3D6 / 4P1L(?) Amp

So Dennis has mentioned several times about just dropping the power stage on a full sized amp to get a small amp. That sounds like there is some common-sense behind that.

Well, what if you dropped the power stage of this amp, and just used the 3D6 and 6AG7/6AK7. Darn, just noticed the 3D6 is in the first position. Still, I wonder if Dennis is on to something, and if this would be pretty cool.

Yes, I see the positvie feedback on the 6AG7.

Jamie

Big speakers and little amps blew my mind!

no triode curves, posted on November 23, 2014 at 11:35:19

GSH

It's connected as a triode in the schematic, too bad the data sheet doesn't cover that operation. But with 600mw output in pentode, you can bet on less in triode, which would be too little for an output stage, probably.

Sometimes I wonder why nobody builds a reverse logic amp, like a 45 driving
3 5687's in parallel or something like it. It's often said that it's the driver that gives the sonic signature of an amp, if so, then why not?

Ok sure, DC on the 45's filament (as a driver) but then the output stage should be quiet, even on very sensitive speakers.
Someday I'll come back to my box of 10's, and try a 10 as a driver, it's been done already by others.

RE: no triode curves, posted on November 23, 2014 at 12:00:36

Mr_Steady
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Posts: 2042
Location: North Florida
Joined: August 19, 2014

GSH,

Thanks for the response.

Yes, and the 6AG7 pentode is a compromise also. Just a thought excersize.

" It's often said that it's the driver that gives the sonic signature of an amp, if so, then why not?"

I have heard that said many times, but I disagree with it. I have always found that the output tube had the biggest impact on the sound. That is, tube swapping the output tube resulted in the greatest changes in the sound, not swapping the driver tubes.

The reverse logic amp you describe sounds interesting. I have always like the idea of Broskie's 5 paralleled EL84 amp, with no driver stage at all.

I lost an auction on ebay for a little amp that had small step up transformers from a reel to reel as a driver stage, and paralleled 6SN7 for output tube with one watt output. This was before I went small, and I wish I had it.

Jamie

Big speakers and little amps blew my mind!

RE: Dropping the Power Stage, posted on November 23, 2014 at 14:05:20

Al Noakes

6AG7 is similar to 6197/6CL6 , you can get about 1.5 watts as a triode but it won't make a very good triode as an output stage for SE . If you want a power amp that only uses a driver stage , build a spud . 6E5P and 6S45 are ideal for this . Low parts count , no coupling capacitors , compact , good-sounding and cheap . Use 330 ohm grid stoppers and 100 ohm for g2 triode strap resistor and 100 ohm Rk for 6E5P , 470uF bypass cap with B+ 205V . 330 ohm grid stoppers , 56 ohm Rk and 820uF bypass cap with 6S45 235V . Both are suitable for 3K5 output transformers

RE: 3D6 / 4P1L(?) Amp, posted on November 23, 2014 at 14:32:45
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	Sakuma has done things like that. It generally requires some unusual interstage iron to get it to work properly.

Really? A Chinese Schematic???, posted on November 23, 2014 at 18:08:55
Triode_Kingdom Audiophile Posts: 10048 Location: Central Texas Joined: September 24, 2006	You sound as though you might be capable of a more scratch-built design. No need to stoop so low. :)

RE: Dropping the Power Stage, posted on November 24, 2014 at 01:48:01

Mr_Steady
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Posts: 2042
Location: North Florida
Joined: August 19, 2014

"you can get about 1.5 watts as a triode but it won't make a very good triode as an output stage for SE."

Thanks for that Al, and for all your post.

I should have built a spud amp a long time ago. Shame on me. I've just never wanted to take the time to build something I didn't want. I suppose you could deck out a spud amp with all the high-end parts since it's so simple. How about a spud with silver opts? You don't think I'm crazy do you Al? I mean, you think I got it under control, right?

Heck, for the price of a spud, you might as well just ask Bottlehead to sell you a SM 45 kit with no opts. So many paths lead to foggy bottom.

If I build something, it's going to be some esoteric output tube like 01A, PX25. 10y as output tube? And on a Tubelab SE board as it is adjustable. Maybe I could get the operating points right.

Oh, they've come to take me back to my cell.

Jamie

Big speakers and little amps blew my mind!

RE: 3D6 / 4P1L(?) Amp, posted on November 24, 2014 at 01:56:01
Mr_Steady Audiophile Posts: 2042 Location: North Florida Joined: August 19, 2014	"It generally requires some unusual interstage iron to get it to work properly." Oh, I was figuring that the RC, and bias circuits would stay the same, and that only the power supply would need to be revised. That is, the opt connected to the plate of 6AG7 with the positive feedback removed. Am I incorrect in this? Jamie Big speakers and little amps blew my mind!

RE: Really? A Chinese Schematic???, posted on November 24, 2014 at 02:35:27

Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014

"Really? A Chinese Schematic???"

I knew that was coming! :) I knew there was no way I could get away with it twice. ;)

I've studied these schematics because they are so old-fashioned. They conform to the models in the ancient texts I've tried to learn tube electronics with. They have taught me enough to understand something about Gary Pimm's schematics, and Gary Pimm's scematics seem to be - the bomb.

