Supratek power amp

[Herbyj]

Hi

 

I see Mick is now back making power amps again. 

 

Looks great and should sound very good too.

 

http://supratekaudio.blogspot.com/

 

Dual mono, balanced, beautiful case work and  pretty cheap at USD 4000!

 

Cheers

 

Herby

 

[Ittaku]

Says it has zero feedback... Well, strictly speaking zero global negative feedback I'm guessing which means you are really going to want to have very easy to drive speakers. There's also no mention of what impedance taps it has. He mentions efficient horns so I suspect that's what this will be ideal for, in which case 40W is huge.

[Ihearmusic]

At 40w output you don't need very high efficient speakers.

As long as the speakers don't dip to much bellow the nominated impedance it will be fine.

Feedback or not does not mean you will have to have a certain type of speakers either.

The amp will likely come with an 8 ohm tap with options for others.

 

Good on Mick for adding a power amp to his range and good luck to him.

 

Edited July 30, 2019 by Ihearmusic

[Ittaku]

19 minutes ago, Ihearmusic said:

As long as the speakers don't dip to much bellow the nominated impedance it will be fine.

Feedback or not does not mean you will have to have a certain type of speakers either.

Feedback most certainly affects its ability to maintain a flat frequency response across dips and troughs in speaker impedance.

[andyr]

15 minutes ago, Ittaku said:

Feedback most certainly affects its ability to maintain a flat frequency response across dips and troughs in speaker impedance.

 

You mean having  some global NFB helps an amp to cope with dips and troughs in speaker impedance, Con?

 

Andy

 

[Ittaku]

11 minutes ago, andyr said:

 

You mean having  some global NFB helps an amp to cope with dips and troughs in speaker impedance, Con?

Correct. It also increases the much debated damping factor.

[andyr]

6 minutes ago, Ittaku said:

Correct. It also increases the much debated damping factor.

 

Thanks, Con. 

 

However my experience is that amps with a lot of global NFB ... do not exhibit much in the way of sound-stage depth.

(So Mick's new power amp should have plenty of it!  )

 

Andy

 

Edited July 30, 2019 by andyr

[Ittaku]

34 minutes ago, andyr said:

 

Thanks, Con. 

 

However my experience is that amps with a lot of global NFB ... do not exhibit much in the way of sound-stage depth.

(So Mick's new power amp should have plenty of it!  )

I'm quite sure it sounds great, if his preamps are anything to go by. And you're probably right, none of the serious amps I've ever bought have ever had a lot of GNFB. Some amps proudly advertise their massive damping factors while my power amps have a whopping great factor of 10.

[sir sanders zingmore]

they sure look good

 

[Wayne Elliott]

@TerryO

[Wayne Elliott]

Even with our crap exchange rate, around $5800 seems quite reasonable.

[Marc]

34 minutes ago, initforthemusic said:

Even with our crap exchange rate, around $5800 seems quite reasonable.

As he's Aussie, I'm sure there will be a more favourable AUD price.

[andyr]

1 minute ago, Marc said:

As he's Aussie, I'm sure there will be a more favourable AUD price.

 

We can hope so, Marc.    But I'm wondering - as an Aussie - he doesn't simply put an A$ price on it?

 

Andy

 

[Marc]

Like many Aussie Hi-Fi manufacturers, probably sells more overseas than locally.

[Marc]

Enough speculation, let's hear from @statman himself

[Wayne Elliott]

8 minutes ago, Marc said:

Like many Aussie Hi-Fi manufacturers, probably sells more overseas than locally.

I believe the Suprateks sell well  in the States.

[Steve M]

I think Mick is being quite conservative with his power rating for that amplifier, it uses 8 x EL34 valves and many other manufacturers using that many EL34 output tubes would call their amp a 100 watter.

 

In my experience, being a push-pull design with that many output tubes I think you will find the Malbecs to be powerful sounding. He does say in his blog that the amp continues to put out good sounding power with a clean wave form well beyond 40 watts.

 

I’ll have to try and get hold of pair of these amps for a serious listening session as I do like the lush sweet sound of the EL34 tube. I have owned a Anthony Michaelson (Musical Fidelity) amp and a Jadis JA30 monobloc ...both fabulous sounding EL34 amps.

 

Steve.

[Ihearmusic]

6 hours ago, Ittaku said:

Correct. It also increases the much debated damping factor.

That old chestnut again.

To my mind, global negative feedback is used to fix problems like unstable drive/split stage and/or to correct excessive distortion from careless designs.

The little difference it make in a valve amp in regards to the damping factor are inconsequential.

But this in only my opinion.

I have yet to build a tube amp with GNF. So far I have had no call for it.

 

In a given situation, this may very well be true. R_s is a byproduct of negative feedback. The more such feedback that is thrown into a power amplifier circuit, the lower the generator impedance and the higher the damping factor. The point is simply that if a lot of feedback has to be used to lick the distortion in a particular circuit, fine - use it. But don't believe that the reason it sounds good because of some astronomically high damping factor.

