View Full Version : Escoed Troika arrives. SUT advice
Hi all,
Well, the Troika has finally arrived and after about 30 seconds it was obvious that here was a much better match for my Ittok LViii than my previous 103Pro with its extra weight. It sounds much more refined with loads of texture and detail in the bass and also higher bass volume in the mix. Funnily enough, treble detail is also much improved and piano sounds so much more authoritative so I guess the Esco fineline tip is also doing its bit in comparison with a stock Troika.
Anyway, not here to extoll the virtues but rather to ask for advice regarding SUTs. I already had my Audio-Technica AT-650 adjustable, always using the 40 ohm setting with the 103. Then I got hold of the Haufe transformers (also 40 ohms) and made my own little box of tricks up and I found it an improvement on the AT. Now with the Troika I have just tried my AT again and my first impression is that it sounds better than the Haufe job, especially on the 3 and/or 20 ohm ohms setting although that could be down to the fact that I seem to get greater gain on the 3 ohm setting, although perhaps a bit too bright. I believe these ohms settings on the AT are really meant to represent 10x their value as far as load impedance is concerned. Anyway, can anyone confirm what should be the correct setting for the Troika and I´ll take it from there.
Chris
Hi all,
Well, the Troika has finally arrived and after about 30 seconds it was obvious that here was a much better match for my Ittok LViii than my previous 103Pro with its extra weight. It sounds much more refined with loads of texture and detail in the bass and also higher bass volume in the mix. Funnily enough, treble detail is also much improved and piano sounds so much more authoritative so I guess the Esco fineline tip is also doing its bit in comparison with a stock Troika.
Anyway, not here to extoll the virtues but rather to ask for advice regarding SUTs. I already had my Audio-Technica AT-650 adjustable, always using the 40 ohm setting with the 103. Then I got hold of the Haufe transformers (also 40 ohms) and made my own little box of tricks up and I found it an improvement on the AT. Now with the Troika I have just tried my AT again and my first impression is that it sounds better than the Haufe job, especially on the 3 and/or 20 ohm ohms setting although that could be down to the fact that I seem to get greater gain on the 3 ohm setting, although perhaps a bit too bright. I believe these ohms settings on the AT are really meant to represent 10x their value as far as load impedance is concerned. Anyway, can anyone confirm what should be the correct setting for the Troika and I´ll take it from there.
Chris
Whilst I have no experience of the Linn Troika (the only Linn cartridge I have used was the Asak), in general all mc cartridges should be loaded by at least 100 Ohms. Moving coil cartridges are voltage sources and so have a comparatively low source impedance. They should be fed into a device offering a load impedance several times higher than that of the coil resistance. I have recently been playing with a Denon 103 and run it into 100 Ohm, but am thinking of trying 470 Ohm.
If you know the turns ratio of your Haufe transformers and also the load impedance of the preamplifier into which they feed, then the load presented to your cartridge is the load impedance of the amp/(turns ratio)^2. Thus with the usual 47 kOhm preamp impedance and with a 10:1 turns ratio (i.e.10x or 20dB), the load presented to the cartridge will be 470 Ohm (i.e. 47000/100 = 470).
As always your ear should be the final arbiter, but intially I would suggest you try something > 150 Ohm and see how you get on.
Regards
Barry
Linn and Naim always loaded the Troika at about 470 Ohms as I remember and I believe naim tinkered around with the EHF response a little, hence their "K" boards.
Am I right in saying that under-loading such a cartridge may make it a little bass-light by comparison? I don't know how much extra top that EsCo put back (Troika's lose it as they age...) but re-built as it has been, it should be a great sound.
I've heard EsCo "do" good things to a 103 as well.......
I have reached the conclusion that this SUT business is a veritable minefield. I do wish that someone would just point to a trannie and say this is the one for the Troika but it would seem that when Troikas were kings, then SUTs were not in favour. I get the impression that I should be getting more bass slam than I am with my haufe DIY job and my AT-650 on any of its 3 settings. I´ll have to borrow a mate´s Black Cube and see if I am missing out.
Anyone heard the Hagerman Piccolo active head amp ?
Oh for goodness sake, let me put you out of your misery :D
Try asking Les at Avondale about his phono box based on Naim bits (no, don't spit!)
The typical Troika had a rising bass and a presence dip (the EsCo one may have this tamed to a large degree, judging from one I had re-cantilevered years ago) which was countered in part by Naim's "K" boards. With a few well chosen cap replacements and an external power supply of good quality, they can sing very well I feel, without the rest of the bandwidth limited nightmare to slug them out of existance. Les does, I think, a little box for the boards to fit in and a not unreasonably priced power supply too to power it, which can be sited remotely.
