On this website you will find tube (valve) amplifiers I designed, repaired, built and collected.
The PA amplifier was designed and built by myself for use at motorcross events to adress the visitors.
The Marshall clone is a guitar amplifier built by myself. Look here how it's done.
During my research for Philips amplifiers over the world I was asked if there was also information of tube (valve) amplifiers called the EV44xx series. All what I found you can find here.
Specialy I collect Philips amplifiers of the EL64xx series. It was very hard to find and get the information of these amplifier series. For some amplifiers was it impossible to get, if you look here you will see why!
In the "extra" part you will find some special amplifiers I found during my investigation. Such as amplifiers used in movie theaters, the AG90xx series and some Philips organs.
In the last two parts service manuals of the different units are available.
This amplifier is designed by myself and built together with a friend which is very good in the mechanical part of the design. Each amplifier is built with 4 times the EL34 in PP class B mode. The complete amplifier consists of 6 power modules connected together for a very high output power. The application of these amplifiers was first for PA purposes in motorcross events. First a photo of the complete amplifier, which was split into 2 cabinets, because of its weight. Each cabinet contains 3 power modules connected in parallel and can be switched on separately. Photo 1 is the overview of the two cabinets.
Photo 2 is the front plate of 1 cabinet. The mA meters give the value of the anode current of each module. The voltmeter in the right position gives the loudspeaker line voltage up to 200 volts. You can also look at the separate power on switches. Each amplifier can be switched on or off in case of to much power or a broken amplifier.
This complete system is a PA amplifier with a power of 1200 Watts continues and 2400 Watts peak power with a constant voltage line output to the speakers. It can also be used as a 2 times stereo amplifier of 2 x 600 watts. For use as a PA stage amplifier for rock bands or other musicians.
Here some photos of the rest of the cabinet.
The dust is very good to see, but still working with no problems. At the inside you see the 3 separate power amplifiers. The connection of the mains, speakers and the input signal is made by plugs, so its easy to take one out if necessary.
How its built:
In this part of the story you can see how one amplifier is built.
Photo 4 is the front and rear view of one power stage.
One complete amplifier is built on an aluminium frame with epoxy glass fibre print board as chassis for the transformers, electrolytic capacitors, valves and plugs. The next photo shows us the inside or the bottom view of the amplifier.
Drawing 1 is the data of the chassis where the holes are situated and other components.
Drawing number 2 is the schematic diagram of one power amplifier. This whole system uses 6 of these amplifier units. You see that each power unit consists of a power supply for the 4 EL34 tubes, a power supply for the bias of the tubes and an output transformer. The data of the power transformer and the output transformer are written in the diagram.
The bias of the 4 tubes EL34 is set to 20 mA each, so the quiescent current for one amplifier is about 80 mA. The next drawing is the drawing of one complete cabinet. In this cabinet is place for 3 of the above power amplifiers the mains switches, a mains control lamp, the main socket, the input connection and the loudspeaker output connection.
And here the complete connection of the two amplifier boxes, how they were connected to the small controle amplifier (5 watts), the mains and the speakers.
The next two photos gives an example how to connect the several speaker cabinets to the output line of the power amplifier.
This photo gives a detail of the line cable and a detail of the speaker cabinet cable with needles.
This photo gives a detail of the connection of the speaker cabinet to the audio power line.
Description of a 50 Watt guitar amplifier with is a look-alike of an amplifier of the brand MARSHALL.
The next picture is a photo of a real Marshall. The inspiration of this design.
This amplifier uses also the EL34 as the output valve. In this case only 2 tubes are used.
Therefore the max output power is 50 Watts. At the end of this chapter there is a schematic drawing of a 100 Watts amplifier.
It's possible to use the same chassis. Only a few more holes have to be drilled into the chassis.
Next drawing is the schematic diagram of the 50 Watt one.
The description is only the amplifier. The housing can be made out of wood or MDF. I don't have a drawing of that part. The first you have to make is a chassis. I used an aluminium plate of 810 x 300 mm and 1 mm of thickness.
You must use the numbers written into the drawing, because the drawing is not scaled. The best way is to buy all components first and than start building.
The possibility is there that you can not buy the same components I use, and than the holes are not right. The mounting holes of the printed circuit board, tube holders, elko's and transformers are not drawn. These holes are depending on the components you will get. Next the drawing of the chassis.
When ready drilling holes you can bent over the edges over 90 degrees. I welded the 4 corners, but you can put the corners together with screws and bolds of M3.
If this is done we can mount the tube sockets, Elko's and transformers to the chassis. Also the Mains and the standby switch, the pot meters and plugs can be placed in the chassis.
As filter choke I used an old transformer of 66 x 55 x 28 mm. I did 2750 windings of 0,3mm copper wire on the coil form. When ready I drilled then the holes for the choke in the chassis and a hole for the connection wires.
Then the time came for assembling the printed circuit board with resistor, capacitors and diodes. The wiring of the printed circuit board are in grey as they are at the bottom side of the printed circuit board.
Printed circuit board
In the circuit board and the chassis you have to drill 6 holes for putting the board on distance parts and the chassis.
When ready mounting this board in the chassis you can mount the wires from the board to the tube sockets. Next picture is where the wires are going to.
Wiring diagram form circuit board to tube sockets and pot meters. The text near the small holes is where the wires are going to.
The photos placed under this text are for illustrating this part of the building of the amplifier how I did it.
When wiring the ground (GND) wires, look good where these are going to. If doing this different the possibility is there that you make a mistake and the amplifier can hum.
There are 2 ground points. One for the analogue input signal and one for the supply return. At the end, these 2 points are coming together to one point.
The photo's will tell.
