stereo SE kt88 build ... abdellah diyaudioprojects design

[clowkoy]

Let me rephrase my question.
What is the minumum B+ voltage required for this kt88 amp?

 

[costis_n]

To post somethings which is not related is not good at all< sorry. But my first priority is the music that i wanna to hear, which is the orchestra music. So i am not sure KT88 is the best , but i think EL34 is better in Jazz music,cause i have change several tubes of EL34. The environment of the Jazz can be review mostly but i think the base of the Jazz is still a little bit missing.

So i am not sure EL34 can handle so must instruments of an orchestra. The result might be so many unclear things mixed together.... Just my thing< I hope people who have experience would prove ideas. If i have any things goes wrong, corrections are glad to hear.

Ιf the orchestra music reason you want to use a KT88, then I can guess safely that with the same schematic, just having a bigger power supply and replacing the el34 with a KT88 the result will not be a different amplifier that can play orchestra music better. It will be more or less the same amplifier, with more power. I recommend you look for a different schematic. People here that know more than me can help you.

 

[costis_n]

Let me rephrase my question.
What is the minumum B+ voltage required for this kt88 amp?

SE circuits can work with different B+ voltages, you just have to use a lower cathode resistor to bias it properly. The problem here is the current rating of your transformer is marginal. It will get hot in use. Also, does it have enough current rating on the 6.3 volt winding to supply the heaters too? KT88's need 1,6 Amperes apiece for that.

So you can try to get a separate 6.3 volts transformer for the heaters, to offload your main power transformer, or you may order a new transformer.

 

[clowkoy]

SE circuits can work with different B+ voltages, you just have to use a lower cathode resistor to bias it properly. The problem here is the current rating of your transformer is marginal. It will get hot in use. Also, does it have enough current rating on the 6.3 volt winding to supply the heaters too? KT88's need 1,6 Amperes apiece for that.

So you can try to get a separate 6.3 volts transformer for the heaters, to offload your main power transformer, or you may order a new transformer.

Thanks Costis!
The 6.3-volt tap is rated at 4A and the 5-volt at 3A so I think it can handle the filaments but also marginal.
I'll probably set this project aside and just start the Bottlehead Stereomour (2A3) when it arrives.

 

[albertob]

Hi
In this circuit can be replaced the 6n1p by the ECC85?

thanks

 

[Fjd]

Hi
In this circuit can be replaced the 6n1p by the ECC85?

thanks

I believe that the 6BQ7, 6BK7 or 6BZ7 are the closest replacements to the 6n1p. The ECC85 would replace a 6AQ8 tube.

 

[bigaudioscotto]

I am using a pair of RCA 12au7 cleartops
driving a pair of SED EL34
using Alex Gendrano updated schematic of SE KT88
and it sounds amazing I did add more capacitance in
the power supply running 100uf + 100uf JJ and 39uf Solen poly cap
the Solen really added a lot of punch and warmth & tighter bottom end
I highly suggest adding a big poly cap in the power supply
it makes a tremendous difference.

 

[bigaudioscotto]

Mine runs at 474v with no tubes installed,I am a little on the high side.
I would think minimum should be no less than
430v or 440v before putting a load on it.
for instance I am using EL34 and I go from 474v no load to 426v
with tubes installed.

Let me rephrase my question.
What is the minumum B+ voltage required for this kt88 amp?

 

[albertob]

I am using a pair of RCA 12au7 cleartops

Are you using 1K 1/2 w with 100uf 25V in parallel, at the cathode?

I did add more capacitance in
the power supply running 100uf + 100uf JJ and 39uf Solen poly cap
the Solen really added a lot of punch and warmth & tighter bottom end
I highly suggest adding a big poly cap in the power supply
it makes a tremendous difference.

I have a 630V 47UF Mundorf Mkp unused. Would you improve on something if I add it to the existence 100 uF (50uf+50uf)?

regards

 

[bigaudioscotto]

Yes 1k with 100uf bypass cap parallel at cathode that cap give you a little
a few more db gain from the driver tube.


I would strap that cap in there for sure should be an improvement
just tie one end to B+ and other to -

Are you using 1K 1/2 w with 100uf 25V in parallel, at the cathode?


