[Haoleb]

I have built a couple of RA-1 clones and have been pleased with them, but during the sale of one i found out that mine might have a flaw. Being too loud when hooked directly to a cdp output. When i have it hooked up to one, the volume control seems to get more then loud enough with just a tad of volume. If it were to be say halfway it would already be too loud. I used the same value parts in my clone. but the only difference that i made from the original is that the coupling capacitors are before the pot rather then after it like in the original. At the time i did not think this would make a difference. Am i wrong? I know that with L&C circuits it makes a difference but i was not aware of it making a difference in this type of thing.

I thought it was performing as it should because the output of a portable or computer is much less than a cdp so it only made sense that when i hooked it up to a cdp it would be much louder.

Any suggestions? a little help please

 

[amb]

The location of the input coupling cap should have no effect on perceived volume. Your amp simply has too much voltage gain for the headphones you use. You should change the values of the feedback resistors to drop the gain.

 

[Haoleb]

But i used the same value resistors and everything in my clone as in the original, but i have been told that on the original ra-1, the volume control is not as touchy. Im using SR-125 phones with it so its not like i am using different phones for it. Anyone who has the original wanna chime in?

EDIT: I have the amp hooked up to my digital cable box and it works fine. It doesnt get insanely loud. Perhaps the cdp i was using has a rather high output. Or maybe it was just louder than i remember it being.

 

[Tomo]

Hi,

You just have an awesome CDP, Haoleb. Your CDP output stage is giving you ample voltage gain.

Note also, that Gradoes have 32 ohms impedance. This means you will reach EAR-SPLITTING VOLUME even at 1V voltage swing. You can really do well with 0dB Gain (or Gain = 1). What I would do is to set the gain to 2 ~ 3.

But keep in mind that some opamps are unstable at such low gain.

Ad-Hoc approach will be to modify so that your input RCA and the volume control are connected with some resistor. (dunno 10k~100k you should calculate and experiment yourself with the voltage-divider equation.) This will reduce the signal going into your opamps. ...

However, the best solution is to reduce the gain as we have stated. Would you mind telling us the current gain of your amplifier?

Tomo

 

[Haoleb]

thanks for the input, I really have no idea as to what kind of gain im getting out of this thing. As you may know the factory RA-1 is rated at 250mw so i suspect mine has a comparable output power.

 

[Tomo]

Hi,

Sorry about that I need Voltage Gain. You can calculated it yourself from resistors you used.

T