Hi, I am have had this clone Preamp built up board for a while & although it sound very good I cannot overcome the gain of the unit, It is just to high to early. I have now tried a 50K pot (that is what the original was, or so the label said) 100K & 10K & the result is the same for all. I can only get to a 9 'o' clock position & the vol is to high.
can anyone advise how the effectively reduce the vol. I have heard you can do it with resistors, but am not sure how to accomplish this.
Cheers for any replies
can anyone advise how the effectively reduce the vol. I have heard you can do it with resistors, but am not sure how to accomplish this.
Cheers for any replies
what is the signal chain and what is the gain of the preamp? With digital sources you rarely need gain in the preamp these days.
Are you sure you are using a log or audio taper pot for the volume control?
You can check by measuring the resistance at the half-way rotation point.
A log pot will measure 10% on one side and 90% on the other.
A linear pot will measure 50%.
You can check by measuring the resistance at the half-way rotation point.
A log pot will measure 10% on one side and 90% on the other.
A linear pot will measure 50%.
You'll have to post the schematic, or else the only option is a resistor attenuator before the preamp.
Try a series 10k, followed by shunt 5k for about -10dB attenuation.
Try a series 10k, followed by shunt 5k for about -10dB attenuation.
Hi, Thanks for the replies, i have checked all my 4 spare pots & they are all 50/50 so must be linear. My local component supplier (such as it is) lists a 50K log pot, so I will pop down town tomorrow & hopefully they have one in store, or at least can order one in.
Tried the resistors before the pot, actually used higher values as that was I had, shunt was 50% of main resistor. it only made a very small reduction, say now at 10 'o' clock.
cheers Derek
Tried the resistors before the pot, actually used higher values as that was I had, shunt was 50% of main resistor. it only made a very small reduction, say now at 10 'o' clock.
cheers Derek
If the 100k is really a linear pot, you can "law fake" it with a resistor from the wiper to ground. Try something like 10-15k.
Hi, Sorry no schematic, something I just picked up a few years ago.
Anonymous, Not heard of that one before. HOW?
Cheers
Anonymous, Not heard of that one before. HOW?
Cheers
You may be better off with your present linear pot, with added resistors from the wipers to ground to make it quasi-log.
The tracking will be better than most stereo volume pots, since linear pots track very well compared to log types.
Use precision metal film resistors from the wipers to ground, and use about 10% of the pot value for the resistor to start.
The tracking will be better than most stereo volume pots, since linear pots track very well compared to log types.
Use precision metal film resistors from the wipers to ground, and use about 10% of the pot value for the resistor to start.
Hi guys, Well nothing has worked so far. I loading the CD input with resistors. it made a little reduction but nowhere new enough. however on browsing I found this recommendation. Which is a Jensen unit, trouble is cost is to high,
https://www.ebay.com/itm/362577120566
Does anyone know of a reasonable priced alternative.
Cheers
https://www.ebay.com/itm/362577120566
Does anyone know of a reasonable priced alternative.
Cheers
what abouth this:
4:1. a pair for $55, plus $ 15 ship - max input about 2V RMS I guess. It's permalloy, sensitive and very wide-band.
but silly to make a preamp than then discard the gain.
Why not take the route of a 1:2 transformer and use that for 'gain'?
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But
You made a clone. The clone is a preamp with feedback.
The sensible thing is to change the feedback resistors right thre. For instance, the feedback is 20k/2k. Then change the 20k to 5 k. See what happens. Easy to solder a resistor parallen on the 20k resistor of my example.
4:1. a pair for $55, plus $ 15 ship - max input about 2V RMS I guess. It's permalloy, sensitive and very wide-band.
but silly to make a preamp than then discard the gain.
Why not take the route of a 1:2 transformer and use that for 'gain'?
---
But
You made a clone. The clone is a preamp with feedback.
The sensible thing is to change the feedback resistors right thre. For instance, the feedback is 20k/2k. Then change the 20k to 5 k. See what happens. Easy to solder a resistor parallen on the 20k resistor of my example.
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You can make a simple voltage divider at the input with two resistors for any level of reduction needed.
For example, if Z1 is 100K and Z2 is 20K then you get a 6:1 reduction in voltage at the output. With a little experimentation you should be able to find a ratio that works for your circuit. The total (Z1 +Z2) is not critcal but try to keep it in the range of 50K to 100K so, similar to the volume pot value.
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