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Old 17th January 2003, 11:00 PM   #31
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Default OVERDRIVE.

Hi,

Quote:
Yes! I've tried a few of the high current drivers for the 300B and while they were initially impressive they all suffered from upper midrange glare.
Sounds like clipping to me.
It would seem you drove the output tubes into clipping,you may want to bias the output more negative.

Cheers,
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Old 18th January 2003, 03:04 AM   #32
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Default Re: Absolutely not OVERDRIVE.

Quote:
Originally posted by fdegrove
Sounds like clipping to me.
It would seem you drove the output tubes into clipping,you may want to bias the output more negative.
That's more than a little presumptuous to conclude from the info you have, isn't it?

The output wasn't clipping. The 300B was biased at -80V. In some situations it could not possibly have clipped as I didn't have enough overall gain. The upper midrange glare I referred to was present at all volume levels.

The subtext of my original post is that everyone's ears are different. I'm often astonished at how awful I find many other audiophile's systems to sound. I've become conditioned to run the other way when someone starts using words like power, resolution, bandwidth and detail to describe their system as it usually means I'm about to have my ears sliced off by an HF audio death ray. Since these are words often used to describe high current drivers, well...you figure it out.
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Old 18th January 2003, 03:48 AM   #33
halojoy is offline halojoy  Sweden
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Thumbs up Just A Matter of Time

Quote:
Originally posted by dhaen
Halojoy,


There's a cure: Join us!
Revoke your belief that SS is God's gift.
Can you really believe that everyone in this large "tube community" is wrong?
So there must be something in it...........
What to build as a demo?
Well, you build a simple SE amplifier, and see what it sounds like. It could be done with minimal funds: I presume you already have lots of electronic parts in stock.

Just DO IT And to take a quote from Bas Horneman's website:

http://home.zonnet.nl/horneman/

DIY SET is the easiest way..
to audio nirvana

Cheers,
Yes, you are probably very right -
So many STRONG belivers could not be wrong - not all of them ...
must be something ...

I am sure - sooner or later - I will build my FIRST Tube-amp
Will be a Preamplifier - just to put some Valve Sound
to feed my Class A Solide State output Stage.
And it will be Single Ended Tube, of course!!!!
Why use Feedback and Push Pull - to take away what I will be adding ..

I already know about my Swedish Tube Supplier
Have already recommended this link before:

List of ALL Tubes at our Swedish Supplier - LH-MUSIK.se

And I download at least 2 tube-schematics per day.
so my harddisk is beginning to have a considerable lot of Tube-amps schematics.

----------------------------------------------

/halo - knows that there is something about that Glow
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Old 18th January 2003, 07:42 AM   #34
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Default Why does Joels amp sound so good?

Hi Joel,

As I expected I do not have a complete answer as to why your amp sounds so good... but some of the factors are that the 71-A has relatively low input capacitance both grid-cathode and grid-plate. It is a nice valve to drive but your driver is running much lower current than I would expect. To be honest I wouldn't expect your amp. to sound 'tubey' as such as I would expect odd harmonics to be much higher from your driver than is normal and this allied to the even harmonics from the 71-A may actually leave you with a better balanced distortion spectrum. This, hopefully, would result in a neutral and clear sound that is fast and driving.

I would expect that changing the driver to a higher current stage would make the sound open up more and get more relaxing even sweeter... the thing about having lots of current drive available in the driver stage is that it relaxes and opens up the sound. It can make it sound less 'fast' and with less drive on a quick comparision but over time one realises that it is actually more correct. If you try it please let me know...

How do the monoblocks with 01-A sound?

As I said before - if it sounds right to you it is right! But it might be possible for it to sound even more right

ciao

James
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Old 18th January 2003, 08:06 AM   #35
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Default High current pentode drivers...

Hi Jeff,

I would agree with your remarks about high current pentode drivers... In general I think pentode drivers suffer from upper mid range glare and the higher current models are worse than the lower current models...

I have found this feature (upper mid range glare) to be associated with low overall distortion but a distortion spectrum that relatively predominates in mid higher order harmonics and the higher current pentodes generate just this sort of spectrum...

Lower current pentodes such as the 6J7 have a better balanced harmonic spectrum although they might generate higher distortion overall.

