inertial said:
Hi Paolo
Your desired gain may fit well with the gain distribution of the Loesch pre but is definitely not ideal with respect to noise. Adding some sand under the tube will solve your issues technically but you may not like the sound.
Over the last 30 years i have tried a lot of (considered good) transformers and practically any tube or solid state topology at MC levels.
The most pleasing and most resolved sound always emanated from tube input stages but noise and microphony are real issues. Paralleling tubes seem to work for some people and can be seen in many commercial products (Counterpoint SA2, Klimo, Hampton, ARC MCP-33) but has never really worked well for me. Thus, no tube MC pre-pre below 500uV unless you are very tolerant of noise.
PS is hugely important and i have mostly used batteries or Jung type regulators. 3-terminals are pretty much unusable on their own.
While transformers, even very expensive ones, always seem to compromise soundstaging and acoustic cues it is a compromise worth considering.
Re: Re: need suggestion about MC pre-pre
Hi , Excuse me , I don't understand the thing about "sand".
Can you please re-explain me?
Good to know it!
I can make just only suppositions, because I have no true experience about these toys
Things here are complicated! I have suggested to mine friend the more logical thing: change the cartridge with one more "sensible"!
But he is unreasonable about it!
Second possibility: add a transformer man! No, he said!
My patience was on the limit now
Mah! I am not confident .............
Maybe paralleling 2 "strange " tubes, as you are suggesting.....
but wich tube?
I need low mu-tubes, high transconductance and no-microphonic!
Near impossible I believe...
We will see...........
Thanks for your suggestions,
see you tomorrow
Paolo
analog_sa said:
Hi , Excuse me , I don't understand the thing about "sand".
Can you please re-explain me?
Good to know it!
I can make just only suppositions, because I have no true experience about these toys
Things here are complicated! I have suggested to mine friend the more logical thing: change the cartridge with one more "sensible"!
But he is unreasonable about it!
Second possibility: add a transformer man! No, he said!
My patience was on the limit now
Mah! I am not confident .............
Maybe paralleling 2 "strange " tubes, as you are suggesting.....
but wich tube?
I need low mu-tubes, high transconductance and no-microphonic!
Near impossible I believe...
We will see...........
Thanks for your suggestions,
see you tomorrow
Paolo
Ok, you are correct, of course
but our A.Loesch gain is about 1500-1800 ( depends of the tubes).
I have tried a old Hiraga pre pre in front of it, but it gain too much:
65 times!
Then we have modified voltage rails down to 1,5 V ( one duracell)
and a resistor if I well remember but the gain is 20 times. Too much again!
20 x 1500= 30.000 !!
Making this I have deducted I need only about 4 times additional gain.
Now this is the point......
Excuse me, but I continue to not understand what does silicon has to do.............
Cheers,
Paolo
but our A.Loesch gain is about 1500-1800 ( depends of the tubes).
I have tried a old Hiraga pre pre in front of it, but it gain too much:
65 times!
Then we have modified voltage rails down to 1,5 V ( one duracell)
and a resistor if I well remember but the gain is 20 times. Too much again!
20 x 1500= 30.000 !!
Making this I have deducted I need only about 4 times additional gain.
Now this is the point......
Excuse me, but I continue to not understand what does silicon has to do.............
Cheers,
Paolo
First of all, let's be honest. There is no "free lunch" when it comes to MC pre-preamps.
For a good transformer, you need something wound on a high perm core, with small 40 ga wire, interleaved and done by a master. Very few of them around anymore (to be fair most of the coils wound at UTC were done by women). For a good one you are looking at $$$. There is not a lot of voltage (current) from the MC to get the BH curve of the core to "sing".
Anything active is going to add noise (tubes) or add their own sonic footprint (sand) to the sound. So what to do? I depends what you are willing to sacrifice, dynamics, noise or sonic footprint.
As far as active tubes, you have to parallel tube sections to improve noise and have a VERY quiet power supply. I have listened to 6DJ8s and 7308s with CCS and HV shunt regs and heard good results. But you need to select tubes very carefully to get a low noise "golden" pair.
As far as a tube/sand combo, it's hard to beat Allen W's design, and it really sounded best with the bipolar input, not Fet. I have heard a 2SK170/417a combo that was respectable, but again only with CCS and HV shunt reg.
As far as sand, a MC version of the "Pearl" phono stage, is very respectable, but needs a LV shunt reg to make it sing. Both tube and sand designs sound better with shunt regs compaired to battery power supplies.
The other thing, IMHO, to make a good phono stage, it must be balanced (Allen's or other designs...see "Siren Song"). MCs are by nature balanced, so why not take advantage of this low noise type of operation.
