Choke loaded amps are fairly efficient, so powering them with SLA batteries might not be completely out of question.
A simple choke loaded follower with about 13V rail voltage would be capable of ~8W into 8R with 1,5A bias current.
SLA batteries are not that expensive and one 50Ah battery per channel would last quite some time between charging.
A simple choke loaded follower with about 13V rail voltage would be capable of ~8W into 8R with 1,5A bias current.
SLA batteries are not that expensive and one 50Ah battery per channel would last quite some time between charging.
Fuling!
Can you help me in this question: Is it worth to impregnate the EI chokes with Nitro Lacquer?
Greets:
Tyimo
Can you help me in this question: Is it worth to impregnate the EI chokes with Nitro Lacquer?
Greets:
Tyimo
Tyimo: I´m not familiar with Nitro Lacquer, but impregnating chokes and transformers is generally a good idea.
I´ve heard output transformers playing music almost as loud as the speakers😀
I´ve heard output transformers playing music almost as loud as the speakers😀
Hi flg,
To get your square wave to look square, you will need to have a very large inductance, with no saturation and high current handling to drop the rolloff frequency as far down as possible.
An amplifier like this will have a natural rolloff in the low frequencies because as frequency goes down, the inductor becomes lower in resistance, reducing the gain. Like thorstenlarsen said, you need flat gain down to dc for a square wave to be recreated accruately.
So your best bet is to get the biggest inductor with the least saturation you can afford, then either live with the square wave image, (shouldn't give much trouble in music domain unless there is a lot of clipping in the original source material) or use it at higher frequencies. This might be a good amp for fullrange speakers.
To get your square wave to look square, you will need to have a very large inductance, with no saturation and high current handling to drop the rolloff frequency as far down as possible.
An amplifier like this will have a natural rolloff in the low frequencies because as frequency goes down, the inductor becomes lower in resistance, reducing the gain. Like thorstenlarsen said, you need flat gain down to dc for a square wave to be recreated accruately.
So your best bet is to get the biggest inductor with the least saturation you can afford, then either live with the square wave image, (shouldn't give much trouble in music domain unless there is a lot of clipping in the original source material) or use it at higher frequencies. This might be a good amp for fullrange speakers.
Fuling said:
Nitro Celulose Laquer is "Real Laquer" The way it used to be. It is extrmely non-porus, it smells nasty when spraying, and it's dangerous to spray, but, it's the best! Do you recognize the term Nitro Celulose? Otherwise, a sulfur free form of Gun-Powder! You'ld be lucky to find it anywhere actually, Last time I got some I had to custome order it from CH brands I beleive, in the US. Might have been VHT brand stuff??? I can check if your actuaklly interested...
Did somebody say follower??? As in Pathos or broskie??? That would be next...
flg said:The sine waves look good. I haven't done actuall THD measurements yet though...
Ok, something obviously doesn't add up....anyhow, at my place an amp is tested for DC at the outputs, left to run like an hour on the bench, and then checked once again if the DC offset is ok. If so, I go listen, if I like what I hear, I listen some more and try to define the cons and pros of the amp.
Once all that is done....I measure to see if what I thought I heard, corelates with what I measure.
So really, if your amp doesn't seem to endanger the speakers, gfo give it a shot, you may be surprised 🙂
Magura 🙂
Re: Choke question
No, it's worth to impregnate inductors with polyester, just as it's done in the industry. This not only makes the inductors dead silent, but makes them take more abuse physically. It also makes them able to deal with more heat/power.
Magura 🙂
Tyimo said:
No, it's worth to impregnate inductors with polyester, just as it's done in the industry. This not only makes the inductors dead silent, but makes them take more abuse physically. It also makes them able to deal with more heat/power.
Magura 🙂
Re: i like this thread.
Yes I have the data if needed, but do me a favour and think it over if you really are going to make such, before asking for this sort of help, as I will have to search for the info.
If you think it's ok to:
1) spend close to 1000 US$ on such two.
2) Spend a few days making them.
3) that they weigh in around 40Lbs each.
4) go buy an oven to bake the polyester impregnation.
Then I'll help you make such, no problem 😎
Magura 🙂
AudioGeek said:
Yes I have the data if needed, but do me a favour and think it over if you really are going to make such, before asking for this sort of help, as I will have to search for the info.
If you think it's ok to:
1) spend close to 1000 US$ on such two.
2) Spend a few days making them.
3) that they weigh in around 40Lbs each.
4) go buy an oven to bake the polyester impregnation.
Then I'll help you make such, no problem 😎
Magura 🙂
Fuling, Flg, Magura!
Thanks for theanswers.
What polyester do you suggest?
What is the best way to impregnating? I mean how to?
Tyimo
Thanks for theanswers.
What polyester do you suggest?
What is the best way to impregnating? I mean how to?
Tyimo
Tyimo said:
You need the type of polyester that is heat curing. Your best bet to get such in smaller quantities, is to take a metal bucket, a six pack, and go visit your local electro mechanic. AFAIK it's only sold in barrels of considerable size (like 50 pounds or so).
You don't need a vacuum chamber to impregnate an inductor. The trick is to heat the inductor to 60 C prior to dipping, as the polyester becomes thin like water at this temperature, and hence gets in everywhere. To make it perfect, you can vibrate the inductor a bit during the soaking.