Well worth giving him a ring and having a chat about it. Even if you don't go down this route, you'll learn much from the conversation.......
I'd also suggest the WD forum, as they've some real experts who can suggest a good transformer (their own?) and the proper way to adjust the loading.
I have reached the conclusion that this SUT business is a veritable minefield. I do wish that someone would just point to a trannie and say this is the one for the Troika but it would seem that when Troikas were kings, then SUTs were not in favour. I get the impression that I should be getting more bass slam than I am with my haufe DIY job and my AT-650 on any of its 3 settings. I´ll have to borrow a mate´s Black Cube and see if I am missing out.
Anyone heard the Hagerman Piccolo active head amp ?
The advice you are being given here is exactly the same as the advice you have been given on the pink fish media forum.
The Linn Troika is quite happy to be loaded with 470 Ohm, and this is provided by the Naim K boards that have been suggested.
In order to be able to help you further with your Haufe transformers, I would need to know the input impedance of the phono input of the pre amplifier you are using and the turns ratio of the Haufe transformers. If you don't know this, let me know the model number of the transformers.
Barry
Hi Barry,
The data sheet in german that Haufe gave me for my T-7833 capsules says :
1:10
Primary impedance 40 ohms
Final impedance 47 Kohms
primary Gauge 0.05V
20 Hz-20Khz +/- 1db ref 1kHz
1% (Klirrfaktor)
6.8 kohm 1 khz+/-30% an rt-gn Farbe/pin
Wicklungswiderstand 11.5 Ohms : 1.3 kohms +/- 10%
Is this of any use ?
Hi Barry,
The data sheet in german that Haufe gave me for my T-7833 capsules says :
1:10
Primary impedance 40 ohms
Final impedance 47 Kohms
primary Gauge 0.05V
20 Hz-20Khz +/- 1db ref 1kHz
1% (Klirrfaktor)
6.8 kohm 1 khz+/-30% an rt-gn Farbe/pin
Wicklungswiderstand 11.5 Ohms : 1.3 kohms +/- 10%
Is this of any use ?
Chris
Given this information, your transformer will present a load of 470 ohms to your cartridge if the transformer is in turn loaded by the 47Kohms of the phono input of your preamplifier.
I don't understand what is meant by 'Primary impedance 40 ohms'. Are you sure this is correct, and not a misprint? (Iwould expect it to read 470 ohms)
I did a bit of a search for the recommended loading for the Linn Troika. The results areas follows
> 10 ohms, Nominal 150 ohms, 560 ohms recommended
http://www.gb2001.it/sez/area51/sondek-LP12/?page=analogue_addicts
nominal 150 ohm, 560 ohm recommended
http://www.n.mackie.btinternet.co.uk/linn/tlp12faq.html
500 ohm
http://www.diyaudio.com/forums/showthread/t-81459.html
So it would seem that 470 ohms is about right.
Regards
Barry
Chris,
I think I am beginning to understand your (and my) confusion over the terms 'primary impedance: 40 ohm' and 'final impedance: 47 Kohms'. Can you tell me if they are written in German as 'Quellewiderstand' and 'Abschlusswiderstand' respectively?
If so, then these are the source and loading impedances that the transformer will see, when in use. In this case the 'primary' impedance refers to the coil resistance of your cartridge and not to the impedance presented to the cartridge by the transformer, which will be 470ohm.
If you want to reduce the imput impedance to less than 470ohm, then let me know and I'll advise you on the values of the resistors that you can fit across the secondary winding of the transformers.
Regards
Barry
Hi Barry, thanks for going to so much bother. Yes, the 40 ohms value refers to the "quellwiderstand" but the 47Kohms is the value for the "Lastwiderstand"
You can check the data sheet here
http://audio.kubarth.com/rundfunk
Once here, go to "all the rest" in red, top left and then flick quite a way down to the Haufe T-7883.
By all means please advise of the best way to adapt the Haufes to the Troika. I am very grateful for any suggestions.
Chris
Hello Chris,
Thanks for the link. My suspicions that you were misunderstanding the German data sheet were based on another Haufe data sheet that I had; I was unable to find the data sheet specific to the T-7883. So here goes:
Übersetzungsverh. : 1:10 (transformer ratio 1:10)
Quellwiderstand : 40 Ω (source impedance 40Ω)
Lastwiderstand : 47 KΩ (load impedance 47KΩ)
Primarpegel : dBu 0.05V
(Primary level 50mV maximum, this is a misprint: ignore the dBu)
Frequenzberich : 20 Hz 20kHz +/- 1dB ref. 1kHz (frequency response)
Klirrfaktor < : 1% (distortion factor)
Impedanz Z : 6,8 kOhm 1 kHz +/-30% an rt-gn Farbe /Pin
(Impedance 68kΩ at 1kHz +/-30% between red –green coloured leads. Must confess I don’t know what Haufe mean by this.)
