lcr45-userguide-en.pdf
Gotcha, cool. Can't really swing buying this thing though.Manfred wrote:A common capacitance meter do not read the real capacitance because there is a impedance on the measurement clamps.
In some cases the impedance contains resitors and/or LCR-networks in parallel too.
I use the Peak-Atlas LCR45 - LCR Impedance Meter that could measures the real and imaginary part.
Together with the measure freqency it is possible to calculate the capacitance from the imaginary value.
But you have to be careful, because it works not always especially if there are other LCR-circuit in parallel,
with just one resistor in parallel it mostly works well.
In case of LCR-circuits in parallel there remains only an estimation after separate measurement of these circuits.
Yep, 100% agree, I was just messing with the calculator last night.vtguedes wrote:Thanks for the tracing!
To my eyes it looks like the tone stack has something in common with the James tonestack from the Tone Stack Calculator website:
That would give us the idea of the value of a couple of capacitors.
The capacitor in paralel with the 1k resistor I'd test 680n based on Runofgroove Thunderchief schematic. Also based on the same schematic I'd try 2n2 on the last capacitor, in paralel with the master potentiometer.
I guess coupling caps should be somewhere between 22n and 100n, I'd start with 47n and breadboard it.
I'll try to get this breadoarded this weekend
You don't have to do this, I do not receive commission for.Gotcha, cool. Can't really swing buying this thing though.
Trial and error always a practical methode.I'm thinking that just trying to come up with educated guess values for the caps and do listening tests is the right path here?
vtguedes wrote:Still on the tone stack theme, RoG (again) Supreaux Deux bottom switch mod also looks a lot like the bass tone control.
My guess is that the first capacitor on the bass control don't let much bass through it and then the bass potentiometer acts like a bypass to the capacitor. The second capacitor on the bass control should be something like 470pF.
Cool, yeah I'm A/Bing it with the benson now.Manfred wrote:You don't have to do this, I do not receive commission for.Gotcha, cool. Can't really swing buying this thing though.
It should be only a hint regarding messurement.
Trial and error always a practical methode.I'm thinking that just trying to come up with educated guess values for the caps and do listening tests is the right path here?
Sure doespietro_moog wrote:It looks like a Wampler Plexi Drive, kind of
BTW, have you measured the capacitances using a capacitance meter?Really hard to measure capacitance on SMD, if anyone has tips I'm all ears.
Sort of, I tried using my multimeter but could only get readings of which I was really confident on C1 and C2. The rest my multimeter just wouldn't read.Manfred wrote:BTW, have you measured the capacitances using a capacitance meter?Really hard to measure capacitance on SMD, if anyone has tips I'm all ears.
Even if the read values are not 100% correct they could be of help to find the appropriate values.
I hear what you're saying, and I'll try again, but my meter literally would not give readings for some of those caps. As in, the display doesn't change from touching nothing, to touching the contacts on the caps.vtguedes wrote:Maybe you could try comparing capacitance readings between the original board and your breadboarded circuit?
Q1 source: 0.366VManfred wrote:hi atalas,
could you please measure the voltages on the source pins and also the set values of the trimming potentiometers.
I have doubts as to the accuracy of the read value to C5.
With a value of 1.5 nF the roll-off frequency will then between 300 to 400 kHz.
C7 and C9 should be measurable If the treble potentiometer ist set to the maximum value.
To my ears, the benson definitely has more gain or distortion (not sure what the right term is here), and is brighter. The clone is fatter, doesn't cut quite as well.pamaz wrote:hello Guys.
First of all, many thanks to you for this effort. i was hoping to find one of these benson pre to trace , but you have been much faster than me!
Still i have not started a proto, but as a general suggestion, I would try to increase C5 value, as listening to the samples, it seems that the main difference i can hear from the pc ( no headphones on hand just now). is that the clone is
lacking on midbass and a little bit of gain.
Increasing C5 , you 'll get a larger mid low response and a larger gain at the same time. I cannot point out a precise value, but I would expect to get a considerable effect with something in the range of 220- 470 nf .
Thanks again.
Paolo
