Interstage Transformer for Experimentation : Hammond 560L - 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 3rd January 2004, 01:41 PM   #1
diyAudio Member
 
Join Date: Dec 2003
Location: Midwest
Default Interstage Transformer for Experimentation : Hammond 560L

Iím working on an experimental driver stage, and I donít want to lay out the cash for really nice coupling transformers.

I found to transformers that cost about $50: the broadcast-quality Hammond 560L (http://www.hammondmfg.com/560.htm) and the Lundahl LL1544a (http://www.lundahl.se/pdfs/datash/1544a.pdf). However, Iím a bit confused by the ratings.

The Hammond 560L is rated Maximum power level 0 dbm. The Lundahl 560L is rated 22dBU. I need 10V peak-to-peak at the output of this transformer at 300 Ohms (therefore the input will be around 40V peak-to-peak). Output power = (10^2)/300 = 333mW.

So will either of these transformers work?
  Reply With Quote
Old 3rd January 2004, 11:09 PM   #2
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default Yer what?

0dBm = 1mW into 600R. 0dBu = 775mV(RMS), which is the same voltage, but doesn't specify an impedance.

The short answer is, no, those transformers won't work. The Lundahl is specified for a high impedance load (allowing the high dBu rating). What on earth imposes a 300R load?

PS 10Vpk-pk = 41.66mW across 300R
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 3rd January 2004, 11:11 PM   #3
diyAudio Member
 
Join Date: Dec 2003
Location: Midwest
The input impedance of a big MOSFET of a Zen amp.
  Reply With Quote
Old 3rd January 2004, 11:31 PM   #4
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default Oh dear...

Power MOSFETs have huge input capacitance. Transformers hate shunt capacitance.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 3rd January 2004, 11:44 PM   #5
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Transformers hate shunt capacitance.
They do....Deep, deep sigh...

Considering a sabatical year..............

The BS I see....

Guess eveyone's a qualifried enginebeer nowadayys???

Lord...

Pfffffffffft....

Cheers,
__________________
Frank
  Reply With Quote
Old 4th January 2004, 12:17 AM   #6
grataku is offline grataku  United States
diyAudio Member
 
Join Date: Dec 2000
Location: -
Give the guy a break, driving a mosfet with an interstage is not totally unheard of:

http://www.wdehaan.demon.nl/5687_2.html
  Reply With Quote
Old 4th January 2004, 12:22 AM   #7
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Give the guy a break, driving a mosfet with an interstage is not totally unheard of:
Think I don't know that?

Come'on...

Clevor Trevor's smarter than that P. What drives C? C!

Cheers,
__________________
Frank
  Reply With Quote
Old 4th January 2004, 03:12 AM   #8
diyAudio Member
 
Join Date: Dec 2003
Location: Midwest
Looking at the Lundahl LL1544a datasheet, it is rated for 10 kOhm on the primary and 600 Ohms on the secondary (using 4:1 connection).

This seems like the transformer was designed to drive low impedances with the secondary. Using a triode on the primary (10 kOhm), the secondary should be able to drive the input of a Zen.

Iíve messed with the Zen design a bit Ė changed it to source follower configuration Ė and raised the input impedance. However, the gate capacitance issue still exists.

The gate capacitance of the MOSFET is within the specs given on the datasheet (470pF using the 1:1 connection ratio). The 4:1 connection ratio should allow for much more capacitance.
  Reply With Quote
Old 4th January 2004, 03:36 AM   #9
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Iíve messed with the Zen design a bit Ė changed it to source follower configuration Ė and raised the input impedance. However, the gate capacitance issue still exists.
When people start talking SS lingo I'm at a loss, just second guessing what they mean...

I can only suppose the same is true the other way around....Errr, I secretely hope so...

Also, I do get the impression SS'anders have a tendency to complicate where pedestrian simplicity could do just the same?

Cheers,
__________________
Frank
  Reply With Quote
Old 4th January 2004, 12:56 PM   #10
diyAudio Member
 
Join Date: Dec 2003
Location: Midwest
Default This should be simple enough ...

Here's what I'm talking about.

http://www.diyaudio.com/forums/showt...655#post294655
  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
interstage transformer effindi Tubes / Valves 8 10th November 2009 12:51 PM
Interstage transformer for PI. jane Tubes / Valves 4 31st December 2005 06:04 PM
Interstage transformer as OPT? needtubes Tubes / Valves 10 14th March 2005 10:46 PM
Interstage Transformer Nomenclature TerribleT Tubes / Valves 20 16th January 2005 09:04 PM
Hammond 850Q Interstage? Joel Tubes / Valves 10 31st October 2002 08:43 PM


New To Site? Need Help?

All times are GMT. The time now is 06:03 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