I have a 630V 47UF Mundorf Mkp unused. Would you improve on something if I add it to the existence 100 uF (50uf+50uf)?

regards

 

[briansune]

I am using a pair of RCA 12au7 cleartops
driving a pair of SED EL34
using Alex Gendrano updated schematic of SE KT88
and it sounds amazing I did add more capacitance in
the power supply running 100uf + 100uf JJ and 39uf Solen poly cap
the Solen really added a lot of punch and warmth & tighter bottom end
I highly suggest adding a big poly cap in the power supply
it makes a tremendous difference.

seems great, And i also brought the JJ capacitor 400V 100uFx2, could u give me the details of the power supply. I think the case of you is same as mine, i am also updating the EL34B amp into KT88. How is the base of the amp, i mean the sound base.

 

[bigaudioscotto]

Just add 39uf poly across the + & - of the JJ cap
+ on the right side of the JJ.
as far as Bass they are fantastic,I tried the kt88 but
the EL34 sounded much better to me no comparison.
it seems that this design is more optimal for EL34 than KT88
maybe should have been called SE EL34 instead.

Scott

seems great, And i also brought the JJ capacitor 400V 100uFx2, could u give me the details of the power supply. I think the case of you is same as mine, i am also updating the EL34B amp into KT88. How is the base of the amp, i mean the sound base.

 

[briansune]

Just add 39uf poly across the + & - of the JJ cap
+ on the right side of the JJ.
as far as Bass they are fantastic,I tried the kt88 but
the EL34 sounded much better to me no comparison.
it seems that this design is more optimal for EL34 than KT88
maybe should have been called SE EL34 instead.

Scott

i wonder do you still using the pi circuit, and what is the first capacitor value. I noticed that the capacitor of the 39uF is // with the capacitor of the JJ ones.

C1 = 39uF or ...
C2 = 100uFx2 or.....
H1 = 10H 200mA or.....

 

[briansune]

bigaudioscotto: I think i missing understanding your pi circuit, do you mean you use a 39uF poly cap. on the left side of the coke and 200uF in the right hand side of the coke?

 

[bigaudioscotto]

The first choke goes across the 2 positive terimals of the JJ and the
39uf just attaches on the right side positive of JJ and other end of 39uf attaches to the negative of JJ then I used 300 ohm resistor after that feeding the 2x 10uf caps.
you can use 270 ohm choke in place of that 300 ohm resistor personal preference.

Scott

bigaudioscotto: I think i missing understanding your pi circuit, do you mean you use a 39uF poly cap. on the left side of the coke and 200uF in the right hand side of the coke?

 

[bigaudioscotto]

Sub out ?

Do any of you guys know how I could add a Sub output to this design.

 

[scott17]

No need to. Just split the audio and run one set to the tube amp and one set to the subwoofer amp. As long as the cables aren't excessively long.

 

[jmillerdoc]

Sub

Do any of you guys know how I could add a Sub output to this design.

I agree there is really no need for a sub output but.....there are a couple of ways you could do it....a simple pass through from the inputs wired directly to the sub output, either before or after you pot depending on if you want the volume control to effect the output....or, I could conceive you could use the output from the 6N1P as a sort of line driver for the sub output....you could even put a low pass filter on the output of needed.

I guess what is needed is some details about the sub you are planning to use.

 

[scott17]

I agree there is really no need for a sub output but.....there are a couple of ways you could do it....a simple pass through from the inputs wired directly to the sub output, either before or after you pot depending on if you want the volume control to effect the output....or, I could conceive you could use the output from the 6N1P as a sort of line driver for the sub output....you could even put a low pass filter on the output of needed.

I guess what is needed is some details about the sub you are planning to use.

I agree, if the sub you are using has a signal pass-through, do it that way.

 

[albertob]

Hi all,
And I have mine running!.
Absolutely quiet, great sound. It is best to ring, very natural.
I placed a switch to change the bias and another to remove the pot.

I want to apply ccs in the anode 6n1p and eliminate the resistance of 47k. Okay ixscp10m45s with a resistance to regulate the flow?, How many watts must be the resistance?
regards