Hi:
I am wondering if anyone has experience and success building the ETI-466 300W Amplifier:
http://users.otenet.gr/~athsam/power_amp_300w.htm
or
http://www.alphalink.com.au/~cambie/ETI466Web.htm
I've read a couple of threads on here already and would like to hear from other members who have experience with this design.
I've been working on the module for some time now and after some research on the internet, it appears mine is suffering from high frequency oscillaion in the output/driver stage.
Anybody experience the same problem with this design? Any ideas on how to correct it?
Thanks,
Derek
I am wondering if anyone has experience and success building the ETI-466 300W Amplifier:
http://users.otenet.gr/~athsam/power_amp_300w.htm
or
http://www.alphalink.com.au/~cambie/ETI466Web.htm
I've read a couple of threads on here already and would like to hear from other members who have experience with this design.
I've been working on the module for some time now and after some research on the internet, it appears mine is suffering from high frequency oscillaion in the output/driver stage.
Anybody experience the same problem with this design? Any ideas on how to correct it?
Thanks,
Derek
Try some small caps on the driver transistors between base and emitter. a 1nf cap or 500pf cap should work.
Hi:
Thank you for your reply.
Do the addition of the capacitors on the driver transistors alter the frequency response / sonic qualities of the amplifier?
I'm guilty of a few things that may have contributed to the HF oscillation.
1) The emitter resistors are "no name" brand and probably exhibit some induction.
2) I didn't have access to a metal shop to custom fabricate PCB mounted heatsink. Instead I used off the shelf heatsinks extending the power transistors off the pcb.
I assume you have built one of these before. What is your opinion of amplifier?
Best,
Derek
Thank you for your reply.
Do the addition of the capacitors on the driver transistors alter the frequency response / sonic qualities of the amplifier?
I'm guilty of a few things that may have contributed to the HF oscillation.
1) The emitter resistors are "no name" brand and probably exhibit some induction.
2) I didn't have access to a metal shop to custom fabricate PCB mounted heatsink. Instead I used off the shelf heatsinks extending the power transistors off the pcb.
I assume you have built one of these before. What is your opinion of amplifier?
Best,
Derek
Hi Derek,
Many were build years ago. Many burned up years ago. Try to reduce the gain in the output stage, bypass the outputs right where they are.
I don't consider it a great amplifier, but get yours working and you built an amplifier! It's still worthwhile.
-Chris
Many were build years ago. Many burned up years ago. Try to reduce the gain in the output stage, bypass the outputs right where they are.
I don't consider it a great amplifier, but get yours working and you built an amplifier! It's still worthwhile.
-Chris
Hi,
this amp is just like the Tigersaurus amp designed by Daniel Meyer, of Southewest Tecnical Products, only the ouput trannies used the MJ15003/15004 in the ETI466.
this amp like the Tigersaurus packed a lot of punch in the bass end, and is likewise prone to oscilations. personally i did not find this amp good in the mids and highs...
the output stage has a voltage gin of about 4, and this is because the front end is fed off a much lower voltage so that the vas output swing is not enough to drive the amp to full power.
perhaps a 4.7 ohm resistor to the base of the output power trannies may help, although i have not tried this as i have retired all of my tigersaurus amps.
btw, these amps are good for PA duties, for HI-Fi i will stay away from them.
this amp is just like the Tigersaurus amp designed by Daniel Meyer, of Southewest Tecnical Products, only the ouput trannies used the MJ15003/15004 in the ETI466.
this amp like the Tigersaurus packed a lot of punch in the bass end, and is likewise prone to oscilations. personally i did not find this amp good in the mids and highs...
the output stage has a voltage gin of about 4, and this is because the front end is fed off a much lower voltage so that the vas output swing is not enough to drive the amp to full power.
perhaps a 4.7 ohm resistor to the base of the output power trannies may help, although i have not tried this as i have retired all of my tigersaurus amps.
btw, these amps are good for PA duties, for HI-Fi i will stay away from them.
You have no idea how many of those crossed my bench over the years. They are not reliable enough for PA duty.
Try and get it going, and bypass the heck out of the supplies. Due to the output stage having gain, you really do not want to mount the outputs off-board.
-Chris
Try and get it going, and bypass the heck out of the supplies. Due to the output stage having gain, you really do not want to mount the outputs off-board.
-Chris
ETI-466 Amp Progress
Firstly many thanks for everyone's gracious assistance!
I'm from Toronto, Canada and this amplifer was featured in an 1980 ETI article titled simply "The Brute" with no further reference to the designer or author of the article. I've been struggling with it for a LONG time without much success.
