Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

900v B+ Silly time.
900v B+ Silly time.
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 6th October 2004, 06:53 PM   #1
Layberinthius is offline Layberinthius  Antarctica
diyAudio Member
 
Join Date: Jan 2004
Location: nowhere
Default 900v B+ Silly time.

I'm considering a 200mA 900v un-regulated (but well filtered)
power supply for a combined SE 813 Class-A without a seperated power supply chassis, using:

Sowter M045 Centre Tapped.

HT winding: 660vAC RMS!
HT mA: 400

Secondary winding resistance is unknown..

Sure I could email Sowter, but I'd much rather ask you how to calculate the proper operating (after load) voltage for myself..

See, Sowter's closest trafo is 660vAC RMS at 400mA, if I go and buy one for two frontends, I'll be drawing 200mA or thereabouts which will considerably change the voltage.

I /really/ want to use Sowter trafos they're the closest thing I've got to a 900v B+

Anyway, heres the rest:

CLCRC

Diodes: Open to suggestions. PIV needs to be min of 2000v
Plenty of tubes categorise for this but I'll also need to calculate for voltage drop with those!.

C1: 33.5mF (16mF 660vAC + 17.5mF 880vAC = 33.5mF)
L1: Plitron PAT-4173 10H, 50 ohm (PAT-4173 pdf)
C2: 33.5mF (16mF 660vAC + 17.5mF 880vAC = 33.5mF)
R1: 4x 20 ohm 3w (film or carbon?) Resistors in parallel
C3: 33.5mF (16mF 660vAC + 17.5mF 880vAC = 33.5mF)



An isolated bias and (both, bias and filament) regulated CLC 10v filament supply.

Cheers.
  Reply With Quote
Old 6th October 2004, 07:22 PM   #2
Sch3mat1c is offline Sch3mat1c  United States
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Er, your R isn't going to do squat. And where did you find 16,000uF caps rated for that voltage?

So um, what was the issue? Transformers are rated either for AC, or DC output with a certain type of rectifier (usually cap input). In worst case, your transformer will be at full ratings with approx. 250mA DC. It will get hotter if you use excessive capacitance, but >220uF is unlikely to be seen here. And you're going to use what, 200mA (= 160W?) per channel? If so, then hopefully it's 400mA *DC*. If 400mA AC, you'll need two of these things...

660V will run from approx. 933V open circuit to maybe 850V full load, depending on resistance. I would expect 800-900V with tube rectification, 900V typical for silicon. You need >1800 PIV rating, 1A will be fine (three 1N4007's in series per leg).

Tim
__________________
Seven Transistor Labs, LLC
Projects and Resources / Electronic Design and Consultation
  Reply With Quote
Old 6th October 2004, 07:27 PM   #3
Layberinthius is offline Layberinthius  Antarctica
diyAudio Member
 
Join Date: Jan 2004
Location: nowhere
Sorry I was using an old definition of "uF" which was commonly displayed as mF in books/mags/etc... I've been reading too many 1960's UK magazines by the looks of it

Nethertheless,

mF = millifarad, uF = microfarad..

Report me for being indecently charged...=P

Microfarad is what we want =)

I didn't think that in cap loaded trafos the amps were different in converting from AC to DC (When talking about post-rectifier), I thought amperage was defined as DC after any capacitor and only when dealing with choke loaded supplies was the amperage value changed.

OH I see now, this is a centre tapped transformer, not bridge rectification.

I believe you are incorrect.

This is a CLCRC supply, cap, choke, cap, resistor, cap.

No It's 100mA per channel, not 200mA.
  Reply With Quote
Old 6th October 2004, 10:01 PM   #4
Brett is offline Brett
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Calculate it? Bah humbug. Use PSUD. Accurate within a couple of percent and much faster than doing it longhand.

I've used the 813 a lot (my fave tube), but not SE much. It really likes >700V and around 100mA. DC filaments are a painsaver, especially current sourced. If you haven't decided on a driver, try an EL84/D3a/C3m/12HG7 in pentode, with a low anode load. Thorsten's page has a cct called Legacy that uses something similar to what I ended up with, and Pete Millett's has lots of comparisons and other specs on pentode and triode drivers.

If you haven't already seen it, take a squizz at Stephen's 813 journey and Pete Millett's page also has an SE813.

I just picked up a 2600Vct transformer so I'm going to try a PP pentode (with plate to grid feedback) 813 bass guitar amp.
  Reply With Quote
Old 6th October 2004, 10:31 PM   #5
Sch3mat1c is offline Sch3mat1c  United States
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Quote:
Originally posted by Layberinthius
Sorry I was using an old definition of "uF" which was commonly displayed as mF in books/mags/etc... I've been reading too many 1960's UK magazines by the looks of it


Quote:
I didn't think that in cap loaded trafos the amps were different in converting from AC to DC (When talking about post-rectifier), I thought amperage was defined as DC after any capacitor and only when dealing with choke loaded supplies was the amperage value changed.
Well, if the transformer is used for AC, it will be rated in terms of AC output. 120:240V transformer for instance, used for AC. If rated 1A output (240VA), it goes down to around 600mA for DC. But if the transformer is rated for DC output anyway, then yeah you can safely draw rated current.

Quote:

OH I see now, this is a centre tapped transformer, not bridge rectification.

I believe you are incorrect.
Nope, I'm never wrong If it's rated for FWCT, then yeah, you can only draw half when FWB'd.

Quote:

This is a CLCRC supply, cap, choke, cap, resistor, cap.
Not with five ohms between those caps. Or was that a typo?

