Have You Listened to a Low Power Amplifier?

TroyD

My main amps are 25wpc Heathkit W5-M's.....

BDT

mhardy6647

agfrost wrote: »

Have a buddy with a Decware Zen Triode amplifier. Nifty, really good sounding amplifier.

I've got one (the SE-84B version) in its box in the attic. It is in fact not a bad sounding amplifier, but it is at the limit of adequate power for even pretty sensitive speakers - it wasn't really up to the task of my Cornwalls (98 dB/watt@1 meter). It also has 6 ohm secondaries - deliberately chosen by Deckert for modern speakers, but not optimal for the ol' 16 ohm warhorses. The Zen would make a great MR/HF amp in a bi or tri amped system.

dcmeigs

Silver Tuner,

Nice find. That looks like a 175. I have one of those and it is one of the better IMO. If you need a schematic you will find it HERE

You should check out the user group web site HERE.

That one looks well turned out. Have you lifted the hood? Pics? There are several good mods that make a big difference. You can read about them there or at various audio sites (or PM me). The previous owner has probably done them but you never know.

heiney9

I spent the whole evening last night working on the computer and listening to office rig #2 Dared VP-16 - (4) 1950's RCA gray glass blk plate 6V6's and (2) 1950's Sylvania JAN CHS 6SL7WGT's (chrome domes); Polk 5B's.

16 wpc (push/pull) selections included, Norah Jones, Bela Fleck, Keb Mo', Jewel, Anna Nalick, Ditty Bops, Cowboy Junkies, David Thompson, Erin McKeown, Sheryl Crow.......

It sounded absolutely sublime. I use a pair of MIT I/C's, a glass optical to my outboard dac and homemade Canare Star Quad speaker cable in shotgun configuration and Trey's homemade power chord.

This is one helluva enjoyable rig and it will play pretty loud too! Clarity, detail, decay, presence is all there in spades even at lower volumes.

H9

Flash21

Prolly not what you are looking for, but my first "real" receiver was a Realistic circa ~1977 with an flywheel analog tuning and wood sides... rated 16 wpc. It is and was a very nice unit actually, and we still use it at our lake cabin. It sounds quite good and rocks plenty!

mhardy6647

Sounds like the STA-64 :-)
page 11 of http://www.radioshackcatalogs.com/catalogs/1977/

Not what I am thinking of in this context, though (FWIW).

silvertuner

dcmeigs wrote: »

Silver Tuner,

Nice find. That looks like a 175. I have one of those and it is one of the better IMO. If you need a schematic you will find it HERE

You should check out the user group web site HERE.

That one looks well turned out. Have you lifted the hood? Pics? There are several good mods that make a big difference. You can read about them there or at various audio sites (or PM me). The previous owner has probably done them but you never know.

it has a FRESH rebuild on it. im not to worried about any mods, it sounds great, and sounds better and better everytime it gets warmed up. im not going to push my luck lol.

i will get a pic under the hood later today when i start swapping wires!

i have a sta-64 in my arsenal lol...



Uploaded with ImageShack.us

its currently sitting on CL for $30 tho

Tour2ma

mhardy6647 wrote: »

Here's a classic case in point, at 25 watts per channel, with dual power transformers/independent power supplies for each stereo channel:

Cool old ad...

In its day HK personified conservative when it came to power specs...

mhardy6647 wrote:

Those speakers look strangely familiar, too, somehow...
(although that's the funniest-looking Philips GA-312 turntable you'll ever see...)

Yeah... I remember old Phillips using Gimbal tone arm pivots. But google did turn up one with that solid, cylindrical pivot pictured in the ad... no telling which model it is tho...

http://www.gather.com/viewArticle.action?articleId=281474976753420

Flash21

mhardy6647 wrote: »

Sounds like the STA-64 :-)
page 11 of http://www.radioshackcatalogs.com/catalogs/1977/

By Golly, that's the one! Still works great...

mhardy6647

Tour2ma wrote: »

Cool old ad...

In its day HK personified conservative when it came to power specs...


