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Thursday, October 24, 2013

The Integrated Amplifier

Hi!

I often get complaints that my electronics are too big and consist of too many chassis. So I came up with this integrated amplifier. It is not only a full function amplifier with volume control and 3 line inputs, it also has a phono section on board with built in MC step up transformer.






This requires a lot of tubes. 10 Signal tubes in total. the phono stage is implemented with 6SF5 and 6J5 triodes. The circuit is exactly the same as in the Octal Phono Preamplifier. The 6GL7 serves in the linestage which shares the same circuit with the Octal Line Preamplifier. Basically the preamp section is the same as in the Octal Preamplifier MK3. To make the amplifier complete a stereo version of the low cost 6CB5A amplifier was added.





The PSU got it's separate chassis to keep the chassis size and to avoid interference with the phono section. To fill up the PSU chassis it got a full wave bridge rectifier with 4 6AX4 TV dampers and a choke input filter. Two LC section provide the smoothing of the B+. Inside the chassis is a filament transformer which is part of a DC heater supply for the preamp section. The power amp section is AC heated.

Some photos of the assembly steps. The top plate with capacitors and output transformers mounted:






The output transformer had to be mounted sideways so that they fit under the 100mm transformer covers.





The preamp tube sockets are mounted on rubber dampers:





Heater wiring and some of the coupling caps:






Adding solder strips:





Adding all the remaining parts:





Prewiring the back plate:




Ready to be mounted into the wooden frame:




Just two controls, input select and volume:






The backside is quite crowded:





Starting from the right: Phono MC inputs, Ground post and ground lift switch underneath. Next two switches for selecting the step up ratio of the build in MC transformer. Followed by 3 line inputs. The 5th pair of RCA jacks is a line out. The signal after the line stage section is routed to these so an additional amp can be connected or the component can be used as a preamp. The speaker jacks on the bottom and the power supply connector on the left.






The entire amplification chain for an analogue system in just two boxes. Five Amplification stages. All Octal tubes. No more complaints about size please ;-)

Best regards

Thomas

13 comments:

  1. Brilliant . I'm guilty of fancying a smaller set of amps....houseroom is at a premium. This is a rare device...a genuinely high-end single-ended integrated amp, with a fine phonostage. In fact, offhand, I can't think of a direct competitor. And Thomas, perhaps a 'first' for you.....the only 'Thomas Mayer' amp which takes up less room than the competition.
    Am I to assume about five watts? And even a step-up for mc output!
    All we want now is full remote control and a built-in coffee making machine.
    Seriously, this looks a real winner to me.

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  2. Brilliant. I think this is unique in the market; a seriously high-end single ended amp, integrated, with a full-service phonostage, for mc. All in two neat boxes. Thomas, it must be the first amp you have created which is smaller than the competitors. This should be rather successful About five watts I assume?

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  3. Hi Peter,

    thanks for the compliments. It does about 7W per channel.

    Best regards

    Thomas

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  4. Could you build a version of this integrated that used PSE 6HS5?

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    Replies
    1. Hi!

      The 6HS5 concept is not well suited as the basis for such an integrated amplifier

      Best regards

      Thomas

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  5. The integration between the pre and the power are cap coupled?

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    Replies
    1. Yes, no space for coupling transformers in this design...

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  6. If only line inputs are considered, can be integrated with a 6AH4 pre cap coupled?

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    Replies
    1. For cost inquiries please contact me by email. My contact information can be found here: http://vinylsavor.blogspot.de/p/impressum.html

      Best regards

      Thomas

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  7. Hi Thomas, am I right that when I lower the voltage to 400v and change cathode resistor to 560r with 220uf cap. I could chance the tube to a 6bg6? or 6l6?

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    Replies
    1. Hi! I would even go lower to stay within the plate dissipation limits. For the 6l6 the 560 seems about right. I have not looked at triode curves of the 6bg6.

      Thomas

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