Iron

[Shadowdog]

There are OTL amps being made now by at least 2 companies now and there are threads on diy etc. @ diyaudio and AA (audioasylum). Some people say they are better sonically without the transformers (output) , but I couldn't afford the tubes at replacement time plus the heat would be much higher I would think.

Randy

 

[Redboy]

You should have really good arn in that one. IMHO

arn? :scratch2:

 

[Squidward]

I'd say that it's easier to "destroy the sound" with inferior iron than something good. I've also found that even commercial manufacturers who source more expensive components for their higher-end offerings try not to "destroy the sound" with an unwise circuit choice. Granted, these are not absolute rules, but general observations.

Chokes are now "detrimental to sonic quality"? Is that only in the power supply, or any use of any choke, anywhere? (Nothing controversial about those statements. ROFL.)

 

[audiobiker]

That is a neat looking amp :yes:

 

[Wes_in_VA]

There are three transformers in the photo. The power transformer is the one at top left. The PT turns AC at line voltage into high voltage for the B+ that does the heavy lifting in a tube circuit, filament voltage that lights the tubes' filaments to boil electrons off the cathodes to let the tubes do their work, and also may include a 'bias supply' winding for a "fixed bias" circuit design.

The matched pair of transformers on the bottom center and right of the chassis are the output transformers. These OPTs match the high voltage on the plates of the output tubes (at high impedance) to a lower voltage, higher current output for the low impedance speaker "load" for each of the two stereo channels. The design, construction, and materials used in the OPTs is critical to their bandwidth, linearity, and distortion levels. Good iron ain't cheap!

EDIT: In case you didn't know, the output tubes are the pairs of tubes to the left of each OPT - one pair of tubes per channel; one "pushes", and one "pulls", i.e., one tube in each pair is responsible for amplifying half of the music waveform for the pair's channel. The tube just below the PT in the photo is the amp's HV rectifier, which takes the high voltage from the PT's "B+" winding and rectifies it to pulsed DC. That pulsed DC is smoothed or "filtered" using either capacitors (sections of one or both of the grey cylinders top center in the amp) and/or a "choke" (a coil of wire, sort of like half of a transfomer) and "adjusted" with resistors to provide the final, very pure B+ DC. Sometimes the filaments are rectified to DC, too, to minimize "hum" in the amp, and a fixed bias amp will also have a rectifier and filter network for that, too.

EDIT: PS, a solid state amp will also have a power transfomer, and in older ss amps, it will look a lot like the PT in a tube amp. The purpose of the PT in a ss amp is ususally to lower the AC mains voltage for rectification and filtering as described above for the various circuits and functions in the ss amp. Transistors, (very) generally speaking, do their work at lower voltages than vacuum tubes.

You can see the PT in an early 1970s Kenwood KT-88 stereo receiver in the top right of the chassis in the photo below:

Now that's one of the most helpful things I've found here yet! Thanks for all that info. I'm a total noob to tube so that's a real benefit.
Just plugged up a pair of Eico HF20's that my brother in law gave me for my first all-tube system. I'm really enjoying it.

 

[_d5_]

what are people referring to when they reference Iron?

if they use the term "Big Iron", then they're talking Marty Robbins...

There was forty feet between them when they stopped to make their play
And the swiftness of the ranger is still talked about today
Texas Red had not cleared leather fore a bullet fairly ripped
And the ranger's aim was deadly with the big iron on his hip

 

[Squidward]

So the answer is to add resistance to the PS, which isn't frequency dependent? There are no problems with that approach, I take it?

Nice to chat with you again, as well! Hope you and Barry are doing well!

 

[Kegger]

Give me a good well filtered power supply with some nice beefy chokes any-day..:thmbsp:

And for the most part when I'm looking at pieces of audio gear to "acquire" them I am
looking at the transformers(iron) for beefy-ness as to whether it is something I desired.

I don't really pay much attention to the circuitry as I will design my own, it's truly what
that piece has in it for iron that get's my juices going, thinking about what to do with it.

---

So yah you can have all the resistors in your power supply you want, and mediocre iron
to boot, I'd go the upgraded performance route for my standards with supplies utilizing a
Heavy Duty choke or 2 and a beefy power tranny with some nicely sized output tranny's.
(better/best performance come from overbuilt/sized transformers that are designed well)

That's what I look for in pieces, just is no way around it from My Standpoint if you Want
"better than average" Performance, you need the Iron. Then build yourself a good circuit.
(there is some very good vintage iron out there, that's the type of stuff I Try an collect)

Not everything you build or own will have the best of best iron, but if your setting out to
look for the Best or "Very Good" then size is a nice thing to look at when it comes to Iron.
(to big can start to have/create problems of it's own, so it is quality more than just size)

 

[dcgillespie]

Give me a good well filtered power supply with some nice beefy chokes any-day..:thmbsp:

And for the most part when I'm looking at pieces of audio gear to "acquire" them I am
looking at the transformers(iron) for beefy-ness as to whether it is something I desired.

I don't really pay much attention to the circuitry as I will design my own, it's truly what
that piece has in it for iron that get's my juices going, thinking about what to do with it.

Absolutely! Which is also to say, that while other aspects of circuit design "can" destroy the sound, the iron is ultimately
The limiting factor as to just how good the resulting performance Can be.

Dave