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How many KT170

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Posted on July 19, 2024 at 10:09:39
SuperB
Audiophile

Posts: 337
Joined: March 21, 2002
 Hi!
I have a high power opt in hand with 600R primary impedance, probably capable of 500w or more.

As I want to build a high power amp with KT170, how many KT170 should be used in push pull?

Thanks!

 

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RE: How many KT170, posted on July 19, 2024 at 13:22:40
walge
Audiophile

Posts: 140
Location: roma
Joined: September 25, 2008
 In triodo mode the tube has around 700 of Rp so this configuration is suggested
If you think that the amp will work in AB probably you need 4 pairs / channel
Lot of job


Walter

 

RE: How many KT170, posted on July 19, 2024 at 13:31:15
SuperB
Audiophile

Posts: 337
Joined: March 21, 2002
 Between triode and pentode, which one KT170 work best in pp?

Assume operating in class A and loaded to 600R, how many KT170 in triode and how many in pentode?

Thanks!

 

RE: How many KT170, posted on July 19, 2024 at 20:56:29
hahax@verizon.net
Audiophile

Posts: 4435
Location: New Jersey
Joined: March 22, 2006
 It depends on how many watts you want and what class you run in and triode/pentode since class A reduces power as does triode. But based on friends who designed tube amps and discussions I'd pick triode since it is the most linear format and perhaps a rich class A AB amp since you will still be in class A most of the time except on flash peaks.

Then again I'm told that while the KT170 is great for power it isn't the most linear tube. I was told by a very high end tube amp manufacturer that the KT88 is significantly more linear.

And, of course, your speakers enter into it. Their efficiency is a significant factor in how much power you need for your listening preferences.

There isn't a straight forward answer to how many output tubes are needed.

Just to throw another monkey in the discussion, years ago a company, Melos made amps with triode tube outputs over 200 watts per channel using a single pair of EL519 tubes. But I understand this is now a difficult tube to find.

 

RE: How many KT170, posted on July 20, 2024 at 03:32:39
walge
Audiophile

Posts: 140
Location: roma
Joined: September 25, 2008
 Ho
These tubes in triode have a reasonable linearity an a low Rp that help a lot in your case
The splitter must be strong with a low Zout so a 5687 or 7044 or 6BX7 or. 6H30 Soviet are suggested
Maybe the use of fixed bias help the setting of power tube with trimmer for each one

 

RE: How many KT170, posted on July 24, 2024 at 07:51:31
Palustris
Audiophile

Posts: 2436
Location: Cape Cod
Joined: September 12, 2008
 You need to find the triode plate curves and draw the load lines to determine the best operating point.

 

RE: How many KT170, posted on August 2, 2024 at 05:44:13
PakProtector
Audiophile

Posts: 12393
Joined: May 14, 2002
 Wow..double the plate rating and nearly no increase in cathode heating power?

Suggest 4 pairs in pentode. B+ around 350 and idle per tube at 160 mA.

That is not going to be a light amp... :) and mind grid circuit resistance. I suspect the .5M rating is cathode bias. I doubt they'll be happy/stable at anything over 100k each. Which gives you a 25kOhm load to drive. and 8 bias measurements/adjustments...

Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

How many? Just do the simple math, posted on August 3, 2024 at 04:12:10
PakProtector
Audiophile

Posts: 12393
Joined: May 14, 2002
 So, 600 Ohm a-a output will deliver 300 Ohms to each phase in Class A. If we take four pairs, and idle them a bit higher at 175 mA, the quad will carry 700 mA. Break out Ohm's Law. You are looking for how much voltage 700 mA can develop across 300 Ohms. 210 Volts. For how many, figure each can swing 52 volts. That load may take 6 pairs to get up around 300V. B+ can be higher since we'll not be able to swing the plate to zero volts.

Now for the fun part, how much power. You'll be able to put 600V across that 600 Ohms( one side 300V up, the other 300 down ). So a 600W( peak ), Class A amp for your trouble.

Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

Don't forget pics, posted on August 10, 2024 at 14:00:50
PakProtector
Audiophile

Posts: 12393
Joined: May 14, 2002
 Once you get rolling, don't forget pics and a schematic.

Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

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