Hi all,
I have a Mission Cyrus 2 that I would like to modify so it can be used as a power amp only, now I know that it’s preamp stage (besides the phono stage input) is passive so basically as far as I understand I only need to bypass it volume potentiometer.
But the thing is that as an integrated amp with passive preamp stage the power amp stage probably has a higher input sensitivity than an active preamp stage so I assume that if I’ll just bypass the volume pot and connect an active preamp (tube preamp in this case) to the power amp stage it will overload the Cyrus 2 power amp stage input, any suggestions for where in the input circuitry of the Cyrus 2 should I connect the external active preamp so the power amp stage won’t be overloaded by a too high of an input signal from the active preamp?
I’ll include the Cyrus 2 schematics soon.
Thanks
I have a Mission Cyrus 2 that I would like to modify so it can be used as a power amp only, now I know that it’s preamp stage (besides the phono stage input) is passive so basically as far as I understand I only need to bypass it volume potentiometer.
But the thing is that as an integrated amp with passive preamp stage the power amp stage probably has a higher input sensitivity than an active preamp stage so I assume that if I’ll just bypass the volume pot and connect an active preamp (tube preamp in this case) to the power amp stage it will overload the Cyrus 2 power amp stage input, any suggestions for where in the input circuitry of the Cyrus 2 should I connect the external active preamp so the power amp stage won’t be overloaded by a too high of an input signal from the active preamp?
I’ll include the Cyrus 2 schematics soon.
Thanks
The obvious solution is to leave the volume control in and use it as a kind of level preset.
If for some reason you hate that volume control, you can remove it and replace it with a two-resistor attenuator set to the value you need.
But you can do a quick test by turning the volume control all the way up and check if it indeed overloads; I guess you have a volume control somewhere else in your system?
Or check the manual ;-)
Edit: see attachment - yes it looks like you need an attenuator!
Jan
If for some reason you hate that volume control, you can remove it and replace it with a two-resistor attenuator set to the value you need.
But you can do a quick test by turning the volume control all the way up and check if it indeed overloads; I guess you have a volume control somewhere else in your system?
Or check the manual ;-)
Edit: see attachment - yes it looks like you need an attenuator!
Jan
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I would like to keep the volume control but modify one of the inputs for a "bypass" input so I can connect an external tube preamp directly to the power amp stage.
What is the nominal output level of your preamp? What do you see as the advantage of bypassing the volume control?
When you say bypass, you mean you want to keep it but insert the signal directly at the top?
In that case, the bypass is exactly the same situation as the volume control turned all the way up.
If you want to keep the volume pot but modify one input to access the power amp input without being connected to the volume control, you probably need some sort of switching arrangement.
Jan
When you say bypass, you mean you want to keep it but insert the signal directly at the top?
In that case, the bypass is exactly the same situation as the volume control turned all the way up.
If you want to keep the volume pot but modify one input to access the power amp input without being connected to the volume control, you probably need some sort of switching arrangement.
Jan
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Used Cyrus as a power amp for several years.
I have owned Cyrus brand amps for nearly 40 years... they are amazing!
I used a Cyrus *exactly as you stated* for a period of time. In my case,
volume pot straight open... and used my source or pre-amp to control
the volume. I was driving revealing Quad ESL-63 (in volume limited,
apt/home setting, sharing a common wall with a complainer)
The front end switching and control *are indeed neutral enough*
in fact more transparent than many notable pre-amps and power amps
that I have compared / tested.
It would be UNWISE to chop the Cyrus up to make it just a power amp.
it is perfect the way it sits... even better when recapped and updated.
If you want to meddle with it... rebuild it. Don't destroy it...
I routinely use my Cyrus as a "bench amp", as an integrated
or driven with a(ny) source as an amp...
I have owned Cyrus brand amps for nearly 40 years... they are amazing!
I used a Cyrus *exactly as you stated* for a period of time. In my case,
volume pot straight open... and used my source or pre-amp to control
the volume. I was driving revealing Quad ESL-63 (in volume limited,
apt/home setting, sharing a common wall with a complainer)
The front end switching and control *are indeed neutral enough*
in fact more transparent than many notable pre-amps and power amps
that I have compared / tested.
It would be UNWISE to chop the Cyrus up to make it just a power amp.
it is perfect the way it sits... even better when recapped and updated.
If you want to meddle with it... rebuild it. Don't destroy it...
I routinely use my Cyrus as a "bench amp", as an integrated
or driven with a(ny) source as an amp...
Hi,
Sorry for my late response.
I don't have a tube preamp it so I don't know it's output level but as far as I understand there is sort of a standard...please correct me if I'm wrong.
I believe that by insert the signal directly to the power amp stage I'll get a "cleaner" signal so there will be no "degrading" effect of a non used passive components in the signal path.
Looking for a suggestion for the best way to do it.
Thanks
Sorry for my late response.
I don't have a tube preamp it so I don't know it's output level but as far as I understand there is sort of a standard...please correct me if I'm wrong.
I believe that by insert the signal directly to the power amp stage I'll get a "cleaner" signal so there will be no "degrading" effect of a non used passive components in the signal path.
Looking for a suggestion for the best way to do it.
Thanks
I've already kind of rebuilt it, changed all the electrolytics (and non electrolytics in the signal path) capacitors, replaced the original volume pot with ALPS RK27 for better volume tracking and bypassed the balance control, replaced the bipolar capacitors with poly capacitors (not the 470uf ones), changed the rectifier diodes with slow fast recovery diodes, installed multi turn trimmers in parallel to the bias resistors for more accurate bias calibration, removed the ribon cable and relocated the RCA to input selector connections (point to point soldering using Van damme coax cables) to the bottom side of the PCB, installed an on/off switch so the phono stage can be switched off when not in use (instead of keeping it drawing constant power as it was originally), fully dismantled and cleaned the input selector and record output selector.....and more.
My intention is not to "chop" the amplifier, I just want to modify one of it's inputs so it will serve me as a direct input to it's power amp stage.
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