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Old 4th November 2002, 07:51 AM   #11
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Default HENRY VIII

Hi Richt,

What Counterpoint pre do you have?

Putting 375 VDC on the plate of a 6922 is way too high BTW.
You could introduce a good tube regulator on a pro stage basis while you're at it.

That will leave you with your head blown off for sure.

Cheers,
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Old 4th November 2002, 12:15 PM   #12
richt is offline richt  Puerto Rico
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salute to everyone !

an original counterpoint sa3.1 sounds awfully bad & harshy !

first i removed all the the trasistor regulation & all mr.
elliot design ! (i like this pre because it is easy to upgrade &
performs really well).

i installed a mosfet regulating from 375 to 250 volts.
the sound became less harshy & more musical.
still i notice a small saturation on the top end & i found thaT
the 6922 were driven too high on ma. ( plate with 22k resistor
and the pcb completly dark on that area)
i raised the resistors to 100k and the sweetnes of the tube came alive ! (3ma per plate)

now i have a tube preamp!

on another site i heard people glorifying the hexfreds, i tried,
but money was wasted ! abrassive sound overall.

one day i came with the idea of replacing the transformer with
that o ne from mike elliot website (plitron toroidal)
costed me a lot of money and the preamp was running a lot hotter (filament reg) & the sound was awfully bad.
i was so angry that i sold on ebay for 50 bucks and i called
mike elliot to told him where are his ears located?

now i bought a hammond 10vac 4 amp for filament & another
hammond for a 5u4 (filament winding was center tapped so b+
was a lot cleaner that taking out the b+ brom one of the filaments pin.

now that was another preamp !!!!!!!!!!!!!!!1
really creamy & smooth !, very extensive on both ends,
natural floating sound,no coloration at all !

i consider that these preamps are a little gem for the price &
simple designs.

now the choke is on its way.

thanks you people
richt
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Old 4th November 2002, 12:28 PM   #13
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Default CONTRAPUNKT

Hi Richt,

My second tube pre was an SA3.
Didn't sound that bad at all,a bit too noisy and microphonic as hell.
Naturally you heard them flaming Wondercaps' colouration as well.Chocolate/caramel flavour.

I think the main difference with the bigger brother the SA5 was that Mike put in some sort of valve regulation (5661 I think it was).

What you can do too is replace the 100K resistor whith a 3mA constant current diode.
That really tightens the bass.

Give it a shot,
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Old 4th November 2002, 12:49 PM   #14
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Default Re: CONTRAPUNKT

Quote:
Originally posted by fdegrove
What you can do too is replace the 100K resistor whith a 3mA constant current diode.
That really tightens the bass.

Give it a shot,
Hi Richt,

Glad you're having fun with your revamped CP.
I agree with Frank about the CCS. Try it, and I would suggest you leave it in circuit for a few days, because they can have a large affect on the perceived distortion. When the distortion is gone, and you're used to it being there, it sounds strange until you get used to it. When I first got my bass horns they sounded weird and a little weak, even though they measured well and went deeper, because there was so little distortion.

I'd also try running the tubes at much higher currents, like 6-12mA, depending on the stage and the amount of swing required. 6DJ8/6922's sound <i>much, much</i> better when run hot. All the one's I'm currently using/playing with are 9mA per section or more.

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Old 4th November 2002, 01:24 PM   #15
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Default HOT 69XXX

Hi Richt,

Quote:
I'd also try running the tubes at much higher currents, like 6-12mA, depending on the stage and the amount of swing required. 6DJ8/6922's sound much, much better when run hot.
3mA for a phono stage would do.
If you're only using this as a line preamp then I agree with what Brett says.

Brett,

Quote:
When I first got my bass horns they sounded weird and a little weak, even though they measured well and went deeper, because there was so little distortion
Funny how we get used to colourations.

