Joel,
If you are asking the question:
Why have more current drive than seems absolutely necessary?
Then my answer would have to be: slew rate, and the effects of non-linear input impedance, especially of DHT's.
Your designs may sound VERY good for the first watt. But what about loud passages, or transient response?
I refer you to Norman Crowhurst’s writings. They are available on my site.
Cheers,
dhaen said:
Well, since I only have .79 watts to play with...
But you've hit on my point exactly. How many people use all 8 watts of a 300-B? This is (yet another) case of designing for the fringes, when the listening experience day-to-day takes places very far from that territory. I'm told I must design my amp flat out to 200kHz, yet my only source material ends at 20kHz... where does it end?
A large DHT may have a better overload characteristic with large current drive - but who cares??? I don't run mine at clip, do you?
FLIPSIDE
Hi,
OTOH,how many people run .79W amps and have, say 96 dB + efficiency speakersystems?
Seems there are always two sides to a coin.
The point is, it doesn't hurt to have some headroom and as John said it will improve slew rate and subjectively make the amp sound clearer and cleaner across the band.
To paint with a broad brush:
In my OTL amps I need to drive the combined Miller capacitance of 10 // dual 6080 triodes with a 12BH7A.
It works fine, but if I now replace all 6080s with 6336As I can assure you that the 12BH7A won't be able to swing it properly.
And yes,you can tell the highs are starting to roll off.
If you now look at the 845, 211 and other notoriously hard to drive big bottle tubes, you'll often see you almost need an amp to drive one.
Cheers,
Hi,
OTOH,how many people run .79W amps and have, say 96 dB + efficiency speakersystems?
Seems there are always two sides to a coin.
The point is, it doesn't hurt to have some headroom and as John said it will improve slew rate and subjectively make the amp sound clearer and cleaner across the band.
To paint with a broad brush:
In my OTL amps I need to drive the combined Miller capacitance of 10 // dual 6080 triodes with a 12BH7A.
It works fine, but if I now replace all 6080s with 6336As I can assure you that the 12BH7A won't be able to swing it properly.
And yes,you can tell the highs are starting to roll off.
If you now look at the 845, 211 and other notoriously hard to drive big bottle tubes, you'll often see you almost need an amp to drive one.
Cheers,
...work in the way of important things...
Hi Joel,
I'm buried at work today and will be this evening too...
You raise an interesting point - For every rule of thumb or guide I know in designing amps, I also know of at least one exception that breaks it...
I will look at your choice of valves to see if I can find a reason why its so good with such a 'wimpy' driver...probably won't find one either!!! The fun is in the investigating
Bottom line...
If it sounds good to you - then its right - full stop!
more later
ciao
James
Hi Joel,
I'm buried at work today and will be this evening too...
You raise an interesting point - For every rule of thumb or guide I know in designing amps, I also know of at least one exception that breaks it...
I will look at your choice of valves to see if I can find a reason why its so good with such a 'wimpy' driver...probably won't find one either!!! The fun is in the investigating
Bottom line...
If it sounds good to you - then its right - full stop!
more later
ciao
James
Thank God - he didn't mean me ....
.. don't know a tube from a turkey baster
I guess I was reading your post ALL wrong.
Maybe I feel too inferior, when it comes to TUBES.
Sorry, Joel
------------------
/halo - mightn't be that bad after all 
Wasn't you refering to me?Joel said:halojoy - what the hell are you talking about?
.. don't know a tube from a turkey baster
I guess I was reading your post ALL wrong.
Maybe I feel too inferior, when it comes to TUBES.
Sorry, Joel
------------------
/halo - mightn't be that bad after all
Halojoy,
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,
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,
There's a cure: Join us!
Hi John,
Be ware of what you wish for.
Halojoy,
Join the magic and you'll be singing Bob Dylan songs all day long.
Look at Planet10,see how he does it...I'm sure he's feeling more confident every month and hey you know semi-conductors too.
Maybe you can teach us some useful applications for these too?
Not that I want to make hybrids,but you never know what's around the bend.
Cheers,
Hi John,
Be ware of what you wish for.
Halojoy,
Join the magic and you'll be singing Bob Dylan songs all day long.
Look at Planet10,see how he does it...I'm sure he's feeling more confident every month and hey you know semi-conductors too.
Maybe you can teach us some useful applications for these too?
Not that I want to make hybrids,but you never know what's around the bend.
Cheers,
Re: Absolutely not OVERDRIVE.
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.
fdegrove said:
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.
Just A Matter of Time
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
Yes, you are probably very right -dhaen said: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.
Just DO IT
http://home.zonnet.nl/horneman/
DIY SET is the easiest way..
to audio nirvana
Cheers,
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
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
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
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
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
Re: High current pentode drivers...
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.
James D. said:
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.
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
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
Re: Why does Joels amp sound so good?
Interesting, James.
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...
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.
I agree with that.
James D. said:
Interesting, James.
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...
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.I agree with that.
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