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Shocked through a tube sh...
Forum: P1-eXtreme Project
Last Post: Merlin
Yesterday, 09:36 AM
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Wanted: Python expert to ...
Forum: Homebrew Discussions
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Some Questions about a Ha...
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01-22-2020, 10:15 AM
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Old PT question
Forum: Homebrew Discussions
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01-12-2020, 01:15 PM
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Like the new look
Forum: The Lounge
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01-08-2020, 08:54 AM
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Gridleak resistor value f...
Forum: Homebrew Discussions
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01-06-2020, 04:32 PM
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Thank you for your patien...
Forum: Transitioning from AX84 to Guitar Amp Builders Forum
Last Post: Chris Hurley
01-04-2020, 06:06 PM
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HO switches
Forum: Hi-Octane Project
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01-02-2020, 12:46 AM
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Hello and back after a lo...
Forum: The Lounge
Last Post: Sdp1234
12-25-2019, 03:41 AM
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Ibanez TSA30 Amp (sell, T...
Forum: Noncommercial Gear Exchange
Last Post: audiosalvage
12-22-2019, 05:06 PM
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  Some Questions about a Haynes Lead II studio Amp
Posted by: mcneb - 01-19-2020, 04:14 PM - Forum: The Lounge - Replies (4)

.pdf   Hynes_Lead_II_Studio_100206.pdf (Size: 793.61 KB / Downloads: 6)

Going through some schematics I downloaded from the old Ax84 site, a few years ago. I ran across this one. Named the "Haynes Lead II studio" dated 2006. Shows a great deal of similarities to the 4-4-0 and the October power amps. But then the Pre amp is using 3 more stages. Studying this schematic I noticed the second, third, and forth stages do not have the " normal" plate  resister values. Even though they are 12AU7 valves. So, is there anybody here to have ever built this amp, and are there any sound clips? What amp is this a (emulation of) copy or clone? Then why the 12AU7 and the lower plate resister values for these stages. Super clean or what???

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  Shocked through a tube shield!!!
Posted by: Rgates99 - 01-15-2020, 01:37 AM - Forum: P1-eXtreme Project - Replies (2)

Been a long time since building.  Playing a P1-Ex I built several years ago.  Everything going fine, sounds great, then it starts to sound weird like it’s starting to cut out.
Went to wiggle the preamp tube shield thinking maybe the tube is loose and got a shock through the shield.  
Promptly shut it down and turned on another.

Any thoughts on where to start?  My troubleshooting skills are quite rusty...

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  Old PT question
Posted by: Sdp1234 - 01-11-2020, 01:46 PM - Forum: Homebrew Discussions - Replies (2)

I’m back to tinkering and hopefully building a couple more amps.  The first thing I’m doing is replacing a PT and converting a modified pig nose to 6v6’s

My PT has the following secondary taps
2 wires that measure 4 v across them

Forgive me if I should remember this stuff but I’ve been away for 5-6 years and I think I forgot most of what I learned.

What would a 4v tap be used for?
Is there a way to leverage both sides if the 7v to provide additional heater current.

Thanks for looking

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  Gridleak resistor value for 6F6G
Posted by: valvetones - 01-02-2020, 04:57 AM - Forum: Homebrew Discussions - Replies (2)

Hello, im building a true class A amp with a choke input filter and cathode bias with four 6F6G tubes in the output. 
I noticed in several of the cathode biased fender tweed amps that the grid leak resistors to both the 6v6 and 6l6 setups is 250k. Since both of those are tetrodes which are more efficient than a true pentode like a 6F6G, i wonder if a higher gridleak resistor value would be a good idea. Currently on my board i have soldered in two 560k gridleaks to ground (one for each output pair ) However, i think 560k may be too high, and was wondering if 330k would be a better value for these tubes?  Also, how do you determine what value to use in the first place for any given output tube? The topology is 6sj7->6sl7->6sn7->two or four 6F6G (#42) tubes.   Thank you for your thoughtful replys

Other considerations, so its 6sj7 gainstage-> 1/2 6sl7 gainstage -> 2/2 6sl7 gainstage-> bandmaster tonestack->6sn7 phase inverter-> then 6f6g output pair.

