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Old 14th April 2009, 03:11 PM   #21
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Quote:
Originally posted by Wavebourn


Actually, modern standards and taste means stereo (actually, 5 channels) above 200 Hz only, a single channel for frequencies below 200 Hz with a resonant peak around 40 Hz, and a digital equalizer. It is what I heard today in a factory outlet of one modern flagman of an audio industry, they had a show for potential buyers... Quite impressive show, but an artificial water running on the screen sounded very artificially.

Good audio systems were good always, I mean systems that can fool perceptions creating imaginations of live sources of sounds, but today some modern parts may be used to make them more affordable for the general public, but anyway good systems are still expensive.

I respectfully beg to differ. I'm not comparing apples to oranges. I am comparing high quality solid state stereo amplifiers and speakers (not home theater) of modern times to the same levels of previous generations of equipment. The difference is HUGE. Just hear recording from the 30's, 50's and 60's (I am listening mostly to jazz) and compare to those of the 90's and 00's and you can understand what I refer to. If they did not have studio recording equipment that was good enough theses days, you can assume that home equipment was at least as bad as the studio one. The difference is very clear on a double blind test, and I conducted some. The fact that equipment is based on tubes does not guarantee good quality. I have tube radios that sound awful, regardless of their aesthetic value.
So I really do not think that vintage equipment sound as good as high end equipment of our times.
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Old 14th April 2009, 03:31 PM   #22
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Quote:
Originally posted by tubelab.com


CCS chip yes, feedback is optional. I use it when I want to get loud in UL mode, and turn it off in triode mode. The Simple SE was intended to be just that, simple. It uses the minimal amount of circuitry to get good performance. The CCS was added because it reduces the nonlinearity of the 12AT7. A few amps have been built without the CCS.


Can you please refer me to a hybrid design that meets the following criteria:
1. Power amplifier at least 2x60w
2. Tube output stage (no sand for driving speakers)
3. With control and regulation (I can handle DSP) that are means to an end and not for show off.

Thanks
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Old 14th April 2009, 03:38 PM   #23
rknize is offline rknize  United States
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I think that one assumption is that modern SS stuff (typical electronics store stuff) is even striving for the best sound. I would argue that they are most often striving for the most watts from the lowest parts count possible. They get good imaging by using 4 to 7 speakers. I love "turning heads" of people that listen to my system when they are looking for where my rear channel speakers are (I have none). HT seems to be "the thing" and most of the guys I know that are into audio are mainly HT guys. They have some great setups (some mega-bux), but they are not very musical to my ears when the TV is off.

Now I do think that the speakers in this range have improved a lot over the years. Efficiency has been lost due to the copious wattage available now, but a medium-fi pair of speakers sound a lot better than they did 20 or 30 years ago. It's almost pointless to build your own set of budget speakers anymore, because you probably can't outperform what you could get at Best Buy for the same money.

I don't fear the sands of these times. I have a Tubelab SE now as well and I can't stop listening to the thing long enough to take it off the breadboard. My other amps have been sitting quietly for months.
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Old 14th April 2009, 04:27 PM   #24
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Quote:
Originally posted by rknize
I think that one assumption is that modern SS stuff (typical electronics store stuff) is even striving for the best sound. I would argue that they are most often striving for the most watts from the lowest parts count possible. They get good imaging by using 4 to 7 speakers. I love "turning heads" of people that listen to my system when they are looking for where my rear channel speakers are (I have none). HT seems to be "the thing" and most of the guys I know that are into audio are mainly HT guys. They have some great setups (some mega-bux), but they are not very musical to my ears when the TV is off.
Still there are die hard Solid state developers with music in their mind. Hypex and Bell Canto (Class D) to name a few.


Quote:
Originally posted by rknize
It's almost pointless to build your own set of budget speakers anymore, because you probably can't outperform what you could get at Best Buy for the same money.
.[/B]

Sadly, I agree with you on that (from own experience)
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Old 14th April 2009, 05:04 PM   #25
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Default Re: Re: Re: Modern tube amplifier designs?

Quote:
Originally posted by richwalters



The Williamson concept, concertina front end and diff drivers is my set-in-stone design for both low & high power.

richy
Sorry to hear of that.

Using a single loop of NFB around the multi-stage amp is *NOT* the way to go I think. The power supply needs multiple de-coupled nodes... Now the high quality OPT is useful anywhere, but to select a design that *NEEDS* one seems rather short-sighted. Cathode FB with tertiary windings is one way...Chicago has several designs of that type. E-Linear connection of the two-stage amp is another Way...
cheers,
Douglas
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Old 14th April 2009, 05:16 PM   #26
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From reading this thread... I think I'm missing something, but there have been a lot of innovations that have occurred since the 50s and 60s.

There are now tube amps that have 20Hz square wave response without any tilt.

There are fully differential balanced amps, innovative all-tube, effective CCS circuits, there's been a lot of research into how the human ear/brain system works, and designs that reflect the knowledge that came from that research. There's been a lot of materials and component improvements as well.

