Ad Widget

Collapse

Announcement

Collapse
No announcement yet.

THD Univalve questions

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
  • #1

    THD Univalve questions

    Hi All,
    Ran across a description by THD of its Univalve

    http://www.thdelectronics.com/produc..._UniValve.html

    Its a single ended cathode biased amp. The odd thing, I don't understand, would like to better, is that they claim the user can swap all these tubes:

    6L6, EL34, 6550, KT90, KT88, KT77 and KT66,

    without modification to the amp. I expected a very complex circuit that would help impedance match the output side of the tube to the output transformer, and also, adjust the incoming signal to the output tube, but its even more simple looking than most old fixed biased amps.

    How can this work? If you swap a 6L6 with a KtT88, or KT66, the output transformer can't be the same for all three, no matter how they do the biasing, right?

    Would this amp 'eat' some tubes, over others?
    The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.
    Tags: None
  • #2
    Schematic is here:

    https://el34world.com/charts/Schemat..._41_062104.pdf

    Nothing that special about it. I suspect some mid range OT impedance to work with a variety of tubes. As Enzo always says, it's just a guitar amp not lab equipment.
    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

    Comment

    • #3
      Say it to yourself over and over until you believe it: It is just a guitar amp. There is nothing precise here, there is no super critical impedance.

      SO what if one tube is less efficient than another? So what if the impedance is "wrong"? it still works.
      Education is what you're left with after you have forgotten what you have learned.

      Comment

      • #4
        I doubt it would particularly 'eat' tubes, but agree it may give different lifespans for the various types (due to extent of mismatch).
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


        ​

        Comment

        • #5
          Originally posted by Enzo View Post
          Say it to yourself over and over until you believe it: It is just a guitar amp. There is nothing precise here, there is no super critical impedance.

          SO what if one tube is less efficient than another? So what if the impedance is "wrong"? it still works.
          I guess I take these things a bit too seriously sometimes. Thanks. And, these amps used are going for like 450 bucks even on overpriced Reverb. Couldn't build an amp for that price.
          The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

          Comment

          • #6
            Not to hijack this thread but this is a great time to throw in a question I have but haven't found much info on. If an output transformer is used in a circuit that can support a few types of few power tubes, what tonal differences are there in the mismatch? For example if an EL34 likes to work with say a 5k output transformer primary... how does it respond at say a 4k or 6K OT?

            Dale
            Last edited by tubedood; 09-20-2018, 01:05 PM. Reason: had wrong values sorry

            Comment

            • #7
              Originally posted by mikepukmel View Post
              I guess I take these things a bit too seriously sometimes. Thanks. And, these amps used are going for like 450 bucks even on overpriced Reverb. Couldn't build an amp for that price.
              Right on! Git yourself one before they're "discovered." Along with THD's BiValve and Flexi 50, all in the same old "toaster" chassis format. Well built and very tough.

              At one time THD made their version of the Fender 5F6A 4x10 Bassman, built solider than a brick outhouse, that would make the crown jewel in anyone's amp collection. Why they don't make these terrific items anymore is beyond my comprehension. Maybe the company owner got tired of dealing with this "pearls before swine" world.
              This isn't the future I signed up for.

              Comment

              • #8
                Originally posted by tubedood View Post
                Not to hijack this thread but this is a great time to throw in a question I have but haven't found much info on. If an output transformer is used in a circuit that can support a few types of few power tubes, what tonal differences are there in the mismatch? For example if an EL34 likes to work with say a 5k output transformer primary... how does it respond at say a 4k or 6K OT?

                Dale
                its way more complex than this,first there is no such thing as a 5k primary impedance,there is a primary/secondary impedance ratio,and that means once you attach a typical cone speaker with no external compensation networks,your primary impedance will be the reflection of the speaker impedance,which has a big value at resonance point and its never constant,it rises with frequency rising.
                If you want an engineer explanation check out the Deep blue harp Youtube channel he's doing a series of videos on inductance load lines,dc and ac.

                Comment

                • #9
                  Originally posted by Leo_Gnardo View Post
                  ... Why they don't make these terrific items anymore is beyond my comprehension. Maybe the company owner got tired of dealing with this "pearls before swine" world.
                  It's too loud! Wah! Wah! Nobody lets me play it for real! Wah wah wah! It hurts my fragile little eardrums that can't handle real sound from anything bigger than an earbud! Wah wah wah wah!!!"

                  That's my theory...

                  Justin
                  "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                  "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                  "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                  Comment

                  • #10
                    Originally posted by Enzo View Post
                    Say it to yourself over and over until you believe it: It is just a guitar amp. There is nothing precise here, there is no super critical impedance.

                    SO what if one tube is less efficient than another? So what if the impedance is "wrong"? it still works.
                    That is all very well to say now, but rock and roll never would have existed without reasonably efficient push pull pentode (or beam power tetrode) amplifiers. You would have needed a fork lift to get those single ended triode amps into the room if you wanted the required sound levels from a guitar in any room larger than a small bar!

                    Comment

                    • #11
                      Originally posted by Mike Sulzer View Post
                      That is all very well to say now, but rock and roll never would have existed without reasonably efficient push pull pentode (or beam power tetrode) amplifiers. You would have needed a fork lift to get those single ended triode amps into the room if you wanted the required sound levels from a guitar in any room larger than a small bar!
                      Ahhh, but take a teeny amp, and mic it up, and pipe that through a bazillion watt PA system and you have ...
                      The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

                      Comment

                      • #12
                        Originally posted by Justin Thomas View Post
                        It's too loud! Wah! Wah! Nobody lets me play it for real! Wah wah wah! It hurts my fragile little eardrums that can't handle real sound from anything bigger than an earbud! Wah wah wah wah!!!"

                        That's my theory...

                        Justin
                        But oh MAN did our generation do some damage to hearing. Oh man. I can't even believe the sound systems some of those bands had for the club sizes. It was inhuman.
                        The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

                        Comment

                        • #13
                          Originally posted by mikepukmel View Post
                          Ahhh, but take a teeny amp, and mic it up, and pipe that through a bazillion watt PA system and you have ...
                          You have nowhere near the same feeling as. sovtek Mig100U roaring through 3x15s at full-tilt whackage at your back. Or a VT40 on Destroy...

                          Yes, a teeny tiny amp pumped through a bazillion watts can sound great. But it is absolutely NO substitute for pure unadulterated power through real speakers in a backline.

                          Justin
                          Last edited by Justin Thomas; 09-20-2018, 09:35 PM.
                          "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                          "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                          "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                          Comment

                          Previous template Next
                          Working...
                          X