X-No-Archive: yes

I have finished my design of a 300B stereo amp. I made it AB1
push-pull ouput. A friend wound the driver and output transformers for
me. The output transformers are toroid. The frequency response of the
amp is 20-20,000 c/s with an output of 35 watts/ch. Since this is my
design for my use, I used valves as the B+ rectifiers, filtered d-c on
the heaters and filaments (a polarity reversal relay circuit was used
for each output filament), NTC resistors in the primaries, fan cooled,
a hard wired power cord, 1 watt flameproof resistors for most of the
resistors unless more power was needed and parts from makers like
Ohmite, Sprague and CDE. I made sure to use four bias pots so Ik can be
measued easily from jacks for balance. I have the d-c voltages highly
filtered so it looks like it is run off storage batteries when the
ripple is viewed on the scope. the only noise is the normal shot noise
when in either 78 or RIAA position and the volume turned way up with no
input signal. This is over designed on purpose to make repair time
minimum. Everything was done to maximize the life of all parts and
valves. The line-up is (2) 12AX7LPS, (2) 6J7G, (2) 6C5GT, (4) EH300B,
(2) 5AR4 and 5V4G wich could be a 5Z4 because this rectifier is for the
signal stages at a maximum of 25 ma when the phono stage is turned on.
That power transformer had a 5 volt winding so that is why a 5 volt
rectifier is used. The higher B+ of 400 volts and bias use reactor
input supplies. The signal level stages is a multiple filter with a
dual reactor and resistor, CLCLCRC filter and then dropping resistors
for the other stages.

I did not use or want any feedback because the very low Rp of the
300Bs. The damping is high. Space will be made for it and a surface
that can easily hold 22 kg. This was the first amp I have designed and
built that nothing had to be redone. Only bias adjustment was needed. A
lot of time and work went into this. The layout of parts before any
drilling was done was the hardest part.

I do not have a scammer or access to any binary group so no schematic
can be posted.

Mark

wrote:

X-No-Archive: yes

I have finished my design of a 300B stereo amp. I made it AB1
push-pull ouput. A friend wound the driver and output transformers for
me. The output transformers are toroid. The frequency response of the
amp is 20-20,000 c/s with an output of 35 watts/ch. Since this is my
design for my use, I used valves as the B+ rectifiers, filtered d-c on
the heaters and filaments (a polarity reversal relay circuit was used
for each output filament), NTC resistors in the primaries, fan cooled,
a hard wired power cord, 1 watt flameproof resistors for most of the
resistors unless more power was needed and parts from makers like
Ohmite, Sprague and CDE. I made sure to use four bias pots so Ik can be
measued easily from jacks for balance. I have the d-c voltages highly
filtered so it looks like it is run off storage batteries when the
ripple is viewed on the scope. the only noise is the normal shot noise
when in either 78 or RIAA position and the volume turned way up with no
input signal. This is over designed on purpose to make repair time
minimum. Everything was done to maximize the life of all parts and
valves. The line-up is (2) 12AX7LPS, (2) 6J7G, (2) 6C5GT, (4) EH300B,
(2) 5AR4 and 5V4G wich could be a 5Z4 because this rectifier is for the
signal stages at a maximum of 25 ma when the phono stage is turned on.
That power transformer had a 5 volt winding so that is why a 5 volt
rectifier is used. The higher B+ of 400 volts and bias use reactor
input supplies. The signal level stages is a multiple filter with a
dual reactor and resistor, CLCLCRC filter and then dropping resistors
for the other stages.

I did not use or want any feedback because the very low Rp of the
300Bs. The damping is high. Space will be made for it and a surface
that can easily hold 22 kg. This was the first amp I have designed and
built that nothing had to be redone. Only bias adjustment was needed. A
lot of time and work went into this. The layout of parts before any
drilling was done was the hardest part.

I do not have a scammer or access to any binary group so no schematic
can be posted.

I don't use a scammer either, but I think you mean a scanner,
but then perhaps you'd like to take a pic with a normal old camera
and have a friend scan the photo and post it at
alt.binaries.schematics.electronic
or alt.binaries.pictues.radio, and have him alert our group
that you have posted the pics.

