Jump to content

Output Transformer Secondary Impedance for Forte 1


Recommended Posts

I'm about to upgrade the output transformers on a couple of single ended amps I have built.  One is a 6V6 and the other is an el84 both triode strapped.  Both are using budget Edcor transformers with an 8 ohm secondary only.  The input terminals on the Forte's say 4 ohm but the original Klipsch spec sheet says the nominal impedance is 8 ohms.  Some guy on another forum says that's because many solid state amps only had an 8 ohm tap.  Before I buy a pair of more expensive output transformers I'd like to know I've selected the best sounding secondary impedance.  Does anyone have any experience with the Forte 1 in this regard?  Perhaps the only way to know is to purchase transformers with multiple output impedances but the only ones I know of I could possibly afford are the higher end Hammond transformers and I'm hoping not to spend that much money being an old retired guy.  I must say the Forte's  sound good on the current 8 ohm tap even with the cheapo output transformers.  

Link to comment
Share on other sites

If you're running in Triode mode, the amplifier is a lot less sensitive to speaker impedance variation than a Pentode amp. 

That said, higher level Edcor stuff has a great reputation.  That said, if it sounds good enough as-is, why change?  ;) 

  • Like 1
Link to comment
Share on other sites

Having used both Edcor and Hammonds transformers I would not say one is better than the other. They both build and sell great transformers. Hammond gets my nod now because I do not have the patience to wait a few weeks for Edcor to build them. The drawback is to look nice, IMHO, the Hammonds need to be placed underneath the chassis. That being said many do not and I personally have no problem with them being placed on top. 

Link to comment
Share on other sites

As was stated above by DE, speaker impedance is not an issue for SETs.  If you use an opt tap corresponding to the lowest impedance of the speaker, distortion will decrease as the impedance rises.  I believe Edcor’s bandwidth ratings are at 1 watt whereas Hammond’s are at full rated power.  If used well below that, the Hammonds are capable of amazing bandwidth.  See George Anderson’s measurement of the 125CSE:





  • Like 3
Link to comment
Share on other sites

  • 3 months later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...