It is the difference in distortion spectrum that is the main cause of different sound from different topologies and valves...IMO!!!!

[ ....digs in burrow quick...]

ciao

James
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Old 18th January 2003, 08:18 AM   #36
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Default Re: High current pentode drivers...

Quote:
Originally posted by James D.
I have found this feature (upper mid range glare) to be associated with low overall distortion but a distortion spectrum that relatively predominates in mid higher order harmonics and the higher current pentodes generate just this sort of spectrum...
While I don't have the capability to measure the actual distortion, calculations off the valve curves indicated my operating points should be relatively low in third order distortion. I deliberately sacrificed gain to stay well away from the "knee" in the pentode curves. Still glare. My experience with triode drivers is less, but I do recall a 6SN7 driver running at 14ma had far more glare than any of the pentodes, high current or low.

One of my 300Bs gave up a few weeks ago, so I'm listening to 45s at the moment. In a month or so, I'll have 845s to play with and I'll likely use another power tube as driver stage (46, 71A, 10Y). We'll see how we go there.
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Old 18th January 2003, 09:09 AM   #37
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Default third harmonic and more...

Hi Jeff,

It's not third harmonic I worry about - particularly. That's usually taken care off by the normal concerns about low distortion design such as staying away from the knee.

It's the insidious nature of mid higher order harmonics - specifically 7th, 9th and 11th harmonics and to some degree 5th harmonic. These cause glare.

A triode is more than capable of generating these too... its always topology and application dependent as well as operating points... And passive component choice influences it too... BUT the biggest secondary effect on the performance of any amplifier design is the power supply and this can cause a big difference in the distortion spectrum

Contary to popular belief I find that pentodes are more influenced by power supply design than triodes in that their sonic signature changes more with changes to the psu. This seems to be down to the shape of the distortion spectrum - good (natural..) shape to the harmonic distortion spectrum counts for more than absolute level of THD...ALWAYS

As has been stated on 'the bias forum' thread ( I still owe SY a reply) .. triodes are intrinsically more linear than any other electronic amplification device and, I would add, have a more naturally shaped harmonic distortion spectrum than any other active device... in any specific application one might get better results results with an unconventional choice...

In Engineering: Rules are for the obedience of the unquestioning and the guidance of the wise... another Benny Hill truth

There is a hidden complication here as well. No two people hear things in exactly the same way... yep Benny Hill again...

ciao

James
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Old 18th January 2003, 02:53 PM   #38
Joel is offline Joel  United States
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Default Re: Why does Joels amp sound so good?

Quote:
Originally posted by James D.
...I would expect odd harmonics to be much higher from your driver than is normal and this allied to the even harmonics from the 71-A may actually leave you with a better balanced distortion spectrum. This, hopefully, would result in a neutral and clear sound that is fast and driving.
Interesting, James.

Quote:
I would expect that changing the driver to a higher current stage would make the sound open up more and get more relaxing even sweeter... If you try it please let me know...
I will! As soon as I finish my regulated 5V filament supply I'll be able to plug a Ux-112 in the driver socket, and boost the current from 3mA up to 12. Hmmm... if I move one wire I could drive the 71 with another 71...

Quote:
How do the monoblocks with 01-A sound?
It's too soon to make a full assessment, but I think in the end I will actually prefer the single high mu driver. I can't say why exactly (yet). But they certainly are nice sounding amplifiers, even after an hour of straight listening. That, to me, is a strong test - if I'm still "into" the music after a long listening session.

Quote:
As I said before - if it sounds right to you it is right!
I agree with that.
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Old 18th January 2003, 11:34 PM   #39
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Default BITING MY NOSE OFF

Hi,

Quote:
That's more than a little presumptuous to conclude from the info you have, isn't it?
Probably,it was only a suggestion anyway.

James is spot on though...midrange glare is 9/10 a predominantly high order distorsion components.

A spectral analysis should reveal it anyway.

You'll sort that out all by yourself won't you?

Cheers,
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Old 22nd January 2003, 10:19 AM   #40
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Quote:
Originally posted by dhaen
DIY SET is the easiest way..
to audio nirvana
.....but the best things are often not the easiest.
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