tweeter attenuator transformer

Mids highs attenuator transformer - useful tool for final tuning of mids and tweeter to match listening room conditions, seating distance, and woofer / mids / highs volume level. It can be useful during crossover design phase too, to try with different attenuator taps / levels before deciding on the final attenuation levels. 

For those speakers with bi-wire or tri-wire connections, one can even use this to attenuate or boost the mids and highs if one feels that the highs / mids / bass levels are mismatched with their listening room or listening taste. 

100W Transformer Attenuator

Tweeter attenuator transformer

Attenuator / booster transformer

Tango has made some in the past, model Tango SA-300. 

For ours, we can custom it from 30W to 300W, or even 1KW if required. Pictured above are the 100W version, with total DCR of about 4 Ohm end-to-end, 11-steps at 2dB per step. Other configurations can be made per customer requirements. 

Users can choose the output format (potted, bare frame, stand), cores (Hi-B, Amorphous, Permalloy, NanoCrystalline), wires (OFC, OCC Cu, OCC Ag), taps (10-step to 33-step), power (10W - 1KW), and anything that the user needs.

Applications #1 - attenuate
- connect two ends to amplifier output
- connect the middle steps and return step to the mid/tweeter
- choose the steps to select attenuation levels

Applications #2 - boost 
- connect mid step and return to amplifier output
- connect the higher steps and return step to the mid/tweeter 

- choose the steps to select boost levels

Reference prices for mid/tweeter attenuator transformer: 

30W version
- OFC - U$150/pc 
- OCC Ag - U$490/pc
- OCC Cu - U$260/pc
- Amorphous / Permalloy / NanoC core upgrade +U$50/pc
- other parameters, please email

100W version
- OFC - U$260/pc
- bare frame 
- other versions, please email

* 10 step at 2dB/step (other steps quantity and step size can be made) 
* Potting adds U$30/pc.
* 200Hz and above (mid-high use only)
* Full frequency range unit can be made too 

For bare version, we can only use OFC magnet wire with adhesive property to ensure the wires stay aligned and together during and after winding. For other type of wire, those without adhesive properties, they need to be potted to ensure the coils do not move around. 

For full range version, also known as unity-coupled-transformer, it can be made too. These transformers are used for speaker impedance matching purposes, as well as to gain some "tube sound" by using it as "output transformer" in solid state amplifiers. 

One can connect the amplifier to the 8 Ohm tap, and the right output impedance is chosen to match the speaker impedance. These are useful to drive low impedance speakers, or difficult speakers that have huge dips in the impedance. Or, if one is using 16 Ohm or 4 Ohm speakers, and only have 8 Ohm output tap at the output transformer, they can connect the amplifier to 8 Ohm tap, and use the 16 Ohm or 4 Ohm tap to connect to the speakers.

Tips:
1. If attenuation can be done earlier at the signal chain, do it earlier, such as attenuate the signal at the source (DAC output) rather than at the destination (amplifier output). In such application, TVC (transformer volume control) can be used. 
2. Transformer coupling is better sounding that Autoformer coupling (our findings), YMMV though. Experiment and find out yourself which is better in your application or taste. 
3. Fixed attenuation with single tap will be better than multi-tapped autoformer/transformer. Simpler is better - this rule does not change. Multi-tapped autoformer/transformer offers the flexibility for tuning or matching on-the-fly. This will be good during designing, experimenting, or tuning phase, or even for users that try to tune the system for different type of music / speakers / rooms / taste. Single tap transformer/autoformer could not be as flexible. 


J&K Audio Design
9/28/2019

Voicing of output transformers

Howdy everyone! 

After repairing and measuring sooooooo... many vintage and modern output transformers from no-name to legendary brands, we've had a good grasp on how they voice the output transformers, from the materials used, winding techniques, etc... to the sizing of cores.

If you're going after a certain tone, you can let us know and we can wind towards that. Else, we will do the best for each level (Level 0 to Level 3) of grading for our transformers, using the wide bandwidth winding method, with sufficient dynamic headroom for all sorts of music, including faithful 20Hz reproductions. 

Our Level 2-3 output transformers are usually specified to ~10Hz @ -3dB region (or lower if required or paid for), and therefore anything at 20Hz is of no issues at all. We're not that worried on the high frequency response side as that's something easily manageable and easily achievable. We'd tend to just limit it at ~60k-75kHz to avoid unnecessary side effects but if one still want 100kHz, just let us know. 

Just a refresher to all perhaps, we do offer OCC Cu, OCC Ag magnet wire transformers now, that we previously do not (maybe 2 years ago), due to the wire price, amount of orders and scarcity of such materials. Now, we can say that they're pretty common. 

On the other hand, we have to keep the transformer repair price to at least U$200/pc and above. The amount of work involved are just too labor intensive and charging below that is just PAYING YOU TO REPAIR FOR YOU.  

Each transformer requires around 1 week to complete. Say if we pay a technician to do so, at U$15/hour for 5 days, that would be whopping U$600 labor charge slapped onto the repair price. You see what we mean now? 

Anyhow, we'd like to thank everyone that supported us so far to lead us till today. You're such a gem! 

And, apologies for those that had hiccups in their projects. We will keep on improving ourselves and keep on serving you guys better.

J&K Audio Design
8/9/2019.