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  #1   Report Post  
V-Twin
 
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Default Stages of phono preamp

Hi all!
I'm playng around with the project of my phono preamp.
After many schematics, now i'm thinking about a EC8010 -- RIAA network --
RCA 76, both tubes CCS loaded.
Maybe this isn't a good design, but i'm a rookie in this field, so be
patient...
At the operating point the plate current for the EC8010 is 25 mA and 4mA for
the 76, both are about at 120V on plate.
Therefore the EC8010 drives more power than the 76. I wonder if this makes
sense. Maybe i'm wrong, but it seems to me that usually every stage drives a
following more powerful stage. It has to be so, or there is no relation
between the power dissipated in a stage vs. the power dissipated in the
following stage?
I' didn't found much information about this.


  #2   Report Post  
Patrick Turner
 
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V-Twin wrote:

Hi all!
I'm playng around with the project of my phono preamp.
After many schematics, now i'm thinking about a EC8010 -- RIAA network --
RCA 76, both tubes CCS loaded.
Maybe this isn't a good design, but i'm a rookie in this field, so be
patient...
At the operating point the plate current for the EC8010 is 25 mA and 4mA for
the 76, both are about at 120V on plate.
Therefore the EC8010 drives more power than the 76. I wonder if this makes
sense. Maybe i'm wrong, but it seems to me that usually every stage drives a
following more powerful stage. It has to be so, or there is no relation
between the power dissipated in a stage vs. the power dissipated in the
following stage?
I' didn't found much information about this.


Some folks use a lot of current in the input stage of their phono
amp to allow the chosen triode to work where its Gm is the highest,
and its noise the lowest.
Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a step up
tranny.

I used to use the circuit shown at
http://www.turneraudio.com.au/htmlwe...tubepreamp.htm
but now I have a 2SK369 in cascode with a frame grid pentode, the 6EJ7,
running in triode, with 6 mA of Ia and this gives me
20 dB less noise when MC is used, and 10 dB less noise with MM.

Once you have got past the first stage, there is no need for high current
following stages,
since the SNR isn't a problem, and a gain stage with 3 mA is ample.

CCS loadings can be achieved with transistors, j-fets, or pentodes.
The CCS load is a vet high impedance load, and thus the gain of the triode
becomes cloas to its Mu, and the thd falls to the lowest it can be
without using a balanced circuit, which reduces the thd even further.
IN phono input stages, thd isn't a main concern,
and typical thd figures at 100 mV of of output is maybe 0.01% of 2H,
even when the load is a resistor of say 5 times the RA of the tube.
The noise of the stage is determined by the grid input noise, the shot noise,
and the flicker noise of the tube, which is worst at LF,
and spoils many tube phono amps, so tube choice and
careful selection is very important.
The CCS needs to be low noise, as would the R used instead,
but the Ra is in shunt with the anode R load, so R has little effect
if Ra is a small fraction of it.
Same goes for the following grid bias R, which is effectively
in parallel with the load R supplying DC to
triode.

Patrick Turner.


  #3   Report Post  
TubeGarden
 
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Hi RATs!

I used a SV572-30 to drive a 2A3.

Nothing to do with phono amps, but, I just like telling that one

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead
  #4   Report Post  
Ronald
 
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Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a step up
tranny.


But that won't work with a total max. gain of 600 x .....
Ec8010 (on ccs) x # 76 (on ccs) = 60 x 10 = 600 .....
Way to low ! Even for MM ......

Ronald .


  #5   Report Post  
Centifolia
 
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OK, what am I missing? My Sumiko, which is a high output MC, has an output
of 3mV times a gain of 600 is 1.8V. Add a line stage and you have more than
enough gain for any amp. My amp drives to full output with a gain of .8V so
no line stage would be needed with this phono stage.

Sandy Brown


Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a step

up
tranny.


But that won't work with a total max. gain of 600 x .....
Ec8010 (on ccs) x # 76 (on ccs) = 60 x 10 = 600 .....
Way to (sic) low ! Even for MM ......

Ronald .






  #6   Report Post  
Ronald
 
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And it'll sound like sh*t since you don't use a Riaa correction .... ;-))
A total (unfiltered) gain of about 3600 for MM is quite normal ....


