Running 4 ohm speakers with my Simple SE - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 18th July 2009, 03:23 PM   #1
diyAudio Member
 
Coreyk78's Avatar
 
Join Date: Sep 2008
Location: Farmington, MN
Default Running 4 ohm speakers with my Simple SE

Hello all,
I have a Simple SE that I built a few months back and I have been very happy with.

Currently I am using some Edcor GXSE 15-8-5k OPT in triode mode and they seem to work great running the 8 ohm and 6 ohm speakers that I have.

However, I've started gathering parts to build a pair of Zaph BAMTM speakers which are a solid 4 ohm speaker, so I'm thinking of changing my OPTs for something that can better handle a 4 ohm load. Here are my questions:

1. What would happen if I tried running 4 ohm speakers with what I have now?

2. If I switch to transformers that have a 4 ohm secondary, like some big Edcor CXSE 25-4-5k will I have weak power output into 8 ohm speakers?

3. I know the Hammond 1628SEA has multiple taps for different speaker impedance, which would be nice for me, but they are kind of expensive for my budget. Anyone know of a cheaper option?

Thanks for any help, its probably obvious by my questions that I don't really understand how output xformers work, I've just been following other's recommendations on here, hehe.
  Reply With Quote
Old 18th July 2009, 08:10 PM   #2
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
Hi.

Edcore does custom power transformers at a reasonable cost. Maybe the would make you an output with a 4 ohm tap as well?

Rolf.
  Reply With Quote
Old 19th July 2009, 01:37 AM   #3
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Default I don't think it will burst into flames, but...

Hooking up 4 ohm speakers to your 8 ohm taps will half the primary impedance of your transformer from 5K to 2.5K. If you look at the "tubes and transformers" page on Tubelab George's website, the tables show simulations with 5K, 3K loads for the tubes. Notice at high B+ and 3K loads, most of the tubes are exceeding their dissipation limits as shown by the red font.

So your 2.5K load is a little less than a 3K load.........

So running 4 ohm speakers on your 8 ohm taps is certainly do-able with a low enough B+ voltage, resulting in a little more power out and a little more distortion, depending on the B+, tube, and load impedance.

For question #2, yes, the power into 8 ohm speakers on the 4 ohm taps would be reduced, since the transformer primary would effectively be 10K (5K x 2)
  Reply With Quote
Old 19th July 2009, 01:57 AM   #4
diyAudio Member
 
Coreyk78's Avatar
 
Join Date: Sep 2008
Location: Farmington, MN
Well following the chart, it looks like I can get away with using my current transformers. I have a pair of chinese 6L6GCs right now, and 620 ohm bias resistors so it looks like it should be borderline ok with a GZ34 rectifier, otherwise I have some other rectifier tubes to drop the B+. And I have been looking at trying some KT88s and it would be more than safe with those tubes.

Thanks for pointing me in the right direction boywonder!
  Reply With Quote
Old 19th July 2009, 02:23 AM   #5
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Speaker impedance curves are anything but flat, and vacuum tubes are very forgiving with respect to specification tolerances. In other words, it'll probably be just fine and in all likelihood you won't even be able to hear the difference.

The transformer is mostly just a ratio device. With regards to impedance ratio, a 5K:8 transformer is the same as a 2.5K:4. The ratio of the number of turns on the primary winding to the number of turns on the secondary winding will be the same. Look at the datasheets, examine the plate curves. Figure out where your loadline will be at the equivalent load and decide if you are happy with it. The general guideline is that higher loads give less distortion, and lower loads can extract more power.

I did say the transformer was mostly a ratio device. There's also an inductance component (good thing) and a DC resistance component (necessary evil). To get more inductance, you need more turns (and possibly a bigger core). But, as you add turns you increase the DC resistance. More inductance gives better low frequency response. Higher DC resistance robs power and reduces efficiency. There's also things I don't understand, like leakage inductance and shunt capacitance.

At a relatively high impedance, you need less primary inductance to get a desired low frequency response. I think the formula is Fo = Z / (2 * pi * L). If you use an output transformer with sufficient inductance to achieve the desired low frequency response at a high impedance load, it should have more than enough inductance at a lower load. In other words, the low frequency response will be even better. The cost is additional dB of insertion loss from the many turns in the winding. Yet another way of saying things is that output transformers "ratio down" relatively well, maintaining (nay, improving!) their low frequency response in exchange for a small loss in power. On the other hand, they don't "ratio up" as nicely, potentially losing precious Hz of response on the bottom end due to insufficient inductance.
  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
Yaqin VK-2100 hybrid running 4 ohm speakers Rockmore Tubes / Valves 2 9th April 2012 01:55 PM
Running a passive sub with main speakers off an integrated amp! Village Plank Subwoofers 5 28th January 2009 02:10 AM
What advantages running ported midbass if you are running a sub? mitchyz250f Multi-Way 3 20th May 2008 02:34 PM
Simple, SIMPLE Digital volume control -_nando-_ Digital Source 5 21st December 2006 01:20 PM
new to this need major help building simple speakers newtothis Full Range 7 2nd September 2005 06:41 PM


New To Site? Need Help?

All times are GMT. The time now is 03:19 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki