Andy,
Honestly, you can find loads of information on how stages can be coupled.
Often a capacitor is most practical (think of blocking DC at preamp outputs, or prevent DC from entering inputs).
Between stages in tube amps an interstage transformer can be used instead of a combination of anode resistor - coupling capacitor - grid resistor. Info on benefits of IT coupling can be found on this forum and many other places.
Abraxalito already mentioned Lynn Olsen; when you visit his website (Nutshell High Fidelity) you find good reads on capacitors and transformer coupling.
Honestly, you can find loads of information on how stages can be coupled.
Often a capacitor is most practical (think of blocking DC at preamp outputs, or prevent DC from entering inputs).
Between stages in tube amps an interstage transformer can be used instead of a combination of anode resistor - coupling capacitor - grid resistor. Info on benefits of IT coupling can be found on this forum and many other places.
Abraxalito already mentioned Lynn Olsen; when you visit his website (Nutshell High Fidelity) you find good reads on capacitors and transformer coupling.
Someone recently bought an AKSA 'Paris' headamp from me who had been using a Cinemag SUT with his Koetsu. He much prefers the sound using the headamp (I lent him mine for a comparison).
However, in terms of the title of this thread ... an unexpected 'pro' has arisen - which is, he can adjust the gain on each channel to compensate for the fact that his Koetsu has a slight imbalance in channel output!
So he can centre his soundstage with the headamp ... which he couldn't do with the SUT. An unexpected benefit - as well as sounding better.
Andy
However, in terms of the title of this thread ... an unexpected 'pro' has arisen - which is, he can adjust the gain on each channel to compensate for the fact that his Koetsu has a slight imbalance in channel output!
So he can centre his soundstage with the headamp ... which he couldn't do with the SUT. An unexpected benefit - as well as sounding better.
Andy
I rather suspect that transformers have the edge in a front-end when resistance to RF is paramount - as it would be when bipolar transistors are used in the input stage. Its one reason why JFET input stages are so sought-after in pre-amps as they have no means to rectify (and hence demodulate) any RF present on the signal cable (which after all is an antenna).
Good point but AIUI, connecting the earth tags of the input RCA sockets to chassis earth, using a 0.1uF ceramic cap ... will short any RF picked up by the shields of the phono cable, to ground (so it doesn't get into the gain stage JFETs in the headamp). The input RCAs on the MM phono stage should be 'treated' the same way.
Andy
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In the world of RF, there's really no such thing as a 'short to ground'. Every wire has inductance. The nearest thing to a 'short to ground' in RF is what's called a 'feedthrough capacitor' - it needs to be mounted in a screened (earthed) enclosure so that the earth connection is provided not by a wire, but rather the surface of the enclosure.
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A follow-on from what you appear to be saying ... is that any LOMC-rated phono stage which, by definition, doesn't use a SUT (as it has enough gain inside the case to cope with a LOMC) ... must suffer from RF breakthough?
Andy
Someone recently bought an AKSA 'Paris' headamp from me who had been using a Cinemag SUT with his Koetsu. He much prefers the sound using the headamp (I lent him mine for a comparison).
However, in terms of the title of this thread ... an unexpected 'pro' has arisen - which is, he can adjust the gain on each channel to compensate for the fact that his Koetsu has a slight imbalance in channel output!
So he can centre his soundstage with the headamp ... which he couldn't do with the SUT. An unexpected benefit - as well as sounding better.
Andy
Not all SUTs are top quality, so you generalize suggesting that all SUTs sound the same, being inferior to a headamp
Why couldn't a combination of SUT and MM phono stage adjust gain per channel? This has nothing to do with a SUT but depends on the properties of the phono stage.
Not all SUTs are top quality, so you generalize suggesting that all SUTs sound the same, being inferior to a headamp
Not exactly, Pieter. I believe Cinemag is considered quite good - and the guy said he could actually sell it for more than he paid for the 'Paris' headamp!
I'm sure there are much more expensive SUTs which sound better than his Cinemag ... what I am not sure about is whether they sound so much better than the Paris.