Vormagnetisierung DC : 0mA
(DC magnetising current 0mA, i.e. don’t allow any DC to flow through the windings.)
Wicklungswiderstand : 11.5 Ohm : 1.3 kOhm +/-10%
(coil/winding impedance (resistance))
Thus the transformer has a turns-ratio of 1:10 and will, when terminated with the 47KΩ input impedance of your preamplifier, present an impedance of 470Ω to your cartridge.
I cannot say what the correct loading impedance for your Linn Trioka should be, since I don’t use one. All I can do is point you to what Linn themselves recommend and to what other Troika users use. The recommended value seems to be 470Ω, so this is where you ought to start. If you find the sound too bright at the top end, then you may need to reduce the value from 470Ω. To do this you will need to connect a shunting resistor across the secondary winding of each transformer. The value of this resistor (in Ohms) can be calculated using the formula:
Shunt resistance = (4700000 x required load impedance)/(47000 – (100 x required load impedance)).
Thus if you want to reduce the load impedance to, say, 200Ω, then you will need to shunt the transformer secondary windings with (4700000 x 200)/(47000 – 20000) = 34815Ω, or 33KΩ. Strictly speaking the impedance of the transformer windings need to be taken into account, but this formula will get you into the ballpark.
So now it’s down to you and your ears to proceed.
Trust this has been of some help.
Regards
Barry
Thanks a lot Barry.
By no means do I find the sound too bright, quite the opposite I might say, it doesn´t surprise me at either end of the frequency range - a bit over controlled, especially in the bass but maybe my expectations were too high. Just as the loading impedance can be lowered if too bright, can it be raised without touching my P10 ? I believe the Naim K cards were 560ohms but if I´m not mistaken that will give a negative figure with the formula.
If it´s of any help, the 20 ohms setting on my AT-650 sounds better especially in the highs with the Troika whereas the Haufe sounded much better than the AT with the Denon DL103. Does this make any sense to you ?
Maybe an active solution would be easier, as others have already suggested.
Thanks again,
Chris
If it´s of any help, the 20 ohms setting on my AT-650 sounds better especially in the highs with the Troika whereas the Haufe sounded much better than the AT with the Denon DL103. Does this make any sense to you ?
Chris
No, not at the moment - let me think about it.
You can only reduce the impedance through using shunting resistors. If you really want to increase the impedance to 560 Ohm, then I suppose you could insert a series resistance of 56 kOhm - 47 kOhm = 9 kOhm into the secondary side of each transformer. This would, however, reduce the effective gain of the transformers from x10 to x8.4 (or a loss of 1.52dB). I have never heard of anyone doing this, so you could be the first. I wouldn't have thought the difference between using 470 Ohm or 560 Ohm would be that great.
Let us know how you get on.
Regards
Barry
Hi Chris,
I’ve been thinking about your experience regarding the use of the Haufe transformers with the Denon and Troika cartridges. Despite their simplicity the performance of transformers does depend to some extent on both the source and load impedance. As the data sheet shows, the Haufe T-7883 transformer is designed for a source impedance of 40Ω and a load impedance of 47kΩ.
The Denon DL103 has a coil resistance of 40Ω and the Troika has a coil resistance of 4Ω [1] (similarly, the Asak has a coil resistance of 3.5Ω). It would thus seem that the 7883 is operating under ideal conditions with the Denon but not with Troika. This may go some way to explaining why you prefer the 7883 with the Denon. Loading any cartridge will dampen it; the lower the load impedance, the greater the damping. For the Denon the Haufe transformer presents an impedance ratio of 470/40 ≈ 12, whereas for the Troika it is 470/4 ≈ 120, so under these conditions the Troika may be under-damped. Devices with a lower than specified source resistance can sound over bright with a curtailed bass.
Doing a search, it would seem that the recommended loading for the Troika is 560Ω (in parallel with 5.6nF) [1], so I cannot be too dogmatic about the Troika being under damped with 470Ω loading. Similarly the Linn LINNK preamp, made for Linn by Naim and based on Naim’s 323 circuit boards, was designed to partner the Asak and presents a load of 390Ω (in parallel with 7.5nF).
