...and I get a tip (from member Megajocke) that Arrow is selling off the thermal track transistors dirt cheap, so I order some. Now, what to do with these? I think to change an existing design for these to work in but then I remember seeing...somewhere...an amp that is made for these. It looks complicated and it has some "features" that I don't want. I figure I can make a few changes so I go to the trouble of capturing the schematic in Multisim to try and get an impression of the performance. Very nice this amp looks in simulation and my changing the input from jfet to bjt didn't seem to make that big of a...
Enough of that. First, I'm not looking for any input here and I fully expect this thread to be ignored by many BUT I have something too good not to share. Admittedly, it is not original - I ripped off another DIY design for this (apologies have been made). I made changes. I corrupted the design and produced a truly offensive board layout. I made a prototype and populated it with unholy parts. I ran it and low, I saw that is was good- sing praise. 😀
In all seriousness, the schematic. Yes, it looks familiar.
Enough of that. First, I'm not looking for any input here and I fully expect this thread to be ignored by many BUT I have something too good not to share. Admittedly, it is not original - I ripped off another DIY design for this (apologies have been made). I made changes. I corrupted the design and produced a truly offensive board layout. I made a prototype and populated it with unholy parts. I ran it and low, I saw that is was good- sing praise. 😀
In all seriousness, the schematic. Yes, it looks familiar.
Attachments
Is that a CFP driver setup ?? how would the EF oriented
T-track bias track tempco??
Is that why I noticed jumpered diodes in the Abomination
pix you posted??, to compensate.
OS
T-track bias track tempco??
Is that why I noticed jumpered diodes in the Abomination
pix you posted??, to compensate.
OS
AKSA said:
Thanks Hugh,
Yes, I twisted his into a new animal. It has very similar performance across the board. I'll be posting results as I go.
ostripper said:
CFP like the original with the drivers running hot. They are all on the main heatsink along with the outputs. The TT diodes will track the temp. I have 5 of the 6 diodes in circuit but shorted one to allow for a lower idle current (50-60mA) to start. To use a higher idle current (140mA or more!) use 5 of the diodes. The schematic is not correct in this detail, I forgot to put the 5th one back in.
Here is the Fourier analysis of both simulated amps. This is not to show one being better than the other, but just to demonstrate how similar they are.
The simmed RMI first:
And the Abomination!:
These were done at the same output power, idle current and load.
very good,mjl .I like that strange LTP/vas .. will "steal" it for sims.
But I thought you said LEDs were GAUDY...🙂 (I happen
to like the idea of a Xmas tree amp).
BtW, Just for reference , is the general topology of this one a "balanced cascode"? I never followed roenders thread (too
many trannies)
But I thought you said LEDs were GAUDY...🙂 (I happen
to like the idea of a Xmas tree amp).
BtW, Just for reference , is the general topology of this one a "balanced cascode"? I never followed roenders thread (too
many trannies)
ostripper said:very good,mjl .I like that strange LTP/vas .. will "steal" it for sims.
But I thought you said LEDs were GAUDY...🙂 (I happen
to like the idea of a Xmas tree amp).
BtW, Just for reference , is the general topology of this one a "balanced cascode"? I never followed roenders thread (too
many trannies)
I used all green LEDs that I'll paint black 😉
That's it operating at the full +/-70 rails.
It's a folded cascode. I'd explain but I'm not sure I know how. Maybe Hugh could pop in again. 🙂
Here's 20kHz clipping performance from the actual amp. This is at full power:
Mild clipping shows no sticking. This is about 5Vpp over the amps input sensitivity.
🙁 DRab black ..I'll resim it so I can use red,blue ,green..
I like LED's.
I,m jealous of your nice boards , maybe i'll take take you up on your offer.. my layout is almost done..
A folded cascode is pretty much any common emitter amp which operates directly into a common base circuit.
That is, a LTP collector drives the emitter of the voltage amp, with the base kept at a constant voltage (just like any other cascode).
