Products

:::   INTEGRATED STEREO HIGH PERFORMANCE TUBE AMPLIFIER   :::

If you are looking for an integrated amplifier for your rack instead of Prometheus monoblocks, the Assistant 100 – Mark 2 is the best choice. Assistant 100 has two mono channels from Prometheus in one housing and has the name “male amplifier” in the scene – because it takes two men to act. But first to the story of why an update for Assistant 100 was announced. Back in 2000, after a long period of work, I finally had the 6C33 with 2 tubes per channel – 4 of which i planned a stereo integrated amplifier – in a push-pull circuit. That was also a challenge, as in the end there should be at least 80 watts available per channel. No sooner said than done at the end of a load of 8 ohms about 25 volts at the output of the transformer.

So far so good. But the balance sheet with regard to the performance made me frown. On the one hand, there was the heating power of the 4 x 6C33, which already faded 200 watts alone, and there was also 200 watts of anode power loss in Class A operation – making a total of at least 400 watts and all of this from scratch without first a single tone in the Speaker. In the further course of sales of the integrated amplifier it turned out that the 6C33 is extremely capricious.

It could not tolerate more than 200 volts at the anode anyway and when the anodes were still supplied with signal voltage by the transformer, the day was over and the tube was in the bucket. That was the situation with 80 to 100 watts of output power per channel. The situation only got better if you reduced the signal level, but then you were at 30 watts – and that with the effort. So the concept had no future, I had to recognize it here with a heavy heart. A 2 x 30 watt amplifier can be developed just as well with less effort.

So I decided to discontinue the product over the years. I had “burned” an infinite amount of time with the construction and a great circuit board so that you could build more than one amplifier. With hand-wired devices, the replica is a single ordeal. In conclusion, I have to state that the tube is only suitable for what it was made for, namely as a series regulator in power supplies, there is no voltage increase on the anode, which ultimately always caused the tube to die. That was a very bitter experience. And that applies to both PP and SE concepts, just keep your hands off this part, you will quickly lose the fun of it. I still have about 100 printed circuit boards in stock, if you are interested, you can inquire and try an amplifier with reduced power with it – and my circuit on board doesn’t hum either – like all my amplifiers don’t hum!

Enough words about the past, let’s turn back to the current model. There was also a lot to observe at the beginning of development with the GU50. This tube did not like the max. Values ​​of e.g. the anode voltage. This is set to the safe value of 650 VDC. As always, we donated a fully automatic bias circuit to both tubes on the end tubes. I am glad that we at AudioValve have this construction, which does the setting up of the optimal anode quiescent current completely on its own. I really wonder how the competition believes without being able to sell this device for the future ?? !!

Also when choosing a base for this tube, you have to do the right thing, otherwise it will take revenge. In the first samples we had china – base made of ceramic, which led to glass breakage of the GU 50, because the mechanical prestress on the contacts was great. These sockets belong in the trash. We then found the original base for the tube in Ukraine and since then the problems have been over. Another great thing about this base is that it secures the tube to prevent it from falling out. The base “defends itself” to give the tube back – well done!

As always, the circuit board is made of one piece. Power amplifier, pre-amplifier, power supply and all other necessary components, all together on a perfectly routed circuit board. Then you only have to pull a few wires, to the mains transformer and transformer and you have a super integrated amplifier with 2 x 80 watts. I am also happy to make this circuit board available to interested users – for a fee. The two control grilles of the end tubes of a channel are fed from 12AU7. Basically, the driver is the same as the one we use in Assistant 50. This driver has enjoyed great popularity among Assistant 30 and 50 users for over 20 years.

There are LEDs on the bias controller that signal the intact function of the end tubes. If they are off, everything is fine and the regulation is working. If one of you lights up, the tube must be replaced at the relevant place. And what does the Assistant 100 – Mark II sound like? The GU50 is an audio tube through and through. In our concept, it is inexpensive to obtain and does not require any selection because the autobias arranges everything independently. Ok, this tube is also looking for your master, who knows how to handle it. But because of its originally intended use, it offers a completely different basis for a promising concept than the 6C33 – so it is all long.

Compared to the “part” with the 6C33, the power loss of the amplifier has dropped by half – however the weight has remained the same, I hope this is not a drawback for you now ;-). The Assistant 100 is similar to its little brother Assistant 50 to operate via an FB and also preconfigured for retrofitting with our DAC. In addition to 5 x RCA inputs, there are also 2 inputs for XLR cables on the back. The LS terminals are arranged next to it. There is also a TAB-REC that loops through the signal from the selected source.

Our logo is lasered and illuminated on the windscreen. The desired color of the LED lighting must be specified when ordering. Otherwise the product is easy to use. On the back is the main power switch, which must be set to ON if you want to switch on the device via the FB, because it has no power otherwise. On the left on the front is the display for the selected input. If the amplifier is in “Operate Mode”, the LED of the selected source lights up, this LED flashes during the MUTE function and in STAND BY mode all sources LED are off. Have fun with the assistant – the AudioValve team wishes you 100 Mark 2