I read that the bandmaster TS is pretty high impedance and somwhat lossy , also i am NOT using a cathodyne PI as the tweeds do, im trying to get higher voltage swing from the PI to really distort the output tubes, and since the amp is class A there is much lower B+ than would be required to use the cathodyne to achieve this.
Probably 315 VDC at the first node WITHOUT any tubes installed to draw current.
The Amp is currently under construction so no tests or checks are possible yet, but will be soon. Im just trying to tie up loose ends before i solder any further.
A bonus question in addition to the grid leak value for 6F6G,, is one for the preamp, I basically ran the 6sj7 champ circuit right into 1/2 of the 6sl7 for the next fain stage. What would be the appropriate grid stopper and gridleak value 6sj7 going into 6sl7?
Thank heeps

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  HO switches
Posted by: matt_GTR76 - 12-28-2019, 10:09 PM - Forum: Hi-Octane Project - Replies (3)

Hi all

Didn't realise the forum was up and running somewhere so this is great!

Anyway, a simple one really. I'm in the process of putting a HO together for a bit of fun at home so I can see if I want to build more amps and at the moment I'm gathering all the components and I was wondering what people (in the uk, if there are any) are using for the power and standby switches and where your favourite place to get them is?

I will be photographing the build as it commences. I also won't be building the cab as I've got a Mesa MkivA that I'll use the EV in for now until I decide what to do about a cab.

Any help/pointers would be appreciated



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  Like the new look
Posted by: Joe Kavanaugh - 12-25-2019, 05:37 PM - Forum: The Lounge - Replies (3)

Just went to AX84.com to discover we have a new site. I just registered. Love the new look. See you around!

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  Hello and back after a long time
Posted by: Sdp1234 - 12-25-2019, 03:41 AM - Forum: The Lounge - No Replies

hello all.  I’ve been away for years.  This was the place I got started with tube amps, thought maybe I was finished but I’d like to slowly get back to it a bit.  I have a lot to learn and almost just as much to relearn.  I want to say thanks to the community that cot me started with this hobby.

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  Ibanez TSA30 Amp (sell, Trade)
Posted by: audiosalvage - 12-22-2019, 05:06 PM - Forum: Noncommercial Gear Exchange - No Replies

I have an Ibanez TSA30 amp head in good working order.  I put a larger heat sink on the regulator because I thought the tiny one they give you was insufficient.  I will sell it out right for $300 shipped, or I will trade for the right guitar or amp.  This amp is just too clean for my use.  Let me know what you have.  Thank You.

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  Changing a EL81 from class B to AB?
Posted by: JaapK - 12-07-2019, 08:15 AM - Forum: Homebrew Discussions - Replies (3)

Hi guys, i'm changing an old Philips tube amp into a guitar amp. That amp has a PP amp with 2 EL81 tubes in class B. Plate voltage 400V. Screen V around 200V. Fixed bias -24V. 
Sounds fine but not when overdriven.. 
Is it possible to bias the tubes more into AB? I don't think so...given the available voltages but maybe someone has a good idea?
What else can I do? Large grid resistors? Now its 1K, maybe go to even 100K? To avoid grid current as much as possible? Something else?

I appreciate it if you guys can think along with me! Thanks for response.
Here is the schematic:

Btw I don't want to change to other output tubes.
Maybe change the cathodyne phase inverter to a 12au7 instead the 12at7 cause the au can handle grid current better?

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  Diagrams ? Schematics , etc
Posted by: sam.morris1963@gmail.com - 11-30-2019, 02:43 PM - Forum: Site and System Discussions - Replies (2)

Russ, et al,

are the AX84 schematics and layout diagrams still available? I was troubleshooting my October build and started thinking about them.


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