Integrated HiFi restoration

Taking a little break from the valve world, this wonderfully sounding SANSUI AU-7700 came in for recapping and restoration work.


Capacitors by Nichicon from the ‘Gold Tune’ and ‘Muse’ series were ordered and  installed, replacing the old ones that were giving breath to the amplifier since the mid-70s.


The broken Headphones jack was replaced with an Amphenol stereo jack, and a three-prong power cord was also installed grounding the chassis, conforming to modern Safety Regulations and protecting the user in the rare case a live component should touch the chassis.


After putting the unit back together, it was then tested with a pair of Wharfedale Diamond 225s filling the room with jaw-dropping depth, fidelity and dynamics! One can only imagine the quality and dynamics after the caps are properly broken-in.

Needless to say, this is one unit that has been an example since its release back in the Seventies, where even nowadays it is being used as a reference in recording studios. 


Repairing a Vibrolux Reverb…

This old vintage Fender amp had noise issues and old capacitors that had to be replaced.
Redesigning the bias section by adding one filtering stage as well as recapping all electrolytics eliminated the noise issues and all voltages came up to factory values.

Here is the edited video, audio recorded and edited in Ardour and video done in Cinelerra-CV.


“Shields!… Power up!”

That’s what the in-game voice in Project X would say when you would choose to upgrade your shields… But…wait a minute! There were no shields in Project X! Oh, heck, anyway…

I took the chance to celebrate this year’s Midsummer by giving a present to my guitar, namely shielding the electronics with aluminium tape. Now it’s much quieter with less hum when having coil-tapped the pickups. Here are some pics!

Guitar shielding.

Guitar shielding.


Guitar shielding from another angle.

Guitar shielding from another angle.

Neat, huh? 🙂

UPDATE: I am posting the materials needed as well as some tips should anyone wishes to do this.
So, first of all here in this picture are the necessary things you need:
I’ve seen  copper tapes somewhere on the net, although they are a bit more expensive. People on many guitar forums state, though, that aluminium is better at shielding against noise from fluorescent lamps.
Anyway, whatever tape you are planning on buying, make sure that the adhesive on the back is conductive, i.e. it can transfer electricity. Having a Digital Multi Meter handy when going to the store is always good to check this. If your tape does not have a conductive adhesive, it is a good idea to solder the foils together (or spill some solder, if you use aluminium, since it won’t solder).

Some tips on applying the tape to the guitar cavities:

  • Plan your steps on where to apply the foil. You will want to enclose everything inside the foil, making this way an effective Faraday cage. That means the guitar cavities as well as the backside of the pickguard.
  • Go slow and carefully. Doing this fast will result in sloppy results that won’t work properly. It took me approximately
    4 hours to do this, having breaks when I felt I couldn’t concentrate. Knowing your own limits and taking a break whenever necessary without rushing things is wise!
  • Press firmly when applying each piece. Some times it felt that a piece would slide when on top of another piece. If this happens, discard the top piece and just cut another.

Well, that’s it. Good luck and drop a comment with feedback if you feel like it! 🙂

Project: Serenity Part 5

Back to part 4

Serenity is now complete, after 3 years of R & D. I know it’s a lot of time but life has its ways of getting in the way…
Anyways, on with the review!

Serenity in the great outdoors.

Serenity in the great outdoors.

This amp has been my testbed for all these years. High-gain designs are so difficult becouse you have to have large chassis and be very careful with the topology and grounding. Needless to say, I am very happy with the result in this not-so-big chassis. Shielding all signal cables was a must and, although tedious, it was sure as hell worth the effort and time.


As loud as a whisper…

One of the final modifications I installed in this baby was the Power Scaling mod by London Power. After I installed it and played, I realized that this thing should be in every high-powered amp out there by any player that values his/her hearing health and his/her music. Hell, I could even play at 2 in the morning having a great sound at such a low level that my guitar’s strings were more audible.

Of course, the speaker has to be low power for the best results in such low volumes, high rating devices can sound a bit sour. Yet, it is always safer having a speaker whose power rating matches that of the amp (actually double the amp’s power rating), just in case you forget and turn up the power settings into Party Mode. 🙂

Power scaling mod

The two pots controlling the power scaling mod

The two pots have to be turned in unison for maintaining the same tone with the power variance, but having the ‘OUTPUT’ pot at, say, 12 o’ clock, I could use the ‘COMP’ pot from 12 o’ clock down to 7 o’ clock using it as a Master Volume with great results! One would wonder why not put both controls in a dual pot, but the ‘COMP’ pot is actually a dual pot.

Kevin O’ Connor himself helped me out whenever I needed assistance, so kudos and many thanks to him!
For more info on the Power Scaling mods you can visit this page.


Other Features…

Overall, Serenity is a 0-50W variable-power, switchable-gain, 2-channel amplifier.

