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6N1P conflicting heater/cathode voltage specs



 
 
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  #1  
Old July 28th 08, 04:11 PM posted to rec.audio.tubes
Ian Thompson-Bell
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Posts: 493
Default 6N1P conflicting heater/cathode voltage specs

I have two data sheets for the 6N1P, both Russian with English
translations, which seem to give conflicting values for maximum heater
to cathode voltages.

One specifies Ukh as +100V and -250V. As the k precedes the h I assume
these are cathode voltages relative to the heater, so this spec says the
cathode can be at most 100V positive with respect to the heater.

The other describes these parameters in words. It says: Voltage between
cathode and heater:

- with heater at positive potential 100V
- with heater at negative potential 250V

I take this to mean the heater can be up to 100V above the cathode or
250V below it, which seems to me to be the exact opposite of what the
other spec says.

So, which is right?

Cheers

Ian
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  #2  
Old July 28th 08, 09:17 PM posted to rec.audio.tubes
tubegarden
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Posts: 343
Default 6N1P conflicting heater/cathode voltage specs

Hi RATs!

I am not sure, neither. I love the 6N1P and have used it in many
circuits. I do not design circuits with anything near 100V between
heater and cathode.

I put a a V-Cap between the 6AU6 and 6BN8 in an AA-161 amp today. It
is new, so it will be some weeks before I can feel confident in saying
it seems to work. I used a similar rated MusiCap in the other 161 in
the same location and circuit. They measured 0.1047 and 0.1044 uF, so
no meaningful comparison can be made

I love soldering new parts into old amps

I am easily amused.

What drives people to build circuits with 250 volts between the
cathode and the heater?

Perhaps some folks are even crazier than me?

Happy Ears!
Al

  #3  
Old July 28th 08, 09:47 PM posted to rec.audio.tubes
Iain Churches[_2_]
external usenet poster
 
Posts: 1,719
Default 6N1P conflicting heater/cathode voltage specs



"tubegarden" > wrote in message
...
> Hi RATs!
>
> I am not sure, neither. I love the 6N1P and have used it in many
> circuits. I do not design circuits with anything near 100V between
> heater and cathode.
>
> I put a a V-Cap between the 6AU6 and 6BN8 in an AA-161 amp today. It
> is new, so it will be some weeks before I can feel confident in saying
> it seems to work. I used a similar rated MusiCap in the other 161 in
> the same location and circuit. They measured 0.1047 and 0.1044 uF, so
> no meaningful comparison can be made
>
> I love soldering new parts into old amps
>
> I am easily amused.
>
> Happy Ears!
> Al



Hi Al. Nice to come back from holiday and see you
posting. Hope you are well.

> What drives people to build circuits with 250 volts between the
> cathode and the heater?
>
> Perhaps some folks are even crazier than me?



Not at all. With cathode folllowers and mu followers
the cathode is always at a considerably higher potential
thant the DC heater. I usualy put the heater at 95V to
decrease the differential with a floating heater suply.

Regards
Iain



  #4  
Old July 29th 08, 03:27 AM posted to rec.audio.tubes
Patrick Turner
external usenet poster
 
Posts: 3,915
Default 6N1P conflicting heater/cathode voltage specs



Ian Thompson-Bell wrote:
>
> I have two data sheets for the 6N1P, both Russian with English
> translations, which seem to give conflicting values for maximum heater
> to cathode voltages.
>
> One specifies Ukh as +100V and -250V. As the k precedes the h I assume
> these are cathode voltages relative to the heater, so this spec says the
> cathode can be at most 100V positive with respect to the heater.
>
> The other describes these parameters in words. It says: Voltage between
> cathode and heater:
>
> - with heater at positive potential 100V
> - with heater at negative potential 250V
>
> I take this to mean the heater can be up to 100V above the cathode or
> 250V below it, which seems to me to be the exact opposite of what the
> other spec says.
>
> So, which is right?
>
> Cheers
>
> Ian


Probably all is misleading.

I'd never run a cathode at a dc potential of more than +/- 70V with
respect to the heater.

So if you have a CF where the cathode swings maybe 135Vrms, as might be
the case if driving
an 845 grid in class AB2, then be prepared to have the filament and its
voltage supply and transformer winding
also swing as well, which may mean you also need a screened tranny
winding to prevent stray C coupling to the mains.

Never believe all the BS about heater to cathode voltage ratings, and
don't
tempt fate by allowing more than +/-70V peak to ever exist.

