KT88 SE schematic wanted.

Hojvaelde · 18th May 2005, 10:13 AM

Hello

I just got 2 chokes 10H 300mA 50 Ohm and 2 mail trafoes
330VAC 300mA ( ~ 400 VDC with solid state rectifiers ) + 70VAC 25mA (bias) + 6,3V 5A. ( under 80 USD brand new )

I think this is OK for a SE KT88 mono amplifier, but I need a schematic. Can You help me with that.

Regards

Benny

EC8010 · 18th May 2005, 10:18 AM

I just did a search for KT88 SE (exact phrase) in the "Tubes" forum and came up with 21 results. Please search before starting a new thread...

Mikael Abdellah · 18th May 2005, 08:04 PM

Since I've got new IP for my server a couple of times, the links I've posted to my schematics doesn't work anymore. Here is the new URL: http://81.224.66.34/se_kt88.gif

Should work for you. I think you should be able to use it for starters and modify it for your needs.

Hojvaelde · 19th May 2005, 06:23 AM

Thanks Mikael

That was what I want.

I got 400 VDC from the power trafo.

I can see that the current is under 100 mA.

Do You know the exact current?

How does it sound?

Regards

Benny

Mikael Abdellah · 19th May 2005, 06:35 AM

I think the draw was about 75mA. The sound is really wonderful with very detailed highs and a lots of dynamic and warm bass. The project has been on hold for over a year now, but I hope to finnish it in the next year. No point in rushing things

Sherman · 19th May 2005, 06:30 PM

Quote:

Originally posted by Mikael Abdellah
Since I've got new IP for my server a couple of times, the links I've posted to my schematics doesn't work anymore. Here is the new URL: http://81.224.66.34/se_kt88.gif

Should work for you. I think you should be able to use it for starters and modify it for your needs.

I can vouch for Mikael's design! I built it as a pair of monoblock power amps rather than integrated and it sounds great. It is simple to build and it appears you have the parts. Mine are biased at 75mA with a B+ of ~400V. (I used tube rectification but with your trafos I think you'll have to go SS to get the 400V.)

The only issue I've had was some oscillation on a particular piece of music. I think I've cured that by following the advice of analog_sa and decoupling the PS ahead of the input tube.

JojoD818 · 20th May 2005, 05:23 AM

Mikael,

Just one question sir about the cathode resistor (470R/25W), I can't seem to find a source for such a high wattage resistor locally.

Can I use 3 pcs of 1500R/10W in parallel? Are there any special considerations for this resistor? I mean should it be a certain type such as those non-inductive types?

Please bear with me....

Thanks!
JojoD

Mikael Abdellah · 22nd May 2005, 07:29 AM

There's really no need for 25W. The actual power running through the resistor is closer to 5, but when i tried with 15W it got awfully hot so I put in a 25W instead. It's a regular wirewound kind since low inductive metal film types aren't available at those power ratings. I could send you a pair of 470R/25W if you want. Just let me know. We enthusiasts and diy:ers gotta stick together

JojoD818 · 22nd May 2005, 03:37 PM

Mikael,

Thanks very much for the kind offer! I will first see if the other parts can be sourced here locally. I already have some 6N1P tubes here and will also have access to the KT88 tubes soon.

Thank you and will keep you guys posted.

JojoD

Simpleton · 1st June 2005, 03:49 PM

Hmm... would this be enough for using in the car with Hertz 91dB 2-way speakers? i already have a sand powered sub in there.

18th May 2005, 10:13 AM	#1
Hojvaelde diyAudio Member Join Date: Jan 2005 Location: Denmark	KT88 SE schematic wanted. Hello I just got 2 chokes 10H 300mA 50 Ohm and 2 mail trafoes 330VAC 300mA ( ~ 400 VDC with solid state rectifiers ) + 70VAC 25mA (bias) + 6,3V 5A. ( under 80 USD brand new ) I think this is OK for a SE KT88 mono amplifier, but I need a schematic. Can You help me with that. Regards Benny

18th May 2005, 10:18 AM	#2
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	I just did a search for KT88 SE (exact phrase) in the "Tubes" forum and came up with 21 results. Please search before starting a new thread... __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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18th May 2005, 08:04 PM	#3
Mikael Abdellah diyAudio Member Join Date: Jan 2003 Location: Sweden	Since I've got new IP for my server a couple of times, the links I've posted to my schematics doesn't work anymore. Here is the new URL: http://81.224.66.34/se_kt88.gif Should work for you. I think you should be able to use it for starters and modify it for your needs.

19th May 2005, 06:23 AM	#4
Hojvaelde diyAudio Member Join Date: Jan 2005 Location: Denmark	Thanks Mikael That was what I want. I got 400 VDC from the power trafo. I can see that the current is under 100 mA. Do You know the exact current? How does it sound? Regards Benny

19th May 2005, 06:35 AM	#5
Mikael Abdellah diyAudio Member Join Date: Jan 2003 Location: Sweden	I think the draw was about 75mA. The sound is really wonderful with very detailed highs and a lots of dynamic and warm bass. The project has been on hold for over a year now, but I hope to finnish it in the next year. No point in rushing things

20th May 2005, 05:23 AM	#7
JojoD818 diyAudio Moderator Join Date: Mar 2003 Location: searching...	Mikael, Just one question sir about the cathode resistor (470R/25W), I can't seem to find a source for such a high wattage resistor locally. Can I use 3 pcs of 1500R/10W in parallel? Are there any special considerations for this resistor? I mean should it be a certain type such as those non-inductive types? Please bear with me.... Thanks! JojoD

22nd May 2005, 07:29 AM	#8
Mikael Abdellah diyAudio Member Join Date: Jan 2003 Location: Sweden	There's really no need for 25W. The actual power running through the resistor is closer to 5, but when i tried with 15W it got awfully hot so I put in a 25W instead. It's a regular wirewound kind since low inductive metal film types aren't available at those power ratings. I could send you a pair of 470R/25W if you want. Just let me know. We enthusiasts and diy:ers gotta stick together

22nd May 2005, 03:37 PM	#9
JojoD818 diyAudio Moderator Join Date: Mar 2003 Location: searching...	Mikael, Thanks very much for the kind offer! I will first see if the other parts can be sourced here locally. I already have some 6N1P tubes here and will also have access to the KT88 tubes soon. Thank you and will keep you guys posted. JojoD

1st June 2005, 03:49 PM	#10
Simpleton diyAudio Member Join Date: Jan 2005 Location: Lisboa	Hmm... would this be enough for using in the car with Hertz 91dB 2-way speakers? i already have a sand powered sub in there.