Hi-End eSSB Radio


Anyone who needs to come out with improved audio, broadcast-like sound, knows that they have to use a good microphone, and then add some external audio module such as a microphone preamp, EQs, effects, etc. This is called eSSB, or Hi-Fi Radio.

Critical point

The problem arises when we already have a magnificent studio microphone, several professional audio modules, getting perfect audio, but that audio comes out of professional equipment in a balanced format, usually on XLR connectors, and at +4 dBu level.
Remember that the microphone connection that our radios have, are unbalanced, and the level is around -40 to -50 dBu.
For these reasons, we cannot directly connect this equipment to the radio, it must first be adapted.

The ideal adapter should perform several functions:

  • Transform from balanced to unbalanced
  • Reduce the level from +4 dBu to ±40 dBu
  • Isolate one end from the other, to avoid noise and ground loops

In addition to doing all these functions, you have to do them by introducing the least possible noise, the least possible losses, as well as the least possible distortion.
This is achieved with good electronic design, and using high-quality components, such as those from the world of Hi-Fi and Hi-End.

The Adapter

I've been building these adapters for years, for my personal use, or for some friends.
Step by step I have been perfecting the design, components and improving the final result.

I have recently decided to manufacture and sell the best version of the adapter to anyone who is interested.
I have designed this adapter myself, the circuit, PCB, I have selected the transformer, components, etc. All looking for the highest quality.  
I have called this adapter Golden Máxima.



The transformer is the centerpiece and most important part of the adapter, also the most expensive.
As everything, there are different qualities, from the simplest to the most sophisticated used in Audiophile and the Hi-End world.
I have decided to offer one of the most renowned and high quality transformers on the market. I 'm talking about Lundahl.
Lundahl transformers are the best around since 1958. They are considered Audiophile. They are hand-made in Sweden, and include all possible improvements such as mu-metal boxes, electrostatic shields, galvanic isolation, etc. In this way they offer the least distortion, the lowest losses and the largest protection against external interference.

As I have already mentioned, the transformer is of very high quality, handcrafted here in Europe. It is enclosed in a mu-metal box, in addition the windings are double and symmetrical, both at the input and the output, to increase the immunity to external noise and interference, and at same time, they are separated by electrostatic shields. They also have galvanic isolation. The core is high permeability mu-metal.
Its frequency range reaches 150 KHz, and admidts up to +16dBu input level.
As a detail to comment, even though it is an audio transformer, the windings have an isolation of up to 4,000 volts.



The attenuator network I use is the Bridge-T, since it offers superior performance and quality than the traditional L or Pi.
This attenuator network does not affect the input and output impedances, which is not the case with L or Pi. The components are SMD, metal film, of the highest quality that is available in the market called "Thin Film", which offer a much lower noise than carbon, they are also the best recognized brands for high fidelity audio such as Vishay, TDK, etc.


Output Capacitor

The electrolytic output capacitor is responsible for giving the sound the final quality punch just before the output. For this reason this component is crucial.
As with the rest of the components, here we are also going to use a special capacitor, made specifically for audio in Hi-End equipment.
We are talking about the Nichicon Fine Gold capacitor.
As I said, this capacitor is specifically created for Hi-End audio, offering a rich sound in the bass register and clearer high end. His response enhances low-level passages offering an incomparable response, beyond the reach of normal electrolytic capacitors.



The XLR input connector is Neutrik, also made in Europe and considered one of the best on the market. The contacts are made of gold-plated bronze, and are soldered directly to the PCB, to improve conductivity and reduce losses. It has good protection against RF interference with the three shielded contacts, with nickel housing, zinc plated.



The case is made of aluminum, which increases the protection against external interference, much better than the plastic ones.
It can be opened for maintenance, or to access the circuit.
The box is topped with a high-resolution color screen-printed aluminum plate, where the logo with the name is displayed, all in black and gold tones, of great beauty and elegance.


PCB Board

PCB is FR4 1.6mm, with 1mm wide double-sided tracks and silkscreen printing with a matte black background and white text.
Although it does not affect the sound, I tried to give it certain beauty finish.
The final design, in addition to being effective, is very elegant.