Yeah... I remember old Phillips using Gimbal tone arm pivots. But google did turn up one with that solid, cylindrical pivot pictured in the ad... no telling which model it is tho...

The ad is from the Gordon-Miller Music hifi catalog (ca. 1977 or so); the tt they illustrate is a Philips GA-406 fully automatic tt
http://www.vinylengine.com/library/philips/ga-406.shtml

EDIT: While I don't doubt that the hk430's 25 wpc FTC spec was 'conservative', I don't think it was a "200 wpc" receiver, even by modern standards!

silvertuner

dcmeigs wrote: »

Silver Tuner,

Nice find. That looks like a 175. I have one of those and it is one of the better IMO. If you need a schematic you will find it HERE

You should check out the user group web site HERE.

That one looks well turned out. Have you lifted the hood? Pics? There are several good mods that make a big difference. You can read about them there or at various audio sites (or PM me). The previous owner has probably done them but you never know.

gain knob added along with new speaker output terminals.

agfrost

mhardy6647 wrote: »

I've got one (the SE-84B version) in its box in the attic. It is in fact not a bad sounding amplifier, but it is at the limit of adequate power for even pretty sensitive speakers - it wasn't really up to the task of my Cornwalls (98 dB/watt@1 meter). It also has 6 ohm secondaries - deliberately chosen by Deckert for modern speakers, but not optimal for the ol' 16 ohm warhorses. The Zen would make a great MR/HF amp in a bi or tri amped system.

He built Steve's HDT towers from plans with decware modded (Fostex?) drivers. Depending on program material and the room, it is pushed to its limits to(or falls just short of) being able to make satisfying bass. But the things it does well, it does very well...

Anyway, that's been my impression.

Jay

mhardy6647

Decware had mods for and/or sold both Fostex and Lowther drivers. I don't think Steve sold Lowthers, but his mod (was it called the "gizmo"?) was supposedly pretty good for those notoriously finicky drivers.

I like many the Fostex drivers; have a nice pair of FE-207E (but they are a tad less sensitive than even the Cornies).

agfrost

Not sure if it's what you're calling "the gizmo,", but one of the mods to the driver was a phase plug which was a 7/16" socket (perhaps Craftsman?). I'm guessing on the size, but it was in fact a socket. There may also have been a cone-coating treatment of some sort involved.

organ

The lowest I tried was a 3w/ch SET amp. Worked very well on every efficient speakers I tried. Spl was never a problem as long as the speakers were efficient (>90db/w/m with friendly imp curve).

All my amps are low powered SET or SE at the moment. I have two 5w/ch amps and an 8w/ch 300B SET amp.

Good flea amps have always been the best sounding to me.

For those who want to learn more about the beauty of low powered single ended, you can check out these very interesting articles by one of my audio heroes Dr. Harvey Rosenberg (RIP) ... http://www.meta-gizmo.net/Tri/index-1.html
The articles on the Decware website are also very good and informative.

mhardy6647

agfrost wrote: »

Not sure if it's what you're calling "the gizmo,", but one of the mods to the driver was a phase plug which was a 7/16" socket (perhaps Craftsman?). I'm guessing on the size, but it was in fact a socket. There may also have been a cone-coating treatment of some sort involved.

Decware's Gizmo http://www.decware.com/gizmo.pdf

Yes, Steve has used sockets (presumably inspired by Lowell George) and vacuum tubes as phase plugs.

And, for anyone who doesn't know, Dr. Harvey Rosemberg was widely and well known as "Dr. Gizmo". He was definitely an interesting fellow, with some nontrivial hifi designer chops. He pretty much single-handedly rekindled interest in low powered single ended hifi amps using directly heated triode output tubes (DHTs) such as the 45, 2A3, and 300B.

zingo

I'm in the process of planning a 1wpc class D amp powered by AA batteries. I have no idea what it might sound like, but it should have a dead silent back ground, and it should be a fun little project just the same.

organ

zingo wrote: »

I'm in the process of planning a 1wpc class D amp powered by AA batteries. I have no idea what it might sound like, but it should have a dead silent back ground, and it should be a fun little project just the same.

