PP Triode 6AQ5. What is the Load Resistance @ 250V?

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 14, 2015 at 14:27:15
Tre' Industry Professional Posts: 17306 Location: So. Cal. Joined: February 9, 2002	Those will all work and they will each have their own max power and harmonic distortion levels. Idle current also needs to be part of the considerations. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 15, 2015 at 04:28:32

Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005

Bobby
A 6AQ5 is basically a 6V6 in a 7 pin bottle. At 250vdc,the ideal impedance is 10k in push pull.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

http://www.r-type.org/pdfs/6aq5-2.pdf

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 15, 2015 at 06:13:25
bcguitar Audiophile Posts: 1328 Location: Maryland Joined: March 2, 2005	So PP triode 6AQ5 is the same impedance as PP 6AQ5?

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 15, 2015 at 08:43:54

Tre'
Industry Professional

Posts: 17306
Location: So. Cal.
Joined: February 9, 2002

I didn't say that.

Load impedance is not a fix or "cast in stone" thing.

The higher the load impedance the less power your will get but the distortion will be lower.

The lower the load impedance the more power you will get but the distortion will be higher.

It's kind of a "pick your poison" thing.

If you want to calculate a "proper" load impedance for your PP triode connected tubes you need to know the plate resistance of the triode connected tubes and you need to take into consideration the idle current you plan to run and if the amp is intended to be Class A or Class A/B.

Assuming you will be running the amp only in Class A, I would use Paul Joppa's rule of thumb for signal ended circuits and double that number.

Load impedance = (plate to cathode voltage / idle current) - (2.38 * plate resistance)

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 15, 2015 at 09:26:08
sony6060 Audiophile Posts: 1465 Location: USA Joined: August 8, 2014	At 250 volts in PP to cathode, 8K will keep the load high enough that distortion products will be low. Operating a 6V6 at 300-325 volts PP should use a 10K PP audio transformer. The Music Machine designer found this out and the spec for the audio transformer was increased from 8K to 10K.

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 22, 2015 at 09:25:53

mqracing
Manufacturer

Posts: 4323
Joined: June 29, 2000

Hello Tre:

you wrote;

"The higher the load impedance the less power your will get but the distortion will be lower."

"The lower the load impedance the more power you will get but the distortion will be higher."

with tetrodes\pentodes the above is not true... in that case the generalization is that the lower the impedance the lower the third with a rising second harmonic.... but since it is push pull the second harmonic is largely cancelled by the output transformers primary.

There is a thread currently running about the 47 tube and there was a link to the data sheet... which clearly shows the relationship stated above.

MSL

Builder of MagneQuest & Peerless transformers since 1989

RE: PP Triode 6AQ5. What is the Load Resistance @ 250V?, posted on March 23, 2015 at 04:56:19
sony6060 Audiophile Posts: 1465 Location: USA Joined: August 8, 2014	The original post is referring to triode connected 6AQ5. Do not use less than a 8K PP primary impedance transformer for best sound with triode connected PP 6AQ5s.

Tube DIY Asylum

PP Triode 6AQ5. What is the Load Resistance @ 250V?

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