"Centifolia" schreef in bericht
news:Bchsb.128916$ao4.403701@attbi_s51...
OK, what am I missing? My Sumiko, which is a high output MC, has an

output
of 3mV times a gain of 600 is 1.8V. Add a line stage and you have more

than
enough gain for any amp. My amp drives to full output with a gain of .8V

so
no line stage would be needed with this phono stage.

Sandy Brown


Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a

step
up
tranny.


But that won't work with a total max. gain of 600 x .....
Ec8010 (on ccs) x # 76 (on ccs) = 60 x 10 = 600 .....
Way to (sic) low ! Even for MM ......

Ronald .






  #7   Report Post  
Phil Allison
 
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"Centifolia"

OK, what am I missing?



** Wait for it.


My Sumiko, which is a high output MC, has an output of 3mV times a gain of

600 is 1.8V.



** The output may be 3mV - but at 1 kHz !!!

At 25 Hz it will be only 0.3 mV - due to the RIAA recording curve.

A phono preamp needs at least 1000 times gain at low frequencies -
even when no NFB is used - much more if it is.





.......... Phil



  #8   Report Post  
Patrick Turner
 
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Ronald wrote:

And it'll sound like sh*t since you don't use a Riaa correction .... ;-))
A total (unfiltered) gain of about 3600 for MM is quite normal ....

"Centifolia" schreef in bericht
news:Bchsb.128916$ao4.403701@attbi_s51...
OK, what am I missing? My Sumiko, which is a high output MC, has an

output
of 3mV times a gain of 600 is 1.8V. Add a line stage and you have more

than
enough gain for any amp. My amp drives to full output with a gain of .8V

so
no line stage would be needed with this phono stage.

Sandy Brown


Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a

step
up
tranny.

But that won't work with a total max. gain of 600 x .....
Ec8010 (on ccs) x # 76 (on ccs) = 60 x 10 = 600 .....
Way to (sic) low ! Even for MM ......

Ronald .





I have used a 6DJ8 with a passive RIAA, followed by a 12AX7,
so total gain at 1 kHz is 30 x 70 /10 = 210, and the
divide by 10 is the loss at 1 kHz of the RIAA filter.

So if you have a 5 mV @1kHz cart at 1 kHz, you just over 1,000 mV at the
output.
But a cart of 2,5 mV, and a second phono stage gain of 35
would still make 250 mV.
But not so good with a Denon 103 MC, whose output is only 0.3mV.
Then you need more gain, or a step up transformer.

FB type EQ might have even greater demand for gain since even at 20 Hz there
is maybe 12 dB of FB operative, and 32 dB at 1 kHz, so an open loop gain
of 4,000 would be appropriate.

Many old phono stages just had two halves of 12AX7 cascaded for an open loop
gain of
about 4,000 at LF.
Some of the better ones had a CF stage added to the output of the second gain
1/2 of
the 12AX7, thus making the stage very low Ro, even at LF.

I prefer the passive RIAA, after a cascode stage, with mu follower topology
following .

Patrick Turner.


  #9   Report Post  
V-Twin
 
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"Patrick Turner" ha scritto nel messaggio
...
Some folks use a lot of current in the input stage of their phono
amp to allow the chosen triode to work where its Gm is the highest,
and its noise the lowest.
Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a step up
tranny.


Therefore is a good idea, or?

Once you have got past the first stage, there is no need for high current
following stages,
since the SNR isn't a problem, and a gain stage with 3 mA is ample.


Ok.

The noise of the stage is determined by the grid input noise, the shot

noise,
and the flicker noise of the tube, which is worst at LF,
and spoils many tube phono amps, so tube choice and
careful selection is very important.


I only have very basic knowledge about this, i need to learn more. Any
suggestion (books, web sites...)?


  #10   Report Post  
V-Twin
 
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"Phil Allison" ha scritto nel messaggio
u...
At 25 Hz it will be only 0.3 mV - due to the RIAA recording curve.

A phono preamp needs at least 1000 times gain at low frequencies -
even when no NFB is used - much more if it is.


I said i'm a rookie...i forgot to consider the 20dB loss of the RIAA
network... )




  #11   Report Post  
Bob Hedberg
 
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I use a 76 directcoupled 6be8 CF. The 76 sounds marvelous when
feeding another driving tube. It sounded even better without the CF
by a tad, but lower freq's really rolled off when driving cables to
the amp (100k input resistor). Maybe the CCS loading will help in
this regard. Let me know if it does, as the 76 is a really
nice-sounding tube.