However its important to understand that tubes are a mature technology. So any improvement in the technology is likely to be an evolution rather than revolution.
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Old 14th April 2009, 06:17 PM   #27
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Quote:
Originally posted by xenu



I respectfully beg to differ. I'm not comparing apples to oranges. I am comparing high quality solid state stereo amplifiers and speakers (not home theater) of modern times to the same levels of previous generations of equipment. The difference is HUGE. Just hear recording from the 30's, 50's and 60's (I am listening mostly to jazz) and compare to those of the 90's and 00's and you can understand what I refer to. If they did not have studio recording equipment that was good enough theses days, you can assume that home equipment was at least as bad as the studio one. The difference is very clear on a double blind test, and I conducted some. The fact that equipment is based on tubes does not guarantee good quality. I have tube radios that sound awful, regardless of their aesthetic value.
So I really do not think that vintage equipment sound as good as high end equipment of our times.
As I said, "good enough" equipment is more affordable today. And very good equipment can be made cheaper even though labor costs in States and the rest of Western world is too high to compete.
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Old 14th April 2009, 06:52 PM   #28
Jeb-D. is offline Jeb-D.  United States
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Quote:
Sorry to hear of that. Using a single loop of NFB around the multi-stage amp is *NOT* the way to go I think.
I used to think that way too, until tweaking with different concepts enough to realize that It really comes down to application. The Williamson concept can make a good sounding amp. The input and phase splitter are single-ended, so a nice spectrum can be attained. I generally prefer the sound of them over PP amps that are balanced front to back. Especially when the output tubes are an easy load and can be driven strait from the concertina (though this isn't a true Williamson).

Quote:
E-Linear connection of the two-stage amp is another Way...
Pete Millets E-Linear amplifier is a good one. But the "partial feedback" concept has it's own issues which can cause it to be mis-applied just as global feedback can be. It's by no means the cure all.

The driver needs a large amount of headroom which can make things difficult and the allowable amount of feedback is usually very limited.

When applied to SE, it can become a real juggle. In many cases the closed loop PSRR will be worse than open loop. One can get good PSRR, by using the ulta-path/WE connection on the output, and then adjusting the feedback ratio. However, the point at which the best PSRR is attained may not be the point where best sonic performance is attained.

The distortion spectra, gain and THD, is unpredictable because the driver is not in the feedback loop. Only the output tube is. Distortion is minimized by the principal of inverse distortion cancellation and not by the typical NFB rules. At a particular feedback ratio in an SE amp, you will find that even-order harmonics have completely nulled, and the odd have gone up to their highest value. This is the point where THD is lowest. Feedback ratio's other than that you will see THD raise as the even-orders start to come back with a slight reduction in odd-order.

Once you have tweaked enough to get what you want, you will find that tube rolling can cause the spectra and THD to significantly change. In an experimental amp I built, THD could vary by 3 fold (between .3 and .9 % @ 1W) simply by tube rolling. Even using different samples of the same brand. I'm not they type that really cares that much about what an amp measures (if it sounds good and channels are pretty closely matched), but I do like consistency.

Partial feedback is most consistent and fail proof when applied to push pull amplifiers (could easily be adapted to a Williamson). Selecting a driver tube that has tight tube-to-tube tolerance is a good idea as well.
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Old 14th April 2009, 09:34 PM   #29
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Default Re: Re: Re: Re: Modern tube amplifier designs?

Quote:
Originally posted by Bandersnatch


Sorry to hear of that.

Using a single loop of NFB around the multi-stage amp is *NOT* the way to go I think.
That is still the old way....note the Ekland Plitron amp (1st mail) with all the credit commentary about it.

Perhaps I should have mentioned the standard diff driver stage is often the source of unseen problems in many designs. It isn't stiff enough.The basic Williamson concept can be massively improved by regenerative cathode-grid feedback within the stage which reduces IM thd and further reduces loading the concertina. The use of video pentodes as triodes (as you mention the right tube for the job) with modest current offers good low Z drive to deal with o/p stage Miller effect. It is the simplest method for driving multiple p-p pairs.
One type of feedback loop which I've never really got a real performance benefit is the inverse feedback within the output stage anode to previous driver cathodes. Perhaps I should examine this in more detail with a spectrum analyser.
The real problem is Miller effect from 4x 6550 which I recon is one of the hardest tubes for combination Miller capacitance of 650pF and low driver Z. It makes sense for fidelity to keep B+ down. It appears any driver stage faces a tough time whatever trouble is taken. Switchmode power designers know too well the currrent drive formula for mosfet current drivers. The same can be applied to tube stages.
I'd be honest that I get exceptional results from the "modified" Williamson concept, 90% due to good quality o/p trannies.

I can see further improvemnts with the regenerative feedback Williamson diff stage, just a matter of getting around planting them.


richy
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Old 14th April 2009, 10:03 PM   #30
gallon is offline gallon  United States
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Quote:
Originally posted by xenu



Can you please refer me to a hybrid design that meets the following criteria:
1. Power amplifier at least 2x60w
2. Tube output stage (no sand for driving speakers)
3. With control and regulation (I can handle DSP) that are means to an end and not for show off.

Thanks

Take a look at the Steve Bench 813 matrix amplifier.
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