So what was the recipe for the IST for coupling?

Patrick Turner.





Mark

Hi,
Try using 5 vac on the filaments. It will sound a lot more open;
better!
I have always thought that dc on the filaments makes the amp sound
constipated. Hum shouldn't be too much of a problem with 5 volts on the
filaments.
Just my opinion.
Dan


wrote:
X-No-Archive: yes

I have finished my design of a 300B stereo amp. I made it AB1
push-pull ouput. filtered d-c on
the heaters and filaments (a polarity reversal relay circuit was used
for each output filament),
Mark

X-No-Archive: yes

Patrick Turner wrote:
wrote:

X-No-Archive: yes

I have finished my design of a 300B stereo amp. I made it
AB1
push-pull ouput. A friend wound the driver and output transformers
for
me. The output transformers are toroid. The frequency response of
the
amp is 20-20,000 c/s with an output of 35 watts/ch. Since this is
my
design for my use, I used valves as the B+ rectifiers, filtered d-c
on
the heaters and filaments (a polarity reversal relay circuit was
used
for each output filament), NTC resistors in the primaries, fan
cooled,
a hard wired power cord, 1 watt flameproof resistors for most of
the
resistors unless more power was needed and parts from makers like
Ohmite, Sprague and CDE. I made sure to use four bias pots so Ik
can be
measued easily from jacks for balance. I have the d-c voltages
highly
filtered so it looks like it is run off storage batteries when the
ripple is viewed on the scope. the only noise is the normal shot
noise
when in either 78 or RIAA position and the volume turned way up
with no
input signal. This is over designed on purpose to make repair time
minimum. Everything was done to maximize the life of all parts and
valves. The line-up is (2) 12AX7LPS, (2) 6J7G, (2) 6C5GT, (4)
EH300B,
(2) 5AR4 and 5V4G wich could be a 5Z4 because this rectifier is for
the
signal stages at a maximum of 25 ma when the phono stage is turned
on.
That power transformer had a 5 volt winding so that is why a 5 volt
rectifier is used. The higher B+ of 400 volts and bias use reactor
input supplies. The signal level stages is a multiple filter with a
dual reactor and resistor, CLCLCRC filter and then dropping
resistors
for the other stages.

I did not use or want any feedback because the very low Rp
of the
300Bs. The damping is high. Space will be made for it and a surface
that can easily hold 22 kg. This was the first amp I have designed
and
built that nothing had to be redone. Only bias adjustment was
needed. A
lot of time and work went into this. The layout of parts before any
drilling was done was the hardest part.

I do not have a scammer or access to any binary group so no
schematic
can be posted.

I don't use a scammer either, but I think you mean a scanner,
but then perhaps you'd like to take a pic with a normal old camera
and have a friend scan the photo and post it at
alt.binaries.schematics.electronic
or alt.binaries.pictues.radio, and have him alert our group
that you have posted the pics.

So what was the recipe for the IST for coupling?

Patrick Turner.

Patrick,

You are right about scanner, my mistake in spelling. If I find anyone
who can get on the binaries, I will get a photo posted. I think the ISP
is the one that determines if any binary group can be used.

The driver transformers were wound first and then I bench tested a
driver stage to determine the gain from the input grid to output grid.
The driver transformers I used were about 1:1,5. Mine are a split
winding so there are three individual windings on them. Winding a high
ratio is more difficult. The gain from grid to plate of a driver stage
is high in relation to and RC coupled stage of the same resistance/Z. I
used driver transformers to keep the grid resistance low. Fixed bias
requires a lower resistance in the grid as you know.

