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A Tube amp without coupling capacitors? Possible?
A Tube amp without coupling capacitors? Possible?
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Old 11th August 2019, 06:14 PM   #21
jhstewart9 is offline jhstewart9  Canada
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Here is the DC coupled amp described in the April 1951 edition of Audio Engineering. There are simpler ccts published more recently.
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File Type: pdf 15W DC Coupled Amplifier p3.pdf (937.7 KB, 54 views)
File Type: pdf 15W DC Coupled Amplifier p4.pdf (300.3 KB, 52 views)
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Old 11th August 2019, 06:52 PM   #22
jhstewart9 is offline jhstewart9  Canada
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Default Thinking Outside the Box

Quote:
Originally Posted by alayn91 View Post
Hello,
There is, at least, one capacitor in the audio circuit: the reservoir capacitor.
For those who want to avoid the PS cap in the audio cct here is an alternative developed by Steve Bench-
No R, No C, No Batteries, No Hum
Steve Bench did some very interesting work outside the box.
See some of it here-
ARTICLE OVERVIEW
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Old 11th August 2019, 09:02 PM   #23
Schmitz77 is offline Schmitz77  Germany
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Quote:
Originally Posted by jjasniew View Post
Ok, I'm going to pull my intellectual pants down and reveal my ignorance for all to see. <snip>
If someone wants to cook an excellent dinner, why rob the chef of one of the strongest spices in the kitchen? If you want a clinical sounding, "neutral" amp, then it has nothing to do with music but a lot with those clinical emergency rooms. No music can survice in such an environment. Seems that you don't have realized what music and its reproduction is all about. For me, the complete wrong way. Done that, been there. It sounds horrible to me.
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Old 11th August 2019, 09:05 PM   #24
Schmitz77 is offline Schmitz77  Germany
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Quote:
Originally Posted by jhstewart9 View Post
Here is the DC coupled amp described in the April 1951 edition of Audio Engineering. There are simpler ccts published more recently.
A direct coupled power amp with a coupling cap after the first stage. I cannot make head or tail of it.
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Old 11th August 2019, 09:28 PM   #25
analog_sa is online now analog_sa  Europe
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A Tube amp without coupling capacitors? Possible?
Quote:
Originally Posted by jjasniew View Post
Any capacitor that has current going in and out of it in response to music being played through an amplifier / speaker system is imparting its flavor into the recipe.
Fully agree. Capacitors are evil and even the most expensive types should be avoided if possible.

And this is why many of us enjoy inductive coupling between the stages. These days it is easy to get spoiled by all the exotic core materials available.

This said, if you really want an amp with no colourations, why are you even looking at valves?
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Old 11th August 2019, 09:41 PM   #26
Wavebourn is offline Wavebourn  United States
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A Tube amp without coupling capacitors? Possible?
Quote:
Originally Posted by jhstewart9 View Post
Here is the DC coupled amp described in the April 1951 edition of Audio Engineering. There are simpler ccts published more recently.
Coupling capacitors are C1 and C2, in power supply. Instead of being coupled through the grid it is coupled through the cathode.

The only place where a coupling capacitor better to eliminate, is in the output stage, especially of a triode amp, where grid current on peaks is audibly non-linear. In pentode or ray tetrode amps with some power headroom it is not so critical. It is not so common to see dependence of control grid current on voltages, but some datsheets show it. 2 best ways to eliminate "capacitor sound" are either to use an interstage transformer, or a source/cathode follower.
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Old 12th August 2019, 02:33 AM   #27
sumotan is offline sumotan  Indonesia
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Hi Guys
Though it's been a while since I build tube projects, I've always wondered why the focus has been on getting rid of C in signal path. From my experiments on dac , some SS amps, PS has greatest influence on the sound be it C in the way of signal or not. Even if you can get rid of C you'll still end up with R & C in the speaker XO unless your speakers are FR. Since C is such a great evil why not focus on getting rid of it on the whole chain, possible ????
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Old 12th August 2019, 02:54 AM   #28
gabdx is offline gabdx  Canada
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Do no remove capacitors, place more.

Caps in the input stage isolate the volume switch = it sounds better

Caps in the interstage = better than transformers

Caps in coupling help too with blocking low frequency, annoying DC elevation etc.

I thought I had built one solid state system with 0 caps, until i learned that all dacs had thousands if not more of capacitors in and out of the signal path

if you want to play God and reinvent the creation, remove all capacitors, use massive chokes , regulators and transformers, go bankrupt.

3 things are fundamentals of electronics: cap/res/coils if you remove one of those the world collapse.
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Last edited by gabdx; 12th August 2019 at 02:57 AM.
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Old 12th August 2019, 03:10 AM   #29
Wavebourn is offline Wavebourn  United States
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A Tube amp without coupling capacitors? Possible?
Quote:
Originally Posted by sumotan View Post
Hi Guys
Though it's been a while since I build tube projects, I've always wondered why the focus has been on getting rid of C in signal path. From my experiments on dac , some SS amps, PS has greatest influence on the sound be it C in the way of signal or not. Even if you can get rid of C you'll still end up with R & C in the speaker XO unless your speakers are FR. Since C is such a great evil why not focus on getting rid of it on the whole chain, possible ????
As I already explained, the problem is not in capacitors themselves, but in coupling of stages with non-linear resistances through capacitors.
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Old 12th August 2019, 04:03 AM   #30
sumotan is offline sumotan  Indonesia
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Hi Wavebourn,
I understand your view but as in anything I feel that you gain something & you loose something as well. This comment is from my own experiment.
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