SUPPORT FORUMS FOR ZKITS >> ZKIT 1 Support forum >> Output Transformer Question Please

Message started by Nate on 02/14/19 at 16:03:45

Title: Output Transformer Question Please
Post by Nate on 02/14/19 at 16:03:45

I am a self-taught newbish amp builder and I ordered the board to build the SE amp. I am not the strongest with calculating the specs for a output transformer, so I was wondering if this OT would be an appropriate substitute for the EDCOR units recommended for the build.


SE - 10W
8 K with 40 % UL Tap to 8 & 16 ohms
Frequency Response: 20 Hz to 80 kHz +/- 1 dB @ 1 Watt

Maximum DC Bias Current: 75 mA

Primary DC Resistance: 400 ohm

Primary Inductance: 50 H @ 120 Hz

Many thanks in advance...

Title: Re: Output Transformer Question Please
Post by Steve Deckert on 03/05/19 at 02:36:38

Hello Nate,

Sorry for the delay in seeing this!

Your output transformer would be just fine.  You simply wouldn't use the ultra-linear taps... or you could use them in place of the 1K 2W resistor on each output tube, your choice.


Title: Re: Output Transformer Question Please
Post by Divasson on 03/24/21 at 13:56:13

Hi, when starting to assemble the latest board, I found that there is a PCB hole for the Ultralinear tap.

  • Is it enough to take out the 1k 2W resistors to use it?
  • More important, as I don't dare to tamper much with the configuration: which are the advantages of one vs. the other? Which one sounds better?

Title: Re: Output Transformer Question Please
Post by bobc on 03/26/21 at 16:11:19


Not familiar with the zkit1 board, but in looking at the picture the ul connection points go no where on the board.

To wire this up you can omit the 1k and connect the ul lead to pin 9 on each output tube. Maybe where the resistor would go? I just looked at picture in documentation.

I have used the zkit2 board. They are very well made so you can certainly experiment by soldering in resistor to try each way. Many times if you are careful removing parts.

I put a dpdt switch in my circuit so you can switch to ul mode.

My feeling after listening each way, the ul taps create more power/louder. Using 6n1p output tubes, me experience was that running the tube this way created more “fatigue”. Maybe different with other tubes and systems... I preferred the 1k resistor, no ul tap. It keeps tube in triode mode as I gather.

Hope this helps!

Title: Re: Output Transformer Question Please
Post by Divasson on 03/27/21 at 01:35:26


I’ll keep it simple at the beginning and I’ll trust your advice - keeping it triode. There are already too many variables different from the original - starting with the power and output transformers.

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