Quote:

No It's 100mA per channel, not 200mA.
Ok, then it sounds like you can do it with just that transformer.

Tim

P.S. Bit of info: CT'd transformers are usually rated "VCT" instead of "VAC", which implies no CT on that winding. So 25VCT = 12.5 - 0 - 12.5V = 25VAC if not CT'd.
__________________
Seven Transistor Labs, LLC
Projects and Resources / Electronic Design and Consultation
  Reply With Quote
Old 6th October 2004, 10:59 PM   #6
Brett is offline Brett
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Default Re: 900v B+ Silly time.

Further thoughts after morning cuppa....

Quote:
Originally posted by Layberinthius
[B]I'm considering a 200mA 900v un-regulated (but well filtered)
power supply for a combined SE 813 Class-A without a seperated power supply chassis, using:

Sowter M045 Centre Tapped.

HT winding: 660vAC RMS!
HT mA: 400

Secondary winding resistance is unknown..

Sure I could email Sowter, but I'd much rather ask you how to calculate the proper operating (after load) voltage for myself..
But you need to know the secondary resistance to calculate the voltages close.
Quote:
I /really/ want to use Sowter trafos they're the closest thing I've got to a 900v B+
At 145 quid and postage for 7kg from the UK, I'd suggest emailling Bob at Lancroft and getting a quote for one of his made in Sydney. His OPTs are great and I'd recommend them as well as Lundahls, which can be purchased in Oz.

Hammond makes excellent filter chokes which are cheapish and available locally, as do Lundahl (excellent!!) and Lancroft.
Quote:
Diodes: Open to suggestions. PIV needs to be min of 2000v
Plenty of tubes categorise for this but I'll also need to calculate for voltage drop with those!.
6CJ3 and 6D22S in that order.
  Reply With Quote
Old 7th October 2004, 01:07 AM   #7
Geek is offline Geek
diyAudio Member
 
Geek's Avatar
 
Join Date: Sep 2004
Quote:
Originally posted by Sch3mat1c
Nope, I'm never wrong
I always get an "A" when Tim does my homework
  Reply With Quote
Old 7th October 2004, 02:52 AM   #8
Sch3mat1c is offline Sch3mat1c  United States
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Default Re: Re: 900v B+ Silly time.

Quote:
Originally posted by Brett
But you need to know the secondary resistance to calculate the voltages close.
And line voltage, and leakage inductance. And diode performance with chosen cap. 10% is good enough for tube purposes, and a simple rule of thumb like 1.3 times works.

IMHO, I hate PSUD anyway. I like doing everything myself. I can calculate it manually, not to mention manipulate it in my mind and on paper faster than digging out the program and so on. Plus I don't break the keyboard if I get bogus results and electocute myself....(and we all know people have had bogus results from PSUD; a product of the user's programming, not the software's ).

Quote:
6CJ3 and 6D22S in that order.
1N4007, 1N4007 and 1N4007, in that order

Tim
__________________
Seven Transistor Labs, LLC
Projects and Resources / Electronic Design and Consultation
  Reply With Quote
Old 7th October 2004, 03:08 AM   #9
jrdmedford is offline jrdmedford  United States
diyAudio Member
 
Join Date: Mar 2004
Location: Medford, MA
Yes. I am considering taken the plunge to high voltage myself.

You seem to be letting your product preferences drive the design.
I'd not do this with a 900V supply. I think a choke input supply would be
best in this situation. Why? The noise induced by the ripple currents
charging the input cap will be very high with 660-0-660 transformer.
These same ripple currents might drive the transformer into saturation
and cause it to buzz, or get warmer than it should..

To do choke input, you'd use a 1000-0-1000 (2000 VCT) transformer.

The downside to choke input is (1) It must draw a MINIMUM load current
at all times otherwise the voltage rises to 1500V. (2) You need to tune
a snubber network to quench switching spikes. (3) Layout and parts
selection is off utmost importance for safety (both fire and electrocution).

Hammond has a bargain-basement 2000VCT tranny for USD$64.00.
CCS service is 150mA, so you'd have to buy two and do a dual mono
supply. They also have various HV chokes.

This sounds more complicated, but in the long haul, its the best choice
for preserving the integrity of the sound reproduction.

Perhaps Sowter can do a custom HV transformer.

-- Jim
  Reply With Quote
Old 7th October 2004, 03:52 AM   #10
rcavictim is offline rcavictim  Canada
diyAudio Member
 
rcavictim's Avatar
 
Join Date: Jun 2004
Location: Next to an open wormhole NW of Toronto
Quote:
Originally posted by jrdmedford

Hammond has a bargain-basement 2000VCT tranny for USD$64.00.
CCS service is 150mA,

-- Jim

Hammond has become so expensive that I figure a doorbell xfmer would be all you could buy for $64.00. This plate xfmer sounds interesting. What is their part number please? It sounds perfect for large single triode monoblock applications.

BTW, I'm with you on recommending choke input filter. If you can switch the plate xfmer on a delay timer you can solve the voltage rise without load issue without resorting to a power wasting, heat generating power resistor minimum supply load bleeder, although a bleeder is still mandatory for safety reasons.
__________________
"There are more worlds than the one you can hold in your hand." Albert Hosteen, Navajo spiritual elder and code-breaker, X-Files TV Series.
  Reply With Quote

Reply


900v B+ Silly time.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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Silly question time... falcott Everything Else 4 21st November 2006 11:08 PM
900v. 100ma. Power supply for 813 tube amplifier noyan Tubes / Valves 31 5th June 2004 12:53 PM


New To Site? Need Help?

All times are GMT. The time now is 06:13 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki