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Threshold T-200. Help me choose a preamplifier

Good day, Colleagues!
Not so long ago, at an auction in Japan, I accidentally won the Threshold T-200 amplifier. I really wanted this brand, but I was looking for the T-800D model. But it turned out to buy this amplifier ... And now I am very tormented with the choice.
I spent two days on the internet looking for balanced amplifiers. Here is a list, is there anything on this list worth seeing?
Pass Labs X1 - 
This preamplifier is sold in Russia at a very good price, it seems to me. 1800 dollars. But I do not know his condition. The photographs show that the cable that connects the power supply and the preamplifier itself is frayed. And the power supply is not complete, but a small black box.
Pass Labs X2.5 - I found this preamp for 2000 euros in Croatia, but shipping will cost around 500 euros, so it is already very expensive for me. 
Black Ice F-360 - A very interesting preamplifier. The ad suggests that this preamp has very high detail and can expand the scene. :) But I don't believe in advertisements.
Leema Acoustics Pyxis ll -  This amplifier is quite expensive, I found it in my country for $ 2500 and this is a showcase sample. It has an impressive range of features, there is a phono stage, which I also need, and balanced inputs and outputs.
Electrocompaniet ec 4.7
Electrocompaniet EC 4.8
Krell KSL-2
Audia Flight Pre
Quad Artera Pre
Rotel RC-5000
Audio research LS-15
audio research LS-2B
Spectron Model 10
Audio research LS 17
BAT VK-30
McIntosh C2200 - But this is already very dear to me.

I really look forward to your help and advice in choosing.

vetusto

Showing 7 responses by imhififan

imhififan's avatar
imhififan
2,137 posts
 

NT-505 XLR → Jeff Rowland balanced preamp → Threshold amplifier (RCA input) - there is sound - This connection worries me a lot.

It depends on the Threshold amplifier input circuit design, some amplifier just simply use a spst switch to connect/disconnect RCA input to XLR pin 2.

If that is the case, you need to pull out the XLR connector from the Threshold amplifier input, only connect the tube preamp to the RCA input of Threshold amplifier and switch the input selector to unbalanced and see if there is sound.

imhififan's avatar
imhififan
2,137 posts
 
For preamp choice, if you intend to use balanced inputs of the Threshold T-200, be caution of its 2kΩ input impedance!

Best to choose a preamp with balanced output impedance 100Ω or less.

imhififan's avatar
imhififan
2,137 posts
 
For good voltage transfer from preamp to power amp it is better to have a low impedance at the output of the preamp and to have a high impedance at the input of the power amp.
We should using a minimum ratio of >1:10 to improve transfer efficiency and I recommend >1:20 which transfers > 95% of the voltage.
100Ω : 2000Ω = 1: 20
2000 / (2000+100) = 95%
If the ratio is low it will affected the system frequency response and noise floor. Also a preamp with high output impedance will has greatest possibility to hear differences in interconnect cables, a very low output impedance preamp will be immune to cable effects.

imhififan's avatar
imhififan
2,137 posts
 
Stereophile measured the input impedance of the T-200 at only 926 ohms
If the input impedance of the T-200 only 926 ohms, the required output impedance of the preamp should be much lower!


imhififan's avatar
imhififan
2,137 posts
 
+1 @invalid
Just go with unbalanced input of the T-200, all preamp on OP’s list are compatible.
imhififan's avatar
imhififan
2,137 posts
 
Just for your information,

Threshold T-200 (1994-98) was designed by Swedish engineer Michael Bladelius. At the time Michael was working in Threshold, the company underwent ownership changes and sold to Dynatech in 1988, and Nelson Pass left it in 1992. Mike Bladelius became the head of the design office at that time.

Threshold T-200 specification:
Output power: 100W into 8 ohms (20dBW), 200W into 4 ohms (20dBW), 350W into 2 ohms (19.4dBW).
Full power bandwidth: DC–80kHz, +0/–3dB. Distortion: <0.1%; typically <0.02%.
Voltage gain: 27.4dB balanced, 28dB unbalanced.
Input sensitivity: 1.21V balanced, 1.13V unbalanced to produce 100W into 8 ohms.
Input impedance: 50k ohms unbalanced, 2k ohms balanced.
Current consumption: 2A, idle; up to 12A full output in mono.

imhififan's avatar
imhififan
2,137 posts
 
There is one question I don't understand: Threshold T-2 was designed specifically for T-series amplifiers, and the specification for this preamplifier says that the impedance at the balanced output is 150 ohms. It turns out that the engineers have made two devices incompatible with each other? It doesn't look right…
Although the general 'rule of thumb' is that it is better to have a low impedance at the output of the preamp and to have a high impedance at the input of the power amp and we should using a minimum ratio of >1:10.
But it is fair to point out there's exception IF THE PREAMP CAPABLE OF PROVIDE THE REQUIRED CURRENT into a low input impedance power amp. For example: krell cast connection, darTZeel 50 ohms BNC and jeff rowland 600 ohms input impedance.

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