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Last Post: dwr435
04-04-2020, 05:05 PM
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How to eliminate canon pr...
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Assignment Help New Zeala...
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What are these resisters ...
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custom chassis and face p...
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Arduino controlling switc...
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PCB for LFO & Bias (newbi...
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NFB - Single Ended Class ...
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Gridleak resistor value f...
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Posted by: dwr435 - 04-04-2020, 05:05 PM - Forum: The Lounge - No Replies

Hello to all, thanks to those who maintain this site.  New member, interested in mods and completing first build in the future.  Am seriously considering ordering a vht special 6 ultra, to play around and mod a bit.  Starting with some books first, then move to actual mods.  Any tips/suggested threads greatly appreciated.


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  How to eliminate canon printer error b200?
Posted by: michaels1 - 04-02-2020, 01:04 PM - Forum: General Core Series Projects - No Replies

While you use your canon printer, you may confront canon printer error B200. This error code arises due to some technical problems displayed in the hardware, which is totally related with the print head. If you are experiencing Canon printer error b200 again and again, you can call online technical professionals to get full technical steps for solving this error immediately. As an experienced troubleshooter, we use the remote access technology to identify actual causes and resolve this technical problem. Our technical support team is available online to provide the permanent resolutions for any type of technical issues.

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  Assignment Help New Zealand
Posted by: oliviacrew - 04-01-2020, 07:50 AM - Forum: General Core Series Projects - No Replies

Livewebtutors base their success on the facilitation of the students ' learning environment. It, therefore, focuses solely on proving successful assignment help to them so that they can pay full attention to their day-to-day studies which would improve their expertise in various subjects and learning areas.

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  What are these resisters called and...
Posted by: mcneb - 03-21-2020, 10:31 PM - Forum: General Core Series Projects - Replies (2)

In this schematic looking at R101, R102, R103. what do you call these resisters?, and what effect do they have on the pre-amp? I have read these resisters load the guitar pick-ups and set the impedance of the first pre-amp tube. So I need to know why some amps have R101 at say 33K some, especially those from AX84 do not have a resister there at all. I have seen the R103 resister at 1M up to 4.7M So please explain to me the use of these and how I can best match my Guitars pick ups  to hit my pre-amp as I need, (or want). I use both single coils and Humbuckers. Whats the math or is there any???????

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  Arduino controlling switching functions and LFO
Posted by: nfisher - 03-14-2020, 02:30 PM - Forum: Homebrew Discussions - No Replies

Something I've been tinkering with. The amp I'm planning to use this with will have a single channel, clean to mean, with the vactrol channels switching out complete tone stacks, gain and master volume controls. There's a startup timer to let the valves warm up before switching on B+, eliminating the standby switch, and a selectable four waveform LFO for tremolo. I might use the LFO in some effects down the road, too.


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  PCB for LFO & Bias (newbie questions)
Posted by: David Staepelaere - 03-08-2020, 06:04 PM - Forum: Homebrew Discussions - Replies (2)

Old AX84 user here, just finding my way to this forum...

For my next project, I'd like to build a deluxe reverb amp -- mostly just AB763 except using bias-wiggle instead of the usual opto-trem. I'll use turret board construction for most of it, but for kicks I'd like to try a small PCB for the LFO and bias supply. For the LFO I'm thinking of using KG Keen's mosfet tremolo http://www.geofex.com/Article_Folders/ss...remolo.htm and the bias supply would be more or less what you'd expect.

Now I've never made a proper PCB before and I don't want to also dive into the whole home etching thing just for this one project, so I was thinking of using one of the services that does low volume prototypes catering to the DIY crowd.

My basic question is what design rules do I need to follow (I guess it's mostly just spacing?) for "tube amp" voltage levels? The LFO will take voltage from a B+ node and regulate it down to 200V for the oscillator. Is there any good intro/primer I should be reading for this stuff?

Also any suggestions regarding the PCB service? I'm not so worried about finding absolute cheapest or quickest, I more interesting in improving my odds of success since I'm new to this whole thing. I've been looking at the purple boards, but in truth that's mostly based on their web site looking warm and friendly. Should I be looking elsewhere?


Regards, David

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  NFB - Single Ended Class A
Posted by: Equinox - 02-27-2020, 06:24 PM - Forum: Homebrew Discussions - No Replies

I want to circle back onto this one...

Since there is no phase inverter like on a push-pull amp, what are the different designs and approaches for applying negative feedback to a Single Ended Class A design?

Looking to add a presence and resonance circuit to my amps.  Attached is the NFB/presence/resonance circuit.  I have not tried it yet.  Has anyone else?

I know on Fender's they just use a resistor and apply it from the 2nd gain stage to the OT and of course resistor value would depend on output transformer tap.  The reason I understand the 2nd gain stage is used is that the phase is inverted after each gain stage, so goes from positive to negative.  Is this so?


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  Ordering Heyboer/Doberman Universal SE OT
Posted by: Chris Hurley - 02-20-2020, 02:29 PM - Forum: Homebrew Discussions - No Replies

Hi Folks,

I'm thinking about doing a batch order of the great Heyboer/Doberman universal single ended output that we used to get.  These were well loved back in the day and I don't remember anybody ever having anything but good things to say.

These had 2.5K,4k and 6k  primary taps and 4/8/16 secondary taps.  Heyboer told me these will handle 144ma full duty and probably a bit more for audio duty.  We figured these are good for about 20 watts single ended.  I used them on all kinds of amps from little bitty things up to KT88 and they rocked.

The price looks like it has gone up a lot from where it was ten years ago (imagine that).  I think cost on them will be about $60USD before shipping to you.

If you're interested in ordering one (or hopefully more), shoot me an email at chrish at ax84 dotcom and we can talk about it. 

Best regards,

Chris Hurley

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  Epiphone Valve Junior - Low Output Issue ?
Posted by: mjones32 - 02-05-2020, 01:11 AM - Forum: Homebrew Discussions - Replies (1)

Hi , good to see the new site running.   My old Valve Junior head is suddenly very quiet, somewhat distorted but not humming or buzzing at all.   This amp has not been modded since 2012 so nothing has changed.

So far I have....
- swapped out both tubes
- chopsticked
- cleaned the pots and jacks
- checked the ohms to ground at all pins
- checked connectivity between key points
- retensioned sockets
- checked B+
- checked heater voltage
- visually checked electrolytics
- checked the OT via this method - https://www.premierguitar.com/articles/t...r-tester-1

Everything looks perfectly fine and so far nothing made any change at all to the weak sound.    I originally thought it could be the OT but that seems unlikely now.

At this point I am thinking I need to start looking at electrolytics, but I'd expect hum to be an issue.

Any suggestions most welcome.


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  Update on Mary (Old-timers will understand)
Posted by: yecrom - 02-04-2020, 07:09 PM - Forum: The Lounge - No Replies

Hi all,

I used to be a regular contributor here but my wife's health went south for quite a few years.  Everyone on here was amazingly supportive when it first started (including one member offering part of his liver Big Grin ).  Well, we reached the end last wednesday.  Mary passed away on January 29th surrounded by her family.  It had gotten to the point that we knew she was either going to be getting a liver in the next couple of weeks or she would be passing away in that same time.  We were hopeful for a liver but we knew it was a long shot for the last couple of months.  Her condition degraded very quickly during the the last two weeks of her life and it was very bitter-sweet to watch her pass simply because of the amount of pain that she had been in for the last few years.  She's not feeling that now and is free. I just wanted to update everyone on this and thank everyone for the support.  I would still get the occasional email from members asking about her.

Not a time for sadness, but for celebration and rememberance.


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