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6n9p+6p3p Tube Amplifier Kit SRK-10 help needed

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Alfi1966

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Joined 2013
#1
Hello friends

I have alias wanted to try to learn about tube amps, but dont want to build something cheap, i need more power than they usually have.
Later i will build a set of monoblocks with quad kt88 or kt120.
So i have lokkende for something cheap nearby, and yesterday i found a 6n9p+6p3p Tube Amplifier Kit SRK-10 just down the road from me, very little used. So i drive over and got it, and payed what in norway is near to free.
But i dont have any info on it, i need diagrams, values on the parts, etc.
Could anyone help me with this? I would appreciate any upgrade tips also, and a explenation on how to solder in bleeder resistors, so it will be more safe to work on.

Alf david
 
#3
thank you very much for that

do you have any recommandations for where to put, and value of, bleed resistors for this amp?
and any upgrade recommandations?
i want to use this as a learning experience, and to upgrade it as much as i can, within reason when it comes to money.
i have ordered some new tubes for it already, so i hope they will work well. i ordered a set of sylvania 5y3gt, rca nos/nib 6sl7gt black plate, and a platinum matched pair of sovtek 5881wxt/6l6wgc.
from what i could find out on the amp, they should work, or am i wrong on that?
if i am wrong, can i make any changes on the amp to make them work?
also, any suggestions for better caps that sound good, what should i look for there?

alf david
 
#6
Hi again
I have been looking for info on the bennic 0,33uf capacitors you mentioned, but i do not find anything on bennics pages about it.
I understand it is a metalliced polypropylene axial tubular non-polar cap?
Would that be correct?
I would like the amp to be as linear as possible, and to have as good top and bottom response, and detail as possible, since i play a lot of sacd, DVD-audio, and other hi-rez materiale.
So anyone please chime in with tips on best caps for this, and a possible better OPT

Alf david
 
#7
Alfi1966 said:
thank you for the recommandations
do you have the values i need for a better OPT?
im a complete novice on tubeamplifiers, so i need a little more guidance than the incredibly vise members on this forum ;-)

alf david
Click to expand...

Take a look at these OPTs:

EDCOR - GXSE15-8-3.5K
or
EDCOR - GXSE10-8-5K

Check the size compared to what you have they should be pretty close.

I like a 3.5 to 5K load for 6L6 so there's one of each. Although if you want the best for YOU we would need to know what speakers you will be using with this amp.

As Ray mentioned that .33uF coupling capacitor can be upgraded to a better quality cap, all the signal goes directly thru that cap so the best you can afford will work. There are several, and you could spend a lifetime trying to figure out which is best there.

Russian k40y-9 should be good there and easy to get where you are.
They have a significant break in period tho and will sound a little harsh at first.
Another good capacitor is a Sprague Orange Drop 716P (has to be the 716 NOT the 715). These are cheap and good for this amp will go along with the rest of the parts here.

The .33uF cap will need to have a voltage rating no lower than 400vdc.

For a bleeder resistor ~40k Ohm 5 watt resistor across the + and - pins on cap2 (c2) 330Ohm 450V cap the largest capacitor in the amp. If you want to get clever you can add a LED diode long with the resistor, the LED will stay lit as long as there's voltage indicating no touchy. Even then you should ALWAYS use a DMM and meter the caps to be sure there's no voltage. Safety first it's the only way. 450v is going to hurt if your hand discharges it.

Cheers,
Bob
 
#13
bobrown14 said:
Take a look at these OPTs:

EDCOR - GXSE15-8-3.5K
or
EDCOR - GXSE10-8-5K

Check the size compared to what you have they should be pretty close.

I like a 3.5 to 5K load for 6L6 so there's one of each. Although if you want the best for YOU we would need to know what speakers you will be using with this amp.

As Ray mentioned that .33uF coupling capacitor can be upgraded to a better quality cap, all the signal goes directly thru that cap so the best you can afford will work. There are several, and you could spend a lifetime trying to figure out which is best there.

Russian k40y-9 should be good there and easy to get where you are.
They have a significant break in period tho and will sound a little harsh at first.
Another good capacitor is a Sprague Orange Drop 716P (has to be the 716 NOT the 715). These are cheap and good for this amp will go along with the rest of the parts here.