Patrick Turner.
  #5  
Old July 29th 08, 05:22 AM posted to rec.audio.tubes
ZACK.
external usenet poster
 
Posts: 15
Default 6N1P conflicting heater/cathode voltage specs

does the 6922 tube tell you anything

"Ian Thompson-Bell" > wrote in message
...
>I have two data sheets for the 6N1P, both Russian with English
>translations, which seem to give conflicting values for maximum heater to
>cathode voltages.
>
> One specifies Ukh as +100V and -250V. As the k precedes the h I assume
> these are cathode voltages relative to the heater, so this spec says the
> cathode can be at most 100V positive with respect to the heater.
>
> The other describes these parameters in words. It says: Voltage between
> cathode and heater:
>
> - with heater at positive potential 100V
> - with heater at negative potential 250V
>
> I take this to mean the heater can be up to 100V above the cathode or 250V
> below it, which seems to me to be the exact opposite of what the other
> spec says.
>
> So, which is right?
>
> Cheers
>
> Ian



  #6  
Old July 29th 08, 01:16 PM posted to rec.audio.tubes
Iain Churches[_2_]
external usenet poster
 
Posts: 1,719
Default 6N1P conflicting heater/cathode voltage specs



"Patrick Turner" > wrote in message
...
>
>
> Ian Thompson-Bell wrote:
>>
>> I have two data sheets for the 6N1P, both Russian with English
>> translations, which seem to give conflicting values for maximum heater
>> to cathode voltages.
>>
>> One specifies Ukh as +100V and -250V. As the k precedes the h I assume
>> these are cathode voltages relative to the heater, so this spec says the
>> cathode can be at most 100V positive with respect to the heater.
>>
>> The other describes these parameters in words. It says: Voltage between
>> cathode and heater:
>>
>> - with heater at positive potential 100V
>> - with heater at negative potential 250V
>>
>> I take this to mean the heater can be up to 100V above the cathode or
>> 250V below it, which seems to me to be the exact opposite of what the
>> other spec says.
>>
>> So, which is right?
>>
>> Cheers
>>
>> Ian

>
> Probably all is misleading.
>
> I'd never run a cathode at a dc potential of more than +/- 70V with
> respect to the heater.
>
> So if you have a CF where the cathode swings maybe 135Vrms, as might be
> the case if driving
> an 845 grid in class AB2, then be prepared to have the filament and itsa
> voltage supply and transformer winding
> also swing as well, which may mean you also need a screened tranny
> winding to prevent stray C coupling to the mains.


If you don't have a dedicated winding, you can use a pair of
resistors across one of the B+ first filter caps to total 1M and adjust
their values to give you the elevated voltage you need at the centre
of these two. You then apply this voltage to both sides of the heater
cap via 100 Ohms resistors. The heater supply must, of course,
float. It works well. Details are given in Rozenblit's book. a small
decoupling cap (I use 0.1F) is required at the junction of the two
resistors, and also on each leg of the heater at the tube socket.


Regards to all
Iain



  #7  
Old July 29th 08, 01:36 PM posted to rec.audio.tubes
Nick Gorham
external usenet poster
 
Posts: 134
Default 6N1P conflicting heater/cathode voltage specs

Iain Churches wrote:
> "Patrick Turner" > wrote in message
> ...
>
>>
>>Ian Thompson-Bell wrote:
>>
>>>I have two data sheets for the 6N1P, both Russian with English
>>>translations, which seem to give conflicting values for maximum heater
>>>to cathode voltages.
>>>
>>>One specifies Ukh as +100V and -250V. As the k precedes the h I assume
>>>these are cathode voltages relative to the heater, so this spec says the
>>>cathode can be at most 100V positive with respect to the heater.
>>>
>>>The other describes these parameters in words. It says: Voltage between
>>>cathode and heater:
>>>
>>>- with heater at positive potential 100V
>>>- with heater at negative potential 250V
>>>
>>>I take this to mean the heater can be up to 100V above the cathode or
>>>250V below it, which seems to me to be the exact opposite of what the
>>>other spec says.
>>>
>>>So, which is right?
>>>
>>>Cheers
>>>
>>>Ian

>>
>>Probably all is misleading.
>>
>>I'd never run a cathode at a dc potential of more than +/- 70V with
>>respect to the heater.
>>
>>So if you have a CF where the cathode swings maybe 135Vrms, as might be
>>the case if driving
>>an 845 grid in class AB2, then be prepared to have the filament and itsa
>>voltage supply and transformer winding
>>also swing as well, which may mean you also need a screened tranny
>>winding to prevent stray C coupling to the mains.

