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Build OTL = transistor
P: 65W
Vin: 0.775V
Rin: 400 kΩ
BW: 30Hz - 17kHz
0,2%
CMRR: 70 dB

i don't know where to start. Help me please ((

Thanks a lot

[Peter Wieck]

On Monday, November 7, 2016 at 9:52:50 AM UTC-5, wrote:
Build OTL = transistor
P: 65W
Vin: 0.775V
Rin: 400 kΩ
BW: 30Hz - 17kHz
0,2%
CMRR: 70 dB

i don't know where to start. Help me please ((

Thanks a lot

What are you asking? There are thousands of options out there, from packaged (modular) devices to separate output transistors from many sources.

Do a simple search on Google, and you will find all sorts of options at all sorts of levels.

Peter Wieck
Melrose Park, PA

[Big Bad Bob]

On 11/07/16 06:52, so wittily quipped:
Build OTL = transistor
P: 65W
Vin: 0.775V
Rin: 400 kΩ
BW: 30Hz - 17kHz
0,2%
CMRR: 70 dB

i don't know where to start. Help me please ((

Thanks a lot


what exactly are you attempting to do (or ask)? When I look at this I
go "uh, ok..." and that's about it.

you have what appears to be a standard audio amplifier with comporable
specs to a zillion other things. I've designed and built a couple of
them that are similar. One of them is set up to either be 25W per
channel stereo, or (in a bridged mode) run as an ~80W RMS mono amplifier
[like for a bass or guitar]. I used low noise FET input op amps and
MJE2955+MJE3055 for the output. The power supply has two 24V
transformers rated at around 2A on the secondary, one for each leg
(positive and negative). It was a cheap alternative to finding a single
transformer to do the job. But as I built it in the 1980's I'm sure I
could do a switcher, now, that would do an even BETTER job.

/me wishes I still had that old '6L6GC equivalent' based PA amplifier,
though... I used it for a LONG time until the output transformer lost a
primary winding. The output tubes were 12-pin compactrons, though, but
had the same spec as a 6L6GC. 25WRMS nice and clean, too.

[John L Stewart]

[quote=Big Bad Bob;995651]On 11/07/16 06:52, so wittily quipped:
Build OTL = transistor
P: 65W
Vin: 0.775V
Rin: 400 kΩ
BW: 30Hz - 17kHz
0,2%
CMRR: 70 dB

i don't know where to start. Help me please ((

Thanks a lot


Sounds like an engineering student looking for a hand up on an assigned project. But I've been wrong before. Many times, for that matter!

Cheers to all, still hanging on here at RAT.

[Patrick Turner]

On Tuesday, 8 November 2016 01:52:50 UTC+11, wrote:
Build OTL = transistor
P: 65W
Vin: 0.775V
Rin: 400 kΩ
BW: 30Hz - 17kHz
0,2%
CMRR: 70 dB

i don't know where to start. Help me please ((

Thanks a lot

This is a tube based discussion group. But some ppl who have been here since about 1995 don't mind solid state, aka Squalid Stait. There used to be magazines with details for kits you could build for SS, but the Internet killed mags and Pulse Width Modulated amps with solid state and circuit boards so tiny and complex there is nothing for a DIYer to do.
Nevertheless, a DIYer can build a very good class AB amp if he sticks to all discrete parts. In 1996 I made a stereo amp with BF469 and BF470 for input/driver, and 6 x npn and pnp mosfets 2SK1058, 2SJ162 for output. It can make 350W per channel with +/-65Vdc rails. THD at 200W 0.01%, noise with no signal 0.25mV, so fet inputs are not needed.
I've also used bjts for output stage but I loathe them because they are so much more difficult to stabilize, and suffer cross conduction above 10kHz.

If you do not want to learn about how all the devices devices work and just want to build a box with pre-made modules, then be prepared for smoke and silence after you turn it on. buy 4 modules. This allows you to fry two then maybe you learn why - and you have two spares.
The sound you will hear after you have labored long and hard for 3 month's of sundays might be OK, but maybe it won't be as good as a decent tube amp with OPTs. Probably, you do NOT NEED 65W capability. Nobody I ever knew during 19 years in audio trade ever needed average power of each channel above 0.5W. If they turned up level, their wife & dog would leave.

At least you are not trying to make a tubes OTL amp which IMHO is a pathway to sonic bull****. Men like to believe the sound is better without an OPT but its a complete myth. DIYer construction of a good OTL is prone with all manner of difficulties. One involves buying at least 10 x 6AS7 for each channel for maybe 50W max, and then having to pay high electricity bills.
2 x KT88 in UL mode will sound better than any tubed OTL horror.

If you wish to learn all you can learn, you need to build a preamp using say 1 transistor. Yes, just ONE. PN100 will do. Then you build and READ about bjts from old books, and not jerks online with much to say but nothing about how basic stuff works. Learn & Build needs you to get the gear such as oscilloscope, volt meters, function generators and ability to make a hand made circuit board and how to make a safe PSU - the ONE transistor preamp make take 6 weeks because each step of the way provokes questions you must answer yourself. The single BJT won't be perfect, but its a start. Opamps have dozens of bjts within and you can't ever understand basics with them because you don't yet have any idea about gain of devices, the NFB and many other things.
I've said too much, again.
The 2x300W stereo amp I made sounded just as well as a class A tube amp capable of 50W pure class A with 4 x GE6550A per channel. I had 4 blokes over one evening for listen session, and I switched to SS amp after an hour with a switch I'd rigged up. They were ALL fooled, not one perceived any sound change. When I owned up to this mean nasty trick, they were not happy, but one said, "well, the same ******* designed both amps, so I guess they both sound just as good..." The lynching rope was put back in the bag.

Hardly anyone is building any sound gear at home now. The GFC in 2008 lowered standards of living in USA, guys who were self reliant got old, and the Internet and smart phones seem to be making a whole generation quite dumb, or lazy, or dumb and lazy.
Patrick Turner.

[Peter Wieck]

On Monday, November 7, 2016 at 9:52:50 AM UTC-5, wrote:
Build OTL = transistor
P: 65W
Vin: 0.775V
Rin: 400 kΩ
BW: 30Hz - 17kHz
0,2%
CMRR: 70 dB

i don't know where to start. Help me please ((

Thanks a lot

I am going to go out on a limb he

Look for a Class D modular amplifier. One of many sources is linked.


http://www.classdaudio.com/amplifier-kits/


Quick, simple, not terribly expensive.

Peter Wieck
Melrose Park, PA

[Big Bad Bob]

On 11/15/16 14:49, Patrick Turner so wittily quipped:
The 2x300W stereo amp I made sounded just as well as a class A tube amp capable of 50W pure class A with 4 x GE6550A per channel. I had 4 blokes over one evening for listen session, and I switched to SS amp after an hour with a switch I'd rigged up. They were ALL fooled, not one perceived any sound change. When I owned up to this mean nasty trick, they were not happy, but one said, "well, the same ******* designed both amps, so I guess they both sound just as good..." The lynching rope was put back in the bag.

heh - that's pretty funny.

seriously, though, tubes have their biggest benefit when the tube itself
is part of "the sound" [like guitar amps].

Still doesn't stop me from thinking that glowy glass bottles "look cool"
and actually appear to be doing something when the blue-glow on the side
of the bottle changes brightness along with the music...