Bob Hedberg

"V-Twin" wrote:

Hi all!
I'm playng around with the project of my phono preamp.
After many schematics, now i'm thinking about a EC8010 -- RIAA network --
RCA 76, both tubes CCS loaded.
Maybe this isn't a good design, but i'm a rookie in this field, so be
patient...
At the operating point the plate current for the EC8010 is 25 mA and 4mA for
the 76, both are about at 120V on plate.
Therefore the EC8010 drives more power than the 76. I wonder if this makes
sense. Maybe i'm wrong, but it seems to me that usually every stage drives a
following more powerful stage. It has to be so, or there is no relation
between the power dissipated in a stage vs. the power dissipated in the
following stage?
I' didn't found much information about this.


Bob H.

Just grab that plate in one hand, the chassis in the other,
and FEEL the power of tube audio!!!
(not literally, of course, just kidding. DON'T DO THAT!)
  #12   Report Post  
Choky
 
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Default

it's hard to beat EC8010 with 20 to 25mA in any topology with any tube.
it's ****in' beast ,and I have just a pair-in my WOT ;(((
who want to donate at least 20 pieces to poor ZM?


--
--
.................................................. ........................
Choky
Prodanovic Aleksandar
YU

"don't use force, "don't use force,
use a larger hammer" use a larger tube
- Choky and IST"
- ZM
.................................................. ...........................
"V-Twin" wrote in message
...
Hi all!
I'm playng around with the project of my phono preamp.
After many schematics, now i'm thinking about a EC8010 -- RIAA

network --
RCA 76, both tubes CCS loaded.
Maybe this isn't a good design, but i'm a rookie in this field, so be
patient...
At the operating point the plate current for the EC8010 is 25 mA and 4mA

for
the 76, both are about at 120V on plate.
Therefore the EC8010 drives more power than the 76. I wonder if this makes
sense. Maybe i'm wrong, but it seems to me that usually every stage drives

a
following more powerful stage. It has to be so, or there is no relation
between the power dissipated in a stage vs. the power dissipated in the
following stage?
I' didn't found much information about this.




  #13   Report Post  
V-Twin
 
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"Patrick Turner" ha scritto nel messaggio
...
I have used a 6DJ8 with a passive RIAA, followed by a 12AX7,
so total gain at 1 kHz is 30 x 70 /10 = 210, and the
divide by 10 is the loss at 1 kHz of the RIAA filter.

So if you have a 5 mV @1kHz cart at 1 kHz, you just over 1,000 mV at the
output.
But a cart of 2,5 mV, and a second phono stage gain of 35
would still make 250 mV.
But not so good with a Denon 103 MC, whose output is only 0.3mV.
Then you need more gain, or a step up transformer.


Maybe I don't do the calculations right:
MM cartridges usually have around 4mV rms output voltage and I must have
about 2 Vrms at the phono stage output to match the max output of my CD
player.
Considering about 20dB (maybe 30?) over the nominal 5cm/sec level for the
higest music peak in the vinyl, I have 40mV coming out from the cartridge.
Ergo I need an amplification factor of at least 2/0.04=50, wich becomes 500
considering the nominal 20dB loss of the riaa network.
A EC8010 followed by a 76 should do the work, giving a gain of 600.
Maybe the output impedance of about 9kOhm can be a problem. Should i add a
CF?


  #14   Report Post  
Phil Allison
 
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"V-Twin"


Maybe I don't do the calculations right:
MM cartridges usually have around 4mV rms output voltage and I must have
about 2 Vrms at the phono stage output to match the max output of my CD
player.


Considering about 20dB (maybe 30?) over the nominal 5cm/sec level for the
highest music peak in the vinyl,



** Complete nonsense.

Most vinyl recordings barely go above the reference level.



I have 40mV coming out from the cartridge.