To reply to any who suggest a-c on filaments, I prefer d-c. I have
done AB tests and found that d-c is better and so do customers who
listen. Those who want to use a-c, go ahead, I have no problem with
that. We all have different opinions on things and like to share them.
That is how you can get another perspective and may find another way is
better.

wrote:

X-No-Archive: yes

Patrick Turner wrote:
wrote:

X-No-Archive: yes

I have finished my design of a 300B stereo amp. I made it
AB1
push-pull ouput. A friend wound the driver and output transformers
for
me. The output transformers are toroid. The frequency response of
the
amp is 20-20,000 c/s with an output of 35 watts/ch. Since this is
my
design for my use, I used valves as the B+ rectifiers, filtered d-c
on
the heaters and filaments (a polarity reversal relay circuit was
used
for each output filament), NTC resistors in the primaries, fan
cooled,
a hard wired power cord, 1 watt flameproof resistors for most of
the
resistors unless more power was needed and parts from makers like
Ohmite, Sprague and CDE. I made sure to use four bias pots so Ik
can be
measued easily from jacks for balance. I have the d-c voltages
highly
filtered so it looks like it is run off storage batteries when the
ripple is viewed on the scope. the only noise is the normal shot
noise
when in either 78 or RIAA position and the volume turned way up
with no
input signal. This is over designed on purpose to make repair time
minimum. Everything was done to maximize the life of all parts and
valves. The line-up is (2) 12AX7LPS, (2) 6J7G, (2) 6C5GT, (4)
EH300B,
(2) 5AR4 and 5V4G wich could be a 5Z4 because this rectifier is for
the
signal stages at a maximum of 25 ma when the phono stage is turned
on.
That power transformer had a 5 volt winding so that is why a 5 volt
rectifier is used. The higher B+ of 400 volts and bias use reactor
input supplies. The signal level stages is a multiple filter with a
dual reactor and resistor, CLCLCRC filter and then dropping
resistors
for the other stages.

I did not use or want any feedback because the very low Rp
of the
300Bs. The damping is high. Space will be made for it and a surface
that can easily hold 22 kg. This was the first amp I have designed
and
built that nothing had to be redone. Only bias adjustment was
needed. A
lot of time and work went into this. The layout of parts before any
drilling was done was the hardest part.

I do not have a scammer or access to any binary group so no
schematic
can be posted.

I don't use a scammer either, but I think you mean a scanner,
but then perhaps you'd like to take a pic with a normal old camera
and have a friend scan the photo and post it at
alt.binaries.schematics.electronic
or alt.binaries.pictues.radio, and have him alert our group
that you have posted the pics.

So what was the recipe for the IST for coupling?

Patrick Turner.

Patrick,

You are right about scanner, my mistake in spelling. If I find anyone
who can get on the binaries, I will get a photo posted. I think the ISP
is the one that determines if any binary group can be used.

If you cannot talk your ISP into providing you with access to the binary
newgroups
such as a.b.s.e, and a.b.p.r., then you could think of subscribing
to a news supplier who carries all the groups on his server.
That means you go to a website via your ISP net access service,
then to any NG you wish.

ISP will often carry all the girly groups such as
alt.binaries.pictures.erotica.blondes
But they won't carry our obscure binaries groups relating to radio and
electronics.
I got my ISP to give me a link to news.comindico.com.au
which does provide better access to abse and abpr.
They did this free, after I proved that thay were not able to provide me with NG
access
as they had promised when I signed up.
I have been with 4 ISPs in 4 years.
The first one gave excellent service but he sold out to another guy whose NG
access failed, then the next ISP could not and would not fix continual problems,
and after much emailing and visits, my latest ISP is giving me some access.
I pay usd $16.50 for 1.5GB per month.
4 years ago I paid $22.5 for 180MB.
So I have no excess charges now.



The driver transformers were wound first and then I bench tested a
driver stage to determine the gain from the input grid to output grid.
The driver transformers I used were about 1:1,5. Mine are a split
winding so there are three individual windings on them. Winding a high
ratio is more difficult. The gain from grid to plate of a driver stage
is high in relation to and RC coupled stage of the same resistance/Z. I
used driver transformers to keep the grid resistance low. Fixed bias
requires a lower resistance in the grid as you know.

Fixed biasing of an output stage only need be a low resistance if the stage is
being driven
into grid current.
Where A1 or AB1 is used, the recommended 100k or 220k etc is quite ok for fixed
bias.
The benefits of tranny coupling allow slight gain in the tranny, and a
high impedance load on the driver triode, which reduces the driver triode
distortion.

