The Quest for the "Sound"!

6/2014

Awhile back I was looking into the "Brian May sound" and how it came about. As you know, John Deacon made the infamous 'Deacy' amp from electronics salvaged from a discarded radio/phonograph. With this in mind, I wondered if other old amplified electronics could produce this or a similar sounding likeness. Well this is going to be an adventure into the vintage era of electronics.

The Circuit

After studying the circuit designs from many online references and forums, it appears that this was the most common of the designs:

The circuit generally consisted of 4 Germanium transistors (PNP) and 2 transformers (driver and output).For more details on this circuit, see the Mullard Reference Manual of Transistor Circuits (page 168). You can actually find it online!

The Radio Hack....oh,no!

My first quest took me to an old 1960's transistor radio I got from Ebay (~$12). Initially I thought this would require a bit of circuit tracing to bypass the RF and IF circuitry but in the end, it was simpler than thought. After a few visits to some internet sites where radios were hacked into guitar amps, I read that the volume control section is actually the input to the amplifier circuit. In my application the idea is to remove the combination volume/on-off control and replace it with suitable, separate controls along with a bigger speaker. Once completed, all items will then be rehoused. 

Here's some photos of the transistor radio that I elected to use:

So what does the rehouse look like and how's it sound? Stay tuned...too many projects in progress. I have my doubts that this may not produce that "sound" but anything is possible.

(A note for me: Dude...some pix and clips please!)

Vintage Guitar Amps....???

My next quest was to head down the complex road of portable phonographs and other combination electronics with amplifier type circuits. It did not take me long to realize that finding these devices on Craigslist or garage sales was time consuming and tedious to work with. Even worse was the time spent on Ebay searching for these items and realizing the vintage/antiquity prices were off the scale.....especially when you're going to rip it apart for its electronics. 

So I thought about it a while....what early 1960's device would only use an amplifier circuit? Obviously an instrument amplifier like an old Kay guitar amp (model 700 type) which has a similar circuit design. I actually found one on Ebay that was working but in need of some exterior maintenance/restoration. Once completed, I powered it on and well......needless to say the sound was not as expected. It was just too clean and did not have that 'sound'. I suspect that this was due to the higher wattage rating of the amp (10w) where the Deacy amp was less than 1 watt. If I'm not mistaken, it was in the milliwatts range. Well at least I now own a piece of early solid state amplification history.

(A note for me: Dude...clips please!)


While along the same route, I have heard that early Pignose 7-100 amps were capable of attaining the "sound". I was lucky enough to snag a raggedy looking Pignose 7-100 off of Ebay for under $50. I had to reference some forums on what to look for in regards to the early models....Red/Blue/Silver sticker (which mine is missing), the Patent Pending label, darker color housing, etc.. After some internal cleaning, wire repairs, and external restoration, hooked up the guitar and turned on the power. I was surprised to hear sound coming from it. The amp does have the potential but I think it is still too high in wattage. It does sound great though!!! 

(A note for me: Dude...some pix and clips please!)



Then there's the Vox Brian May Special.... not so vintage and although it doesn't have the original 'Deacy' type circuit design, it was designed and built to sound like a the 'Deacy'. I have to say this nails "the sound" in certain instances (the Brian May settings defined in the manual). It's got a lot of little extras built in like the Treble Booster with Output and extra gain button, headphone/recording out jack, and an external speaker out jack. It's too bad they discontinued this model as I like it a lot. Being that I got this used (~$80), it's got some kind of noise that emanates in the background which could be due to:

• bad grounding
• malfunctioning filter caps in the power supply section or
• possibly bad solder joints

This issue will need more investigation and testing. More to come on this....

UPDATE(9/2014): OK so I found the schematic on the web and took it apart to view the component and trace sides of the PCB. Everything looked fine visually on the components and the grounding looked solid as well. I went ahead and touched up some solder joints that looked suspect and likewise re-routed some of the wiring in case noise was being introduced from the default wire routing. Reassembled it and was disappointed to hear that the noise was still there. I also discovered that the Recording/Headphone output was not working. The schematics indicated that the main component it was tied to was an op amp (NJM072DE) that is discontinued. Did my due diligence and found some vintage ones on EBay. So it's back to the PCB for more work but this time around, I'll install IC sockets first.
UPDATE(10/2014): I was able to find a forum to collaborate with others on this issue as well as get an idea of what 'normal' functionality on this amp is like. There is nothing wrong with the Recording/Headphone output...the Volume control needs to be turned to zero in order to get an output (chalk that one to RTFM!). The replacement of the op amps did not help in addressing the issue as well. A forum member suggested replacing the decoupling caps.... 3 (330mfd) electrolytics. This seemed to have quieted the noise when in high gain mode but did not help in the low gain mode. I'll keep at it....

Check YouTube for video and sound clips of this amp....especially the one that compares it to an aftermarket original Deacy amp.

Telephone Amplifiers...hmmmmm?