Magura 🙂
For the large inductance values needed an air core coil will
tend to be rather large. I have a 10lb coil of #16 wire on a 4
inch coil 4 inches long which measures 80mh and 4.8 ohms.
I could have picked a better coil form. On the other hand an
iron core coil will be a lot more compact but not sound as good.
I saw a refference to using an iron core inductor and a air core
inductor in seriese in the TubeCad journal. John compared it
to the practice of using a film bypass cap with an electrolitic cap.
After reading this I remembered a old inductor loaded single
ended OTL where a small value air core inductor and a iron core
inductor is used in seriese.
tend to be rather large. I have a 10lb coil of #16 wire on a 4
inch coil 4 inches long which measures 80mh and 4.8 ohms.
I could have picked a better coil form. On the other hand an
iron core coil will be a lot more compact but not sound as good.
I saw a refference to using an iron core inductor and a air core
inductor in seriese in the TubeCad journal. John compared it
to the practice of using a film bypass cap with an electrolitic cap.
After reading this I remembered a old inductor loaded single
ended OTL where a small value air core inductor and a iron core
inductor is used in seriese.
I don't remember where on the Tube Cad Journal web page
I saw this refference. It was not a major article only a paragraph
or two saying that the high frequency behavior of an iron core
inductor bad and a small air core choke in seriese could inprove
the overall behavior. This is from memory.... But it made the
connection in this amp make sense.
The cathode load is a 20ohm resistor in seriese with a 1 mh
air core choke then a 600mh choke.
I saw this refference. It was not a major article only a paragraph
or two saying that the high frequency behavior of an iron core
inductor bad and a small air core choke in seriese could inprove
the overall behavior. This is from memory.... But it made the
connection in this amp make sense.
The cathode load is a 20ohm resistor in seriese with a 1 mh
air core choke then a 600mh choke.
Attachments
Ignoring the two inductors for the moment. Because at dc they
will have little resistance. The voltage drop across the 20 ohm
resistor trimmed by the 5k pot define the -grid bias and help
prevent thermal runnaway. The 2 inductors come into play
with the ac signal.
will have little resistance. The voltage drop across the 20 ohm
resistor trimmed by the 5k pot define the -grid bias and help
prevent thermal runnaway. The 2 inductors come into play
with the ac signal.
I´m not Magura, but I´ve tried choke loaded followers (both source and cathode followers). A great and efficient way to build high power SE amps!
A couple of years ago I bought 9 pcs 25mH 3A C-core chokes from a surplus company and made an amp using four in series per channel and a massive 27V PSU. I got 30W out of it but it was never finished due to driver stage problems.
I´ve been thinking about rebuilding the amp but the chokes have found new homes as PSU chokes in other projects.
I also have 4 pcs 112mH 2A EI-core chokes, also surplus stuff of unknown origin. I tried one of them in a small two stage Jfet/mosfet amp that looked promising but it never got past the prototype stage. Someday...
The best sounding choke loaded follower I´ve build uses 4xPL504 low Rp tubes per channel. It wastes something like 300W to get about 2x0,7W out but it sounds quite marvellous...
I will probably build a bigger version someday using PL519 tubes and CCS cathode loads.
There´s a thread somewhere on this forum titled "My first ever class A amp" (or something) where member Circlotron describes his massive L-loaded follower amp. He also shows how to make chokes using cores from old MOTs. It´s a shame copper wire is so expensive these days, transformer cores can be had more or less for free.
A tip from one of Nelson Pass´s articles is to put resistors across the chokes to tame ringing. The efficiency goes down a bit of course, but it might be worth it.
A couple of years ago I bought 9 pcs 25mH 3A C-core chokes from a surplus company and made an amp using four in series per channel and a massive 27V PSU. I got 30W out of it but it was never finished due to driver stage problems.
I´ve been thinking about rebuilding the amp but the chokes have found new homes as PSU chokes in other projects.
I also have 4 pcs 112mH 2A EI-core chokes, also surplus stuff of unknown origin. I tried one of them in a small two stage Jfet/mosfet amp that looked promising but it never got past the prototype stage. Someday...
The best sounding choke loaded follower I´ve build uses 4xPL504 low Rp tubes per channel. It wastes something like 300W to get about 2x0,7W out but it sounds quite marvellous...
I will probably build a bigger version someday using PL519 tubes and CCS cathode loads.
There´s a thread somewhere on this forum titled "My first ever class A amp" (or something) where member Circlotron describes his massive L-loaded follower amp. He also shows how to make chokes using cores from old MOTs. It´s a shame copper wire is so expensive these days, transformer cores can be had more or less for free.
A tip from one of Nelson Pass´s articles is to put resistors across the chokes to tame ringing. The efficiency goes down a bit of course, but it might be worth it.
bogdan_borko said:
Yes, I tried an inductor loaded source follower inspired by Circlotron. Sure it works fine, no doubt about that, but it did not offer the same as a choke loaded cascoded differential pair. The only benefit I can see it that you can get away with just one inductor, so no custom made stuff or distortion analyser required to build it.
Fuling said:
You're just one lucky guy, well aren't you? 😀
Magura 🙂
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