Microcontrollers in tube amps - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 20th August 2012, 04:51 PM   #31
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Quote:
Originally Posted by acceler8 View Post
I'd love to see the details of this! I'm specifically interested in grounding and isolation between the audio amp and the micro-controller. !
I have used opto-couplers to isolate micro from amplifier.
I used a PIC and opto-coupler to control the reset pin on an irs2092 classs d amp.
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 21st August 2012, 02:46 AM   #32
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
I'd love to see the details of this!
I made PDF's of the schematics and typed up a detailed explanation of how it all works, and why I chose what I did.....only to have VISTA eat my post again! This has been going on for a while and it is getting worse. Vista randomly drops the internet connection. Other computers on the same router work fine. The screen displays "internet explorer can not display the web page" or something like that. The text you typed is gone forever.

I spent last weekend building a new computer. I still have a lot of apps to load. I would take this one to the shooting range, but I am convinced there is absolutely nothing wrong with the hardware. The anomalies in function seem to change with "Windows Updates". So this box will be returned to XP which ran OK on it and it will become my FFT audio analyzer. The old one died. It has been a good DVR and media player too. Vista does OK with that.

Either way, here are the schematics. I'll try again with the explanation tomorrow night. It is almost 11PM here now.....good night.
Attached Files
File Type: pdf MinitronAmp.pdf (31.9 KB, 95 views)
File Type: pdf MinitronController_1.pdf (25.2 KB, 66 views)
File Type: pdf MinitronController_2.pdf (28.6 KB, 45 views)
File Type: pdf MinitronController_3.pdf (23.9 KB, 49 views)
File Type: pdf MinitronController_4.pdf (32.0 KB, 50 views)
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 22nd August 2012, 03:51 PM   #33
diyAudio Member
 
Join Date: May 2010
Location: South East USA
Thanks for the schematics! This is exactly what I was looking for!

In my opinion, Vista was never a good OS. Windows 7 is better, if you have that choice. Of course I still have a couple of XP machines that will likely never be upgraded. Windows 8 looks like it'll be Vista part 2, so I wouldn't hold my breath on that.

Thanks again!
  Reply With Quote
Old 22nd August 2012, 05:12 PM   #34
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
Thanks for the schematics! This is exactly what I was looking for!
I'll put up an explanation of how it all works when I have a chance. Got home from work late last night. The local TV is doing their best to stir up a hurricane panic since there is one approaching and another possibility right behind. My guess is that Isaac will go up the west coast of Florida and make life rather soggy for the "occupy" protesters converging on Tampa. If the threat looks real though, the grocery store shelves will be empty by the weekend, so I will go tonight.

Quote:
Windows 7 is better, if you have that choice.
The new machine is already built and running 7 pro. Mid level core i5 mild overclock with SSD for boot and apps, 5TB for storage and 16GB of ram. That should last me for a few years. Loading all my software will take a while. I need Windows for Cakewalk Sonar and they are already reccomending W8. After I listened to them and loaded my current machine with Vista Ultimate early on......lets just say I won't be an early adopter of any MS stuff any more.

Vista was reasonably stable for the first year or so, but became more and more schizophrenic as I loaded more and more stuff on it. Now it will fail to load one or more important driver on boot up quite often. Usually it is the sound module or the printer. Lately it will drop off the internet if inactive for an hour or so. EMu has discontinued the high $$$ external sound box I am using, and doesn't have W7 drivers, so I won't buy any more of their (or Creative's) stuff. The old box will become a media player / DVR. I use XP boxes for stand alone stuff.

I work for a large corporation with several thousand Windows PC's. Most of them still run XP. Vista is not allowed on the network, and new boxes run W7. I think I'll just mimic what they do from now on, since there are some smart corporate IT guys that test all that stuff extensively before allowing it on their network.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 22nd August 2012, 05:25 PM   #35
TheGimp is offline TheGimp  United States
diyAudio Member
 
TheGimp's Avatar
 
Join Date: Aug 2009
Location: Johnson City, TN
I'm downloading Windows 8 preview on a computer I'm building for my granddaughter. It is an old ASUS A7V with an Athlon 1.6G processor. I'm building it from stuff I had laying around (only 500mB RAM). It's main purpose is internet access for school work, music, and Karaoke.

