Impedance match for a CT5

[Vhiner]

Guys, I need some quick advice. I have a CT5 and I'm considering a Classe CT-2300 to go with it. I already love it with my CT-2200 but want more power. The CT-2300 has an input impedance of 50k Ohms.....the output impedance of the CT5 is 800 Ohms. Will this still sound good? My current amp, the CT -2200 has an input impedance of 100K Ohms, which is theoretically ideal. I'm wondering if I'll hear that 50k Ohms difference. Thoughts?

[fgchong]

The rule of the thumb is the input impedance of the power must be more than 10x the output impedance of the pre. In your case, it is well above this value, it should be ok. There will be a some attenuation of the signal provided to the new power amp (CT-2300) due to the reduction in output impedance of the new power amp.

One point to note is that most pre-amp output impedance is not the same throughout the frequency spectrum, this will result in different amount of attentuation at different frequencies and this will affect the tonal balance of the music.

[Vhiner]

The rule of the thumb is the input impedance of the power must be more than 10x the output impedance of the pre. In your case, it is well above this value, it should be ok. There will be a some attenuation of the signal provided to the new power amp (CT-2300) due to the reduction in output impedance of the new power amp.

One point to note is that most pre-amp output impedance is not the same throughout the frequency spectrum, this will result in different amount of attentuation at different frequencies and this will affect the tonal balance of the music.

Thanks so much for the reply. I apologize for being a bit dense....what do you figure I might "hear" as a result of this attenuation....do you mean I may have to turn the potentiometer up? I suppose the tonsil balance changes will be unpredictable. I can't audition this amp before buying but I had hoped that upgrading within the same line would be a safe bet. What do you think?

[fgchong]

Yes, you can compensate by increasing the "volume" of the pre.

[Coppy]

Guys, I need some quick advice. I have a CT5 and I'm considering a Classe CT-2300 to go with it. I already love it with my CT-2200 but want more power. The CT-2300 has an input impedance of 50k Ohms.....the output impedance of the CT5 is 800 Ohms. Will this still sound good? My current amp, the CT -2200 has an input impedance of 100K Ohms, which is theoretically ideal. I'm wondering if I'll hear that 50k Ohms difference. Thoughts?

Don't think you will have any impedance issues but I'd keep the ICs to the amp short as the CT-5s higher output impedance doesn't want to drive long runs. A couple of meters of quality cable should be fine.

[Joe Appierto]

Don't think you will have any impedance issues but I'd keep the ICs to the amp short as the CT-5s higher output impedance doesn't want to drive long runs. A couple of meters of quality cable should be fine.

Exactly. And I believe that the lower the cable's total capacitance, the better.

[Kal Rubinson]

The rule of the thumb is the input impedance of the power must be more than 10x the output impedance of the pre. In your case, it is well above this value, it should be ok. There will be a some attenuation of the signal provided to the new power amp (CT-2300) due to the reduction in output impedance of the new power amp. I doubt there will be any reduction in voltage with this impedance ratio unless the preamp has severely inadequate and puny current output ability. That's why the rule of thumb is 10x.

[fgchong]

I doubt there will be any reduction in voltage with this impedance ratio unless the preamp has severely inadequate and puny current output ability. That's why the rule of thumb is 10x.

Theoretical there will be a reduction in voltage across the output of the pre-amp due to the decrease in input impedance of the power-amp leading to the reduction in signal, this can be explained by Ohm's law.

I tried a couple of combinations of pre & power a few years back when I replaced my all tube pre-power to the current hybrid system i.e. tube pre/ss power. In each combination I tried, there was a need to adjust the output of the pre to maintain the same level of musical output, the difference was how much I adjusted.

[Kal Rubinson]

Theoretical there will be a reduction in voltage across the output of the pre-amp due to the decrease in input impedance of the power-amp leading to the reduction in signal, this can be explained by Ohm's law. It only follows Ohm's law if current is limited or fixed. That is only an issue, as I said, if the preamp is a whimp.

[fgchong]

It only follows Ohm's law if current is limited or fixed. That is only an issue, as I said, if the preamp is a whimp.

Well, you can also try it out yourself to find the truth......

[Vhiner]

Thanks for all of the input so far. I am a registered CJ CT5 owner, yet have been unable to get two phone calls returned by CJ regarding this question. Service is not what it used to be since Ed's departure..,at least that's been my experience.

I will be using one meter Shunyata Python Zitron IC's...so I assume I'm ok with this purchase...at least as far as impedance goes. It'd be great to hear from someone who's hooked the CT5 up to a 50k Ohm amp.

[Kal Rubinson]

Well, you can also try it out yourself to find the truth......

Been there. Done that.

[ronenash]

Rest assured the ct5 will have no problem driving a 50k ohm load without any degradation in sound quality or output level. Just make sure you use low capacitance cables such as Wireworld.

[Vhiner]

Rest assured the ct5 will have no problem driving a 50k ohm load without any degradation in sound quality or output level. Just make sure you use low capacitance cables such as Wireworld.

The Shunyata Zitrons' demonstrate vanishingly low capacitance.....among the best available. So, I should be good to go. Thanks to everyone for the help.

Still no call back from Conrad Johnson after repeated respectful and polite requests......not a good sign.

[Coppy]

conrad-johnson preamps are know for their high output. Some even complain about the output level. The CT-5 output should be plenty to drive any reasonable cable. Maybe this is all by design by c-j to deal with the the higher output impedance of tube designs.

Enjoy the music...

[microstrip]

Rest assured the ct5 will have no problem driving a 50k ohm load without any degradation in sound quality or output level. Just make sure you use low capacitance cables such as Wireworld.

+1. You can add Shunyata, Cardas and Kimber to the list of brands that are known to match well cj preamplfiers and having low capacitance.

BTW, the attenuation due to loading a preamplifier having 800 ohms with 50 Kohms is less than 0.15 dB - you can ignore it. At 20 Hz the attenuation will be around 0.3 dB due to the impedance increase at low frequencies - this means flat response from 20 Hz upwards 0, -0.15dB. And excellent result.

[Sunnyboy1956]

Have been using Cardas Gold Reference throughout my system incl power chords except for two thick Shunyata snakes between the wall and the Triton and power amp/Triton.

[Vhiner]

I've had the 50K Ohm Classe' CT-2300 hooked up to my CT5 for several days now and have a verdict: the two pieces of equipment are a perfect match! The 2300 beats the formidable CA-2200 in every way. I don't miss those extra 50K Ohms at all. My Thiels *do* love the extra 200 watts the 2300 brings to the table. Highly recommended.