Looking forward to hearing your impression. What speakers are you planning to use? Gainclone are also excellent if you're looking into low powered ss.

dcmeigs

Silver Tuner,

That Maggie looks rock solid. He added a 100 ohm resistor between the rectifier and the can cap, as did I, to compensate for todays higher mains voltage. You have a nice set of new coupling caps too. That extra modern cap attached to the hum bucking pot is to replace the original within the multi section can that probably went bad. I can't see it in the photo, but I trust you have a fuse on the 120V mains; if not, that's mandatory prior to the next use:) Remember, you are still using those 50 year old caps in that can and they will fail (short) someday and you want a blown fuse rather than a fire or a melted transformer. I bet it sounds beautiful.

heiney9

organ wrote: »

Gainclone are also excellent if you're looking into low powered ss.

Excellent how? At driving the speakers? Sure. As far as sound? Not so good.

H9

dcmeigs

Here is another interesting low powered amp (receiver actually but they made an amp in the same chassis). It's a VM 1467. It has a wonderful sound and they can be had on the cheap if you're willing to put in some sweat equity to bring them up to snuff.



It is a 5 or 6 watt single ended EL84 and this receiver has a multiplexer on board.



You either love or hate the styling.

It definitely favors sensitive speakers. I'm working on a set of speakers for it using vintage horns and Jensen woofers.

organ

Very cool! I can't believe it looks brand new.

WastelandWand'r

HCT I-pod amp identical to H9's. Denon 3910 with an attached of set of unmolested 7'c with the Peerless.
From low volume to sane loud levels it sounded pretty nice.
Only experience with low powered amps. Everything else is SS and >= 100wpc.
Happy Trails,
Nathan

dcmeigs

organ wrote: »

Very cool! I can't believe it looks brand new.

Sad part is: look closely at the numerals on the tuner scale. They are vinyl or some sort of plastic affixed to the glass and they are slowly falling off. :mad:

Every once in a while I notice another gone. It aint easy growin' old.

stuwee

I'm not sure what the output rating of the EL84's is in this amp but, my God is it glorious, the first stereo I ever heard, it needs a refurb, even in it's decrepet 60 year old state, it still raises the hairs on the back of my neck. The speakers in the console are Jensens, huge magnets (25lbs I think). Interesting how sweet the mids are from these old 15inch cones.

We have an awesome tube tech here in Tucson if anyone needs their 'baby' updated. Fingers crossed I can have mine refurbed with the tax refund check!

mhardy6647

dcmeigs wrote: »

Here is another interesting low powered amp (receiver actually but they made an amp in the same chassis). It's a VM 1467. It has a wonderful sound and they can be had on the cheap if you're willing to put in some sweat equity to bring them up to snuff.



It is a 5 or 6 watt single ended EL84 and this receiver has a multiplexer on board.

You either love or hate the styling.

It definitely favors sensitive speakers. I'm working on a set of speakers for it using vintage horns and Jensen woofers.

It definitely favors sensitive speakers. Yeah, it would, at 4-ish wpc :-)

You either love or hate the styling. Either way, this particular example is in beautiful condition; do you have a shot of its innards?

Wardsweb

Here is my version of the amp pictured in the first post of this thread. It is a 6DN7 at 1.5 watts per channel. I use it with some DIY full range speakers that are about 98dB efficient.

mhardy6647

What drivers are in those DIY FRs, Mr. W?

zingo

organ wrote: »

Looking forward to hearing your impression. What speakers are you planning to use? Gainclone are also excellent if you're looking into low powered ss.

I will be using my 98db custom Klipsch Forte speakers. I have been able to run any amp I've tried so far on them, even though their impedance curve is not flat. I haven't tried a Gainclone, but if this 1wpc class D doesn't sound good, I might try a straight 1wpc class A JFET type. Oh the possibilities...

dcmeigs

Wardsweb wrote: »

Here is my version of the amp pictured in the first post of this thread. It is a 6DN7 at 1.5 watts per channel. I use it with some DIY full range speakers that are about 98dB efficient.

Wow. That is just stunning. My compliments. Very stylish! I like the way the transfos are painted to match the box (among everything else). Thanks for sharing.