J&K Audio Design: June 2015

Saturday, June 6, 2015

Wavac PRT1 Tube Roll

We're helping a friend with a set of very high end audio gears to fine tune is system for better performance. His system consist of full set of Wavac amplification gears and Acapella Campanile speakers (huge)!

The sound was rather noisy and the imaging was messy and rather veiled. Bass was bloated and could not dive as long as it could. A lot of steps had been taken and it brought significant improvements. Still, there were something wrong with the setup. It did not sound that "high end" considering the price paid for the system (>U$200K we think).

Since the Wavac PRT1 never had its' tubes changed, we decided to give it a try. The stock unit were unknown until we opened up the unit. It was JJ. We ordered a batch of Siemes E82CC, long plate, triple mica NOS, matched quads and gave it a go.

The changes in sound is just substantial - deeper and more natural bass, veil is removed, soundstage deepens, tonnes of details revealed, vocals are warmer, clarity improved significantly. Now it sounds like a U$200K system.

After this change, the improvement was so significant that owner asked if we can upgrade the tubes and components inside Wavac PRT1 as well as his Wavac 300B and 805 power amplifiers! Well, that's for another time. We still have his EL84 push-pull power amplifier to complete and other customers' projects to finish before we can come back to his amplifiers again.

Here are some pictures for your enjoyment:

Chassis milled from a solid block of aluminum

Some red wine to add flavors to the sound

Internal of Wavac PRT1

Tango Output Transformers (we think) is used at output stage

A bunch of JJ ECC82 are retired.

JJ ECC82 tube

Tube covers

Tubes rolling.

Siemens E82CC inserted

Observing the components used in Wavac PRT1

Capacitors used in Wavac PRT1 - certainly we have lots of room for improvements!

Input transformers (we guess, cannot see inside) for Wavac PRT1 (botom left)

On top of the tube roll, we've brought a secret weapon along too - a pair of J&K super-interconnects (RM1.2K a pair).

improved signal-to-noise ratio and interference rejection
high frequency shielding
shielding at bents (soft shield)
optimized cable capacitance and inductance, matched pair
meant for high speed transmission
extreme flexible body
multi-core cabling technology

This cable performed so well that 2nd pair were ordered to connect from Wavac PRT1 to Wavac EC300B and Wavac MD-805MK-II power amplifier to biamp his Acapella Campanile speakers, in replacement of his super expensive interconnects that cost many times over this J&K interconnect.

J&K Audio Design
6/7/2015

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Telefunken Integrated Amplifier

This is a an amplifier that we did not even think of building! I've been keep a pair of EL152 power pentode from Telefunken for quite some time. It was more for collection rather than building use. I was waiting for a free time that has yet to come to put the Telefunken EL152 into good use.

Just so happened that I have a good friend that wanted to build a tube amplifier by himself. I've designed the amplifier for him with 6B4G tube in mind for a 3.5W Single Ended DHT integrated. It did not get materialized as he moved to Singapore halfway during the process and now migrated to Australia.

The whole set of transformers, chassis and components were stored at my place for at least 3-4 years if my memory serves me right. I have been bugging him to bring it back to complete it but it just never moved since Australia is quite far away from my place. Things got dragged on until several months ago where we decided to put it into action by building it ourselves using all the materials that were meant for 6B4G.

The Telefunken power tube can output more power but due to the VA and voltages made for the 6B4G, it was generating only ~3W output. Anyhow, we were still quite impressed at the sound it produces. One day, perhaps, we will make the right power transformer to be used with Telefunken EL152 to fully optimize the circuit and output power.

Time for some pictures!