Integrated amp

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sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Integrated amp

Post by sbench »

The concept here is a fully integrated amplifier system. It will be physically be built into (I think) 3 boxes...
1. power supply
2. power amp
3. phono/line and control

The power supply has been built and tested. Barring any changes needed during actual "use", it is complete. :shock:

Power amp is D3a/7721 + EL34 per channel. No R, No C design. Totem pole (series B+) configuraation. The driver transformer and output transformer both use plate and cathode coupling.

Line stage intends D3a/7721 per channel. This will have input selectors, volume/loudness with variable compensation, tone controls (bass/treble) and be able to drive the internal PA or external PA. No capacitors... the loudness and tone controls are LR designs. 7721 is output transformer coupled, using the same transformer as designed for the driver in the PA.

Phono stage
Second generation of LR RIAA compensation. No capacitors. 2xD3a/7721 per channel. This is a 2 stage design. The Output transformer is again the same design used in the line stage and the driver of the PA.

AUDIO IRON...
2x output transformer plate and cathode windings + spkr winding.
2x driver transformer
2x line stage transformer
2x volume/loudness attenuator control (no pots)
2x loudness choke
2x bass tone control tapped inductor
2x treble control tapped inductor
2x phono stage output transformer
2x phono stage interstage transformer
2x phono stage input transformer (optional- depends on cartridge)
2x 1.8Hy RIAA inductors
2x 1Hy RIAA inductors

Transportability.
Unlike most of my designs, this one is intended to be able to hold up under shipping. What this means is that it will be possible to ship this thing around for various people to be able to hear some the various features accomplished in the amp. The PS has been designed and tested to operate correctly on 120/240V and 50/60Hz. IEC "modular" plug and switchable "mains" voltage. If things work out OK, I'll probably take this to ETF 2005 in Germany in December.

Design.
I'll ultimately have the design published on my web pages. If there's interest here, we can go through the concepts and design stage by stage or whatever strikes peoples fancy.

The boxes...
PS 12wx4hx8d, 20 lbs
PA 12wx5.5hx6d
pre 12wx5.5hx6d

Where are we...
Nearing completion of input attenuator for volume/loudness. Next step would be to build up the D3a line stage so that the inductive tone controls can be evaluated.

Steve
sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

Here's the overall project Diagram, showing the vaarious aspects of this design. Each of these will be (have been) described in their own section.

Steve
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sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

And Here's the Input attenuator / Volume/Loudness control that we discussed in the Attenuator portion of the forum.

Steve
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int_pa_2.gif
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mattattnet
Posts: 4
Joined: Fri Nov 11, 2005 8:25 pm

Post by mattattnet »

Hi Steve,

I see the thread has been inactive for quite some time, what is the status of the project....any plans to proceed? I for one, am interested.

Matt
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