Other features include:

– Point-to-point construction.
– Adjustable bias knobs with sensing nodes for each output valve
– Feedback and individual preamp stage switches for accessing a wide palette of
gain levels various playing styles and musical genres.
– All-tube FX loop with adjustable SEND and RETURN pots.
– Foot-switchable channels
– Power-Scaling variable power circuit with adjustable pots that vary the output down to 0 Watts while maintaining the same tone and response.
– Engraved and painted aluminium front and back panels.

Serenity's backplate.

Serenity’s backplate.

Individual Bias adjustment pots, a.k.a. yet another ‘Must’…

No more need in buying matched tubes, this feature not only compensates for that but it lets you recalibrate the valves over time easily, only with the help of a Digital Multimeter, since each valve is unique and ages at a different rate. Plus, you can use different types of tubes with interesting results… if you know what you are doing, that is!

Another detail of the backplate.

Another detail of the backplate.

In the coming days I hope to find the time to record some clips. So stay tuned and
thanks for reading. Catch you later!


1×10 Detuned Guitar cabinet

The newest of my creations. Built following instructions found in London Power’s Speaker Book, this ‘small’ cabinet is a true beast, debunking once more the 4×12 cab myths about loudness etc. Its design allows for clever placing anywhere inside the room, while at the same tine the lower detuned port allows the speaker’s full range of frequencies to escape. It really gives the feeling of a more wide angle of dispersion, which helps the player a lot.

Detuned 1x10 cabinet

Detuned 1×10 cabinet

It’s built with 19mm thick MDF, the speaker element itself being a Celestion Vintage 10″ rated at 60W. The grille cloth (see next picture) is made retractable using black velcro.

As you can see from the picture above, there are 2 parallel input jacks on the left of the speaker, as opposed to the norm where the jacks are situated on the back cover. This is because this particular speaker is part of my gear and it will be sitting in front of me, facing towards my direction. But more on this later…


Sound samples are on the way!…

Formyx F10 Isolation Cabinet

A smaller re-incarnation of the F12, the F10 isolation cabinet had 2 XLR lines and a speaker line, but without the confort of placing the speaker at different angles. There was the possibility of moving the mics around a bit but that was all.
This cab was also used at a live concert with success, however.
Formyx F10 Isolation cabinet

Formyx F12 Isolation cabinet

Some years ago I started experimenting with isolation boxes. The first one I made was made of cheap wood and stone fiber. Inside it was a 12″ cab with a Jensen 100W speaker. Having an SM57 inside I could record at full power, yet the bass frequencies coming out from that box were audible, although not that much. Having the box at the balcony I could only listen a hum from it while listening to what the mic inside it was ‘hearing’ through my monitors.
That iso-box saw live action when I played live with my band, ‘Anelixis’, back in 2005. I had used a powered monitor as a stage speaker and a Marshall 50W… I can’t remember the model, though…

Since that iso-box had inherent design problems (sound isolation problems and static waves) I built a second one, this time using plywood, gypsum blocks, stone fiber and an auralex-type foil. This is the result:

Formyx F12 Iso-cabinet


Its weight was approximately 80kg. Its’ drawback was still the static waves… Yet with careful mic or speaker placement you could easily counter their effect. (You see, when you build stuff like that, you have to have the opposite walls not parallel to each other). I learnt that the hard way, but it was fun!
This box had 2 XLR lines built-in and a speaker cable line.

Here is another pic with a sketchy 10″ speaker inside. The space was enough for various mic placements :
Formyx F12 Isocab close-up

4 x 12″ Detuned guitar cabinet

This is a 4×12″ detuned cabinet I built back in 2008 for Christoforos Gorantwnakis. On top is the Formyx 5W Blues Head.
The speakers are Celestions, 2 x G12 Vintage 30 @ 60W and 2 x G12K @ 100 Watts. Pay attention to the HUGE port on the lower side of the cab.

Formyx 4x12 cabinet

That beast’s sound was terrifying!!!!

And here it is from the side.

Unfortunately there was no recording device at home available….

The amp that started it all…


Formyx 5W Blues head

The first amp I made, a 5W Single-Ended guitar amplifier.

2 Gain stages, 1x 12AX7, 1x 12AT7 for the FX loop, 1x 6V6 or 1xEL84 at the power stage.
Steel chassis enclosed in a magnetic confinement cage at the inside of the wooden outfit.

Formyx 5W Blues Amp with its 1x12 cabinet
Here it is with her dedicated cabinet, a ‘detuned design’ 1×10 cab a la London Power, in the same wooden finish. The speaker is a Celestion G10 Vintage at 60W.

The picture was taken at  Music Station  musical instrument store in Patras, during the time I was working there as a salesman at the Soundcard/Music Literature Dept, sometimes lending a hand at the Instrument Repairs Dept.

Some imperfections and “injuries” are visible on the wood due to live concert usage! 🙂
A great amp for playing the Blues/Hard rock at home or at small venues. You may need to mic it  to a monitor for listening to it through the drums!!! 🙂

Project: Serenity – part 4

Back to part 3

Here is what it looks like when it’s almost done:

Next we will be powering up the amp and playing some riffs just to see how it rocks. I will be making some cool audio files as well, so stay tuned!

Click to continue to part 5