The Sebago Sound Ultra-Phonix Mods
'67 BF Bassman Ultraphonix used in the video
What is the Ultra-Phonix all about?
The Ultra-Phonix (UP) mods are typically performed to Fender amps from mid 1960’s to the early 1970’s. The philosophy of the UP mods is, as the name implies, to extract the ultimate sonic qualities from the donor amp. As some have said, “they sound and feel like the best Fender you ever played”, or “they sound like you always wanted your Fender to sound. It's just bigger, rounder, more...”. The amps are amazingly well balanced, rich, warm and full of wonderful second order harmonic content. Until you plug in to one, it might be hard to imagine why or how someone would better a ’67 Blackface Bassman for example. After you’ve played one, it’s hard to imagine why everyone doesn’t do this to his or her amp, it’s that apparent.
It’s difficult to describe in words and hard to tell from a recording what an Ultra-Phonix voicing is all about. What we can say is that an amp with the dynamic personality of a Sebago UP voiced amp will inspire you to express ideas that are not possible with a stock amp, or many expensive boutique amps for that matter. The stock amps just don’t respond to your playing, touch, and pick attack like a Sebago UP voiced amp does. The notes of your instrument through UP amp are incredibly rich in harmonic content which changes over time as the notes decay, allowing you to craft complex soundscapes with just your hands, guitar and amp. Players have remarked that it sounds like they have a mild chorus effect and/or a compressor in front of the amp. Interestingly, it’s the expansion effect of a compressor they are hearing. We’ve heard many players say “I like my amps very open, touch sensitive, and uncompressed”, and the first thing the do is put a compressor in front of the amp! Least you think we’re either lying or crazy, what they are looking for is that sing and sustain that the compressor gives them, not the initial attack suppression or peak limiting. The UP voiced amps have that same feel as if you had a mild compressor in front of the amp. The feel of the amp is most evident when playing two amps side by side, and why recordings of amps can be a bit misleading. It is also why many players think their new Fender amp sounds great, they don’t have a good reference point for what a great amp should really sound, and more importantly, feel like. If they did, Fender would not sell very many new amps.
What is the Ultra-Phonix voicing?
There are a few different voicings depending on the type of amp being used as a donor. The voicing for the Bandmaster and Showman amps are lower gain, somewhat similar to the donor amps original voicing in terms of frequency response, but with a much more Tweed like breakup when pushed. The amps have a different voicing on each channel. One channel is more “bluesy” with more gain and an earlier breakup great for blues or mild classic rock when pushed. The second channel has a bit less gain and more clean headroom, great for jazz and cleaner blues tones. The Tremolo circuit is converted to a bias modulating type which does not load the output of the channel like the original. It’s a very natural sounding effect, with a much wider range of depth and speed than the original as well. It can be used with either channel.
The Bassman UP amp has both a low gain and a high gain channel. The low gain channel is voiced like a Tweed with a nice bluesy breakup when pushed and a very balanced warm attack and feel. The high gain channel is magical. It has a bit Marshall character but without any of the harsh grainy breakup. It’s very smooth and balanced throughout the range of gain settings, and has a very complex harmonic structure that allows notes and chords to feed back at will, all at a volume that won’t get you thrown out of the house or annoy your singer. With the gain control set lower it’s a great jazz-fusion or blues amp. With the gain control set higher it’s a rock and roll machine, great for classic rock tones of almost any sort.
What do you do to the amps?
The goal of the Ultra-Phonix voicing is to make as few changes to the amp as possible. With the exception of the high-gain channel of the Bassman UP amp, the basic topology of the donor amp is maintained. All of the transformers, potentiometers, much of the original wiring and other infrastructure are left unmodified. We prefer to use donors that are as original as possible, but it’s not absolutely necessary and it would be nearly impossible to tell a UP amp that was build from scratch with new components from one that was built with an original Blackface donor. Some of the preamp board components are reused, most are replaced with different types and values. The result is an amplifier that is built the way Fender should be building them today. In stead they are building them like a laptop computer with a resulting lack of personality and character, and it’s up to us to deliver the holy-grail tone at a price you can afford without having to wait two years to get your amp.
A Blackface Bassman ready for the power supply mods. The main circuit board being prepared for mods.
The original Bandmaster shipped with an undersized output transformer that contributes a congested and flabbly low end. The first thing we do to the Bandmasters is upgrade the output transformer with a wonderful sounding '59 Tweed unit from Mercury Magnetics.
How do I get one?
See our "order" page for pricing on the Sebago Ultra Phonix voiced amps.
There are two options available for the UP amps. The first is to order a brand new scratch built amp with your choice of tolex and grill cloth colors and a Mercury Magnetics output transformer. The second option is to find suitable a donor and send that to us for the conversion. The sonic results will be the same either way, but the lead time for a conversion will be a bit less as there are no parts or cabinets to order. It’s best to contact us through our contacts page and arrange to have the donor sent directly to Sebago Sound while placing your order.