** Not at 1 kHz.


........... Phil


  #15   Report Post  
Ruud Broens
 
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"Bob Hedberg" wrote in message
...
: I use a 76 directcoupled 6be8 CF. The 76 sounds marvelous when
: feeding another driving tube. It sounded even better without the CF
: by a tad, but lower freq's really rolled off when driving cables to
: the amp (100k input resistor). Maybe the CCS loading will help in
: this regard. Let me know if it does, as the 76 is a really
: nice-sounding tube.
:
: Bob Hedberg

Your price, Sir




  #16   Report Post  
Ruud Broens
 
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Default


: : Bob Hedberg
:
: Your price, Sir
Err, never mind, see you've made yours up
Rudy


  #17   Report Post  
Patrick Turner
 
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V-Twin wrote:

"Patrick Turner" ha scritto nel messaggio
...
Some folks use a lot of current in the input stage of their phono
amp to allow the chosen triode to work where its Gm is the highest,
and its noise the lowest.
Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a step up
tranny.


Therefore is a good idea, or?


Not necessarily.
Some folks like this way of doing an amp.
Some folks don't, so I suggest you find by using a soldering iron
and your ears, and a CRO.



Once you have got past the first stage, there is no need for high current
following stages,
since the SNR isn't a problem, and a gain stage with 3 mA is ample.


Ok.

The noise of the stage is determined by the grid input noise, the shot

noise,
and the flicker noise of the tube, which is worst at LF,
and spoils many tube phono amps, so tube choice and
careful selection is very important.


I only have very basic knowledge about this, i need to learn more. Any
suggestion (books, web sites...)?


There is a fair bit around the web on phono tube preamps.

The old book like RDH4 don't have 6DJ8 circuits within it, but it does have lots
of applicable theory, which you should know about,
if you want to fiddle around with tubes.

Patrick Turner.

  #18   Report Post  
Patrick Turner
 
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V-Twin wrote:

"Patrick Turner" ha scritto nel messaggio
...
I have used a 6DJ8 with a passive RIAA, followed by a 12AX7,
so total gain at 1 kHz is 30 x 70 /10 = 210, and the
divide by 10 is the loss at 1 kHz of the RIAA filter.

So if you have a 5 mV @1kHz cart at 1 kHz, you just over 1,000 mV at the
output.
But a cart of 2,5 mV, and a second phono stage gain of 35
would still make 250 mV.
But not so good with a Denon 103 MC, whose output is only 0.3mV.
Then you need more gain, or a step up transformer.


Maybe I don't do the calculations right:
MM cartridges usually have around 4mV rms output voltage and I must have
about 2 Vrms at the phono stage output to match the max output of my CD
player.


Have you measured the CD player output?
I bet it ain't 2vrms, even when measuring with a stream of
heavy metal grunge as a test tone, on an rms meter with 20 kHz of bandwidth.


Considering about 20dB (maybe 30?) over the nominal 5cm/sec level for the
higest music peak in the vinyl, I have 40mV coming out from the cartridge.


Its possible, but rare....


Ergo I need an amplification factor of at least 2/0.04=50, wich becomes 500
considering the nominal 20dB loss of the riaa network.


The RIAA losses are negligible at LF, -20 dB at 1 kHz, and about -38 dB at 20
kHz.

If you had rated 4mV at 1 kHz from the cartridge, and a gain of 5,000
in the amp, and -20dB loss in the RIAA filter,
you get Vo = 0.004 x 5000/10 = 2v.

Most of the signals from a cart are less than 4 mV.


A EC8010 followed by a 76 should do the work, giving a gain of 600.


Including RIAA losses?


Maybe the output impedance of about 9kOhm can be a problem. Should i add a
CF?


You need to measure the Ro to find out properly.
Assume nothing.

If the amp you propose has cabling to a pre or power amp
which has 200pF, and the input R is 100k, and the Ro of your pre is 9k,
then the HF roll off be at 100 kHz, but I bet its lower,
because Ro isn't as low as 9k, and stray C elsewhere won't allow such a
bandwidth.
And the cathode of the outout triode of you phono amp needs to be
bypassed to maintain the effective Ro.

Patrick Turner.

  #19   Report Post  
Bob Hedberg
 
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Pardon?

"Ruud Broens" wrote:


: : Bob Hedberg
:
: Your price, Sir
Err, never mind, see you've made yours up
Rudy


Bob H.

Just grab that plate in one hand, the chassis in the other,
and FEEL the power of tube audio!!!
(not literally, of course, just kidding. DON'T DO THAT!)
  #20   Report Post  
Fred Nachbaur
 
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(Think he meant "prize", referring to the contest)

Bob Hedberg wrote:
Pardon?