"You sound as though you might be capable of a more scratch-built design."

The term, "Cluster F@#$" comes to mind.

"No need to stoop so low. :)"

I dig what you say on a lot of things. Howerver I guard myself never to underestimate the wisdom, intelligence, ingenuity, and shrewdness of the Chinese. For all I know resistors and capacitors are as cheap as dirt to this guy, as compared to CCS modules, and regulated DC filament supply modules.

Jamie

Big speakers and little amps blew my mind!

RE: 3D6 / 4P1L(?) Amp, posted on November 24, 2014 at 11:18:04
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	Oops, I posted that on my phone and was intending to address the "driving a bunch of 5687's with a 45". Without triode curves for the 3D6, it's hard to say what you might be able to get away with.

RE: Dropping the Power Stage, posted on November 24, 2014 at 11:58:29

maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004

Late to the party here, but I will throw in my two cents as you all have been so helpful on my recent posts.

This is in essence a bad idea... the driver stage in any amplifier (except where grid current is expected) is designed to make voltage, not power. The 6AG7 is a strange beast too, I have a whole bunch of them from an ex NORAD site, and the best use I can find is to try to turbo charge the RF amplifier stages in an old shortwave radio.

I think you'd be way better off taking a purpose designed audio tube, and designing a small amplifier around it. For example, triode connect a 6L6, or maybe an EL84... that would give around 1 - 2 W of output in a single ended configuration and super easy to maintain.

"I guard myself never to underestimate the wisdom, intelligence, ingenuity, and shrewdness of the Chinese.", posted on November 24, 2014 at 15:23:12
Chip647 Audiophile Posts: 2652 Location: The South Joined: December 24, 2012	You might want to reexamine your world view, they wish to destroy you, comrade.

RE: "they wish to destroy you...", posted on November 24, 2014 at 17:03:19
Ivan303 Audiophile Posts: 48887 Location: Cadiere d'azur FRANCE - Santa Fe, NM Joined: February 26, 2001	If that's the case, then I would suggest you guard Yyourself never to underestimate the wisdom, intelligence, ingenuity, and shrewdness of the Chinese. First they came for the dumb-asses And I did not speak out Because I was not a dumb-ass

Never underestimate evil, just don't praise it., posted on November 24, 2014 at 17:40:33
Chip647 Audiophile Posts: 2652 Location: The South Joined: December 24, 2012	The U.S. is special in the way we give money to those who wish to destroy us so we can drive SUVs and have cheap TVs.

RE: Dropping the Power Stage, posted on November 24, 2014 at 23:19:08
Mr_Steady Audiophile Posts: 2042 Location: North Florida Joined: August 19, 2014	Max, I think you hit the nail on the head. The driver stage is a voltage amplifier. That's something I knew, but didn't recongnize the significance of in this situation. Many thanks. Jamie Big speakers and little amps blew my mind!

Those Who Wish to Destroy Me Can Take a Number, posted on November 25, 2014 at 00:28:54

Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014

This coming from somebody who has taken a bullet in the head, and lived to tell the tale.

Son, I was fight'n commies when you were at your mother's tit. But it wasn't the commies that got me.

How do I defend myself against my own President, and his minions in The Hive? They are more dangerous, because they can get their hands on me. The Chinese I'm afraid will just have to wait their turn. ISIS too. I know they are in a hurry and everything, but they have to take a number.

Let's just hope the Hive doesn't get the bright idea of importing 200 million Chinese in one day, then they would have the super-majority of unthinking, illiterate peasants they so crave. Actually, the Chinese probably aren't illiterate enough, they can do better than that.

Men and women who care about the ideals of the American Revolution will always be free to work themselves to death, and pay their taxes, while their children or grandchildren are being absorbed by the hive.

Sincerely,

Jamie

Big speakers and little amps blew my mind!

Awesome (nt), posted on November 25, 2014 at 06:14:55
Chip647 Audiophile Posts: 2652 Location: The South Joined: December 24, 2012

RE: Dropping the Power Stage, posted on November 25, 2014 at 07:31:36

maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004

If you want to try some unconventional tubes, there are some things to look for. The triode curves should have a small bend at the low end and fhen be almost perfectly straight, with even Spacing between the lines. The plate dissipation rating should be over 10W or so (usually) go be useful too, preferably much higher. If you leaf though and RCA tube manual and look at a pile of random triodes, then look at a 2A3 and go to western electric.com and download the 300B data, it becomes obvious fast why people like these tubes so much. Designing tubes is a huge compromise - if you improve one thing, others get worse. Optimizing linearity was not a big priority for many tubes, because given the circuits they were designed to work in it just wasn't necessary. In our type of circuit (no NFB single ended) one needs the most linear tube possible, or all you will hear is distortion.

RE: Those Who Wish to Destroy Me Can Take a Number, posted on November 25, 2014 at 11:52:00

tube wrangler
Manufacturer

Posts: 2484
Location: USA
Joined: January 29, 2007

There, you have it!

Should your music amplifier be designed by the HIVE, or should it take a long, honest, hard look at how THE WHOLE THING can serve music?