By chance I discovered some references online to the ETI-466 which turned out to be the SAME amp! This eventually led me to this forum.
Some additional questions:
1) Do the addition of the capacitors on the drive transistors alter the frequency response/sonic qualities of the amplifier?
2) Is this thing supposed to run "warmly" even without signal? Its not hot but warm.
3) Do you need two caps, one across Q7 and Q9?
I added only one to Q9 and it tamed the amp. All of the high current draws disappeared!
BUT, I also needed to add a 150 K resister in parallel to 2K2 bias pot to bring it into range to where I could get a 1 volt drop across the 10 ohm test resistors that are put in place of the fuses during the set-up procedures.
Any thoughts?
Thanks again!
Derek
Firstly many thanks for everyone's gracious assistance!
I'm from Toronto, Canada and this amplifer was featured in an 1980 ETI article titled simply "The Brute" with no further reference to the designer or author of the article. I've been struggling with it for a LONG time without much success.
By chance I discovered some references online to the ETI-466 which turned out to be the SAME amp! This eventually led me to this forum.
Some additional questions:
1) Do the addition of the capacitors on the drive transistors alter the frequency response/sonic qualities of the amplifier?
2) Is this thing supposed to run "warmly" even without signal? Its not hot but warm.
3) Do you need two caps, one across Q7 and Q9?
I added only one to Q9 and it tamed the amp. All of the high current draws disappeared!
BUT, I also needed to add a 150 K resister in parallel to 2K2 bias pot to bring it into range to where I could get a 1 volt drop across the 10 ohm test resistors that are put in place of the fuses during the set-up procedures.
Any thoughts?
Thanks again!
Derek
Hi Derek,
First, read the notes. Inductive emitter resistors were a big problem. You will need to look at the output waveforms both under load and not. Look for oscillations. That will be your guide. I feel that because the outputs are not on the circuit board, your amp may tend to be unstable.
-Chris
First, read the notes. Inductive emitter resistors were a big problem. You will need to look at the output waveforms both under load and not. Look for oscillations. That will be your guide. I feel that because the outputs are not on the circuit board, your amp may tend to be unstable.
-Chris
Derek,
It'll be hard to verify the stability of the amp without an oscilloscope. As others have already posted (and based on Tony's comments) if its anything like the Tigersaurus, you may want to drive just the LF speakers with the amp - any HF oscillations tend to take out tweeters in domestic loudspeakers real quick...
🙂
Cheers!
ps: will the capacitors alter the frequency response - yes, but it will still be audibly better than an unstable amp!
It'll be hard to verify the stability of the amp without an oscilloscope. As others have already posted (and based on Tony's comments) if its anything like the Tigersaurus, you may want to drive just the LF speakers with the amp - any HF oscillations tend to take out tweeters in domestic loudspeakers real quick...
🙂
Cheers!
ps: will the capacitors alter the frequency response - yes, but it will still be audibly better than an unstable amp!
I have a little Pre-amp that ILP Electronics in the UK made years ago based on their encapsulated modules.
i've been build 4x this ETi 466 (well known as 'Raksasa' (mean as : giant ) in Indonesia)
All of them was used for PA (stage apllication) , the output was 'BASS' maker. tight & Deep i think.
The only problem was, that ETI never 'broken', but She (ETI 466) often bring the loudspeaker to repairshop!.
I've heard at least 10 speakers blow up with that amplifier that I build.
nowadays the popular PA amps is 'Blazer' Ebay Amplifier.
All of them was used for PA (stage apllication) , the output was 'BASS' maker. tight & Deep i think.
The only problem was, that ETI never 'broken', but She (ETI 466) often bring the loudspeaker to repairshop!.
I've heard at least 10 speakers blow up with that amplifier that I build.
nowadays the popular PA amps is 'Blazer' Ebay Amplifier.
ETI 466 Amplifier
I made this amplifier in 1990, use for some years and retire it. today i make some changes and use mosfet transistor four pair instead of mj15003 and 15004.
according to me it is a great amplifier with a solid bass.
I made this amplifier in 1990, use for some years and retire it. today i make some changes and use mosfet transistor four pair instead of mj15003 and 15004.
according to me it is a great amplifier with a solid bass.
Hi, Wonder if you can use 2sb600 and 2sc555 nec transistors in this Project ?
I have a lot of transistors and dont want to buy New ones,
i found out on the equvilent list , there arent many suggestions for mj15003/4.
best regards Niklas.
I have a lot of transistors and dont want to buy New ones,
i found out on the equvilent list , there arent many suggestions for mj15003/4.
best regards Niklas.