When I get a letter from someone who is worried about buying a certain amplifier because it has a specified damping factor of "only" 15 to 16, I can't help but remember an old, old joke. It goes like this:

     A scientist is giving a public lecture. During the course of his speech, he predicts that in 100 billion years      human life will become extinct. A man in the audience, obviously upset, asks the lecturer to repeat the      statement.

     "I said", quotes the professor, "that in one hundred billion years, human life will no longer exist."

     "Oh, thank goodness", replies the man, much relieved, "I thought you said one-hundred million!".

Edited July 30, 2019 by Ihearmusic

[Ittaku]

6 hours ago, Ihearmusic said:

That old chestnut again.

To my mind, global negative feedback is used to fix problems like unstable drive/split stage and/or to correct excessive distortion from careless designs.

The little difference it make in a valve amp in regards to the damping factor are inconsequential.

But this in only my opinion.

I have yet to build a tube amp with GNF. So far I have had no call for it.

 

In a given situation, this may very well be true. R_s is a byproduct of negative feedback. The more such feedback that is thrown into a power amplifier circuit, the lower the generator impedance and the higher the damping factor. The point is simply that if a lot of feedback has to be used to lick the distortion in a particular circuit, fine - use it. But don't believe that the reason it sounds good because of some astronomically high damping factor.

When I get a letter from someone who is worried about buying a certain amplifier because it has a specified damping factor of "only" 15 to 16, I can't help but remember an old, old joke. It goes like this:

     A scientist is giving a public lecture. During the course of his speech, he predicts that in 100 billion years      human life will become extinct. A man in the audience, obviously upset, asks the lecturer to repeat the      statement.

     "I said", quotes the professor, "that in one hundred billion years, human life will no longer exist."

     "Oh, thank goodness", replies the man, much relieved, "I thought you said one-hundred million!".

Note you'll see nowhere did I say chasing damping factor was a good thing, and I implied pretty much the opposite. All I did was point out that it increased it.

[statman]

12 hours ago, Marc said:

Enough speculation, let's hear from @statman himself

I'm always wary of the fine line between posting and self advertising , so I tend to let my blog do the talking, but as I've been invited........

Yes almost all of the work is sold in the US . I have US dollar prices on my web site as the higher AUD can be confusing to them.  I always like to instigate an email conversation with potential customers, in order to establish a clear idea of exactly want they want in a product, and if you twist my arm.......

 

In regard to feedback , the amp has no feedback at all, neither global or local.  Not that's there anything wrong with feedback- in the right format and amount it can be very useful.

As pointed out it helps with damping factor and provides better linearity with difficult speakers.

In previous power amps I provided adjustable feedback , from zero to quite a good amount of damping, and even positive feedback for very low output impedance.

And feedback is very useful for minimising hum and noise with less than ideal power supplies and earthing.

And as also pointed out, too much feedback can be very harmful to the phasing effects- imaging, soundstaging, etc.

 

There is something quite pleasant and enjoyable about a zero feedback power amp , AudioNote UK made a big deal out of it in their early days .

Of course you need a relatively easy speaker load to get a flat monitor like frequency response, but in real life there's no such thing as perfect response, in fact the more "flat" the response , the more uninteresting the sound can become, I think we all tend to like a bit of coloration , to our taste. 

 

I tried this no feedback amp with quite a range of conventional and non conventional speakers and I found it enjoyable with all of them.  Of course i didn't even attempt it with my "difficult" speakers - some speakers just need lots of power ( and the compromises that can come with that)

With this no feedback amp, having a quad of power tubes helps , along with a good output transformer to give a reasonable damping factor that will drive most speakers . There might be a bit of coloration , but the openness and vividness of the amp would appeal to those looking for a bit of tube euphonics.

The driver stage is very strong and contributes to a very clean output right up to and beyond its power rating. A lot of high power tube amps these days can be very tiring when they get close to their rated power , and rely on feedback to minimise noise and strident clipping. 

So I decided to leave the feedback out. If someone asked for a "stronger" amp I would probably put a bit of local feedback in it, with maybe a higher power output.

 

Sound quality is all important, but I do like to build gear that is going to last , is  well engineered and devoid of gimmicks and useless gadgets.  A lot of power amps these days have inbuilt obsolescence with so much gadgetry , complex bias arrangements, digital readouts and protection circuits - something will eventually fail. 

I have 4 sets of Trimax monobloc tube power amps. Built in Melbourne in 1956 - a bit ugly but beautifully engineered - good design, very well built transformers . I replaced a few caps in them, but they are basically unchanged from the day they were built , and still sound very good. 

Tube design has come on from then, but the durability and engineering is an inspiration to me and I build the Suprateks to be used in 50 years time - although the audio world might be a lot more different than it was 50 years ago. Probably have emotional inducing full surround AI controlled music in our heads with not a piece of equipment to be seen.