Vacuum Tube OTL power amp!! - Page 7 - 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 25th May 2011, 04:56 PM   #61
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
There's about 10mA drain from the 350V supply when idling.

A 50mA supply will supply both channels adequately....
  Reply With Quote
Old 28th May 2011, 02:25 PM   #62
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
Well, Ive been running the amp now with 6C33C --wired single-cathode with the feedback as in the last diagram.

Its sounds really nice, the FB helping tighten the bass and this shows through on movie soundtracks, where there is a very deep bass...

I'm not sure the longterm effects of running a 6C33 only on 1 cathode, what effect is this having on the unused cold cathode over time...?

Guess you could arrange the heater-supply so as to turn off 'either or' and use them alternately....

Last edited by Alastair E; 28th May 2011 at 02:28 PM. Reason: correction
  Reply With Quote
Old 28th May 2011, 02:55 PM   #63
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Are the values for the feedback you are using the same as quoted before ie 33K / 470K ?
The other way for the heaters would be to use a flip flop circuit that changes the heater over either on start or power down to equal the wear + retentive both switch / push button so the amp always starts in power save mode. Or as you say A/B/Both.

I guess it will be a while before I get the parts togeather. LOL

Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 28th May 2011, 04:20 PM   #64
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
yes, I havent altered the fb loop from the scheme....

I think I like the idea of a 'Left/Right, Both' scenario to contol the heaters.

There is a pretty significant reduction in heat from the tubes running single-cathode....
  Reply With Quote
Old 28th May 2011, 04:26 PM   #65
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Quote:
Originally Posted by Alastair E View Post
yes, I havent altered the fb loop from the scheme....

I think I like the idea of a 'Left/Right, Both' scenario to contol the heaters.

There is a pretty significant reduction in heat from the tubes running single-cathode....
Just as an idea,

Electro-Mech solution

http://www.ia.omron.com/data_pdf/dat...q_ds_csm44.pdf

Haven't given it enough thought at the moment. Also perhaps a minature version with a simple on / off push button so the off button toggles the relay. Could also be done with Cmos.

The switch is easier!

Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 29th May 2011, 08:03 AM   #66
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Alastair,

Regards power Tx's,

Looks like: from AirLink Tx as suggested,

TT0913

VAL 1601

0300225 <<< no hum with a bit of luck.

Do these look OK?


Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 29th May 2011, 09:19 AM   #67
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
Yes, This is the spec from their website --

VA: 400 VA.

Power: 400VA Toroidal Transformer
Secondary: 115-0-115vac Bifilar wound connected in series (200mm flexible leads 16awg)
Primary: 230vac (200mm flexible leads 16awg)
Core: Unisil: M089-27N
Copper: OFC 99.99%
Dimensions: 145 x 65 (mm)
Faraday shield: Electrostatic screen with earth lead
EMI/RFI Shield (2 layers of GOSS steel band)
Standard: EN61558-2-6
Fixing: Standard Hardware 2 pads + steel dish washer

It does look a great Tx, Might even get one myself for a Mk II one day....

I guess there's scope with this Tx to supply 4 6C33C per channel if you wanted to go bigger, definately fine for just the two per channel!....
--But then you're getting Bigger and Hotter, adding complication, something I'm thinking you are trying to avoid!

Ive found that a good, stout power-supply for the O/P stages for Any OTL is one of the deciding factors for good sound...
Weak saggy supplies need not apply!


The 'HT' trans (+B) you're looking at their 'VAL1601' Guess you could use this, although its rectified voltage would be well over 400, and its current rating well higher than you'll ever need for the pre-amp stages--Guess you can 'lose' some volts over CRC filter and maybe a valve rec though....

I use the simple 'Pre-Amp' 250V 100mA and 6.3V 3A from 'Maplin' This gives me 350V rectified, (SS rec.) which is fine...

Last edited by Alastair E; 29th May 2011 at 09:30 AM.
  Reply With Quote
Old 29th May 2011, 10:26 AM   #68
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Quote:
Originally Posted by Alastair E View Post

The 'HT' trans (+B) you're looking at their 'VAL1601' Guess you could use this, although its rectified voltage would be well over 400, and its current rating well higher than you'll ever need for the pre-amp stages--Guess you can 'lose' some volts over CRC filter and maybe a valve rec though....

I use the simple 'Pre-Amp' 250V 100mA and 6.3V 3A from 'Maplin' This gives me 350V rectified, (SS rec.) which is fine...

I have a maplin newton pre Tx..LOL

I agree the B+ is a bit high.
Should have looked closer. VAL3555 would be closer.
Just thinking about using all toroid.

Thoughts at the moment (may change) is to sandwich TX's on the bottom with EMI shielding and using the top as the pre/ power.
Might put one TX on the top to reduce the footprint. Perhaps duct the air with holes at either end of the chassis.

Regards
M. Gregg
__________________
What is the sound of one hand clapping?

Last edited by M Gregg; 29th May 2011 at 10:39 AM.
  Reply With Quote
Old 29th May 2011, 12:03 PM   #69
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Just a thought,

If the ducting created by mounting levels was a sideways "U". I could mount R9 & R10 on a heat sink in the middle of the "U" i.e. the bend in the air path. I might be able to drive the ducted air with the heat from the resistors.

So if the toroids were mounted on aluminium plate bolted onto birch ply with large holes e.g. 40-50mm with a cork insulator pad open at one end. The other side of the ply covered with checker plate for the base + holes finger protection this would reduce vibration and give a stiff base.
That would give venting for the air ect as the first part of the "U". Follow with vertical heat sink + resistors to the top section. Capacitors in a separate partition (maybe).

Just thinking out loud.

As you say you could increase the number of 6c33c's and switch in!

Regards
M. Gregg

__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 18th June 2011, 11:12 AM   #70
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Just a pic,

Got the 6C33c-B's today from Russia. Only took 2 weeks!

Starting to collect the parts..going to take a while.



Just for fun

Regards
M. Gregg
Attached Images
File Type: jpg DSCN3403.JPG (35.0 KB, 858 views)
File Type: jpg 6c33 pic.JPG (173.8 KB, 865 views)
__________________
What is the sound of one hand clapping?
  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
FS: Vacuum Tube Monoblock Power Amp Kit cuibono Swap Meet 13 7th May 2011 12:49 AM
Vacuum tube VCO Bitrex Tubes / Valves 1 15th March 2011 12:07 PM
HLLY MK III 3 Vacuum Tube Headphone Amplifier Pre Amp hllyelec Vendor's Bazaar 2 19th July 2009 05:54 AM
S3E Vacuum Tube angsuman Tubes / Valves 12 15th March 2008 05:12 AM
DIY Vacuum tube amp turbo_h4 Tubes / Valves 2 1st July 2004 01:48 AM


New To Site? Need Help?

All times are GMT. The time now is 02:44 AM.


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