96khz. Both were very quiet and leagues ahead of the linear supply that was in there. The Cobra has more (and easier) convenience options however.
Rail voltages for this amp were +-82V though so YMMV. Both 5W 1 channel connected to 8R load.
Cobra (click to enlarge)
Hypex (click to enlarge)
Hi everyone 👋🏽. I would like to know what is the main difference between the EF3-4 and EF3-3 in terms of distortion and power handing capability ?
^ Read post #1. Read tests conducted by other builders throughout the thread (I'd start with Fireanimal) The overall answer is that it will depend on your choices. Pay particular attention to the power handling table attached in post #1. There's a large span of rated output power for each.
Power => EF3-3 lower than EF3-4
Distortion => EF3-3 same as EF3-4 (for all practical purposes) but it will depend on your personal choices and build quality. The circuit is capable of 'very' low distortion levels.
Power => EF3-3 lower than EF3-4
Distortion => EF3-3 same as EF3-4 (for all practical purposes) but it will depend on your personal choices and build quality. The circuit is capable of 'very' low distortion levels.
Yes I went through the first post but I didn’t get details like for example with the EFT3-3 you can only get 150 watts 8 ohm and 250 watts with 4 ohm you get what I mean ?
With EF3-3 you can get 240 and 430 with 71V rails (unless I'm reading the build sheet wrong).
See that’s maximum you get when you have a 1.2 kva transformer. Now they didn’t specify whether it is with the EF3-3 or EF3-4.
Another choice to make.
Input impedance: 10kOhm or 22kOhm
I'm leaning towards 10kOhm as it seems to have no real downsides and be somewhat of a default value for amps. I guess a tube pre-amp could need higher values, but I don't plan to build one of those.
Input impedance: 10kOhm or 22kOhm
I'm leaning towards 10kOhm as it seems to have no real downsides and be somewhat of a default value for amps. I guess a tube pre-amp could need higher values, but I don't plan to build one of those.
@james mukaz It seems like output wattage will be determined by a combination of rail voltage and the chosen output transistors. As far as I can tell you should be able to reach above 200W in to 8Ohms on both EF3-3 and EF3-4.
If you are really pushing the limits then EF3-4 seems to be the way to go.
If you are really pushing the limits then EF3-4 seems to be the way to go.
Yeah you might be right reason why it’s not the build guide did not specify, now will the distortion remain the same ?
I think the highest the better for you won’t have any issue with impedance mismatch
Hi @james mukaz , Let me try and help you. The EF3-3 & EF3-4 boards are essentially the same. The only real difference between the to is
The EF3-3 board has 3 pairs of output transistors and the The EF3-4 board has 4 pairs of output transistors and the choice of mounting the driver transistors directly to the main heatsink. The EF3-4 also has very slightly lower distortion. But at levels that no body could ever tell.
So which do you choose?
Well this comes down to a few factors.
1. Your speaker impedance.
2. Your speaker sensitivity.
3. How loud you like listing to your music.
4. The size of your enclosure.
5. Your budget.
Now a few notes on each point above.
1. If you have 8 ohm speakers there is no real reason to use the EF3-4 unless you want to.
The whole point of the extra two output transistors is to lower the load seen by each individual transistor. This will in turn allow the amplifier to more effectively drive lower impedance loads. As there will also be less load on each individual transistor the beta droop for the EF3-4 will be less hence the distortion is lower. If you look at the datasheets for each of the output transistors listed and study the SOA (safe operating area) plots you will see how much power (The voltage & current combination) each individual output transistor can deliver.
2 & 3. Speaker sensitivity & how loud you like listing to your music. This will also have an effect on how much power you will need ultimately need.
I'm not sure if you are familiar with rule of thumb for this. I'll attach a video link that may help you.
Basically start with this reference.
The THX specification for the audio reference level is 85dB SPL with usually 20dB of headroom. So we need to be able to reach 105db when accounting for music peeks. So depending on how loud you like to listen your music you will need more power.
This ultimately comes down to your rail voltage and the VA rating of your transformer. The higher the VA rating the less the voltage will drop under high load.
Example and a demonstration of the rule of thumb.
A speaker’s 1W/1m SPL value will tell us how loud a speaker will sound with 1 Watt of input, at a distance of 1 meter.
Lets say your speakers sensitivity is 89dB (1 watt @ 1 meter).
This mean if you have a db meter and stood 1 meter away and powered your speaker with 1W you would see about 89dB on the meter.
Now if your seating position is further away or you like you music louder you will need more power.
How much power do your speakers need?
As I said this is a guide and real life is different. From my own personal testing I found that 57V rails & 8 ohms speakers 89 dB sensitivity.
is more that enough to reach 105 dB peeks at a seating position 4 meters away.
If you want to be sure or you like things a little louder then go for 64V rails.
Please also check post #876 and a few after that
I also attached a draft of excel sheet @fireanimal has been working on. Once its finished I will attach it to the BOM spreadsheet.
It will help you with some of the calculations. Thanks @fireanimal
4. The size of your enclosure.
The EF3-4 will require a larger chassis as the boards are longer.
5. Your budget.
The EF3-4 will cost a little more due to the extra components and larger chassis.
I hope that help you and other members.
The EF3-3 board has 3 pairs of output transistors and the The EF3-4 board has 4 pairs of output transistors and the choice of mounting the driver transistors directly to the main heatsink. The EF3-4 also has very slightly lower distortion. But at levels that no body could ever tell.
So which do you choose?
Well this comes down to a few factors.
1. Your speaker impedance.
2. Your speaker sensitivity.
3. How loud you like listing to your music.
4. The size of your enclosure.
5. Your budget.
Now a few notes on each point above.
