side by side bifilar windings in excess of 1000 volts - Page 2 - 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 7th February 2011, 02:59 PM   #11
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
yes, you have to add the assumption that a tube output xfmr is "impedance matching" and is driven from the high source resistance of the output tube' plate - then increased pri-sec C rolls off the drive V

if you have low driving source impedance at the primary, not "matching impedance" then you can get somewhat better bandwidth with multifilar/high interleave as long as you don't mind the "waste" of driving high current through the pri-sec C shunting the driver

Last edited by jcx; 7th February 2011 at 03:23 PM.
  Reply With Quote
Old 7th February 2011, 03:54 PM   #12
Account disabled at member's request
 
Join Date: Apr 2009
That's why a 6C33 output transformer is a "gimme", and an 813 opt a "challenge".
  Reply With Quote
Old 7th February 2011, 05:48 PM   #13
diyAudio Member
 
Join Date: Apr 2007
I was really looking forward to building this amp with a minimal of tubes. The 813 has such incredible drive. However, with much of the aforementioned information I might be better off driving 4-6 KT88 or the outputs in the Mac MC3500. The extremely high voltages and high impedance required for the 813 tube may well overload my knowledge base on this subject.
There is quite a bit of very good useful transformer data on the web with some rather extensive math. I was hoping to find the winding data I needed without engineering the entire output section. I think I have the power transformer part pretty much in hand.
I will continue to research this output transformer construct and see where it leads.

Tad
  Reply With Quote
Old 7th February 2011, 08:25 PM   #14
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
pieter, I generally agree with you - the increased coupling capacitance is a distinct problem. Can you indicate whether your experience relates to very close coupling of the primary wires to the secondaries (as per enamelled wire in a bifilar arrangement)? One benefit of the insulated wire is an increased separation (even though the insulation has a higher permeability). Another possible difference between your experience is the winding configuration - for example, the proposed winding may be done with a trifilar - where 2x insulated primary are wound with 1x secondary - which would nominally halve the coupling capacitance compared to the 1:1 filar arrangement.

Ciao, Tim
  Reply With Quote
Old 7th February 2011, 10:52 PM   #15
diyAudio Member
 
Join Date: May 2005
Location: California
Quote:
Originally Posted by tryonziess View Post
However, with much of the aforementioned information I might be better off driving 4-6 KT88 or the outputs in the Mac MC3500. The extremely high voltages and high impedance required for the 813 tube may well overload my knowledge base on this subject.
Tad
Hey Tad,
I have a pair of McIntosh MC3500 / MI350 output transformers that are just sitting around taking up space. If you are interested, PM me with an offer...
Daniel
  Reply With Quote
Old 7th February 2011, 11:01 PM   #16
diyAudio Member
 
Join Date: Apr 2007
Dan I would very much like to discuss the trannys. I did not see an email for you under your profile. I think I could put together something very close to what I want with that iron. I have no idea what there worth.
Tad
  Reply With Quote
Old 7th February 2011, 11:44 PM   #17
Account disabled at member's request
 
Join Date: Apr 2009
Quote:
Originally Posted by trobbins View Post
One benefit of the insulated wire is an increased separation (even though the insulation has a higher permeability). Another possible difference between your experience is the winding configuration - for example, the proposed winding may be done with a trifilar - where 2x insulated primary are wound with 1x secondary - which would nominally halve the coupling capacitance compared to the 1:1 filar arrangement.Ciao, Tim
Presume we have to wind the 813 output transformer. For this tube in triode 10k4 related to 8 ohms would be a sensible impedance ratio (winding ratio 36:1).
With your proposed trifilar winding configuration using insulated wire we have to wind a stack of 18 layers, whereby all primary windings are connected in series, and all secondary windings are parallel connected. This means we have 17 nodes where capacitive coupling from primary to secondary ground will compromise the HF bandwidth (one of the 18 nodes, B+, will not harm as it sees secondary ground). These 17 nodes are too many for this pretty high impedance application. A 6C33 might get away with this, not the 813.
A transformer like this will show HF loss under 20 kHz (but because of the distributed coupling it will be without HF resonance ).
IMHO the only way to achieve acceptable results is a balanced configuration of primary and secondary sections not based on bifilar or trifilar winding techniques. For high impedance tubes like the 813, but also 845, GM70, 211 and others the number of sections will be less than for tubes like 2A3, 300B with Rp under 1k.
  Reply With Quote
Old 8th February 2011, 12:54 AM   #18
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
It is worthwhile attempting to clarify the capacitive coupling comparison - in a very simple way - for a better understanding and insight.

A filar winding configuration would have each turn of the primary effectively placed next to the same wire 'length' of secondary (both sides of secondary wire would see a primary wire. Each layer could be wound so that secondaries are positioned directly above each other to minimise intra-layer coupling (simple view only).

A layer winding configuration (Interleaved secondary between two sections of primary)would have each secondary turn next to primary (under and over layers) with an effective length of the secondary wire.

A very simplisitc comparison would see that the interleaved layer configuration would have 1/18 the capacitive coupling (using Pieter's 18 layer example), which would then be about 1/4 the high frequency bandwidth. Of course layer insulation distance etc, etc all contribute to making a comparison not so simple.

The only simple way to improve the filar config (as I see it), would be to use say four or eight insulated primary wires to each secondary wire - on each layer - the separate primary windings would then be connected in series. Then it is back to the old juggling competition.

Ciao, Tim
  Reply With Quote
Old 8th February 2011, 01:45 AM   #19
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
It seems to me that using similar insulation thickness on the secondary wire (relative to interlayer insulation), with multifilared primary wires enclosed around it, can be made equivalent in distributed capacitance to the conventional layered insulation approach.

But the leakage inductance needs to be looked at carefully then. The secondary wire has a short local magnetic leakage path around thru the thick wire insulation. The conventional layered approach has the wires snugged together for each layer so that magnetic leakage pathes have to travel the length of the layer. This makes for long magnetic path length with low leakage inductance. With a long E lamination this can be further lengthened until the leakage path is nearly the same length as thru the lamination, so most flux will stay in the lamination where it is wanted.

The bifilar or multi-filar approach seems only useful to me if the windings have similar AC and DC structure so that the insulation can be kept to a minimum. Only way around would be to use common mode inter-connect chokes on each of the multi-filar windings so that they can be common moded in the layup. This would really eat up the winding space then for the common mode choke windings. And a much higher resistance total too.
__________________
"Most Universes are not quite parallel."

Last edited by smoking-amp; 8th February 2011 at 01:50 AM.
  Reply With Quote
Old 8th February 2011, 02:04 AM   #20
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Agreed smoky. 'Robbing Peter to pay Paul' seems appropriate.

It's worth a review sometimes - old ways and new materials.
  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
DIY build sound better than a good commercial design in a side-by-side comparison? smellygas Multi-Way 66 25th November 2009 09:26 PM
My GC is up and running, side by side with P3A Jean Chip Amps 2 21st July 2004 11:38 AM
Low side driver as a High side fr0st Parts 0 8th May 2004 03:14 PM
Side fire sub, how close can magnet be to side? tim_rule Multi-Way 2 2nd February 2003 09:22 PM


New To Site? Need Help?

All times are GMT. The time now is 06:43 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