https://worldradiohistory.com/UK/Wireless-World/70s/Wireless-World-1970-03.pdf
That's not what it says. He meticulously calculates 46.4% efficiency for the 15 Ohm loading. His design gets lower efficiency in 8 and 3 Ohms because of his home-made 0.56 Ohm bias resistor. (This does not include the low efficiency (85%) of his power regulator.)
Attachments
Efficiency Class A - Single End
My daily life last few Decades is constructing Class A Amps, besides working..
My Single End gives me 17% with
Rail +-42 and
RE7.5Ohm = 5.,6 AMPS
Vout RMS is "14Volts",
Exactly 13.885RMS @8Ohm Distortion 0.0245%@ 1Khz
0.564% 100Khz and
0.0306% @20Khz
I would like to get 15Volts RMS,
And I get15.245Volts 0.776% @ 1Khz
But it clips before that at 100Khz.
Distortion 1.004%@100Khz
So I use the Lowest level under 1 % with 100Khz which can be achieved. =13.885RMS for my measurements
Clipping level is 13.885 @8 Ohm..
I do not use a Tornado to cool the heat off, but a dedicated fan control and MAC G5 Active Cooling sinks.
Anyway Case is almost ready- soon the AMP will find it's way into the case
You will be happy if you get 20% with a Push Pull
My daily life last few Decades is constructing Class A Amps, besides working..
My Single End gives me 17% with
Rail +-42 and
RE7.5Ohm = 5.,6 AMPS
Vout RMS is "14Volts",
Exactly 13.885RMS @8Ohm Distortion 0.0245%@ 1Khz
0.564% 100Khz and
0.0306% @20Khz
I would like to get 15Volts RMS,
And I get15.245Volts 0.776% @ 1Khz
But it clips before that at 100Khz.
Distortion 1.004%@100Khz
So I use the Lowest level under 1 % with 100Khz which can be achieved. =13.885RMS for my measurements
Clipping level is 13.885 @8 Ohm..
I do not use a Tornado to cool the heat off, but a dedicated fan control and MAC G5 Active Cooling sinks.
Anyway Case is almost ready- soon the AMP will find it's way into the case
Attachments
1. I can not find any writing where it states that this amp delivers 33% of the Rail Voltage
2. Also he doesn't state if this is RMS or Peak to Peak..and it doesn't matter.
3. Anyway 33% of 36 Volts is 11.88 Volts. But 10 watts are not 10 Volts or visa versa. Output Power is calculated 11.88*11.88:8OHM = this equals 17.6 Watts approximately. And since it's a single Rail Amplifier I doubt if the Amp delivers actual that Power which is stated.
4. Then also he states that the working point is placed in the middle of these 36 Volts, this means at 18 Volts on the working point of the Output Transistor.
I doubt that this amp delivers 10 Watt in Class A mode. At best 10 Watt Peak to Peak.. but not RMS
May I will simulate this Amplfier with National Multisim 14, then may we will know..
@PRR you are the Master of Class A Specifications, so do you think this Circuit delivers 12.5 Wattss with given Credentials?
Seems all sorts of questions that you did not ask are being answered :-(
For your supply rail, and since you say you are a beginner, I would earnestly suggest you build the original ‘JLH’ single rail class A amp.
There’s a thread elsewhere on this site. Hundreds have been built and it’s a great starter project.
🙂
@Bonsai
Actually his Transformers would eventually fit the make of a F7 from Nelson Past, if he split up Powersupply, as well.
I remember to have posted a similar content like that.
I don't know if Pass F7 would fit, but it's easy to build as there are only a few parts.
Per Side 4 Transistors, OK input Transistors or the Jfets he acutally need to buy from PASS LABS, the ones, on the market will not be good enough to build the F7, and also the Output Transistors which are Mosfets ALF08N16 and ALF08P16 are quite hard to get. this werer the numbers, but I'm sure if he searches a bit he eventually will find them, and last but not least he also could order these from Pass Labs, I hope..
Any Question just ask
The F7 uses only one Toroidal Transformer . Rail voltages are at 24+ 24 -. I thought to have seen the PSC of this Amplifier here on this Forum..
Otherwise there are enough other HIGH END CLASS A AMPS out there to build.
@Gilera take a look at ROD ELLIOT Site, he is also one of the special Designers when it comes to Amplifiers, he might also answer questions when asked. you can find him on ESP or Elliott Sound Products - The Audio Pages (Main Index)
But from my Knowledge Base 32.5 Volts with only 1.4 amps is for my understandings not enough to power a Class A above 10 Watts..
Actually his Transformers would eventually fit the make of a F7 from Nelson Past, if he split up Powersupply, as well.
I remember to have posted a similar content like that.
I don't know if Pass F7 would fit, but it's easy to build as there are only a few parts.
Per Side 4 Transistors, OK input Transistors or the Jfets he acutally need to buy from PASS LABS, the ones, on the market will not be good enough to build the F7, and also the Output Transistors which are Mosfets ALF08N16 and ALF08P16 are quite hard to get. this werer the numbers, but I'm sure if he searches a bit he eventually will find them, and last but not least he also could order these from Pass Labs, I hope..
Any Question just ask
The F7 uses only one Toroidal Transformer . Rail voltages are at 24+ 24 -. I thought to have seen the PSC of this Amplifier here on this Forum..
Otherwise there are enough other HIGH END CLASS A AMPS out there to build.
@Gilera take a look at ROD ELLIOT Site, he is also one of the special Designers when it comes to Amplifiers, he might also answer questions when asked. you can find him on ESP or Elliott Sound Products - The Audio Pages (Main Index)
But from my Knowledge Base 32.5 Volts with only 1.4 amps is for my understandings not enough to power a Class A above 10 Watts..
How on earth would this transformer fit a F7 amp? First off, F7 will not be in DIY format for some years. It needs 2x18Vac transformer or a 18-0-18Vac CT transformer (like allmost all First Watt amps). A 32-0-32Vac transformer is really a missfit to be mild. and 260VA 32-0-32Vac transformer for any class A amp?. not even for 1 ch.
To tread starter. Find an amp you want to build, and get a suitable transformer for that amp. It's never a good idea to use a transformer from a class A/B amp to drive a class A amp. Maybe if that class A/B amp was a 5 ch amp.
Last edited:
I'm guessing thread starter is totally confused right now 🙁 hope all this didn't scare him off into further audio diy.
The Pass Aleph 4 will run on those rails and is a 100W / Ch Class A amplifier but it needs a 500VA transformer.
He asked for some advice and what happened was an 'argument' about efficiency.
He wants to build a class A amp. He was a transformer with the correct secondary voltage - whether split or not it doesn't matter - that will be perfect for a JLH.
Focus on helping the OP and argue about stuff in a new thread!
He wants to build a class A amp. He was a transformer with the correct secondary voltage - whether split or not it doesn't matter - that will be perfect for a JLH.
Focus on helping the OP and argue about stuff in a new thread!
Perfekt for jlh1969 is a single 18Vac sec winding. So far from this 32-0-32Vac CT transformer.
A 2x18Vac 150VA transformer with a seperate singel rail PSU for each ch would be a real good match for that amp.
A 2x18Vac 150VA transformer with a seperate singel rail PSU for each ch would be a real good match for that amp.
Last edited:
An author can buy a set of parts and a board JLH1969.
Also suitable transformer, diode bridge, capacitors for power supply or SMPS.
Large heatsink. A box. Assemble Class A Amplifier DIY.
He need a soldering iron, a multimeter.
Also suitable transformer, diode bridge, capacitors for power supply or SMPS.
Large heatsink. A box. Assemble Class A Amplifier DIY.
He need a soldering iron, a multimeter.
Here is a link to a copy of the original article
http://hifisonix.com/wordpress/wp-content/uploads/2018/02/JLH-10-Watt-Simple-Class-A-Amplifier.pdf
The output is AC coupled and JLH specified a 30 V secondary for 8 Ohms. A few volts more will do no harm for the OP.
Better still, he can buy pre-assembled boards on eBay as a first step to DIY audio.
http://hifisonix.com/wordpress/wp-content/uploads/2018/02/JLH-10-Watt-Simple-Class-A-Amplifier.pdf
The output is AC coupled and JLH specified a 30 V secondary for 8 Ohms. A few volts more will do no harm for the OP.
Better still, he can buy pre-assembled boards on eBay as a first step to DIY audio.
Well. it says 30Vdc. So you can go up to 22Vac transformer.
It's a long way from 30Vdc to 42Vdc that a 32Vac transformer will give you.
Also. since its a centertap transformer, and only one sec is in use, it would be a 130VA transformer and not a 260VA. For 8ohm use the jlh needs 1.25A bias.
1.25Ax42Vdc=52.5W dissipation pr ch. so 105W for 2 ch. all that from a 130VA transformer.
Last edited:
Yeah you might be right, didn't know about that F7 isn't in DIY..
Saw these all over the place in Southeast Asia, selling like Cookies..
In the meantime you can't even buy the Mosfets for it.. not to talk about the JFETS.. And believe me I know the specs of the F7.
BTW this was 2 Years ago..
And about the transformer, yes your right,, it's too weak..I actually misread the thread of Gilera thought he has two of them, my Bad,.
SometimeI think we are talking not about the same Subject.. Class A is asking for Power, and when I read ther forums there then I have to ask how they do build this amps.
You see the thread starter he wants to build it and I'm sure he will find some Cirquit which fits his needs..
Regards Chris
Strange that nobody is interested in the OP actual questions. Bonsai has a simple, practical and very pleasing solution. He suggests JLH of 1969, If the transformer is a centre tap than use each tap to power one channel, if it is two separate windings the use a two two rectifier full-wave configuration.
Hi Andrew, been following your web-site with genuine interest. It is very, very nice, informative and professional. My sincere congratulations with what you have achieved and the products that you offer.
Hi Andrew, been following your web-site with genuine interest. It is very, very nice, informative and professional. My sincere congratulations with what you have achieved and the products that you offer.
Member
Joined 2009
Paid Member
I agree with Bonsai and Nico - great advice. You learned two things:
a) build a JLH, it's proven, has few risks to trip you up, there's lots of support available from here, it will sound good
b) this thread is typical of many such threads, the signal to noise ratio is often very poor, sometimes I've been known to add noise. Bonsai is keeping us honest - good job!
a) build a JLH, it's proven, has few risks to trip you up, there's lots of support available from here, it will sound good
b) this thread is typical of many such threads, the signal to noise ratio is often very poor, sometimes I've been known to add noise. Bonsai is keeping us honest - good job!