Documented Single Ended Triode EL84 Build

[tizman]

Hello All.

I built a Decware SE84CS based clone a few years ago and was intending on documenting the build and posting photos but never got around to it. I came across the photos on my hard drive a few days ago and decided to finally do it. I, like many others, have a lot more time on my hands than usual...

 

[tizman]

Alps Blue Velvet potentiometer, power, driver tube bias and coupling capacitor switches, input and speaker jacks, 4 tube sockets and heater wiring installed. Heater wiring is shielded, and shield is grounded, to avoid introducing hum into the circuit. This was complete overkill, but what the hay....

 

[tizman]

The top plate completed. Hammond 272FX power transformer and two Edcor GXSE 15 Watt, 10K Ohm to 6 Ohm output transformers. These output transformers are over specified for a 2.5 Watt per channel amplifier.

 

[tizman]

Capacitors and Ground

Capacitors for power supply added. These are all film caps for extra long lifespans. The caps are secured to the top plate with Goop, which is a very effective way to secure capacitors that also damps vibration. It makes the capacitors removable (albeit not easily). A 10 Gauge ground wire, to which all ground attachments will be made, is added and connected to inputs and volume pot. The output transformers are connected to the speaker output jacks.

 

[tizman]

Ground connections to Alps Blue Velvet pot, input jacks and power transformer bolt.

 

[tizman]

Shielded wiring

All connections made with shielded wire. Shield is grounded.

 

[tizman]

Driver tube bias switch

This amp has a switch that allows you to increase/decrease the bias of the driver tube for a different sound signature. PRP 9372 metal film resistors are used for biasing the driver tube.

 

[tizman]

Alps Blue Velvet to 6N1P-EV grid wiring

A couple of high quality (and ridiculously expensive) Amtrans AMRG resistors. Only their gold plated leads are used to complete the connection. Teflon tubing protects against shorts near the socket.

 

[tizman]

6N1P-EV Socket to Coupling Capacitor Switch

This amp has a switch for choosing between two different coupling capacitors.

 

[tizman]

Coupling Capacitors and Resistors Added to EL84 Power Tube Socket

Coupling capacitor can be switched between Russian Teflon FT-3 and Mundorf Supreme Silver Oil. Both capacitors sound great. High quality Amtrans AMRG resistors and PRP metal film resistors.

 

[tizman]

Cathode Bias Capacitor

High quality Kemet power tube cathode bypass capacitor. Rated at 1500 hours at 150 degrees Celsius. The only electrolytic capacitor in this amplifier, and a very durable AEC-Q200 compliant part. Bypassed by a nice ERO film cap.

 

[tizman]

Hazen Mod Sprague 716P Orange Capacitor

This capacitor comes into play when this amp uses 6P15-EV tubes instead of EL84. Either tube will work in this amp. Search Hazen Mod for more details. Amtrans AMRG resistor closeup. Takman resistors top right.

 

[tizman]

Completed Amp Internals: Three views

Front, rear and side views.

 

[tizman]

Completed Amplifier Front View

All tubes installed. The top plate is a thick aluminium sheet that has been etched with a swirl pattern. This is an extremely durable finish that is immune to fingerprints and hides any future scuffs and scratches. Very low maintenance and worry free.

 

[tizman]

Completed Amplifier Rear View

This shows the power inlet with integrated fuse in the wood frame, and the 5U4 rectifier tube in its socket.

 

[tizman]

Floating Top Plate

This is my preferred way of building tube amps. Everything except the power inlet is attached to the top plate. The top plate is gapped from the wood case so that air can flow through the bottom and out of this gap. This guarantees that all components will be kept cool for extended life.

 

[tizman]

Perforated Aluminium Bottom Plate

This allows plenty of air to flow through the bottom of the amp and out through the gapped top.

 

[tizman]

Well that's it for now. Hope you like the build "documentary". I highly recommend this circuit for anyone who has very efficient speakers. I use Klipsch La Scala and Heresy. This amp sounds wonderful with both. 2500 milliwatts....

 

[carlthess40]

Great build. I wish I had the talent to do that type of work. Or the funds to buy a diy tube amp. I’d like one that can output 10watts

 

[piano3]

Nice work! Gapped top is a great idea (assuming little fingers can't get in).