She gets to be the guinea pig. I may go ahead and take advantage of the early release sale just to get a couple licenses and actually load it later on my system as well.
  Reply With Quote
Old 22nd August 2012, 08:56 PM   #36
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
I'm downloading Windows 8 preview.......I may go ahead and take advantage of the early release sale just to get a couple licenses
Not me......I bought 2 early copies of Vista. One is still unopened in the box.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 22nd August 2012, 09:02 PM   #37
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Quote:
Originally Posted by TheGimp View Post
I'm downloading Windows 8 preview on a computer I'm building for my granddaughter..
Windows 8 RTM free trial is available now.
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 23rd August 2012, 01:38 AM   #38
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Amp details now.....controller next time.

Quote:
I'd love to see the details of this!.......witchcraft
OK, you asked for it. The witchcraft, magic, and smoke containment is all in the modulated boost converters. The rest of the stuff is pretty straight forward. First I will cover the tube amp since it is the easiest to understand. Both the amp and the digital controller share the same ground although this is not obvious in the schematics. In fact during the debug sessions I found I had to run a short fat copper strap between the ground planes in the two boards. The power supply ground is soldered to this strap. This was needed to solve voltage transients and general instability in the boost converters. Everything worked great until the converters approached max voltage. Here there are 450 volt P-P square waves at 1 MHz

See the amp schematic.

The input stage is the small section of a 6EM7. It is a typical gain stage with LED bias and resistive plate load. No processor control is provided, or needed.

The second stage is a grounded cathode amplifier with a CCS load using the big section of a 6EM7. This tube and topology was selected for its ability to swing the plate from 30 volts to 450 volts. I can get over 350 volts P-P ov clean drive from this tube. 6EM7's are highly variable even between tubes of identical construction. There are at least 6 different constructions too. Gain in the first stage, and bias voltage in the second stage vary a lot. Select a pair of tubes with similar first stage gain. The bias for the second stage is microprocessor controlled. R20 and R28 bring bias in from the controller. C12 and C22 form a low pass filter to remove any noise that sneeks in from the boost converter. R8 and R9 (R7, R17) form a voltage divider to reduce the plate voltage to about 50 volts to travel to the logic board. 50 volts or so is safe for the ribbon cable and the SMD parts on the controller. This signal will be split to two circuits. One measures the DC plate voltage for adjusting the bias. The stage operates at a constant current fixed by the CCS, so the bias voltage sets the plate voltage. The other feeds audio into the high speed ADC inside the processor for modulating the boost converter.

The output stage consists of both sections of a 6AS7, 5998A or 6336A paralleled, but with independent bias adjustments controlled by the processor. These tubes are notorious for mismatched sections, so selecting a tube with similar gains and reasonably close bias voltages will allow for the most power output since both sections will share more equally. As with the second stage R26, R34, R30 and R33 brings in the bais and the caps remove noise. R3 and R4 allow for cathode current measurement by the processor. One section is cutoff (max negative bias) while the bias voltage for the other section is determined. Then the process continues for the other section.

The output stage provides all of the current gain for the amp. It operates with a constant DC voltage across it. That voltage depends on the tube in use. Optimum was about 90 volts for the 5998A. The first and second stages provide all of the amps voltage gain.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 23rd August 2012, 12:25 PM   #39
TheGimp is offline TheGimp  United States
diyAudio Member
 
TheGimp's Avatar
 
Join Date: Aug 2009
Location: Johnson City, TN
OT...

Quote:
Originally Posted by nigelwright7557 View Post
Windows 8 RTM free trial is available now.
Preview won't load, I get an error 0x00005D which I have found nothing about by Google.

I'll try the RTM download, but I think my problem may be insufficient RAM. I've only got 896Meg and the min looks like 1GB.

I've still got the old drive with XP on it I can install, but it's small.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help finding a tube tester for Stereo tube amps. Fasterdamnit Tubes / Valves 8 19th July 2010 01:43 AM
For Sale: Tube Amps, Class-A Amps, BG Ribbons, Chassis and Other Goodies! opc Swap Meet 23 2nd November 2009 05:04 PM
Help Please with tube amps!!!!! bobcat1979 Instruments and Amps 1 28th June 2009 11:29 AM
Microcontrollers vs. FPGAs for dummies rtarbell Digital Source 3 11th November 2006 09:24 PM
Best clocks for microcontrollers/DACs rtarbell Digital Source 0 24th February 2006 01:16 AM


New To Site? Need Help?

All times are GMT. The time now is 12:44 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2