The complete amplifier:
Detailed mains transformer, output tranformer and elco's.
Detail of the choke, other elco's and the tubes.
Mains and standby switch.
Presence pot meter and analogue ground point. The analogue ground point is a copper wire that is soldered at the housing of all pot meters. The pot meters are isolated from the chassis. The pot meters I used have plastic front sides.
Here the view of all pot meters and there connections.
As you can see, not all components are on the circuit board, some are connected in the air. For better servicing and overview I used different colours of wires. Yellow for the cathodes. Brown for the anodes. White is going to the pot meters, and the green colour for de grid's Red/black for the filaments, the wire I use for this purpose is a double wire.
This is a detail of the power tubes, and also a detail of the fuse. (0,5A for the DC voltage).
Each power tube has its own ground. Pin number 1 and 8 are put together and soldered to a solder pin./p
Near the left power tube the 2 resistors of 47 ohm are grounding the filaments.
Near the first Elko the mains ground is connected. Yellow-green is the colour of this wire. All zero points of all Elko's are coming together here. The black wire is the wire coming from the pot meters. Next some more detail photo's of the amplifier.
Details of the circuit board and it connections.
This schema is the 100 Watts version of this amplifier. The drilling has to be modified for 2 more EL34's The numbers written near the transformers are the order numbers of these parts if ordered by AMPLIMO.
100 Watt version of the amplifier.
Philips amplifiers of the EV44xx series
This amplifier is custom made in Australia, but there were only some pictures of it. The type number of this amplifier is EV4417 and was used in a cinema for the audio. Sometimes four of these units were used and controlled by the projector.
Text plate type number and other data of the EV4417.
Here the schematic diagram for of this amplifier.
Schematic diagram EV4417.
For the pictures. Thanks to Kieren Davis Australia.
This amplifier was discovered also in Australia by Tim Robbins. After some searches in my old library I found some data about this amplifier. You will see that this design has been used in about all EV44xx marked units. The following photos were sent to me by Tim Robbins. I redrawed the schematic because the original drawings were very bad.
The inside of this amplifier.
Tim Robbins modified his amplifier to a guitar amplifier for his son. Follow the link for the modifications and an explanation how he did it.
After some searching and asking around I discovered that there was something of a system in this numbering.
Here the result of tis investigation. The EV441x where only the power amplifiers, the EV443x amplifiers were the complete amplifiers with tone controls and additional inputs.
The EV4415 and the EV4435 series were reserved for amplifiers with 2 EL36 (6CM5) power tubes.
At the bottum of this page you will find my latest discovery: "The LOWLINE" with ECL86 (6GW8) tubes. Called the EV4438B.
Pictures of this solution are shown here.
Schema of the EV4415.
The EV4435a frontview.
The EV4435a rearview.
The EV4435a topview.
The EV4435a view inside.
Schema of the EV4435(a).
There was also a discovery of an old record player with a built in amplifier of the EV44xx series.
This amplifier was built as by using the chassis of the power amplifier, but when using it with a record player you miss the tone and volume control.
Philips solved this problem by building an extra tube inside the amplifier. They used the same circuit as the complete amplifiers.
Pictures of the recordplayer amplifier. Type number of this amplifier is EV4411. This type number is for me still a mystery !!
The inside of the record player.
The inside of the amplifier.
The preamp built near the tone and volume controle.
For schematic diagram of this amplifier see the EV4431.
The EV4411, the EV4416, the EV4431 and the EV4436a series were reserved for amplifiers with 4 EL36 (6CM5) power tubes.
Frontside of this amplifier with cover.
Backside without cover.
Frontside without cover.
Inside of this amplifier.
Same amplifier, another built.
Schema of the EV4411.
Schema of the EV4431.
The EV4416 and the EV4436a are new discovered amplifiers in the EV series.
Jonn Connolly changed his EV4416, which he got from Steve, with the help of Graham, into a guitar amplifier and was very pleased of the sound.
Front view of the EV4416
Rear view of the EV4416
The EV4436a amplifier
Front side without a cover (EV4436a).
Rear side (EV4436a).
Bottom side (EV4436a).
Output transformer connection.
Schema of the EV4436a.
The EV4417 and the EV4437 series were reserved for amplifiers with 6 EL36 (6CM5) power tubes.
Backside of this amplifier without cover.
Inside EL36 (6CM5) part.
Inside supply part.
Schema of the EV4417.
Schema of the EV4437.
There is also another variant of this amplifier: The EV4437a. This amplifier looks very much the same as the EV4437.
In this amplifier there is a limiter circuit built in. This part is drawn in the schematic diagram of the EV4437a.
Typenumber plate EV4437a.
A picture of the limiter part.
Here some extra data of the outputtransformer.
For the pictures and OT data of the EV4437a I thank Tim Robbins who is the owner of this amp.
The EV4418 amplifier:
From Ken Stone I got the folowing pictures of a modified EV4438a for a special purpose with relais control for a microphone input.
Thanks for that Ken
Front view open.
Inside view, you can see the extra relais for remote perposes.
Rear view, type and serial number.
The EV4438B "LOWLINE 10" amplifier:
Front view open.
Another front view with 2 more potmeters.
Rear view open.
Type plate EV4438B.
Inside the amplifier.
Schematic diagram of the EV4438B "LOWLINE 10".
Maybe there are more types of this design. If I find them I will post them here.
Philips amplifiers of the EL64xx series
Other Philips amplifiers
The data of the EL6910 echo unit I got from EKADEK (www.ekadek.com)
Philips organs PHILICORDA
An unknown Philips amplifier:
Pre amp. Pots and elco's.
Pre-amp. without tubes.
Inside the amplifier.
The schematic diagram of this unknown Philips type amplifier.