Just as the transformer reduces the input impedance of the preamp by a factor of 100 from 47kΩ to 470Ω, conversely it increases the capacitance of the preamp by the same factor. A typical phono-preamp will have an input capacitance of say 180pF. The effect of the transformer then is to effectively make this 18nF, which again may be too much for the Troika, as the recommended capacitative loading is 5.6nF. Excessive preamp capacitance can modify the treble response by depressing it. This may help counteract the effects of under-damping, but if overdone the overall effect could be a dull sounding cartridge. I think you complained of the cartridge sounding ‘shut in’.
There is another problem with using transformers. Just as they modify the load impedance, they also modify the source impedance, by the same amount. A typical phono input stage is designed to achieve a good noise performance (and bandwidth) for source impedances < 1kΩ. The effective source impedance of the Denon is thus 4kΩ, whereas that for the Troika is better at only 400Ω.
Turning to your question about active devices, these are unaffected by either the source or load impedance, so their performance is more consistent. They come with their own set of problems. For example, being active they are an additional source of noise, but overall the total noise (from the cartridge + mc amp) is probably less than that caused by the effective increase in cartridge source impedance.
Finally, the impedance settings on your AT 650 puzzle me. It would seem that they refer to the source impedance of the cartridge. That is the only way I can reconcile the gain with the impedance. For example the ‘20Ω’ setting provides a gain of x15. With a load impedance of 47kΩ, the impedance presented to the cartridge will be 47000/15² = 209Ω. As a rule of thumb voltage sources should be loaded with approximately 10x their source impedance, thus the assumed load impedance to source impedance ratio of 10:1 is reasonable. The effective capacitance now seen by the Troika is 40.5nF, considerably greater than the recommended 5.6nF.
Maybe your Troika sounds better to your ears when loaded by 200Ω, rather than 470Ω; so try shunting the Haufe transformer secondary windings with 28kΩ (i.e. 27kΩ + 1kΩ) and see if that works. For the latter calculation, I have taken the resistance of the transformer coils into account.
[1] http://www.pinkfishmedia.net/forum/archive/index.php/t-24159.html
Regards
Barry
Wow, thanks Barry.
I have just read your reply and I think I´ll need to read it another ten times to get my head round that but I´ll go straight to the bottom line and get hold of some shunt resistors. When you say to place them across the secondary, that is the output terminals right ?
A friend has just lent me his Black Cube SE to test the active angle, too - this is going to be good. The search for my missing bass slam is on.
Thanks again and will be in touch.
Chris
Hi Chris
Yes, connect the resistors across the output of each transformer. I assume you are using phono sockets, these then would be a convenient pace to fit the resistors.
I may have mislead you regarding the capacitance presented to the cartridge by the transformer. 50pF is a more realistic input capacitance for the phono input on amplifiers. Through a 1:10 transformer this will effectively become 5nF; virtually the same as recommended by Linn. Your AT-650 transformer on the '20Ω' setting (x15) will change the capacitance to 11nF, a bit high.
Sorry about the 'information overload' - I'm always doing that. I’ll summarise the main points as follows:
● Transformers are designed to perform at their best between specific source and load impedances.
● The Haufe 7883 will perform optimally with the Denon, but not with the Troika.
● According to other Troika users and Linn themselves, the recommended load for the Troika is 560Ω (in parallel with 5.6nF).
● The AT-650 on the ‘3Ω’ setting ought to be a good match for the Troika. You prefer the ‘20Ω setting, so try 28kΩ shunting resistors across the output of the Haufe 7883s.
● The performance of active devices (so called pre-preamplifiers) is independent of the source impedance of the cartridge feeding it as well as the load impedance of the phono input of the main amplifier.
Regards
Barry
Hi Barry,
Just to let you know the outcome. I shunted the secondary on my Haufes with 27kOhms and yes, it improved, cleaning and opening up a fair bit. I still prefer my AT on the 20 ohm setting though, finding the 3 ohm setting too overpowering, not in gain, but just not inducive to relaxation. I have also tried a Black Cube SE active phono stage but it didn´t do anything for me, I suspect my PureSound P10 is much better all round.
So I will carry on with my AT-650 until such time as I find an active pre-pre stage. A friend has just bought the Hagerman Piccolo and I´ll wait and see what the verdict is - he uses a Karma which is not a million miles from a Troika.
Once more, thanks for all your help.
My pleasure Chris,
Glad to hear that you at least had partial success with loading the Haufe transformers. Again let usknow how you get on with the Hagerman amp.
Regards
Barry
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