That is theoretically feasible, Pieter. But please name a commercial MM phono stage that allows you to adjust channel gain. (I am not aware of any.)
Regards,
Andy
You don't have to pay more than some 100-120 dollars for a MM phono stage with adjustable gain control:
https://hermanproav.com/product/7602/RDL-STPH1-STPH1-Stereo-Phono-Preamplifier
This is the more expensive one....
https://hermanproav.com/product/7602/RDL-STPH1-STPH1-Stereo-Phono-Preamplifier
This is the more expensive one....
If 'RF breakthrough' means it must suffer some RF on its input, I think its practically inevitable yes. I think this only makes a difference to the SQ when bipolars are used though - so a JFET input stage (as you appear to be using) doesn't need the transformer to remain immune to the vagaries of RF.
Indeed you don't - very well found, Pieter.
But as it's undoubtedly opamp-based ... I wonder how good it sounds. And I suspect people who love tube phono stages (and who subsequently therefore choose a SUT rather than a ss headamp) are not going to use it.Andy
Well there are pretty good sounding opamp based phono preamps nowadays, Andy.
Very likely the examples I linked to are not in the class of a high quality solid state or tube design.
I just wanted to point you to the fact that the option to adjust channel gain has nothing to do with a SUT being into play or not.
Very likely the examples I linked to are not in the class of a high quality solid state or tube design.
I just wanted to point you to the fact that the option to adjust channel gain has nothing to do with a SUT being into play or not.
All that I've listened to have not been up with the best-sounding phono stages.
I would agree with you.
Well, yes - except you've veered the discussion around (IMO). My argument is that people who love tube MM phono stages will be better off - for a number of reasons - using a well-constructed headamp than a SUT. One of these resons is the ability to adjust channel gain.
Can you point to a well-regarded tube phono stage which allows this?
Andy
There are not many around, unless part of a preamp like Vacuumstate RTP3 (with line stage).
By the way, if I'd invest in a 1k+ dollars high end cartridge like Koetsu I would not accept audible channel imbalance and return it to the seller rightaway.
High quality MC cartridges should not need channel imbalance adjustment, so it is not strange not to see the option for adjustment on the majority of phono preamps.
Please explain your remark on "veering the discussion around". I understand and respect (from a commercial point of view as you seem to be a (re)seller) that you promote your headamp. Until now however I haven't heard one single convincing argument why a headamp would be preferable to a high quality SUT.
By the way, if I'd invest in a 1k+ dollars high end cartridge like Koetsu I would not accept audible channel imbalance and return it to the seller rightaway.
High quality MC cartridges should not need channel imbalance adjustment, so it is not strange not to see the option for adjustment on the majority of phono preamps.
Please explain your remark on "veering the discussion around". I understand and respect (from a commercial point of view as you seem to be a (re)seller) that you promote your headamp. Until now however I haven't heard one single convincing argument why a headamp would be preferable to a high quality SUT.
Well, the specs for my Benz LP say "channel balance within 0.5dB"!
It seems to me that if Benz thought they could make carts which had exactly the same output in both channels, they wouldn't such a statement on the spec sheet.I suggest, rather, you simply skip over points that I raise!
So let me repeat a point I have made several times: using an MM phono stage (having the default 47K loading resistance), you cannot load a 0.28mV Benz LP at 3K3 ohms when using a SUT which delivers enough gain to make it useful.Andy
Well, the specs for my Benz LP say "channel balance within 0.5dB"!
Andy
That is a good (but normal in that price range) specification, ensuring that you will not hear audible channel unbalance when playing records (because we humans are not able to detect less than 0.5 dB unbalance
).In case of channel unbalance more likely there are issues with speaker placement wrt room acoustics, and you would need volume control per channel or a balance control.
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So change the input resistor to (say) 1 meg. Changing one resistor is a far simpler solution than building a whole new gain stage including a power supply.
Changing a load resistor from 47K to a meg is not something that should be done without knowing (from the designer of the circuit) what effect this will have. It may have negative consequences in terms of the way the circuit operates (and sounds).
Plus, not too many buyers of expensive tube phono stages have the ability to make a change like that.
Andy
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