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Post by reverendkansas on Mar 7, 2023 8:44:43 GMT -7
On a recent Dr. Z AMA, the Doctor talks about the Z-80 being individually class A running in parallel. Is that a quadruple single ended amp or did I misunderstand his point.
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Post by j4gitr (John) on Mar 7, 2023 10:09:23 GMT -7
That’s the way I understood his explanation of the Vox AC80/100 upon which the Z-80 is modeled. One would assume he followed that path, but only the good Dr. Himself knows for sure. Maybe he will chime in.
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Post by frankie on Mar 7, 2023 12:35:03 GMT -7
On a recent Dr. Z AMA, the Doctor talks about the Z-80 being individually class A running in parallel. Is that a quadruple single ended amp or did I misunderstand his point. How something is biased is does not necessarily equate to how the output section is configured/what style of output transformer it is using. A lot of the confusion comes from some class A amps happening to also be single ended, as they utilize one tube. Early fenders like Champs, can be both. Then also, the marketing aspect that Vox grabbed and ran with calling the Vox AC30 Class A does not help (it is not class A, it is A/B, despite being cathode biased). Dr. Z was describing that each power tube runs a single cathode bias resistor, which runs each tube in Class A.
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Post by reverendkansas on Mar 7, 2023 14:22:46 GMT -7
On a recent Dr. Z AMA, the Doctor talks about the Z-80 being individually class A running in parallel. Is that a quadruple single ended amp or did I misunderstand his point. How something is biased is does not necessarily equate to how the output section is configured/what style of output transformer it is using. A lot of the confusion comes from some class A amps happening to also be single ended, as they utilize one tube. Early fenders like Champs, can be both. Then also, the marketing aspect that Vox grabbed and ran with calling the Vox AC30 Class A does not help (it is not class A, it is A/B, despite being cathode biased). Dr. Z was describing that each power tube runs a single cathode bias resistor, which runs each tube in Class A. Thanks.
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Post by adam on Mar 7, 2023 16:32:58 GMT -7
All I know is the Z80 sounds incredible and is a beast to be reckoned with.
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Post by DRZ on Mar 8, 2023 7:54:53 GMT -7
Frankie nailed the explanation of the bias used on the Z 80. It has a very unique Phase Inverter 12AU7 , and a very different output tube configuration one that I have never seem before on any guitar amp. This makes for its special tone . I tried to use a Fixed Bias as VOX moved to in the on later AC 100's, but it lacked the original tone that the single Cathode Biased design offered, so I returned to Cathode Bias. I have been told by many pro players the Cathode Bias design is the way to go, they are right. There may be less then 100 in operation as CB left worldwide, with less the 300 built originally.
I hope to have the Z 80 ready for release at years end .
Z
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Post by j4gitr (John) on Mar 8, 2023 8:25:37 GMT -7
The electrical knowledge I contain can be summed up in few words, “plug it in, turn it on.” I don’t know what you do under the hood Doc, though I try to comprehend. All I know is your amps sound great, and for me it comes down to which great sound(s) I wish to employ. Wish I had the means to use ‘em all.
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Post by pcns on Mar 8, 2023 10:58:04 GMT -7
I saw a guy at the Ohio guitar show with a sign that read he had a AC 100 for sale. If I had realized how rare they I might have seen what he wanted for it . . . missed that one
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Post by DRZ on Mar 8, 2023 11:41:57 GMT -7
I saw a guy at the Ohio guitar show with a sign that read he had a AC 100 for sale. If I had realized how rare they I might have seen what he wanted for it . . . missed that one Todd, there are many AC 100 Fixed Bias units they made over a thousand of those and very many still in operation . It's the AC 80 Cathode Bias units that are very rare, and superior in tone. Z
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Post by Jaguarguy (Mike) on Mar 8, 2023 11:52:47 GMT -7
I hope to have the Z 80 ready for release at years end . Z Make sure you have my name on one of them
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Post by doctorice on Mar 9, 2023 6:29:22 GMT -7
I hope to have the Z 80 ready for release at years end . Z Doc, have you altered the design from the one you had at Z Fest 2018? That was a mighty beast. KeithA has one, I think.
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Post by DRZ on Mar 9, 2023 7:35:05 GMT -7
I hope to have the Z 80 ready for release at years end . Z Doc, have you altered the design from the one you had at Z Fest 2018? That was a mighty beast. KeithA has one, I think. Yes " Enhancements ". I added Mid control in place of the 10 K resistor which did that function with no adjustment. I added PPIMV, works great for a very powerful and LOUD amp. I added a 240 V /50 Hz tap to the power transformer for export use. And I added a Metro loop , seems many demand a loop now a days, and it works very well I must say. These are small but useful changes made under the request of Jamie @ Earthquaker Devices. Same great tone Cathode Biased operation, with a couple of say MKII updates pre -release. Z
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Post by KeithA on Mar 9, 2023 7:49:58 GMT -7
I hope to have the Z 80 ready for release at years end . Z Doc, have you altered the design from the one you had at Z Fest 2018? That was a mighty beast. KeithA has one, I think. I do indeed. Actually, it's been pulled out this week for noodling
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Post by KeithA on Mar 11, 2023 6:49:11 GMT -7
Doing some cleaning today, so opportunistic time for a quick pic.
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Post by adam on Mar 11, 2023 7:39:30 GMT -7
"ooh, ahh". I like the coasters, good idea.
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klmn
New Member
Posts: 26
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Post by klmn on Mar 12, 2023 19:09:00 GMT -7
Doc, have you ever experimented with grid leak biasing or paraphase phase inverters?
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Post by KeithA on Mar 13, 2023 2:45:39 GMT -7
"ooh, ahh". I like the coasters, good idea. These are actually felt pads that can go under furniture legs, etc. I keep the paper backing on the adhesive side and put the felt side down. You can get pieces without the adhesive side as well. Works great, especially for these heavy heads. That’s similar to the white project board that the amp and cabs sits on. It’s not there to prevent the feet making marks in the carpet 😊 My downstairs has carpeted rooms. So, when I want to move the cabs/amps around they simply slide on the carpet like butter. No lifting.
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Post by DRZ on Mar 13, 2023 3:39:23 GMT -7
Doc, have you ever experimented with grid leak biasing or paraphase phase inverters? I have not incorporated Grid Leak bias as I use often my own parallel dual triode design in many of my amps. As for paraphrase PI, yes I appreciate their unique tonal drive on lower wattage amps . Z
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Post by premiumplus (Dave) on Mar 13, 2023 12:27:13 GMT -7
On a recent Dr. Z AMA, the Doctor talks about the Z-80 being individually class A running in parallel. Is that a quadruple single ended amp or did I misunderstand his point. How something is biased is does not necessarily equate to how the output section is configured/what style of output transformer it is using. A lot of the confusion comes from some class A amps happening to also be single ended, as they utilize one tube. Early fenders like Champs, can be both. Then also, the marketing aspect that Vox grabbed and ran with calling the Vox AC30 Class A does not help (it is not class A, it is A/B, despite being cathode biased). Dr. Z was describing that each power tube runs a single cathode bias resistor, which runs each tube in Class A. So it's a push-pull output section, right?
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Post by DRZ on Mar 13, 2023 12:55:41 GMT -7
Dr. Z was describing that each power tube runs a single cathode bias resistor, which runs each tube in Class A. So it's a push-pull output section, right? Yes
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