How does one chose a good class A output transformer? I'm looking to build = a simple class A low power < 15W that can drive 4, 8, or 16 ohms and has hi= gh linearity with a separate negative feedback coil(so switching load sizes= does change the feedback path).
Any recommendations?
simple class A low power< 15W that can drive 4, 8, or 16 ohms and has high linearity with a separate negative feedback coil(so switching load sizes does change the feedback path).
Would you please make up your mind:
a) a tube amplifier with an output transformer, or b) high linearity.
-- Tauno Voipio
simple class A low power< 15W that can drive 4, 8, or 16 ohms and has high linearity with a separate negative feedback coil(so switching load sizes does change the feedback path).
-- What makes you think the two are mutually exclusive?
simple class A low power < 15W that can drive 4, 8, or 16 ohms and has high linearity with a separate negative feedback coil(so switching load sizes does change the feedback path).
-- What's your target toob or transistor, and if you have a separate negative feedback coil, how does that change the feedback path if different load resistances are selected?
ld a simple class A low power < 15W that can drive 4, 8, or 16 ohms and has= high linearity with a separate negative feedback coil(so switching load si= zes does change the feedback path).
Any of the common(i.e., cheap) standard tube amp tubes. 6L6, 6V6, EL34, etc= ...=20
I could go with a standard class A output transformer replacement but looki= ng for a some theory so I don't end up with a doozie.
Also, I'm looking for some transformers for coupling. Need a good linear hi= gh mu audio transformer(something that has good flat response in the audio = range) that is not too terribly expensive.
"Archival" John Fields wrote: Archival
Any of the common(i.e., cheap) standard tube amp tubes. 6L6, 6V6, EL34, etc...
I could go with a standard class A output transformer replacement but looking for a some theory so I don't end up with a doozie.
** You thinking of class A push pull or single ended ?You thinking of SET or pentode mode ?
Also, I'm looking for some transformers for coupling. Need a good linear high mu audio transformer(something that has good flat response in the audio range) that is not too terribly expensive.
** See the tooth fairy - he has just what you need..... Phil
d a simple class A low power < 15W that can drive 4, 8, or 16 ohms and has = high linearity with a separate negative feedback coil(so switching load siz= es does change the feedback path).
transformers in audio amps are so 70s
simple class A low power< 15W that can drive 4, 8, or 16 ohms and has high linearity with a separate negative feedback coil(so switching load sizes does change the feedback path).
Experience. I've building electronics since 1960's, and the only viable active components were tubes, at the beginning.
-- Tauno Voipio, (OH2UG since 1960)
"HardySpicer"
** Huh ??Coupling and output transformers were eliminated from nearly all transistor amps in the mid 60s.
Only place they lingered on for a while was in portable radios and loud hailers that used Germanium devices.
Of course, 70V and 100V line amplifiers still mostly use output transformers.
... Phil
simple class A low power < 15W that can drive 4, 8, or 16 ohms and has high linearity with a separate negative feedback coil(so switching load sizes does change the feedback path).
for a some theory so I don't end up with a doozie.
mu audio transformer(something that has good flat response in the audio range) that is not too terribly expensive.
>-- http://www.hammondmfg.com/5caud.htm
Single ended or push-pull ?
If single ended, please remember to use the air gap in the core to avoid any DC current saturation issues.
16 ohms and has high linearityfeedback path).
Apart from safety issues (especially in AC/DC receivers), what is the need for a separate feedback winding ?
The amplifier open loop output impedance must be huge, if using the transformer secondary as the feedback winding with some unspecified load, would make any difference.
16 ohms and has high linearity
feedback path).
My first audio amplifier was a DS-501 direct driving a speaker in parallel with a big-ass choke... ~6W out into 8 Ohms, running on a car battery :-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
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I love to cook with wine. Sometimes I even put it in the food.
And enough leakage current to self bias. :(
-- You can't have a sense of humor, if you have no sense.
The only transistor course I had at MIT was in regard to biasing Germanium. ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
Germanium transistors are the liberals of the semiconductor family. Fortunately there aren't many left. ;-)
-- You can't have a sense of humor, if you have no sense.
Slow, leaky, can't take the heat, tend to run away?
Why is SiGe better than Si?
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
No idea. I've never worked with them.
-- You can't have a sense of humor, if you have no sense.
Much higher mobility, both electrons and holes, so for a given device size you get lower extrinsic base resistance. Plus you can do interesting strained-layer things, plus the heterojunction makes the built-in field in the CB region larger, which reduces the Early effect amazingly. The spice models for SiGe devices like the BFP640 all say VAF=1000, which is probably an underestimate. Some of them actually show a negative collector resistance in the datasheet curves, which I strongly suspect is thermal rather than electronic in origin.
(I just started using them myself in the last 6 months, and have been reading up on them. I dropped my graduate solid state class halfway through, when my first daughter was born. I had to do a bit of academic triage, and it looked like the one it would be easiest to pick up on my own afterwards. Still working on that.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
SiGe is an EMITTER implant in an otherwise Silicon-only process. It results in dramatically higher fT. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Are there any good tutorials / books for designing toroidal transformers for audio use ?
My searching has found companies that will design one for me.
I would like to know the design parameters I need to use before I search out a manufacture.
Thanks
hamilton
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