The .33uF cap will need to have a voltage rating no lower than 400vdc.

For a bleeder resistor ~40k Ohm 5 watt resistor across the + and - pins on cap2 (c2) 330Ohm 450V cap the largest capacitor in the amp. If you want to get clever you can add a LED diode long with the resistor, the LED will stay lit as long as there's voltage indicating no touchy. Even then you should ALWAYS use a DMM and meter the caps to be sure there's no voltage. Safety first it's the only way. 450v is going to hurt if your hand discharges it.

Cheers,
Bob
Click to expand...

hi, im slow with my answer on this.
i use a set of system audio mantra 50, rated at 4ohm for the fronts.

alf david
 
#14
Hello again
I have changed the sockets in the amp now, and put in the new tubes.
Im going to change the two condensators next.
What im wondering is how do i bias the amp with the new tubes?
Is it selfbiasing? Or are there a fixed bias?

Alf david
 
#15
Alfi1966 said:
Hello again
I have changed the sockets in the amp now, and put in the new tubes.
Im going to change the two condensators next.
What im wondering is how do i bias the amp with the new tubes?
Is it selfbiasing? Or are there a fixed bias?

Alf david
Click to expand...

This amp is CATHODE BIASED or self biasing. If say you wanted to up the current thru an output tube you would typically change the cathode resistor to a different (lower) value. That's assuming your power transformer has enough current available (it should). If you are just changing to another 6L6 family tube you will not need to change anything, just the tubes and enjoy.

So Cathode bias = self bias (no adjustment)

fixed bias = adjustable with usually a trim pot and needs adjusted from time to time and when changing tubes. Not the case here.

Cheers,
Bob
 
#16
hi
thank you for the answer. i have changed the tubes to sylvania 5y3gt, rca nos/nib 6sl7gt black plate, and a platinum matched pair of sovtek 5881wxt/6l6wgc, and would like to get them performing as good as possible, so im wondering if i can change the bias resistor to get a little more power from them. what bias voltage do they need, and what is the safe range of resistors i have to play with?

alf david
 
#17
Alfi1966 said:
hi
thank you for the answer. i have changed the tubes to sylvania 5y3gt, rca nos/nib 6sl7gt black plate, and a platinum matched pair of sovtek 5881wxt/6l6wgc, and would like to get them performing as good as possible, so im wondering if i can change the bias resistor to get a little more power from them. what bias voltage do they need, and what is the safe range of resistors i have to play with?

alf david
Click to expand...

Why 6SL7? 6N1 I think is closer to the 6SN7/6N8S tube. The 6SL7 is closer to the 6N2 not the 6N1. You will have to recalculate your tube curves for that swap to be sure you're driver tube is where it should be. That and of course the pins are different but you should know that already??

6SL7 - gain (Mu) = 70
6SN7 - gain (Mu) = 20

6N1 - gain (Mu) = 35

There are other differences but this is a starting point and looking at the gain on the 6SL7 you will need to re-design the driver stage, you'll be over driving the output tubes causing distortion. The 6N1 tube is a VERY good driver tube. You are not gaining anything IMHO going to a 6SL7, I'd probably opt for the 6SN7 if you want an octal triode (since I've got a bunch of good old stock ones) but that's me.
Going old school triodes in place of the newer 9 pin 6N1, I'm not real clear on any advantages there?

Cheers,
Bob
 
#18
Hi

I think you have looked at the wrong pre tube, it is a 9n6p, and that has the same mu as a 6sl7gt.
Im looking at optimising the voltages and bias for the new tubes, and there are a 40v difference between the two output tubes, so i would like to get that as similar as possible.
When im looking at the pre-tube, on the cathode resistors, do i add the 1k resistor to the 100 resistor, or calculate only the first one from the pin?

Alfi
 
#19
Alfi1966 said:
Hi

I think you have looked at the wrong pre tube, it is a 9n6p, and that has the same mu as a 6sl7gt.
Im looking at optimising the voltages and bias for the new tubes, and there are a 40v difference between the two output tubes, so i would like to get that as similar as possible.
When im looking at the pre-tube, on the cathode resistors, do i add the 1k resistor to the 100 resistor, or calculate only the first one from the pin?

Alfi
Click to expand...

40V difference at the output tube? Which pin are you measuring?
 
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