>
>
> If you don't have a dedicated winding, you can use a pair of
> resistors across one of the B+ first filter caps to total 1M and adjust
> their values to give you the elevated voltage you need at the centre
> of these two. You then apply this voltage to both sides of the heater
> cap via 100 Ohms resistors. The heater supply must, of course,
> float. It works well. Details are given in Rozenblit's book. a small
> decoupling cap (I use 0.1F) is required at the junction of the two
> resistors, and also on each leg of the heater at the tube socket.
>
>


I think Patricks point was if you have a valve where the cathode moves
+- 190v then no fixed reference will work for that heater, and the only
choice is a supply for that valve that only feeds that valve and is
allowed to swing with the cathode. This of course implies that for two
chan, you need two of the supplies.

And then as mentioned, the cathode will have to drag the supply around
with all its associated capacitances.

--
Nick
  #8  
Old July 29th 08, 02:55 PM posted to rec.audio.tubes
Alex
external usenet poster
 
Posts: 111
Default 6N1P conflicting heater/cathode voltage specs


"Ian Thompson-Bell" > wrote in message
...
> I have two data sheets for the 6N1P, both Russian with English
> translations, which seem to give conflicting values for maximum heater
> to cathode voltages.
>
> One specifies Ukh as +100V and -250V. As the k precedes the h I assume
> these are cathode voltages relative to the heater, so this spec says the
> cathode can be at most 100V positive with respect to the heater.
>
> The other describes these parameters in words. It says: Voltage between
> cathode and heater:
>
> - with heater at positive potential 100V
> - with heater at negative potential 250V
>
> I take this to mean the heater can be up to 100V above the cathode or
> 250V below it, which seems to me to be the exact opposite of what the
> other spec says.
>
> So, which is right?
>
> Cheers
>
> Ian


I doubt it can reliably stand 250V. Quality control was not that good at
Russian factories to guarantee such strong insulation.

Also measuring cathode-heater leakage I found that Russian tubes 6N1P, 6N2P,
6N6P might have up to 10uA leakage even at about 10V between caathode and
the heater, while European, Japanese and American tubes ECC83, ECC85, etc.
leakage well under 1uA.

Excessive leakage in Russian tubes can cause hum, if cathode to ground
impedance is not low.

Regards,
Alex


  #9  
Old July 29th 08, 03:56 PM posted to rec.audio.tubes
Lord Valve
external usenet poster
 
Posts: 289
Default 6N1P conflicting heater/cathode voltage specs

Alex wrote:

> "Ian Thompson-Bell" > wrote in message
> ...
> > I have two data sheets for the 6N1P, both Russian with English
> > translations, which seem to give conflicting values for maximum heater
> > to cathode voltages.
> >
> > One specifies Ukh as +100V and -250V. As the k precedes the h I assume
> > these are cathode voltages relative to the heater, so this spec says the
> > cathode can be at most 100V positive with respect to the heater.
> >
> > The other describes these parameters in words. It says: Voltage between
> > cathode and heater:
> >
> > - with heater at positive potential 100V
> > - with heater at negative potential 250V
> >
> > I take this to mean the heater can be up to 100V above the cathode or
> > 250V below it, which seems to me to be the exact opposite of what the
> > other spec says.
> >
> > So, which is right?
> >
> > Cheers
> >
> > Ian

>
> I doubt it can reliably stand 250V. Quality control was not that good at
> Russian factories to guarantee such strong insulation.
>
> Also measuring cathode-heater leakage I found that Russian tubes 6N1P, 6N2P,
> 6N6P might have up to 10uA leakage even at about 10V between caathode and
> the heater, while European, Japanese and American tubes ECC83, ECC85, etc.
> leakage well under 1uA.
>
> Excessive leakage in Russian tubes can cause hum, if cathode to ground
> impedance is not low.
>
> Regards,
> Alex


The Sovtek (Russian) 7199 was so bad in this respect, they did away with it
entirely.

LV


  #10  
Old July 29th 08, 04:28 PM posted to rec.audio.tubes
Patrick Turner
external usenet poster
 
