• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Looking for Phono Stage ...

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Hello there yet again Folks. I am asking for some input from those that have so much more knowledgeable than myself. I really appreciate the way that ALL the Folks out there are so willing to share their information with those that are less experienced. Just what a great forum diyAudio is... MANY THANKS...

OK now down to the nitty-gritty... I have attached a part-circuit of just what I have at present and this amplifier is for CD input only at present. The input tube is a single ECC83 ( 1/2 per channel ), driving a single 6V6 in Class A mode. I am using a single 50K log pot on the input at this stage.

What I imagine for the additional PHONO input is that I would have to use a full ECC83 per channel now, to get more gain for the phono input. The cartridge output requires 47K impedence and has an output of 4.5mV. ..... 2 RCA inputs with a switch between 'CD' and 'Phono' would be my idea ????

Any help with a SIMPLE circuit would be very much appreciated and I look forward to hearing form anyone that is willing to help....

Many thanks yet again....

Keith, New Zealand
 

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Keith,

No phono preamp is truly simple, sorry. However, some designs are not overly complex. The tweaked RCA setup I've uploaded is about as easy as it gets. You live in a 240 V./50 Hz. mains zone. You have to come up with a PSU that produces 300 mA. of 12 VDC for the heaters and about 10 mA. of well filtered B+, in the 270 to 300 V. range. Install a LR8 regulator configured for 250 V. in the B+ line of each channel.
 

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Keith,

No phono preamp is truly simple, sorry. However, some designs are not overly complex. The tweaked RCA setup I've uploaded is about as easy as it gets. You live in a 240 V./50 Hz. mains zone. You have to come up with a PSU that produces 300 mA. of 12 VDC for the heaters and about 10 mA. of well filtered B+, in the 270 to 300 V. range. Install a LR8 regulator configured for 250 V. in the B+ line of each channel.

Thanks Eli, your help personalized help is much appreciated.... Yes, it is very frustrating when know just what one wants, but do not have the skill... At over 60.... not much chance of catching up now is there ...;) :rolleyes: :D

Attached is a pic of the little amp as I have it now, suppose there is much that is not totally correct :rolleyes: :confused:.... But in the end it does sound great on CD, but as requested... A bit of CD AND MM Phono would really be nice....

Thanks yet again....

Keith ..... NZ
 

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I have been tweaking my Tubecad.com Tetra Sans PS now for a few weeks.

It is a pretty simple build of a CCDA topology and the board is very high quality.

One thing is certain, the coupling capacitors are CRITICAL to the sound. I initially had cheap WIMA's in and just switched to Solens. The improvement was soooo good that I will now save up for some Mundorfs or Auricaps or something like that. This one has 4 so it is easily an $80+ upgrade after shipping etc...
 
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