I have a diy(ish) preamp, that have padded inputs (360kohm, in series). I don't want to pad there any more (I think) that is as high as the kit supplier suggest (to avoid noise floor problems). The problem is that the volume at the first click on the pot (DACT 10k) is as loud as I would normally listen, meaning low volume listening is not possible. The designer suggests padding the amps input, which leaves me with two questions.
1. Would there be any difference between adding a series resistor to the output of the preamp, and adding one to the input at the amp? (interconnects are short, 1 meter). Adding to the preamp out is easier at this point.
2. How do I best determine which value resistor I should use? (avoiding willie-nillie attemps) and what effect will this have on the preamp? (impedance that is sees etc.) It sounds great! just not sensitive enough in terms of volume control.
I don't have a sound meter, but I suspect the first click an the DACT is close to 82dB I see is used to calculate such things (I saw this on some website).
The preamp is 12au7 based, I have measured the output voltage, It is very low in the current configuration (0.1Vac peaks and averaging about 0.05Vac measured at the rca out jack, inner-outer, which seems low to me (but what do I know?)
The amp is 300B SE and works fine with a commercial preamp (another option, but its not homemade).
Speakers are rated as 97dB sensitivity.
Any help you can give a newbie is appreciated!
1. Would there be any difference between adding a series resistor to the output of the preamp, and adding one to the input at the amp? (interconnects are short, 1 meter). Adding to the preamp out is easier at this point.
2. How do I best determine which value resistor I should use? (avoiding willie-nillie attemps) and what effect will this have on the preamp? (impedance that is sees etc.) It sounds great! just not sensitive enough in terms of volume control.
I don't have a sound meter, but I suspect the first click an the DACT is close to 82dB I see is used to calculate such things (I saw this on some website).
The preamp is 12au7 based, I have measured the output voltage, It is very low in the current configuration (0.1Vac peaks and averaging about 0.05Vac measured at the rca out jack, inner-outer, which seems low to me (but what do I know?)
The amp is 300B SE and works fine with a commercial preamp (another option, but its not homemade).
Speakers are rated as 97dB sensitivity.
Any help you can give a newbie is appreciated!
If the first click on the volume pot is too loud then you probably don't need a preamp.
If you want to attenuate the signal then a potential divider may be better than a single resistor. A resistor at the input may add noise. A resistor at the output may interact with the capacitance of the cable. In either case a potential divider will have less problems.
If you want to attenuate the signal then a potential divider may be better than a single resistor. A resistor at the input may add noise. A resistor at the output may interact with the capacitance of the cable. In either case a potential divider will have less problems.
I tried my idea, It seems to work, I only had things running long enough to see how the volume worked. Volume control was much better. The way I have it now is, output wire is connected to the 1k the 330 connected at the opposite end of the 1k the junction of the two goes to center pin of rca the opposite end of the 330 to ground (L-pad).
I will try upping the values, but keep in mind this change is after the tube stages, will the source see the difference? If so, then I will definitely change to the higher values.
I will try upping the values, but keep in mind this change is after the tube stages, will the source see the difference? If so, then I will definitely change to the higher values.
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