Cheers,
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Old 4th November 2002, 10:31 PM   #16
richt is offline richt  Puerto Rico
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salute guys !


i notice that applying excessive current to a tube, tends to
sound harshy (on a extreme case as m. elliot did).

a ccs is a circuit or a component (diode) ??

i will try the choke this week and i let you know folks.


the cathode is tied to ground directly in this case.
(usually a 1 to 4 k omh resistor is used)

i am glad to answer any questions.

thanks
richt

p.s. some new pre are using the 6c33.
if anyone have a feedback from this tube?
it is pin by pin with the 6922
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Old 4th November 2002, 10:48 PM   #17
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Quote:
Originally posted by richt
p.s. some new pre are using the 6c33.
if anyone have a feedback from this tube?
it is pin by pin with the 6922
Richt,

The 6C33 is a power tube used in the BAT power amps and some OTLs etc.

Could you be meaning the 6N1P? That is compatible with the 6922 series in many but not all instances. The filament current is higher and the u is lower. Many people like this tube. I have some but have only played with them breifly, so no firm comment on the sonics.
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Old 4th November 2002, 11:21 PM   #18
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Default KONTRAPUNKT II

Hi Richt,

Quote:
a ccs is a circuit or a component (diode) ??
CCS:

Constant Current Source,this can be a single component such as a Constant Current Diode,a fet made to behave like that or in some more complex situations a circuit made for that particular application such as Mr.Pimms as described on his website and discussed in this tube section.

Quote:
the cathode is tied to ground directly in this case.
In which case your tube has no negative gridvoltage and will go into positive gridbias when presented with voltages of over 0 VAC.
This 6922 can take a lot but 2 VRMS from a CD player is way too much.

A cathode resistor in the 500R range would be a good start to try out.
Unless this negative voltage is derived from the PSU which could be the case.
I remember Mike Elliot did that quit often in his designs so if you have a VOM you can check this.
In the SA 3 I think he used high value grid resistors (~10M) but check it anyway.

Quote:
p.s. some new pre are using the 6c33.
This is a big voltage regulator tube.You can build an amp with just one of them.

People building preamps with that are $$#@*^ ,you know what I mean.

And no it is not pin to pin compatible with a 6922.It is about 20 times as big.

Are you still running your circuit from the original Counterpoint board??

What section are we discussing here?Line ? Phono ?

Sorry if I spoil the fun but if you want to build a decent circuit we're going to need a lot more information.

Don't loose any sleep over it we'll work it out,

Brett,

Sorry,I didn't notice you replied to this already.

BTW,I've seen linestages whith 6C33C,so this could be what Richt means.
What's going to be next I hear you mutter??

Cheers folk,
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Old 4th November 2002, 11:44 PM   #19
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Default Re: KONTRAPUNKT II

Quote:
Originally posted by fdegrove
BTW,I've seen linestages whith 6C33C,so this could be what Richt means.
What's going to be next I hear you mutter??
Frank,

I was looking at using the 6C19 as a linestage recently. Run it at lowish voltage, say Va=90V B+= 130V, 40mA/tube differential with a CCS as each tube's load. Output Z would only be a few hundred ohms and it should have no trouble driving just about anything with no headroom issues. With a near horizontal loadline it would be very linear, and the low u would make it ideal for CD based linestages. Tubes are only a couple of dollars each and 6.3W of heater should help it sound powerful.

Whaddya reckon?

Cheers
Brett
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Old 5th November 2002, 12:01 AM   #20
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Default Whaddya reckon?

Hey Brett,

Have been thinking along the same lines,that valve is the perfect candidate for the job.
Have you ever seen the TFK ED8000?

Make a very good well regulated shunt reg (you know how I would do that) PSU for it and you can drive even the silliest length of interconnect with it.
Hmmm,you can even use an 6C19P as a series pass in that reg there...

I'm all for it and it makes perfect sense to me.

Cheers,

P.S. Fred has written up a very good article on PSU regulators in the Digital section.
Some people there are still struggling,I may drop a bomb or two there.
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