Pad jumper

Looking always to improve, I have recently added an internal jumper to select between 17dB or 40dB positions.
17dB position is good for rear ACC/Data input. Output level is around -17dBu or 100mV RMS
40dB position is good for front MIC input. Output level is around -40dBu or 7.0mV RMS
This way, you get flexibility to configurate the box for either audio input.


Bespoke Cable

I offer a couple of custom cables to connect the Golden Maxima to your radio.
Radio´s connector could be standard 8-Pin front MIC connector, or rear ACC/Data input DIN, jack or RCA plugs.
If you have a RJ45 MIC connector, I can provide you the cable ended with jack, to use it with available RJ45 to jack PTT+MIC adaptors (not provided by me).
There are two cable options; Professional Tour grade, or Limited Edition Golden Cable.
Limited Edition Golden Cable got gold braid and gold connectors too, making it the perfect combination to your Golden Maxima. Moreover the great audio, you get an exclusive touch of style and luxury.


Opening the box

1. - Remove four bolts, top two bolts from each side, as seen in next photos:
2. - Lift the top cover to access inside the box.
3. - Place the jumper in the required position.
4. - Place the top cover back in place and tight all four bolts back in place.


Bandwidth Test



As you can see, I have tried to get the best design, using the best components, trying everything to reach the radio with the highest audio quality.
There is nothing comparable to this quality in the ham market.


PDF Document

Golden Maxima


User reviews

Call Comments
"Yes, it looks more crystal clear!
It has improved the sharpness!
I have tried it and sounds great!
RFI in 28 Mhz with amplifier has disappeared."
José "El Solitario"
“Crystal clear transformation without affecting or manipulating audio quality,
0% RFI with 1KW in TX.
The Golden Maxima is the best I have tried in the station so far.
Thanks Máximo 73's from KG5UHS.“
“It works well and does not cut the frequencies 👌👌"
“This box is very transparent, sounds same as last audio module output.
Not every box performs that good.
Big surprise how good is audio quality, with no colour at all."
“Very easy to use, and works flawless.
Impedance adaptation is perfect.
Very high quality at an affordable price.>
“I did some testing between a W2IHY iBox and yours, yours is much cleaner with a flatter frequency response when I sweep it with my signal gen.
I was very impressed how clean the waveforms were, square, ramp and sine wave, made nice sine waves down to 4Hz!
The Golden Maxima blew away the iBox, but the transformer is not in the same league.
I can honestly hear my TX audio is cleaner via some Web SDR recordings and comparison.
“Taken delivery of the transformer today.
I have wired the output as advised by you and everything is working 100% with no RF issues at all with the amp on 20 mtrs 400w.
The audio sounds much smoother and I had to adjust the EQ curve a little, mainly on the low frequency.
I'm very pleased and would like to say thank you for the great communications regarding wiring, I appreciate it very much.
I will let other friends know how good this transformer is and the excellent build quality.
Take care and again, thank you.
Kind regards John G0TIY
“Hello Max I have had the Maxima for about a week.
In my opinion the Maxima works great as a stand alone, meaning go from the Mic to the Maxima then to the radio.
What you will observe is how clean the signal is to the radio, no noise hum or artifact.
Now the good part.
You can hit the Golden Maxima with a lot of signal because the transformer loves it.
The lows are lower with such warmth and clarity the mids and the highs are delightful.
73 Tony K7AO"


The price of the Golden Maxima is £150 GBP / €180 EUR / $190 USD.
Shipping £15 GBP / €16 EUR / $19 USD
The price of the standard cable with connectors is £15 GBP / €17 EUR / $20 USD.
The price of the Limited Edition Golden Cable with connectors is £40 GBP / €46 EUR / $49 USD.  
Then you can pay with Paypal, Wire transfer, or contact me; EA1DDO@HoTMaiL.com



Golden Máxima + S/H.................

Standard cable............................

Limited Edition Golden Cable......


Wire Transfer

Following bank account is multi-currency, it admits € Euros, £ Pounds or $ Dollars..

IBAN: GB10REVO00997054077105