Posts: 3,915
Default 6N1P conflicting heater/cathode voltage specs



Nick Gorham wrote:
>
> Iain Churches wrote:
> > "Patrick Turner" > wrote in message
> > ...
> >
> >>
> >>Ian Thompson-Bell wrote:
> >>
> >>>I have two data sheets for the 6N1P, both Russian with English
> >>>translations, which seem to give conflicting values for maximum heater
> >>>to cathode voltages.
> >>>
> >>>One specifies Ukh as +100V and -250V. As the k precedes the h I assume
> >>>these are cathode voltages relative to the heater, so this spec says the
> >>>cathode can be at most 100V positive with respect to the heater.
> >>>
> >>>The other describes these parameters in words. It says: Voltage between
> >>>cathode and heater:
> >>>
> >>>- with heater at positive potential 100V
> >>>- with heater at negative potential 250V
> >>>
> >>>I take this to mean the heater can be up to 100V above the cathode or
> >>>250V below it, which seems to me to be the exact opposite of what the
> >>>other spec says.
> >>>
> >>>So, which is right?
> >>>
> >>>Cheers
> >>>
> >>>Ian
> >>
> >>Probably all is misleading.
> >>
> >>I'd never run a cathode at a dc potential of more than +/- 70V with
> >>respect to the heater.
> >>
> >>So if you have a CF where the cathode swings maybe 135Vrms, as might be
> >>the case if driving
> >>an 845 grid in class AB2, then be prepared to have the filament and itsa
> >>voltage supply and transformer winding
> >>also swing as well, which may mean you also need a screened tranny
> >>winding to prevent stray C coupling to the mains.

> >
> >
> > If you don't have a dedicated winding, you can use a pair of
> > resistors across one of the B+ first filter caps to total 1M and adjust
> > their values to give you the elevated voltage you need at the centre
> > of these two. You then apply this voltage to both sides of the heater
> > cap via 100 Ohms resistors. The heater supply must, of course,
> > float. It works well. Details are given in Rozenblit's book. a small
> > decoupling cap (I use 0.1F) is required at the junction of the two
> > resistors, and also on each leg of the heater at the tube socket.
> >
> >

>
> I think Patricks point was if you have a valve where the cathode moves
> +- 190v then no fixed reference will work for that heater, and the only
> choice is a supply for that valve that only feeds that valve and is
> allowed to swing with the cathode. This of course implies that for two
> chan, you need two of the supplies.
>
> And then as mentioned, the cathode will have to drag the supply around
> with all its associated capacitances.


> --
> Nick


Yes, you got my point OK.

In many amps the swing is less than we need to be concerned about,
eg, say a driver tube ahead of a trioded KT88 etc, and where the driver
has Ek at say +10V.

But when the output tube is an 845, or where there is a lot of CFB, say
in a McIntosh,
where the drive voltage to an output grid can be 150Vrms, and there is a
cathode follower,
then you have some concerns about exceeding specs sometimes.

McIntosh were not concerned though. They never empoyed floating heater
windings.
If McI did id, then why not everyone else?

Well, I have to fix a lot of failed and badly designed hi-end brandname
amps
and this all teaches me that McI and others are
eternal optimists, and that **** happens!!!!

Chinese tube making quality control standards leaves much to be desired.

Big Vswing + chinese tube = probable disaster.

In ARC VT100, I have seen 6922 used as direct coupled CF to drive output
tubes.
There is +450V at the CF anodes, but cathodes are at -60V for biasing
the output tubes
and wanted max swing is 65Vrms to the 6550 grids with the mild CFB with
UL.
The heaters are at 0V and the whole set up using 6922 stinks of brown
smoke sooner rather than later.
I replace the whole gain stage with with 12BH7, and **** those 6922 outa
there,
no CF and just have normal C&R coupling to output tubes with individual
biasing,
so the whole **** load of unreliability is jetisoned.

A CF will typically have an Rout = 1/gm = say 400 ohms if gm = 0.0025A/V
..

The capacitance between a 6.3V winding and 0V or some shield in a small
1:1 tranny used between an existing 6.3V winding and the CF is next to
nothing, maybe 200pF,

So the amount of C "dragged around" is SFA depending how much effort you
use to set things up.
But of course at above 100kHz the C does cause an extra phase shift so
with FB the C does no good,
but then with a good knowledge of critcal damping, a wise designer will
get over that little
problem like all the rest. 0.002uF would be a much worse problem!

In a bloomin VAC 7070 amp with 8 x 300B for both channels,
there are 8 heater supplies taken from 4 small transformers, 2 windings
per tranny.
With direct heated tubes, you MUST have floating heater windings.

So having a couple is child's play if you need them.

As I said, to avoid the C between a 6.3V winding and a nearby mains
winding, and the
ingress of switching noise, a second small 1:1 tranny may be used
with a larger gap between P&S to reduce the stray C to mains by 1/10.
Or fit a screen between P&S, which is the best.

One could then even connect the CT of the heater winding directly to a
live
indirectly heated cathode.

I have often thought of doing a 211 amp which
might run in class AB2, so CF drive is a good idea, and a high swing is
needed.
I would probably use a an EL84 in triode as the CF driver, Rout <
200ohms,
so noise from stray C probably won't affect it much.



Patrick Turner.
 




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