The VDR or Varistor only pass high voltage peaks that come along the mains cables with the 50/60Hz 115/220Vac.
These spikes are usually very short duration.
The purpose of the interference suppressor is to short the HV spike to neutral.
It will do nothing for the amplifier switch on or switch off.
These spikes are usually very short duration.
The purpose of the interference suppressor is to short the HV spike to neutral.
It will do nothing for the amplifier switch on or switch off.
Thank you so much Andrew.
So I can use it to protect the equipment for spikes. Does it leave any signature ? any noise ?
To avoid switch on thump maybe I could use a 0.1u in parallel with the switch... just to avoid arcing... right ?
So I can use it to protect the equipment for spikes. Does it leave any signature ? any noise ?
To avoid switch on thump maybe I could use a 0.1u in parallel with the switch... just to avoid arcing... right ?
I doubt it.
A switch on thump seems more like the output conditions of the amplifier are taking time to settle to the audio signal level. At OFF the output has zero volts.
As the amp starts up the output can go +ve or -ve or both at various times in the few ten's of ms that all the circuits take to stabilise to quiescent conditions.
A spark at the switch only occurs at switch OFF and this can give a sharp RF transient to be amplified and transfered to the speaker.
When I wrote about switch on thump, I meant at switch off... I am sorry for the mistake.
To avoid this spark on the switch can I use a 0.1uF or should I use other value ?
To avoid this spark on the switch can I use a 0.1uF or should I use other value ?
fit a switch interference suppressor across the switch.
fit RF filter at the input of every receiver.
fit RF filter at the input of every receiver.
The OPAMP version was a kit we once sold where I work. The kit came with inexpensive OPAMPs and I upgraded them to OPA2134s. I upgraded a lot in the kit and converted it to a battery powered unit.
The phono preamp is very good and a few friends use the same one and liked it. I used mine for years before the boozhoundlabs unit.
I sold one of the OPAMP ones tonight (still have another) at my audio club swap meet. Hope the guy likes it as much as I did.
Thank you AndrewT
Would you please suggest a cap value for the interference suppressor ?
My search led me to the Vishay MKP 336 X2 but there are too many values to choose from.
Regards
Ricardo
Hello Salas and all,
so o finally took the time and measured my Version (posting 4141) of the
Salas njfet for LyraDorian.
Salas, could you please be so kind and tell me if everything is within the
range?
Q7 d = 17,2 Volts
Q7 g/s = 5,96 V
Q6 c = 11,95 V
Q6 e = 5,3 V
Q3 d = 15,1 V
Q4 d = 14,7 V
Ahhh and forgot: i changed R11 as you mentioned to 2,7K
Greetings Ulf
so o finally took the time and measured my Version (posting 4141) of the
Salas njfet for LyraDorian.
Salas, could you please be so kind and tell me if everything is within the
range?
Q7 d = 17,2 Volts
Q7 g/s = 5,96 V
Q6 c = 11,95 V
Q6 e = 5,3 V
Q3 d = 15,1 V
Q4 d = 14,7 V
Ahhh and forgot: i changed R11 as you mentioned to 2,7K
Greetings Ulf
Hi Salas,
so you mean 1,8K instead of 2,7K and vice versa?
What are the exact expected voltages at all those points?
Thanks and greetings Ulf
so you mean 1,8K instead of 2,7K and vice versa?
What are the exact expected voltages at all those points?
Thanks and greetings Ulf
Yes that is what I mean. Your other voltages are as expected, but Q3 pulls lower current than predicted and squeezes Q4's voltage frame. By exchanging those resistors I expect the voltages around output buffer to change to what I would like more. Let me know Q3d-gnd and Q4d-gnd when you will do. There can be no exact voltages expected with various Jfets, just correct ranges. Its possible it will play better also, give it a listen after the resistors change too.
Can any one suggest why the RIAA compensation in a phono preamp would stop working when it is only a few Rs and Cs. The preamp is boosting the signal but the sound is bright and tinny with little bass. If I replace the phono stage and change nothing else the sound properly balance.
Any clues how this could just happen for no reason???
Any clues how this could just happen for no reason???
You are talking about the Boozhound Labs one, right? To suddenly lose some passive parts on both channels is highly unlike. Could be oscillating. Did you change any interconnects, or did anything new that could upset it? I would check bias voltages and PSU also. Output Jfets could have been damaged if you had exchanged connections and was alive too. Has no buffer stage and no buffer series resistor I think.
All good suggestions thanks. trying some 10uf polies as input caps.
I could increase the tracking force a little. That usually darkens the sound a bit.
Why would you need any input caps? A jfet input has no gate current to leak towards the cart. We do that in BJT input phono stages with enough base current. Use 100R in series with your output cap. Maybe there is oscillation in the output stage with your interconnects. Take out or jumper that 100R input gate stopper also. Adds enough noise, and it ain't necessary. Use a 100K trimmer instead of a 47K resistor input load and hunt from 10K up listening to your probably MM cart since you got a circa 40dB gain circuit. That will give you a wider tonal range than any mechanical tweaks can. Shapes mid high a lot.
Hi there,
what do you think about the following concerning two psu-regs.....?
Which way will anticipatory be better
A: Using one psu (Salas shunt for MC) each channel
or
B: splitting the circuit between R1 and R10 and use one reg. for the first
stage of both channels (reg goes to R1/R7) and the second reg goes to
the second stage (R10/R11)?
Would you expect problems with the Sense of the regulator because of the
splitted wire to the channels?
Greetings Ulf
what do you think about the following concerning two psu-regs.....?
Which way will anticipatory be better
A: Using one psu (Salas shunt for MC) each channel
or
B: splitting the circuit between R1 and R10 and use one reg. for the first
stage of both channels (reg goes to R1/R7) and the second reg goes to
the second stage (R10/R11)?
Would you expect problems with the Sense of the regulator because of the
splitted wire to the channels?
Greetings Ulf
Use one per channel since the shunt regs are very low Zo and the demands of first stages are not taxing them so to prefer the per stages split. Did you exchange the R11-R12 by the way?