I think you mean 2SD555 and 2SB600.
Take a look at the comments on substitutes for that pair in this thread:
http://www.diyaudio.com/forums/solid-state/157722-sub-mj21194-nec-2sd555-not.html
Essentially, they don't have sufficient power ratings for use in the ETI 466 and will also have a real stability problem (Ft is 15 Mhz compared to 2 MHz for original Motorola transistor types) This is inviting more trouble in an already marginally stable design.
Take a look at the comments on substitutes for that pair in this thread:
http://www.diyaudio.com/forums/solid-state/157722-sub-mj21194-nec-2sd555-not.html
Essentially, they don't have sufficient power ratings for use in the ETI 466 and will also have a real stability problem (Ft is 15 Mhz compared to 2 MHz for original Motorola transistor types) This is inviting more trouble in an already marginally stable design.
I built one of these back in the mid 1980s.
The power output is wholly dependent on the transformers you use and whether or not you decide to add at least one other pair of 15003/4s to safely drive 4 ohms.
I built mine with two (2) Ferguson 47-0-47v 300vA transformers and stuck with the 4x2500uF 80v Elnas (very marginal but worked ok) per channel. If you get Noble brand non-inductive 0.1ohm emiiter resistors and the zobel is carefully wound, you'll have no problems.
Mine went into a 3U rack mount with twin heatsinks on each side out the back. The 10ohm RCA sheath to ground 1/4 resistors will burn up if you have earthing issues with some attached gear.
We used it for years, it was my party amplifier back in the day, hooked up to a big 19" DJ mixer. It sounded quite ok at the time, but I sold it on to a friend who ran a mobile disco. I saw him recently (after 20 years) and the 'brute' is still going strong, so reliabilty was only a function of construction techniques, component selection and careful use. The basic circuit was pretty solid, apart from the over zealous current limiting into low impedances. Do what I did and run at least 3 pairs of 15003/4s per amp. The only problem is, 6 TO3s per amp will rule out 2 in a 3U rack cabinet.
I have the ETI article construction reprint if you need them.
The power output is wholly dependent on the transformers you use and whether or not you decide to add at least one other pair of 15003/4s to safely drive 4 ohms.
I built mine with two (2) Ferguson 47-0-47v 300vA transformers and stuck with the 4x2500uF 80v Elnas (very marginal but worked ok) per channel. If you get Noble brand non-inductive 0.1ohm emiiter resistors and the zobel is carefully wound, you'll have no problems.
Mine went into a 3U rack mount with twin heatsinks on each side out the back. The 10ohm RCA sheath to ground 1/4 resistors will burn up if you have earthing issues with some attached gear.
We used it for years, it was my party amplifier back in the day, hooked up to a big 19" DJ mixer. It sounded quite ok at the time, but I sold it on to a friend who ran a mobile disco. I saw him recently (after 20 years) and the 'brute' is still going strong, so reliabilty was only a function of construction techniques, component selection and careful use. The basic circuit was pretty solid, apart from the over zealous current limiting into low impedances. Do what I did and run at least 3 pairs of 15003/4s per amp. The only problem is, 6 TO3s per amp will rule out 2 in a 3U rack cabinet.
I have the ETI article construction reprint if you need them.
Hi, thanks for reply, I read about the stability problem, and will make a good psu and non iductive resistor of 0.5 ohms. 🙂 , and I have mj15022/23 laying around .but also have 2n3555/mj2955 also,
plus a bunch of to3 transistors,
plus a bunch of to3 transistors,
Here are the original ETI magazine article schematic details, technical design details, SOA graphs and pics for reference: eti300
http://www.onsemi.com/pub_link/Collateral/MJ15003-D.PDF
http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF
The power supply rail voltages are +/- 60-70V. Don't even waste time thinking of using 2N3055/MJ2955 because their Vceo for instance, is far too low at 60V and this means a low power that any simple, smaller and cheaper design can achieve. Even 2 pairs of MJ15003/4 are already close to their limit with a Vceo of 140V for 300W output.
http://www.onsemi.com/pub_link/Collateral/MJ15003-D.PDF
http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF
For a 47Vac transformer the absolute minimum Vceo of the drivers and outputs should be >150Vceo.
But you need to check what current these devices can pass @ normal rail voltage i.e. permitted Ic when @ 70Vce and the devices are warm (not @ 25°C).
This is the condition that occurs regularly when driving a reactive speaker load.
But you need to check what current these devices can pass @ normal rail voltage i.e. permitted Ic when @ 70Vce and the devices are warm (not @ 25°C).
This is the condition that occurs regularly when driving a reactive speaker load.