Back to the HIVE-- they ARE right about current, voltage, and Network Theory.

But will they compare their best efforts to the best commercial units out there and figure out why those top commercial units are so good?

Can they improve on those? Some of them are very deviant! Some don't follow HIVE theory at all unless they have to (like voltage & current calculations, etc., which are Universal).

Who has improved on those "best" out there? Are they independent, or do they follow HIVE rules? A mixture of BOTH?

Will the hive-mentality beat-out the independent thinkers? Well, if they don't, it won't be for lack of trying!

Were the HIVE "rules" made to be broken, or are they designed to enslave/institutionalize your "correct" thinking? Remember: THEY are ALWAYS right! Aren't they? No? OH, OH!

STAY TUNED for more thrilling episodes.....

---Dennis---

RE: 3D6 / 4P1L(?) Amp, posted on November 25, 2014 at 12:52:37

Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014

Hey Paul,

I just closed the deal on the Paramount SR2a3 that is on the Asylum trader. I wouldn't be surprised if you were the one who did the mod at the shop. Care to say anything about it?

I read the threads on the BH forum about the shunt regulated amps. From what I got out of it, the driver stage is fully shunt regulated and the output tube is shunt regulated? If anybody cares to explain the distinction to a layman, then I would greatly appreciate it.

Jamie

Big speakers and little amps blew my mind!

RE: Dropping the Power Stage, posted on November 25, 2014 at 12:59:34

Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014

Hey Max,

I just snagged a BH shunt regulated 2a3 Paramount on the Asylum trader. It uses a 6DN7 for a driver. I guess I got my low gain amp with a fancy schmancy power supply. How 'bout that!

And I got it for the price of the kit alone. I'm glad I farmed the design work out to Paul Joppa. It saved me a ton of work, and it got done better.

Jamie

Big speakers and little amps blew my mind!

RE: Those Who Wish to Destroy Me Can Take a Number, posted on November 25, 2014 at 13:27:01

Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014

Dennis,

Nothing to say about this thread you posted to? You were the one who suggested dropping the power tube stage to make a smaller amp, and yet you didn't contribute to the discussion. Well, does a voltage amplifier make a good current amplifier?

Well, as regards the ongoing saga.

I read in the old textbooks I studied that the design equations they published were listed by the author as, "rules of thumb." That is, very general rules that would get you an amplifier up and running without a lot of headache. The designer was then free to tweak the circuit to their liking. If they tweaked to far in the wrong direction, then it would show up on their scope, or would do unpleasant things like oscillate or motor-boat. Rules-of-thumb are very different from unchanging law, as most people would agree.

IMHO, it takes a good engineer with good taste and good ears to design an exceptional SET amp. Anybody like me could get on TubeCad and a couple of other programs and design a mediocre amp. Who wants to listen to that?

Jamie

Big speakers and little amps blew my mind!

RE: Those Who Wish to Destroy Me Can Take a Number, posted on November 25, 2014 at 14:02:40

tube wrangler
Manufacturer

Posts: 2484
Location: USA
Joined: January 29, 2007

All excellent points-- no argument from me!

As far as running a driver stage into a speaker-- that would depend on how much power the driver stage in question-- has. If it's enough to drive your speaker, then an output transformer will convert what is primarily voltage swing into what is primarily current drive.

The answer to this question is simple: if a given amp stage has enough power to run a speaker, then why not do so-- why add more stages on to it??

If it doesn't have the power you're looking for, then you can add-on a higher power stage. That becomes one too many stages for an ideal amp, and is why we design 2-stage amps.

I didn't answer because I knew it would be blasted all out of context, and I didn't have time for a Dog/Cat fight over nothing at all!

---Dennis---

RE: Those Who Wish to Destroy Me Can Take a Number, posted on November 25, 2014 at 17:11:49

Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014

"All excellent points-- no argument from me!"

Somehow I think this should be immortalized.

So, is the power tube in a three stage amp also a voltage amplifier, and the OPT transforms it to current power? Sorry, no more basic questions. I'll stick to questions nobody knows anything about, like voltage regulation circuits. FETs loading the plate anyone?

Jamie

Big speakers and little amps blew my mind!

RE: Those Who Wish to Destroy Me Can Take a Number, posted on November 25, 2014 at 20:54:23
tube wrangler Manufacturer Posts: 2484 Location: USA Joined: January 29, 2007	Power is usually expressed in watts, or volt-amperes. Watts equals Voltage times current: VA (watts)= amperes (current) X voltage. ---Dennis---

RE: Those Who Wish to Destroy Me Can Take a Number, posted on November 26, 2014 at 05:06:56
Mr_Steady Audiophile Posts: 2042 Location: North Florida Joined: August 19, 2014	Thus endeth the lesson. Big speakers and little amps blew my mind!

RE: Dropping the Power Stage, posted on November 26, 2014 at 13:57:29
maxhifi Audiophile Posts: 584 Location: Alberta, Canada Joined: August 4, 2004	That amplifier looks like a real beauty, I saw it on trader - nice buy

SET Asylum

3D6 / 4P1L(?) Amp

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