Chief disadvantages are:
More noise
Poor offset control
Reduced output swing
All you need to know about them is
HERE.
I still like 'em though, because they are fast. Could you replace the VAS current mirror with simple resistors, do you think? That would improve offset control, and remove an area of non-linearity, though at the expense of OLG.... (but you could pick that up again if the output from the LTP was buffered through an EF).
Hugh
That is, a LTP collector drives the emitter of the voltage amp, with the base kept at a constant voltage (just like any other cascode).
Chief disadvantages are:
More noise
Poor offset control
Reduced output swing
All you need to know about them is
HERE.
I still like 'em though, because they are fast. Could you replace the VAS current mirror with simple resistors, do you think? That would improve offset control, and remove an area of non-linearity, though at the expense of OLG.... (but you could pick that up again if the output from the LTP was buffered through an EF).
Hugh
AKSA said:
Thanks again,
I can't comment on noise (yet) but the offset is as low as I've ever seen - less than 1mV. Output swing is not an issue in my case as I'm not utilizing the full voltage potential of the power supply anyway.
It is supremely stable with next to no compensation and very well behaved.
20kHz squarewave:
An externally hosted image should be here but it was not working when we last tested it.
I have tried a few different things, including resistor loads for the VAS, but all had a negative effect on the distortion spectrum - increases in the odd order harmonics, especially the 3rd.
It is the best amp that I have simmed (so far).
ostripper said:
Anytime, no problem. 🙂
"I see a red LED and I want to paint it black...No colors anymore I want them to turn black...
Hi John,
No criticism - it's cool.
If you are OK with this, I will email you a bit later when I have some time, I'm battling the clock at present.
VERY nice amp, chief disadvantage of the folded cascode here is the lack of current amplification; any grounded base design will have current gain of one, which keeps OLG lower. This is, I think, the reason Mihai went differential, to pick up more OLG.
Hugh
No criticism - it's cool.
If you are OK with this, I will email you a bit later when I have some time, I'm battling the clock at present.
VERY nice amp, chief disadvantage of the folded cascode here is the lack of current amplification; any grounded base design will have current gain of one, which keeps OLG lower. This is, I think, the reason Mihai went differential, to pick up more OLG.
Hugh
It is very good to try to increase something
We cannot be the first one to discover things when differential, CCS, Mirrors, Cascodes and all stuff is there, posted, published to all of us... impossible not to be influenced in something or receive influences from someone's schematic.
To produce something really different, a really brand new pioneer idea, we need to come from Mars, and never had studied earth electronics, never had observed a differential amplifier or a LED.
So.... let's go folks, let's increase, develop and produce our nice franksteins for our communitty happyness and our own joy!
Very good thread... real things, truth conversation.
regards,
Carlos
We cannot be the first one to discover things when differential, CCS, Mirrors, Cascodes and all stuff is there, posted, published to all of us... impossible not to be influenced in something or receive influences from someone's schematic.
To produce something really different, a really brand new pioneer idea, we need to come from Mars, and never had studied earth electronics, never had observed a differential amplifier or a LED.
So.... let's go folks, let's increase, develop and produce our nice franksteins for our communitty happyness and our own joy!
Very good thread... real things, truth conversation.
regards,
Carlos
Re: It is very good to try to increase something
Hi Hugh,
No criticism taken 🙂 I'm open to suggestions. I have tried out quite a few changes in an attempt to "improve" the circuit but it may well be as good as it can be. The biggest change I made was to convert the front end from jfet to bjt while maintaining the same current through the VAS. This wasn't an improvement but the main thing that I wanted to do.
I eliminated the cascode on the CCS for the LTP and with it an LED. Changed the cascode devices on the LTP to lower power units, but these still get fairly warm. Most of the devices are different from those in the RMI.
Very true Carlos. I don't want to build anything directly from plans, but like to make little changes to leave my mark on it (like a dog marking his territory 🙂 ) and to learn something. It's more fun that way. The reaction that I got from doing this was unexpected - something like: "you have ruined it!"