1. If you have 8 ohm speakers there is no real reason to use the EF3-4 unless you want to.
The whole point of the extra two output transistors is to lower the load seen by each individual transistor. This will in turn allow the amplifier to more effectively drive lower impedance loads. As there will also be less load on each individual transistor the beta droop for the EF3-4 will be less hence the distortion is lower. If you look at the datasheets for each of the output transistors listed and study the SOA (safe operating area) plots you will see how much power (The voltage & current combination) each individual output transistor can deliver.
2 & 3. Speaker sensitivity & how loud you like listing to your music. This will also have an effect on how much power you will need ultimately need.
I'm not sure if you are familiar with rule of thumb for this. I'll attach a video link that may help you.
Basically start with this reference.
The THX specification for the audio reference level is 85dB SPL with usually 20dB of headroom. So we need to be able to reach 105db when accounting for music peeks. So depending on how loud you like to listen your music you will need more power.
This ultimately comes down to your rail voltage and the VA rating of your transformer. The higher the VA rating the less the voltage will drop under high load.
Example and a demonstration of the rule of thumb.
A speaker’s 1W/1m SPL value will tell us how loud a speaker will sound with 1 Watt of input, at a distance of 1 meter.
Lets say your speakers sensitivity is 89dB (1 watt @ 1 meter).
This mean if you have a db meter and stood 1 meter away and powered your speaker with 1W you would see about 89dB on the meter.
Now if your seating position is further away or you like you music louder you will need more power.
How much power do your speakers need?
As I said this is a guide and real life is different. From my own personal testing I found that 57V rails & 8 ohms speakers 89 dB sensitivity.
is more that enough to reach 105 dB peeks at a seating position 4 meters away.
If you want to be sure or you like things a little louder then go for 64V rails.
Please also check post #876 and a few after that
I also attached a draft of excel sheet @fireanimal has been working on. Once its finished I will attach it to the BOM spreadsheet.
It will help you with some of the calculations. Thanks @fireanimal
4. The size of your enclosure.
The EF3-4 will require a larger chassis as the boards are longer.
5. Your budget.
The EF3-4 will cost a little more due to the extra components and larger chassis.
I hope that help you and other members.
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Lower is better. Please search the thread for the discussion on this. There is no point talking about it again.
I'll see if I can add something to the build guide that people can refer to.
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The cobra needs it's 0v tied to ground or ground lift to fix that
My main amplifier is a Pass XA30.8 clone, took me years to make, etc... It is a 30W Class-A, and probably I'm using only 5W out of 30W at most. My speakers are pretty efficient (Wilson Sasha clone, eff around 90dB/watt), but again it doesn't take a lot to fill a leaving room with blasting sound levels....
Keep in mind though the crest factor of the source and the peaks. There is a lot of material that will easily clip the peaks when underpowered even at low to moderate listening levels.
Thanks Stuart that’s much clearHi @james mukaz , Let me try and help you. The EF3-3 & EF3-4 boards are essentially the same. The only real difference between the to is
The EF3-3 board has 3 pairs of output transistors and the The EF3-4 board has 4 pairs of output transistors and the choice of mounting the driver transistors directly to the main heatsink. The EF3-4 also has very slightly lower distortion. But at levels that no body could ever tell.
So which do you choose?
Well this comes down to a few factors.
1. Your speaker impedance.
2. Your speaker sensitivity.
3. How loud you like listing to your music.
4. The size of your enclosure.
5. Your budget.
Now a few notes on each point above.
1. If you have 8 ohm speakers there is no real reason to use the EF3-4 unless you want to.
The whole point of the extra two output transistors is to lower the load seen by each individual transistor. This will in turn allow the amplifier to more effectively drive lower impedance loads. As there will also be less load on each individual transistor the beta droop for the EF3-4 will be less hence the distortion is lower. If you look at the datasheets for each of the output transistors listed and study the SOA (safe operating area) plots you will see how much power (The voltage & current combination) each individual output transistor can deliver.
2 & 3. Speaker sensitivity & how loud you like listing to your music. This will also have an effect on how much power you will need ultimately need.
I'm not sure if you are familiar with rule of thumb for this. I'll attach a video link that may help you.
Basically start with this reference.
The THX specification for the audio reference level is 85dB SPL with usually 20dB of headroom. So we need to be able to reach 105db when accounting for music peeks. So depending on how loud you like to listen your music you will need more power.
This ultimately comes down to your rail voltage and the VA rating of your transformer. The higher the VA rating the less the voltage will drop under high load.
Example and a demonstration of the rule of thumb.
A speaker’s 1W/1m SPL value will tell us how loud a speaker will sound with 1 Watt of input, at a distance of 1 meter.
Lets say your speakers sensitivity is 89dB (1 watt @ 1 meter).
This mean if you have a db meter and stood 1 meter away and powered your speaker with 1W you would see about 89dB on the meter.
Now if your seating position is further away or you like you music louder you will need more power.
How much power do your speakers need?
As I said this is a guide and real life is different. From my own personal testing I found that 57V rails & 8 ohms speakers 89 dB sensitivity.
is more that enough to reach 105 dB peeks at a seating position 4 meters away.
If you want to be sure or you like things a little louder then go for 64V rails.
Please also check post #876 and a few after that
I also attached a draft of excel sheet @fireanimal has been working on. Once its finished I will attach it to the BOM spreadsheet.
It will help you with some of the calculations. Thanks @fireanimal
4. The size of your enclosure.
The EF3-4 will require a larger chassis as the boards are longer.
5. Your budget.
The EF3-4 will cost a little more due to the extra components and larger chassis.
I hope that help you and other members.