Now what? Possibly pursuing a lower powered amplified circuit as referenced in the book of transistor circuits. This quest lead me scouring the internet, mainly forums, for ideas. I happen to find one that had an old Radio Shack advertisement for a ready built amplifier kit. This search led me back to Ebay searching vintage electronics until I came across a picture of a circuit attached to a telephone amplifier. I was taken back to find it exactly matched the referenced design...JACKPOT! Back in the 50's/60's/70's these devices functioned to pickup and amplify the 'listening' end of the telephone handset. They were generally used in conferencing or for the hard of hearing. Anyways I came across a few different vintage models within my budget (mainly $15 or less).

• My first purchase was a Lafayette model which looks to be a late 60's/early 70's manufacture due to the modern PCB layout (etched board process).  

• My second purchase was a Jaguar model which looks to be an early 60's issue due to the point to point (tagboard) wiring process. Sorry no picture of the model on this one because this bonehead forgot to take/save one....and Ebay has purged all of its archived pictures in the purchase history. :(

UPDATE(8/2014): Just purchased a similar model to this one called the Chronovox on eBay. It has a very similar circuit as well but a bit more modernized approach to the circuit board design...etched traces as opposed to point to point wiring.

Jaguar

Chronovox

• My third purchase was a Ampliphone model which looks to be a 50's/ early 60's issue due to the point to point (free style) wiring along with the vintage capacitor (cardboard covered) and cylindrical 9 volt battery. No manufacturer's circuit diagram available but the one referenced comes close.

UPDATE(11/2015):Just purchased another telephone amp by Heathkit with a similar circuit design as the Ampliphone except much more modernized (etched PCB). This purchase was a bargain and actually had 2 kits - 1 completely assembled and the other assembled. I'll need to test the assembled unit to see if the previous owner didn't fry the transistors soldering them onto the PCB. 

Ampliphone circuit

Heathkit circuit

All of the telephone amplifiers had the typical circuit design except for Ampliphone and Heathkit amps which had 1 less transistor driving the first transformer. A few are rated for 9 volt operation - Lafayette, Ampliphone, and Heathkit and the others - Jaguar and Chronovox were rated for 6 volts. All amps were employing an 8ohm speaker usually 2.5 to 3 inch in diameter. The ones I mount into enclosures will employ 5, 6.5, or 8 inch speakers at 8ohms. 

The Lafayette Model...the holy grail?

The Lafayette model was rehoused in a broken Pignose (7-100) amp that I happen to get on Ebay for about $25. The only other item I needed to purchase was the Jensen MOD speaker (5",8 ohm). I have yet to wire it to an external power source as I need to make a voltage regulator circuit to keep the power source steady at 9 volts. Wall warts (especially overseas made ones), when measured, are ridiculously over voltage and one should use caution when applying them to your vintage electronics. For now, the 9 volt battery will do. It powered up without issue and needless to say, I was really pleased with this build. Hooked it up to my trusty strat and it definitely has the potential for that "sound".

UPDATE(8/2014): Upon playing through the amp over time, I discovered some shortcomings. At higher volumes, the amp becomes a fuzz box which eventually breaks up and sputters. A lower volume setting on the amp is required or better control on the guitar volume. Hmmmm...disappointing, at least for now.
I read somewhere that Brian May added a Treble Booster to better accommodate the impedance mismatch of the guitar to the amp. I guess it's time to build a 'Brian May' type treble booster and give it a try. More to follow.....
UPDATE(10/2014): I used the Treble Booster output from the Vox VBM1 into the Lafayette amp and WOW what a difference! I seemed to have less of a breakup and fuzz sound. Time to build a Brian May treble booster for this one!  

(A note for me: Dude...clips please!)

The Jaguar Model...close but??

The Jaguar model was rehoused in a suitcase speaker case that I got from Ebay (about $30). I wanted to go for that nostalgic look and I felt that this exemplifies that era for the circuit. After building the 6 volt regulator (not shown) for the external power source, it powered up without issue. Another project that I am happy about and could have the potential of that "sound".

(A note for me: Dude...clips please!)

The Ampliphone Model....what the *#!%* ?

The Ampliphone model...not quite sure what to do with this one as it's so antiquated. I think this amplifier will need that extra front end boost to bring out the "sound". This is a work in progress but may not have my immediate interest. Kind of looks like a school science project.....hmmm, maybe I'll leave it as such. Modernize it a bit and make a working display model. 

(A note for me: Dude...some pix and clips please!)

Do-It-Yourself build....the next frontier.

One of my last projects on this circuit is going to be a DIY build using a vero board or tag board process. I thought about purchasing the KAT kit but once I learned it was an overseas item, I decided to go with other resources within a lower cost budget. I guess if I screw up going this route, I'll consider purchasing the kit minus the transformers. I have all the parts to start the project but it comes down to finding the dedicated time to do the work. I may start a whole new blog with this adventure... 

In the meantime check out a few of the Deacy builds posted on YouTube and various DIY forums. Most vary in the components employed from the transistor types to the driver and output transformers but one thing they all have is that "sound".