Some guys here are afraid to change one TO-92 in an amp thinking it will destroy the "sound". Nonsense.
AKSA said:
Hi Hugh,
No criticism taken 🙂 I'm open to suggestions. I have tried out quite a few changes in an attempt to "improve" the circuit but it may well be as good as it can be. The biggest change I made was to convert the front end from jfet to bjt while maintaining the same current through the VAS. This wasn't an improvement but the main thing that I wanted to do.
I eliminated the cascode on the CCS for the LTP and with it an LED. Changed the cascode devices on the LTP to lower power units, but these still get fairly warm. Most of the devices are different from those in the RMI.
Thanks salas. 🙂salas said:The amp is cool, and more so the thread's title.😀 Nice one.
destroyer X said:
Very true Carlos. I don't want to build anything directly from plans, but like to make little changes to leave my mark on it (like a dog marking his territory 🙂 ) and to learn something. It's more fun that way. The reaction that I got from doing this was unexpected - something like: "you have ruined it!"
Some guys here are afraid to change one TO-92 in an amp thinking it will destroy the "sound". Nonsense.
Re: Re: It is very good to try to increase something
No, the reaction was to not call it ronder's RMI-FC100.
By the way, do FFT comparing analyses at 20Khz and with the same feedback factor 😉
Anyway, good job.
MJL21193 said:
No, the reaction was to not call it ronder's RMI-FC100.
By the way, do FFT comparing analyses at 20Khz and with the same feedback factor 😉
Anyway, good job.
Hi MJL21193
I was wondering what part the 2x 15pF of dominant-pole caps would be doing to keep the topology stable.
Would you be able to elaborate on this for me?
🙂
I was wondering what part the 2x 15pF of dominant-pole caps would be doing to keep the topology stable.
Would you be able to elaborate on this for me?
🙂
Re: Re: Re: It is very good to try to increase something
Hi roender,
I couldn't call it anything else in good conscience. I thought I was giving credit to the designer, but you make it seem as though my version doesn't deserve to be associated with yours. Mine is beneath yours. So, I called it Abomination! It's a good name. 🙂
OK, you asked. Your RMI:
My Abomination!:
Thanks.
I respect your opinion and abilities and I certainly respect the amp that you designed. It has stunning performance and I'm not sure if the simulator is telling the whole story. I will build it one of these days (I still have that board that I made) using the parts that you recommend.
roender said:
Hi roender,
I couldn't call it anything else in good conscience. I thought I was giving credit to the designer, but you make it seem as though my version doesn't deserve to be associated with yours. Mine is beneath yours. So, I called it Abomination! It's a good name. 🙂
roender said:
OK, you asked. Your RMI:
My Abomination!:
roender said:
Thanks.
I respect your opinion and abilities and I certainly respect the amp that you designed. It has stunning performance and I'm not sure if the simulator is telling the whole story. I will build it one of these days (I still have that board that I made) using the parts that you recommend.
KLe said:
Hi KLe,
Not to understate my ignorance: I don't know. The simulation actually shows the amp to be stable without those caps. I haven't tried this with the real amp though.
Lets wait for an explanation. 🙂
More pictures?? Yes!
200kHz squarewave into 8 ohm dummy load:
No comp, let's see now, unity gain will be in the MHZ, Cdom
will be the Cob of the tranny. Will make a good RF
amp..😀
OS
Pete,
Why not try second order phase lead?
Fantastic results, BTW, love that 200KHz square wave..... that clearly indicates that bandwidth is approaching 2.2MHz, that it's stable is a great feature, indicating pole frequency is very high for an amp of this topology.
Hugh
Why not try second order phase lead?
Fantastic results, BTW, love that 200KHz square wave..... that clearly indicates that bandwidth is approaching 2.2MHz, that it's stable is a great feature, indicating pole frequency is very high for an amp of this topology.
Hugh
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