Hi Everyone,
Just a little warning why you should NOT buy this thing.
It is a remote controlled preamplifier based on a well known CJ preamp.
The case and badge is a Goldmund copy.
The good stuff, the case and front panel is nice and well made, the display
looks good with big digits.
Hifi Remote PRT-05A Tube Preamplifier 128 Steps Relay Refer Conrad-Johns Circuit is its full name, the input
volume selection and standby transformer
is from Sengterbelle.
Everything fits well no nasties to see, except and here comes
The bad stuff, the knobs were not properly fitted and wobbled on the shafts
of the rotary encoders.
Alu tape around the shafts fixed this.
The shafts of the encoders were loose as well too loose so the heavy knobs would hang against the front panel.
The switch funktion stopped working on both after a day.
New rotaries cured this.
The relay controlled volume part has a build in high cut filter above setting 65.
Very audible and visible on the scope, no idea how this can happen!
It does Not have constant in and output impedance as is stated in the separate
volume part, only the input impedance stays the same.
Sometimes the volume would go down when pressing up.
The capacitors next to the little heatsink on the standby board are no name brand, 1000uF plus 1000 uF each and getting quite warm, replaced it with something better.
The CJ part of this thing I won't write about as I removed it and put something good in instead.
Is it worth the 375 plus 90 usd shipping?
Certainly Not especially if you have to ad custom and vat etc. to it.
Regards, Veeren
Just a little warning why you should NOT buy this thing.
It is a remote controlled preamplifier based on a well known CJ preamp.
The case and badge is a Goldmund copy.
The good stuff, the case and front panel is nice and well made, the display
looks good with big digits.
Hifi Remote PRT-05A Tube Preamplifier 128 Steps Relay Refer Conrad-Johns Circuit is its full name, the input
volume selection and standby transformer
is from Sengterbelle.
Everything fits well no nasties to see, except and here comes
The bad stuff, the knobs were not properly fitted and wobbled on the shafts
of the rotary encoders.
Alu tape around the shafts fixed this.
The shafts of the encoders were loose as well too loose so the heavy knobs would hang against the front panel.
The switch funktion stopped working on both after a day.
New rotaries cured this.
The relay controlled volume part has a build in high cut filter above setting 65.
Very audible and visible on the scope, no idea how this can happen!
It does Not have constant in and output impedance as is stated in the separate
volume part, only the input impedance stays the same.
Sometimes the volume would go down when pressing up.
The capacitors next to the little heatsink on the standby board are no name brand, 1000uF plus 1000 uF each and getting quite warm, replaced it with something better.
The CJ part of this thing I won't write about as I removed it and put something good in instead.
Is it worth the 375 plus 90 usd shipping?
Certainly Not especially if you have to ad custom and vat etc. to it.
Regards, Veeren
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Hi there Veeren.
No doubt you spent some time evaluating the preamp, and it is really nice to see that you are sharing your findings with others.
Cheers,
Nick
No doubt you spent some time evaluating the preamp, and it is really nice to see that you are sharing your findings with others.
Cheers,
Nick
Hi Nick, thanks!
I forgot to mention that the badge also fell of, re glued it .
What still baffles me is how the relay controlled volume section can work as a high cut filter as there are no capacitors in there!
Regards, Veeren
I forgot to mention that the badge also fell of, re glued it .
What still baffles me is how the relay controlled volume section can work as a high cut filter as there are no capacitors in there!
Regards, Veeren
They stuffed-up impedance; usually you get a constant impedance at almost all relay settings, but you need to be careful with resistors' selection... for each step.
So above that setting of 65, as you said, the input impedance as seen by the source, is most likely very low.
So above that setting of 65, as you said, the input impedance as seen by the source, is most likely very low.
Thank you Extreme_Boky,
In a while I will measure the thing to see what happens above setting 64.
For now I know that the attenuation at 65 and 66 is higher than below 65
meaning it gets softer a few steps before it gets louder again.
The output impedance changes from 2k4 to 5k2 above setting 64.
In a while I will measure the thing to see what happens above setting 64.
For now I know that the attenuation at 65 and 66 is higher than below 65
meaning it gets softer a few steps before it gets louder again.
The output impedance changes from 2k4 to 5k2 above setting 64.