"Ruud Broens" wrote:


: : Bob Hedberg
:
: Your price, Sir
Err, never mind, see you've made yours up
Rudy



Bob H.

Just grab that plate in one hand, the chassis in the other,
and FEEL the power of tube audio!!!
(not literally, of course, just kidding. DON'T DO THAT!)


--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+



  #21   Report Post  
V-Twin
 
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Patrick Turner wrote in message ...
Have you measured the CD player output?
I bet it ain't 2vrms, even when measuring with a stream of
heavy metal grunge as a test tone, on an rms meter with 20 kHz of bandwidth.


Specs says max output 2Vrms, i don't have yet a test CD to do mesures.
No doubt that the "normal" output level is lower, since plugging the
CDP directly to the amp don't saturate it (1V sensitivity).
I think the 2V are the max voltage the output stage of the CDP can
reach.

The RIAA losses are negligible at LF, -20 dB at 1 kHz, and about -38 dB at 20
kHz.

If you had rated 4mV at 1 kHz from the cartridge, and a gain of 5,000
in the amp, and -20dB loss in the RIAA filter,
you get Vo = 0.004 x 5000/10 = 2v.


Uhm...but i want that the 2V are reached only during the peaks, like
the CDP, therefore i must consider a 20dB (Morgan Jones measured +16dB
playing the Beethoven's Ninth Simphony) larger signal coming from the
cartridge. That makes 40mV at 1kHz, or 4mV at 20Hz due the riaa curve.
The first stage of the phono preamp gains 35dB, the riaa network
equalizes the signal cutting 20dB@1kHz and further 20dB@20kHz, thus
after the riaa network i have 240mV at all frequencies. CCS loaded,
the 76 gains about 15, thus 240mV*15=3.6V, wich is more than enough.
Considering instead the nominal output of 4mV, I ends up with 24mV
after the riaa network and 360 mV at 76's output, wich should be not
too far form output voltage of CDP.
Where I'm wrong?
  #22   Report Post  
Phil Allison
 
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"V-Twin"


Specs says max output 2Vrms, i don't have yet a test CD to do measures.
No doubt that the "normal" output level is lower, since plugging the
CDP directly to the amp don't saturate it (1V sensitivity).
I think the 2V are the max voltage the output stage of the CDP can
reach.



** 2 volts rms sine wave is the max level set by the "Red Book" standard.

But my Sony CDP101 produces nearly +/- 6 volts peak using a digital
white noise test disk.



Uhm...but i want that the 2V are reached only during the peaks, like
the CDP, therefore i must consider a 20dB (Morgan Jones measured +16dB
playing the Beethoven's Ninth Simphony) larger signal coming from the
cartridge.



** What a blatant lie.


That makes 40mV at 1kHz, or 4mV at 20Hz due the riaa curve.


** More mad lies.





............ Phil


  #23   Report Post  
Patrick Turner
 
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V-Twin wrote:

Patrick Turner wrote in message ...
Have you measured the CD player output?
I bet it ain't 2vrms, even when measuring with a stream of
heavy metal grunge as a test tone, on an rms meter with 20 kHz of bandwidth.


Specs says max output 2Vrms, i don't have yet a test CD to do mesures.
No doubt that the "normal" output level is lower, since plugging the
CDP directly to the amp don't saturate it (1V sensitivity).
I think the 2V are the max voltage the output stage of the CDP can
reach.

The RIAA losses are negligible at LF, -20 dB at 1 kHz, and about -38 dB at 20
kHz.

If you had rated 4mV at 1 kHz from the cartridge, and a gain of 5,000
in the amp, and -20dB loss in the RIAA filter,
you get Vo = 0.004 x 5000/10 = 2v.


Uhm...but i want that the 2V are reached only during the peaks, like
the CDP, therefore i must consider a 20dB (Morgan Jones measured +16dB
playing the Beethoven's Ninth Simphony) larger signal coming from the
cartridge. That makes 40mV at 1kHz, or 4mV at 20Hz due the riaa curve.
The first stage of the phono preamp gains 35dB, the riaa network
equalizes the signal cutting 20dB@1kHz and further 20dB@20kHz, thus
after the riaa network i have 240mV at all frequencies. CCS loaded,
the 76 gains about 15, thus 240mV*15=3.6V, wich is more than enough.
Considering instead the nominal output of 4mV, I ends up with 24mV
after the riaa network and 360 mV at 76's output, wich should be not
too far form output voltage of CDP.
Where I'm wrong?