UPDATE(4/2015): I finally got the time to start on this project although I did a lot of procrastination on whether to go the vero board, turret board, or printed circuit board route. I ended up with the PCB route after finding a circuit on the internet.....corrections and redesigns made (verified working!).
The components could have been compacted into a smaller circuit but as a hobbyist, I chose the easier component placement and accepted the board size (about 6" x 3.5").

For this build I used 2 - AC125 (Q1 hfe = 110 and Q2 hfe = 137) and 2 -  AC128 (Q3 and Q4 hfe = 185). One thing to note if using the LT44 transformer, the primary side windings need to be swapped (crossed) when installed. As pointed out in another forum, this transformer is reversed wound and thus causing an oscillation (squeal) sound upon power up. 

The initial test for the 'sound' was OK but I think some more tweaking is needed in order to achieve it. So far, so good as it works as designed and built!!
I also placed a filter circuit on the 4 ohm (6 in.)speaker being used. This was definitely a good addition as it gave a hint of that 'sound'.

Other items that I plan to put into the amp housing include a 'recording interface' which will be switchable with the speaker, an internal 9 vdc regulator (circuit in the next section), and a Treble Booster..... Brian May type circuit with the BC182L transistor which will can be bypassed to the amp circuit.  

The amp control panel should look a lot like this below (please excuse the bad cut and paste job.

UPDATE(5/2015): Everything is progressing well but I have decided to go the Rangemaster booster route (OC44) as opposed to the BM Treble Booster. The headache with the supply power to both boards was getting to me, one positive ground and the other a negative ground. I think the Rangemaster's switchable input capacitor can be employed to provide a treble boost or fat boost along with grit. Should be done soon.....
UPDATE(5/2015): finally pieced together and wiring completed....I'm impressed with this build though not a professional looking product, then again it's my own signature custom/boutique build.
Now the moment of truth - the power up. WTF!!!! no sound, LED not lit. Oops...wired the hot to the wrong terminal on the DC jack.
OK, corrected....one more power up. SUCCESS!
 I get the amp to return sound but once the Rangemaster is switched on, I got a 'squealing' noise when the gain knob is varied. If fully 'dimed', no squealing is heard and that 'Brian May SOUND' is definitely there! Now it's time to figure out what is causing that squealing noise. 
UPDATE(7/2015): tried a few wiring techniques especially on the true bypass switching that turns on/off the Rangemaster. It still squeals but a little less now....below 8 on the dial is when it starts. Other than that, I'm very happy with the overall build and that 'sound' of a Deacy type amp. Just a joy to hear!!

Here are the pictures of the build:

Housed in a broken Sundown amp

Circuit view from the top

Circuit view from the side

Speaker with LC filter

 

 Top view of the amp with controls

(more to follow.....)

A note for me: Dude...some pix and clips please!)

Shifting Gears....circuits into pedals

This is a new concept for me. As I started looking at all of my projects, I realized the clutter they've been creating in my music 'man-cave'. I also got tired of Ebay bids on broken amps for their enclosure (w/ speaker) or vintage wall speakers. The bids were usually no issue, it's the shipping costs for these weighted items that make it tough to swallow on a planned budget.

Anyways as I was multitasking builds with effects pedals, I thought to myself..."why not place the amps in pedal boxes?". Many amp pedals and only one speaker box. Don't know why I didn't think of that earlier! So the first in this product line will be the Chronovox and Heathkit amps. 

More to follow....

(A note for me: Dude...pictures please!)

Partners in Crime....

Other contributing factors to the "sound" lies with a prerequisite pedal as well as the guitar type and wiring configuration. It was noted that Brian May employed the use of a Treble Booster pedal before the Deacy amp. He also used single coil pickups in his guitar, aka the 'Red Special', which had a configuration allowing phase reversal of the pickups. I know I will be definitely wiring one of my strats with this configuration.  


This is my P-90 equipped Squier Mahogany Strat. The plan is to place a phase reversal circuit as a push/pull switch in the tone control position. It's no 'Red Special' but being that the P-90s are just fat single coil pickups, I'm hoping it will get that "sound" or add a new dimension to it.

UPDATE(8/2014): I completed the phase reverse push/pull switch on the tone control. I can achieve the 'honking' type sound associated with phase reversed pickups.
I just realized that one of my other strats, a 3 pickup one, was equipped with a Chromacaster switch from Deaf Eddie which has a phase reverse setting. I'll definitely have to test this out as well.

UPDATE(10/2014): Started on a build of a Brian May Treble Booster. Got the circuit board from GGG (General Guitar Gadgets) and the same transistor type (BC182L) from Small Bear Electronics. Results to follow....  
I also wanted to post the wall wart voltage regulator circuit I elected to use with all of my telephone circuit amps.....and now with my effects pedals. It works like a charm and highly recommended if you're concerned about your valued electronics.

A Work in Progress....

I'm hoping to complete this blog with some sound clips going through all of the amplifiers mentioned above, so stay tuned for updates. Thanks for visiting and I hope this blog helps others in pursuit!