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The Leben CS300XS Thread - Page 124

post #1846 of 2118

http://en.wikipedia.org/wiki/Choke_%28electronics%29

 

It even doesnt have to cost to much,I have used a little transformer from a old powersupply.

post #1847 of 2118

Another new-bee question:

What is the difference in dB's between a 100x gain tube and say a 50x or a 20x gain tube?

Is going from 100 gain to 50 gain 6dB electrically (and then 3dB in the speakers/headphones)?

post #1848 of 2118

BTW, in my CS300 (without X or XS) the following tubes are fitted (alledgedly from factory):

Input tubes are Golden Dragon ECC83T (2 pcs)

Output tubes are Golden Dragon EL84/6BQ5 (4 pcs)

 

On the plate inside the amp, next to the tubes, is written:

For input tubes: 5751 / ECC83

For output tubes: EL84 / 6BQ5

 

This means that the stock input tubes has a gain of 100?

 

Edit: Sorry, it's GOLDEN Dragon of course.


Edited by LarsHP - 8/4/13 at 6:33am
post #1849 of 2118
Do you mean Golden Dragon? In any case I'm sure those tubes are current production Chinese, and IMHO there are much quieter and better available tubes.
post #1850 of 2118

Thanks Skylab, but I frankly don't know what to look for, because these spec's aren't stated.

 

However, the "T" in the end of ECC83T is for "Trustworthy", which is supposed to mean better spec's and measurments. Spec'ed to European standards or the like.

 

I have seen a pair of "Telefunken ECC83" up for sale, but they are incredibly expensive. USD290 for a pair, sold by a private person. Are these creme de la creme or what?


Edited by LarsHP - 8/4/13 at 6:38am
post #1851 of 2118
Do you have a local hi-fi store that sells current production tubes? If so, you might pick up a pair of the reissue Tung-Sol 12AX7's which are Russian / New Sensor corp and are pretty decent. But the best IMHO would be to find some NOS 5751 tubes. These can be easily (if not cheaply) purchased in the US from places like TubeDepot.com; not sure what that means for you.
post #1852 of 2118

There aren't any shops locally, unfortunately. I expect a lower gain than the stock will be a good idea. As I have understood, then ECC83 has a gain of 100, which means I should try getting 5751 (gain 70) or perhaps 12AT7 (gain 60). It's no problem to order from the states or elsewhere.

 

BTW I have found that the terrible distortion when playing Prelude from "Carmen" is caused by a very high input signal, and that lower level tracks play louder without distortion. The Prelude from Carmen starts off with a big bang on the drums and this reaches the digital limit (0dB) with full power which then puts the full 2.5 volt signal into the amp. When listening to pop etc. with less than thunderous levels at -1dB or so, then I can have higher loudness / listening levels.

 

In other words, it points to getting less gain than stock, I think. I listen at from 9 to 12 o'clock on the volume dial - with the HE-6!

post #1853 of 2118

There are certainly better tubes than Golden Dragon but you should not get different results with other tubes regarding output and distortion, or only marginally. 5751 has a lower gain than ECC83 but the difference is not great. It is not sure that the amplification will be lower with 5751. Often amplification is controlled by the circuit and not by the tube and this seems probable for Leben because it is self-biasing. I didn't get the impression of lower volume with 5751 when I tried but I didn't compare tubes for this reason and am not sure. It there would be a difference it is not night and day.

 

It has been repeatedly reported that HE-6 require more power than is possible with Leben's headphone output. It is a 12/15 W amplifier but not on the headphone output. Other tubes should not make much difference.

 

You can get better sound with other tubes. Telefunken are much overrated in my opinion. Learning about tubes takes some time and work and there is no quick fix, but it is worth it in sound quality and fun.
 

post #1854 of 2118

Edit * Anders was just ahead of me

 

Out of my own expeirience, changing the drivertubes for lower gain ones doesn't do a lot.

The CS300 is a beautifull amp made with excellent parts and should sound great out of the box but I think it was sold to you with cheap chinese tubes in it .

 

If I where you I would start with replacing the Chinese tubes with decent ones and start from there .

I reccomend :

4 Reactor 6p14p output tubes

2 JJ or Electro Harmonix 12ax7/ecc83 or any nice afordable NOS tubes you come across .

I have allso tried  the NOS RCA or General Electric 6211A (70% gain), a very microphonic but excellent sounding tube, you should be able to get those under 10 Euro.

 

I use 2 NOS Adzam ECC83 and 4 Reactor 6p14p and have placed a Choke in the ECC83 powersupply .


Edited by Raaf - 8/4/13 at 10:34am
post #1855 of 2118

I really think it does sound great as it is, except for the slight noise when using LCD-2 and of course that it doesn't drive the HE-6 from the headphone output (as it is), but this was frankly not a surprise to me. However, the HE-6 sounds well bodied and has good weight in the mids and bass - though not the same tight and punchy bass as my two solid state amps (Master-6 and Soloist).

 

It seems to excel with slow, soft music like Norah Jones (naturally, now we saw that she has the amp herself) and violin / classical / vocal music.

 

Edit: typo


Edited by LarsHP - 8/5/13 at 10:45am
post #1856 of 2118
What is the going price on the CS300XS these days?
post #1857 of 2118

I just ordered a pair of Siemens & Halske 5751 NOS tubes from the grand old (NOS-tube) man here in Norway. These should be as good as it gets, as far as I understand. This reduces the gain of the input tubes back to the original level (70). It's supposed to be very silent tubes, so hopefully it will decrease the slight hiss I hear with LCD-2 (and my 91dB speakers).

 

BTW he told me that the Golden Dragon ECC83T is a VERY good tube, comparable to the best NOS tubes. List price in Norway is US$50 each (plus VAT), so it's not that the input tubes in the amp are bad or very noisy, they just have a little too much gain.

post #1858 of 2118

Ah well , it is with tubes as it is with cables wink.gif

I hope your new tubes do perform as you expect, let us know.
 

post #1859 of 2118

I got an answer from Leben via the official dealer, that the distortion I hear on the Prelude from Carmen isn't caused by the higher gain with the ECC83, but more likely that either the input or output tubes are getting worn out. This is of course something I have to check out. I got extra tubes from the seller also, so it's quite easy to do.

 

EDIT:

Talked to the seller of my amp. The tubes in the amp haven't even used for more than 30 hours, so this is obviously not the reason.

 

Maybe it's because I use hard to drive headphones? 50 Ohms is not bad itself, but with a sensitivity of 91dB (LCD-2) and especially HE-6 (77,5dB according to Inner Fidelity) this could ask more current, than the headphone output can deliver, when a maximum level heavy bass transient hits the input? Maybe the full 2.5V input exceeds the input circuits? (In other words it expects max 2V?)

 

The HD800 has a much easier load (for this amp), so this might be another reason to go for it for the Senn's.

 

For the HE-6 and LCD-2 it might be better to use the speaker outputs with a resistor in parallel. I have asked Leben how high impedance they recommend as maximum (with 8 Ohm setting on the selector). This will give me an idea how much power the headphones will be able to receive. It should be able to handle more than 8 Ohms, I expect, but how much, I don't know.


Edited by LarsHP - 8/7/13 at 9:44am
post #1860 of 2118

I also believe that the distortion depends on the power demand of HE-6.

 

Please tell us what Leben say about driving headphones on the speaker outputs. It has been reported earlier that the power is enough for HE-6 but the impedance mismatch could possibly damage the transformers. That is probably the only part of the amplifier that can't easily be repaired, and would be expensive too.

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