I have never seen 40 mV coming from a cartridge at 1 kHz.

I have never studied the CRO trace during the 9th symphonie's cannon shots.

4mV is the high side of what comes from a cartridge.

The signal going to a record cutting machine amp
has its signal equalised so relative to 1kHz, the bass is reduced a maximum of 20 dB,
and the treble is boosted at 6 dB/octave after 2,110 Hz, until about
50 kHz, when the boost is curtailed.

Therefore, if a source of constant level sine waves are fed in
to the cutter amp, the bass amplitudes are much reduced, and treble increased,
and there are limits as to how much boost to treble can be applied,
lest the cutter run out of headroom.
The noise of a cannon shot contains a potpourrie of F above 1 kHz.
The sound you hear from the vinyl is nothing like a real cannon 50 feet away,
since the system is utterly incapable of containing the dynamic range,
and a lot of limiting is going on, or they moved the cannon to 500 feet away.
A nice big bash of cymbals can easily over load the recording system.

The engineers allow for all this, and at the end of the day,
when we make a tube phono stage, the tubes' dynamic headroom ability
even with high output MM is quite able to take whatever is thrown at it
from the cartridge.
In fact, if you have 40 mV input at 1 kHz, which is a 20 dB overload,
with the amp set up with a gain at 1 kHz including RIAA of say 400, then you'd get 16 v output,
which is still below the tube limit of perhaps 64 v
but way above what most SS might achieve, using +/- 12v rails and opamps.

I am not sure what the maximum signal at 10 kHz would be compared to
what might be maximum possible at 1 kHz.
But if you feed in a range of F at the same amplitude to the record cutter to get
4mV at 1 kHz, then expect around 40 mV at 21 kHz from a record cut this way.
Fortunately, HF content in music reduces a lot above 3 kHz,
so the HF is accomodated, despite being boosted, to improve the snr.

In the preamp, the 21 khz cartridge signal of 40 mv is treated differently
depending on whether the amp has its RIAA eq done either passively,
or by way of NFB.
The passive stage needs to be able to take 40 mV without saturating, or
running into cut off or grid current, so if the 12AX7 gain is 90,
like it is in my amps, then 3.6 v output shouldn't cause any problems.
In fact, 400mV input at 21 kHz won't either, because the first stage of a decent
passively eq'd tube amp is capable of well over 36v output.
Its almost impossible to ever overload a tube phono amp.

The possibly high 21 kHz output from stage 1 is reduced 40 dB by the passive
eq so the next stage won't be overloaded either.

The feedback type of eq has the first stage recieving two signals,
one is the possible 40 mV at 21 kHz, and the other is the fed back signal,
and the difference between the two is all that is amplified, and its a heck of a lot
less than what the passive stage has to endure.
Thus RIAA FB stages have good overload capability, and far less thd,
because the network feeding back the signals from the output also
feedback any thd, which then gets reduced by nfb action, like most other amps,
except that LF errors are corrected less than HF errors, since more FB occurs as F rises.
However the feedback network itself becomes a low impedance load
for the tubes at HF, and this itself can cause overloading
of the final stage in the FB type phono amp, if output voltage is high enough,
and the design of the FB network has R values which are too low.
The V2 of the amp, if it is a ****ant tube like the 12AX7
should perhaps be coupled to a medium U triode cathode follower,
itself a case of lotsa local FB, and it then can take the brunt of the load
imposed by the FB network itself at HF.

The use of FB RIAA is almost universal in the world of SS amps,
which need all the FB thay can muster to compete with triodes.
Hence opamps are so often used.
With tubes, FB is optional because tubes have emormous
dynamic range, and triodes can be extremely linear at low signal levels,
even without the slightest use of loops of FB.
All my SE phono and line stages produce less than 0.1% thd at 10vrms output.
All have passive RIAA eq.
With a balanced set up, like what you may find at vacuumstate.com,
the thd is even a lot lower.

Anyway, to cut a long story short,
Perhaps you should just try building a two stage
triode amp, so that the gains of the two tubes equal say 4,000, +/- 50%,
with a passive RIAA filter between V1 and V2,
and have a measure, and have a listen.

