What tubes for a tube amp? - Page 11 - 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 2nd March 2010, 01:16 PM   #101
diyAudio Member
 
Join Date: Apr 2009
Send a message via MSN to bacon665
When you rectify 120volts you get the Peak output voltage which is some 147 volts.
Essentially (if your in america) you can take two 1:1 transformers, run the primaries in parallel, on the secondaries tie the negative of the first to the positive of the second. where the secondaries connect is your ground. the other two leads go to the bridge rectifier and the +/- of the bridge is your +/- 147. The rest of the circuit for the powersupply is the float/filtering/smoothing/protection/regulation
  Reply With Quote
Old 2nd March 2010, 01:38 PM   #102
markusA is offline markusA  Sweden
diyAudio Member
 
markusA's Avatar
 
Join Date: Dec 2009
Location: Gothenburg
Blog Entries: 1
Let's remember there are a lot of us guys out here with 240VAC.
  Reply With Quote
Old 2nd March 2010, 01:57 PM   #103
diyAudio Member
 
Join Date: Mar 2005
Location: Midwestern US
Quote:
Originally Posted by bacon665 View Post
What are these values and is it safe to go to the closest size instead of exact values?
So far, it's not a case of "close, but no cigar"; instead, we miss by a wide margin. For the Class-A2 output stage, we need to target inductors that can, at an absolute minimum, reliably pass a continuous 500mA, so we need something rated for at least 1A in order to conservatively operate the components. If we're going to design power-supplies that can sustain the rated 60-watt (RMS) output specification, the steady-state current requirement becomes something closer to 2.4A. Of course, we don't want too large of a voltage-drop across the inductors or the power-output levels will start to modulate against the power-supplies; low DCR values will be important.

So we need moderately high-inductance value inductors with a low DCR and a high heat-dissipation rating. A possible candidate would be something like the Jantzen copper-foil air-core inductors (DCR: 0.85-ohms, power handling: 350 watts RMS for 16 gauge, 500 watts RMS for 14 gauge and 650 watts RMS for 12 gauge). The problem is that the largest inductance value in that product line is 4.7mH, which when flanked by a pair of ~3000uF capacitor banks (C-L-C filter configuration) only gives us a -3dB corner-frequency of 42Hz. To best serve the M-60 signal path, we really need to have a corner-frequency that is well below the audio frequency band. The more traditional iron-core choke designs can certainly provide higher inductance values, but their current/heat-dissipation capacity is limited and they can easily reach core saturation (degrading performance). Before we start stacking-up multiple off-the-shelf inductors, I wanted to see if some custom inductors might offer us an alternative that saves space/weight in the chassis at a decent price-point.
__________________
Mullard EL34
  Reply With Quote
Old 2nd March 2010, 01:58 PM   #104
diyAudio Member
 
Join Date: Mar 2005
Location: Midwestern US
Quote:
Originally Posted by markusG View Post
I suppose it'll be linear psu's?
Keeping with the kiss principle would imho be a good idea since we're talking about a diy project.
Yeah, Class-A vacuum-tube circuits and linear power-supplies are natural partners...
__________________
Mullard EL34
  Reply With Quote
Old 2nd March 2010, 02:00 PM   #105
diyAudio Member
 
Join Date: Mar 2005
Location: Midwestern US
Quote:
Originally Posted by markusG View Post
Let's remember there are a lot of us guys out here with 240VAC.
Not to worry; that's why I had targeted power-transformers that have primaries which can be wired for either 120VAC or 240VAC...
__________________
Mullard EL34
  Reply With Quote
Old 2nd March 2010, 08:19 PM   #106
diyAudio Member
 
atmasphere's Avatar
 
Join Date: May 2007
Its nice to have the windings on three different transformers. The windings talk to each other so if one is loaded it will affect the others. That's why we use a separate B+ transformer for the output, a separate filament transformer and a separate driver B+/B- transformer.

We don't use a choke in the output section, just a 1 ohm 5-watt resistor. If the output section is really balanced, the sawtooth isn't a problem. We do use a choke in the B- of the driver, solely for V4 cathodes. The B- for V3 is fed by a 1K 1 watt resistor that comes directly off of the rectifiers, in parallel with the choke. We don't have any chokes in the B+; the 3K device that feeds V4's plate comes off the rectifiers, and is in parallel with another 1K unit for the plates of V2. We bypass the plates of V4 w/200uf, same for its cathodes. 100uf bypasses the plates and cathodes of the voltage amplifier.

The output section supplies are typically about 6600uf each.
  Reply With Quote
Old 3rd March 2010, 12:02 AM   #107
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
I am currently selling some tubes on ePay. I collected some sweep tubes, but since they are unique and not in current production I decided to sell them for those who want to use them. I will stick with GU-50 output tubes, there are still plenty of them. But 6LW6 and another similar tubes will go.

NOS 6LW6 vacuum tube - Admiral - eBay (item 180476307383 end time Mar-09-10 16:57:59 PST)
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers. -- Plato, 447-367 BCE
  Reply With Quote
Old 3rd March 2010, 01:13 PM   #108
diyAudio Member
 
tympani1d's Avatar
 
Join Date: Dec 2009
Location: Northern Illinois USA
Quote:
Originally Posted by atmasphere View Post
Its nice to have the windings on three different transformers. The windings talk to each other so if one is loaded it will affect the others. That's why we use a separate B+ transformer for the output, a separate filament transformer and a separate driver B+/B- transformer.

We don't use a choke in the output section, just a 1 ohm 5-watt resistor. If the output section is really balanced, the sawtooth isn't a problem. We do use a choke in the B- of the driver, solely for V4 cathodes. The B- for V3 is fed by a 1K 1 watt resistor that comes directly off of the rectifiers, in parallel with the choke. We don't have any chokes in the B+; the 3K device that feeds V4's plate comes off the rectifiers, and is in parallel with another 1K unit for the plates of V2. We bypass the plates of V4 w/200uf, same for its cathodes. 100uf bypasses the plates and cathodes of the voltage amplifier.

The output section supplies are typically about 6600uf each.
atmasphere:
Any chance you'd post power supply schematics for the M60's?
__________________
I think; therefore will NOT be Politically Correct.
  Reply With Quote
Old 3rd March 2010, 06:44 PM   #109
diyAudio Member
 
atmasphere's Avatar
 
Join Date: May 2007
Here ya go... the transformers are proprietary and the usual copyright restrictions apply.
Attached Images
File Type: gif m60-power-117.gif (56.0 KB, 1029 views)
  Reply With Quote
Old 3rd March 2010, 10:50 PM   #110
diyAudio Member
 
Join Date: Apr 2009
Send a message via MSN to bacon665
Quote:
Quote:
Originally Posted by markusG
Let's remember there are a lot of us guys out here with 240VAC.
Not to worry; that's why I had targeted power-transformers that have primaries which can be wired for either 120VAC or 240VAC...
Those 120/240 1:1 ct's are good for america but if your on 240 all you need is a regular center tap. half of 240 gives you +/- 120 RMS. In this sense it *SHOULD* be cheaper for those of you on 240 by a few units (dollars euros pounds or what have you (rubels maybe))

as for the inductors triad might be your best bet if your trying to get your corner frequency way down.
Inductor; Common Mode; Ind 8mH; Cur 3.2A; Thru-Hole; DCR 0.12 Ohms $4.17 might be steep. how many inductors are we talking about here 2,4,8?
  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
New to Tubes, just bought first tube amp josefgabriel Tubes / Valves 28 7th April 2010 07:20 AM
FS: 1626 Tube Amp, Van Alstine pre, tubes, crossover. xecluded Swap Meet 1 30th April 2009 07:27 AM
Tube Noob! need help with tubes lots of tubes therapy_fan Tubes / Valves 15 29th January 2009 09:01 PM
Adding more power tubes and make a tube amp switching them? Nicko_Lps Tubes / Valves 3 7th January 2009 12:31 AM
"The Fisher" tube amp 7189 output tubes laflamme Tubes / Valves 4 28th August 2004 12:40 AM


New To Site? Need Help?

All times are GMT. The time now is 01:09 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