Hi all
there's a little confusion on the web and I would like to know which new valves to buy to spruce up the 2nd hand Rose I recently bought. It has 4 x ECC82, but I have read that the phono section should be ECC83. Meanwhile I have a 2nd Rose with 4 x ECC81 (which seems to be ok but for a slight rustle on one channel (albeit that in the same channel one of the valve flares mightily on turn-on).
Any comments gratefully received
Best
Adrian
there's a little confusion on the web and I would like to know which new valves to buy to spruce up the 2nd hand Rose I recently bought. It has 4 x ECC82, but I have read that the phono section should be ECC83. Meanwhile I have a 2nd Rose with 4 x ECC81 (which seems to be ok but for a slight rustle on one channel (albeit that in the same channel one of the valve flares mightily on turn-on).
Any comments gratefully received
Best
Adrian
Get the schematic and populate accordingly. 12AU7s in the phono section are highly suspect. 12AX7s would be quite normal.
Thanks Eli. Unfortunately no-one seems able to locate a schematic for this ageing amp. My 'tube guy' said the same as you but the ECC82s are ok and there is no gain problem. Will track down some ECC83s and see if they are an improvement
Thanks again
Adrian
Thanks again
Adrian
Some European valves of the 12A_7 variety have filaments that glow brightly at first turn on.
If it is not that, it may be a tube that can not take the voltage it gets until the filament warms up and the plate voltage goes down as it begins to warm up. That might be Gas, or a short. I would expect this would be either a problem of the tube, or a failure in the rest of the circuit.
If it is not that, it may be a tube that can not take the voltage it gets until the filament warms up and the plate voltage goes down as it begins to warm up. That might be Gas, or a short. I would expect this would be either a problem of the tube, or a failure in the rest of the circuit.
Using ECC82 in a phono preamp designed for ECC83 will not only drop the gain (which may be acceptable) but will also almost certainly affect the frequency response, as it is difficult to design a valve phono preamp which is completely independent of the valve characteristics such as anode impedance.
Hi 6A3sUMMER
thanks. The odd thing is that only one valve flares, but does not do so when in another base in the preamp. Meanwhile any valve swapped into the original position of the flaring valve also flares. I'll need to check the circuit I think.
Adrian
thanks. The odd thing is that only one valve flares, but does not do so when in another base in the preamp. Meanwhile any valve swapped into the original position of the flaring valve also flares. I'll need to check the circuit I think.
Adrian
Hi DF96, I can't hear any difference between the various valves in the phono stage, so not sure what is happening.
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