The output you may get from such an arrangement may be above what you might get from
many CD players.

Once you have done this, you will know more what to do next.

Patrick Turner.


  #24   Report Post  
V-Twin
 
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Tanks for such a long, clarifying and kind ansewer, I hope i'm not
misusing your patience...

Patrick Turner wrote in message ...
I have never seen 40 mV coming from a cartridge at 1 kHz.

I have never studied the CRO trace during the 9th symphonie's cannon shots.

4mV is the high side of what comes from a cartridge.


Well, i read that book and i have no reason to doubt what MJ says
until i don't found proofs that he's wrong. After all he is definitely
more expert than me )
But i never considered it like a bible...

Anyway, to cut a long story short,
Perhaps you should just try building a two stage
triode amp, so that the gains of the two tubes equal say 4,000, +/- 50%,
with a passive RIAA filter between V1 and V2,
and have a measure, and have a listen.


It's too early to build something, i have a lot to study and learn
before trying to put tubes together.
  #25   Report Post  
Patrick Turner
 
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V-Twin wrote:

Tanks for such a long, clarifying and kind ansewer, I hope i'm not
misusing your patience...

Patrick Turner wrote in message ...
I have never seen 40 mV coming from a cartridge at 1 kHz.

I have never studied the CRO trace during the 9th symphonie's cannon shots.

4mV is the high side of what comes from a cartridge.


Well, i read that book and i have no reason to doubt what MJ says
until i don't found proofs that he's wrong. After all he is definitely
more expert than me )
But i never considered it like a bible...

Anyway, to cut a long story short,
Perhaps you should just try building a two stage
triode amp, so that the gains of the two tubes equal say 4,000, +/- 50%,
with a passive RIAA filter between V1 and V2,
and have a measure, and have a listen.


It's too early to build something, i have a lot to study and learn
before trying to put tubes together.


Its OK, make a chassis, put 4 valve sockets in,
make a PSU, and you learn by doing,
one bit at a time; or one triode at a time.
You may need a CRO, to SEE what you are doing.
You gotta start someplace....

Patrick Turner.




  #26   Report Post  
V-Twin
 
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"Phil Allison" wrote in message . au...
Uhm...but i want that the 2V are reached only during the peaks, like
the CDP, therefore i must consider a 20dB (Morgan Jones measured +16dB
playing the Beethoven's Ninth Simphony) larger signal coming from the
cartridge.



** What a blatant lie.


That makes 40mV at 1kHz, or 4mV at 20Hz due the riaa curve.


** More mad lies.


I have no elemets yet to refute what MJ says.
If he says he measured +16dB above the level at 5cm/sec i cannot
disagree until i do my own measures or i found documents wich prooves
the opposite.
Maybe you can share your opinion about other than simple judgments.
  #27   Report Post  
V-Twin
 
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"Patrick Turner" ha scritto nel messaggio
...
It's too early to build something, i have a lot to study and learn
before trying to put tubes together.


Its OK, make a chassis, put 4 valve sockets in,
make a PSU, and you learn by doing,
one bit at a time; or one triode at a time.
You may need a CRO, to SEE what you are doing.
You gotta start someplace....


Perhaps you're right...study without applying has no sense...
Maybe i can find a chep used CRO (no way i can get a new one...).


  #28   Report Post  
Phil Allison
 
Posts: n/a
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"V-Twin" wrote in message
m...
"Phil Allison" wrote in message

. au...

Uhm...but i want that the 2V are reached only during the peaks, like
the CDP, therefore i must consider a 20dB (Morgan Jones measured +16dB
playing the Beethoven's Ninth Simphony) larger signal coming from the
cartridge.



** What a blatant lie.


That makes 40mV at 1kHz, or 4mV at 20Hz due the riaa curve.


** More mad lies.



I have no elemets yet to refute what MJ says.



** You have NO reason to believe him EITHER !!!!!


If he says he measured +16dB above the level at 5cm/sec i cannot
disagree until i do my own measures or i found documents wich prooves
the opposite.



** You are the one making the mistake - not MJ. Such an extreme level
may exist on ONE recording somewhere - SO ****ING WHAT !!!!

You cannot use that figure as a reference for deciding on the appropriate
gain of a phono pre.

Every amp maker in the world assumes 2-5 mV at 1 kHz as the reference
level for MM - so should you !




.............. Phil


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