"Which CineMag transformer are you referring to? The CMMI-10C I referenced above is rated
(1% THD @ 20 Hz) at +5dBU which is about 1.4 volts RMS."
http://cinemag.biz/mic_input/CMMI-10C.pdf says"it puts out up to +24.5dBu before reaching
core saturation (1% THD at 20Hz)"
My mistake, +24.5 dbu is 13V RMS output which would give you 21 watts into 8 ohms.
Michael
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It looks very similar to my Mega Phone device I made when I was a kid. It was LOUD loaded on a 10 Watt metal folded horn speaker that looked like a big bucket (like one of speakers in the array on the picture, each of them is something like 115 dB/W/M).
I grounded collectors too; I used Germanium PE-4B transistors then, they had flanges and 4 holes for bolts in each. However, the mic was electro-mechanical, the single condenser one I saw then in a Sony tape recorder imported from Japan.
Ah, ok. I thought you were referring to the input spec.
And of course you can use a pair of them in a bridged circuit and get even more than that.
se
Right, Your note was to put the secondaries in series for another 6db...
~80 WPC then!
I got the megaphone and step-up circuits mixed up in my calculator 😱
The reason I checked into it was I looked through my iron collection and
nothing comes close for both step-up and high secondary voltage. I have
UTC A-10s that are 1:10 (or 1:20 in MC SUT duty) but +15dbu output
which is only 5.6V RMS... So these Cinemags are great for this use.
Now I'm interested in hearing this... another project
There is a section on this inside "Radiotron" 4th Ed. which was written in 1953, more than 50 years ago. The idea was not new then either. Westinghouse (Basically the old telephone monopoly in the US) held patents dating from at least the 1930's
By the 50's text books like Radiotron were having to explain why this was not used so much in Hi Fi applications. The book explains the problems with the idea namely that there is no gain in power, limited bandwidth and high cost. Transformers coupled amps existed from the very beginning of the tube era.
Anyone who is interested in audio, tubes, transformers or to like should have a copy of this book. The copyright has expired and it is now in the public domain. It was written in 1953 and has now become a standard text. The technical level is about right for the serious and motivated audio hobbyist but below the level of a university level engineering textbook.
Download all 1,500 pages of it below.
http://www.pmillett.com/Books/RDH4.pdf
Takes me back to the first amplifier I ever built. I was 9 or 10 years old.
The circuit was from "The Boys Fourth Book Of Radio And Electronics" or similar.
I remember it was the fourth because the first 3 only covered tubes and the
fourth had the magical transistors!
Anyway it was pure simplicity with a 6 volt lantern battery wired in series
with the speaker coil and transistor C-E, with a carbon button microphone
in the base circuit and I think one resistor to set the bias. Yep, class AB
single ended and it sounded like it! but it was loud.
I took it to school to show it off (in a cardboard box enclosure with a 6x9
oval 3.2 ohm radio speaker probably) and some older boys took it from me and
used it to harass girls. Then the teacher confiscated it and I had to go back
with my parents and promise never to bring it to school again before I got
it back. (Lucky the nuns didn't keep it until the end of the year.)
The microphone had a coiled cord and a PTT switch. Things were simpler then
My first amp was transformerless, I made it for a bass guitar (I was in a 5'th grade then). 😀
The schematic was almost copy of a mono vinyl player's amp except one more gains stage.
The power tranny was made from a tube radio one; I cut high voltage secondaries by a saw. 😀
The schematic was almost copy of a mono vinyl player's amp except one more gains stage.
The power tranny was made from a tube radio one; I cut high voltage secondaries by a saw. 😀
That's what the active follower is for.
I don't consider 100kHz to be limited bandwidth.
The 1:10 CineMags aren't terribly costly. Around $45 if memory serves.
se
You think, what except you nobody knows history of evolution of audio? 😉)
Transformers were always used in audio, but first of all coordination for impedances of stages. As, for example, in that transistor circuit which has displayed Wavebourn.
To use transformers as voltage amplifiers in sound applications, it is necessary to have high level of a current for a primary coil. And a special construction of the transformer. Otherwise turn out sound degradation. Therefore transformers were never used as a basic element amplification voltage. And consequently transformers were always used as current amplifiers.
You understand about what I speak? I hope))
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The CMMI-10C, when properly loaded, has an input impedance of approximately 1.5k ohms. If you're driving it with 2 volts, you need to provide a whopping 1.3mA of current. 😀
se
No, ne polimayu.
I currently use Altec transformers in one of my amps; they are 600 Ohm : 15 kOhm transformers, I'm getting about 6V from standard 0 dB sources.
What means "high level of current"? 1 uA? 10mA? 100 Giga Amp? Why special construction? Why sound degeneration?
Please clarify.
It's right. If N2/N1=10 then V2/V1= 10 and I2/I1= 1/10 so there no power amplification.
Here we want only voltage amplification by transformer and then is more easy to get current amplification by active device. At the end it is possible obtain power amplification by both.
In this apparatus, the transformers not were used for voltage amplification, as here intended, seems to me.
Susan Parker and other have been dimostrated that is possible to build a real good amp.
But my question is: what can is good an amp built in this manner?
Can we should realize a very very good musical amplifier as the best as tubes or ss amplifiers or eventual more?
There is anyone that put a schematic with good components to try this?
Also i think that is better to place first the active device, then the transformer, and then the other active device, in a push-pull topology to cancel the dc current in winding transformer.
Best regards, Francesco.
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I built a version of it and it works very well. The one limitation is that it requires a low Z source. To make it more universal, it needs a buffer at the input. If you want to stay away from cap coupling, you could just build a small signal version of of the input stage using a 1:1 transformer/splitter and feed the power stage with that.
Sheldon
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You can use pair of emitter followers, and a step-up transformer between them. Or you can use pair of common emitter amplification stages, and a step-down transformer between them.
In any case it will be an impedance matching transformer.
That is because i said that i prefer devices/transformer/devices topology in my last post.
Another two questions here:
The first:which devices to use: tubes, jfets, mosfets, transistors ?
More time ago i have read that transistors are more suitable as followers than others because its much transconductances, little input cap and high swing voltage capability (Vbe=o,6V against Mosfet Vgs=4V). It's true?
Another question: if we use SS devices it's better to use similar devices (all N or P) or complementair pair?
Btw if we use complementair, it's possible to design a circuit without input or output caps.
On the other hand, for the output circuit is possible to employ same devices in circlotron topology.
Yours advices are welcome here.
Thanks a lot, Francesco.
This is DIY. It's also DIYOW (Do It Your Own Way).
I'd recommend either tubes, JFets, Mosfets, or BJT's.
Yes, those are factors you may want to consider.
Yes.
Yes.
A complementary pair in circlotron topology? I'm curious to see that one.
Sheldon
Sorry if my english isn't perfect.
In this case, i would say that if we not will employ a complementair pair in output stage to eliminate the coupling capacitor, we can employ circlotron topology with same devices (all N or all P).
Francesco.
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