But what sized core and what type of core material was used?
How many turns did you use?
What was the F response at low and high levels?
How much distortion was generated in your transformer?


To reply to any who suggest a-c on filaments, I prefer d-c. I have
done AB tests and found that d-c is better and so do customers who
listen. Those who want to use a-c, go ahead, I have no problem with
that. We all have different opinions on things and like to share them.
That is how you can get another perspective and may find another way is
better.

I can't see how AC cathode heating would make the slightest difference.
Bias is about -75v for 300B, and the cathode voltage has 5v change along its
length,
and the emission variation is negligible.

Maybe its easier to null out the AC cathode hum with a PP circuit
compared to an SE circuit, one reason being that the AC hum
applies itself to the signal path via common mode application.

A customer of mine uses DC on the cathodes and music is fine, and
hum is absent; he uses Altec horns.
But it did take a bit of careful earth pathing to get the amps he'd bought
from ValveMark in a closing down sale to stop humming, as well
as improving the CRC cathode supply filtering.
So the source of hum needs to be carefully analysed.

Before SS rectifiers became available, AC cathode heating was the only
thing that was practical.


Patrick Turner.

To reply to any who suggest a-c on filaments, I prefer d-c. I have
done AB tests and found that d-c is better and so do customers who
listen. Those who want to use a-c, go ahead, I have no problem with
that. We all have different opinions on things and like to share them.
That is how you can get another perspective and may find another way is
better.

I can't see how AC cathode heating would make the slightest difference.
Bias is about -75v for 300B, and the cathode voltage has 5v change along its
length,
and the emission variation is negligible.

Maybe its easier to null out the AC cathode hum with a PP circuit
compared to an SE circuit, one reason being that the AC hum
applies itself to the signal path via common mode application.

Yes, but one still needs to be careful with the AC phasing of the heater connexions.

Otherwise, the hum component becomes additive rather than cancelling. JLS

A customer of mine uses DC on the cathodes and music is fine, and
hum is absent; he uses Altec horns.
But it did take a bit of careful earth pathing to get the amps he'd bought
from ValveMark in a closing down sale to stop humming, as well
as improving the CRC cathode supply filtering.
So the source of hum needs to be carefully analysed.

Before SS rectifiers became available, AC cathode heating was the only
thing that was practical.

Patrick Turner.

John Stewart wrote:



To reply to any who suggest a-c on filaments, I prefer d-c. I have
done AB tests and found that d-c is better and so do customers who
listen. Those who want to use a-c, go ahead, I have no problem with
that. We all have different opinions on things and like to share them.
That is how you can get another perspective and may find another way is
better.

I can't see how AC cathode heating would make the slightest difference.
Bias is about -75v for 300B, and the cathode voltage has 5v change along its
length,
and the emission variation is negligible.

Maybe its easier to null out the AC cathode hum with a PP circuit
compared to an SE circuit, one reason being that the AC hum
applies itself to the signal path via common mode application.

Yes, but one still needs to be careful with the AC phasing of the heater connexions.

Otherwise, the hum component becomes additive rather than cancelling. JLS

With PP amps, if the heater windings have a CT it shouldn't matter which side
the phase is, if the CT is at the true centre.
Where there is just one winding, and hum is present, swapping the connections of one
tube to
see if it helps does no harm.

And perhaps each tube has its own RC cathode bias circuit, so there should have to be
two
separate 5v windings. Some adjustment of the centering or nulling of the hum
from each tube may be needed by using resistors to get the best hum null.

Patrick Turner.




A customer of mine uses DC on the cathodes and music is fine, and
hum is absent; he uses Altec horns.
But it did take a bit of careful earth pathing to get the amps he'd bought
from ValveMark in a closing down sale to stop humming, as well
as improving the CRC cathode supply filtering.
So the source of hum needs to be carefully analysed.

Before SS rectifiers became available, AC cathode heating was the only
thing that was practical.

Patrick Turner.