So what to do? Just remember only God has attained perfection.
For a good transformer, you need something wound on a high perm core, with small 40 ga wire, interleaved and done by a master. Very few of them around anymore (to be fair most of the coils wound at UTC were done by women). For a good one you are looking at $$$. There is not a lot of voltage (current) from the MC to get the BH curve of the core to "sing".
Anything active is going to add noise (tubes) or add their own sonic footprint (sand) to the sound. So what to do? I depends what you are willing to sacrifice, dynamics, noise or sonic footprint.
As far as active tubes, you have to parallel tube sections to improve noise and have a VERY quiet power supply. I have listened to 6DJ8s and 7308s with CCS and HV shunt regs and heard good results. But you need to select tubes very carefully to get a low noise "golden" pair.
As far as a tube/sand combo, it's hard to beat Allen W's design, and it really sounded best with the bipolar input, not Fet. I have heard a 2SK170/417a combo that was respectable, but again only with CCS and HV shunt reg.
As far as sand, a MC version of the "Pearl" phono stage, is very respectable, but needs a LV shunt reg to make it sing. Both tube and sand designs sound better with shunt regs compaired to battery power supplies.
The other thing, IMHO, to make a good phono stage, it must be balanced (Allen's or other designs...see "Siren Song"). MCs are by nature balanced, so why not take advantage of this low noise type of operation.
So what to do? Just remember only God has attained perfection.
cygnus x1 said:
Hi Cygnus,
thanks for precious suggestions
I agreed about all.
Things are complicated with MC . Last day I was listening to mine friend's ( another one) preamp: Pass X-ono + X1.
It is incredibilly quiete, zero noise
But the sound,....... mmmhhhhh..........., maybe it was guilt of the Rega planar9, I don't know, but they was more "digital" than the wadia DAC25!
Have tried various loads but, nada: fragile, anemic sound.
My friend was desperate! And then?
I can't think the X-ono sound so bad , IMO the Rega have to go " out of the window" !
In any case I have the impression that the "magic" of the A. Loesch, can't be replicated with Fets...
We will see.......
inertial said:Ok, this is the schematic mine friend have build:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Note the different B+ , only 150 V respect the "toccata" 250 V.
Why he has increased so high?
Cheers,
Paolo
Hey guys,
Maybe I had a idea:
Why do not try to bypass that cathode resistor on the 5842?
Can I expect 4-5 dB of gain?
Does I have to add a little series resistance on the output of the 5842 for "compensate" and in order to avoid of modificate the RIAA ?
Am I totally wrong?
thanks,
Paolo
Paolo,
I think you mentioned the "best" solution to the problem early in this thread. Change the cartridge! Nice HOMC carts., whose O/P is well matched to the preamp being used, are available from Goldring, Ortofon, and Dynavector.
You can't get to where you want to be and bypass both "sand" and SUTs, if the LOMC is retained.
I think you mentioned the "best" solution to the problem early in this thread. Change the cartridge! Nice HOMC carts., whose O/P is well matched to the preamp being used, are available from Goldring, Ortofon, and Dynavector.
You can't get to where you want to be and bypass both "sand" and SUTs, if the LOMC is retained.
inertial said:
But the sound,....... mmmhhhhh..........., maybe it was guilt of the Rega planar9, I don't know, but they was more "digital" than the wadia DAC25!
Have tried various loads but, nada: fragile, anemic sound.
My friend was desperate! And then?
I can't think the X-ono sound so bad , IMO the Rega have to go " out of the window" !
There is something seriously wrong if your friends P9 sounds anemic through a X-ono. What cartridge is he using?
Jeff
inertial said:<snip>
Excuse me, but I continue to not understand what does silicon has to do.............
Cheers,
Paolo
He is referring to the JFET (it is silicon) that would make up the lower device in your cascode front end.
You could try to get more gain out of the existing front end design with a D3A and a CCS load, but even so a single triode connected D3A is going to be about 10dB noisier (or maybe even worse) than the johnson noise produced by the particular cartridge resistance. (5 ohms?) Put two in parallel (must be closely matched!!) and reduce the noise by a further 3dB, use led biasing as the cathode bypass caps required for good noise performance and maximum gain are large enough (>1000uF) to create issues. You will need to adjust the EQ network to compensate for the change in source impedance, note even with a ccs load this might give you as much as 6dB of additional gain which probably isn't going to do it for you. You might also change that second 6DJ8 to a 5842/417A (reduce plate load resistance to about 10K and keep the current up) and get a couple of extra dB that way..
Note that there are only the two series resistor values in those stage's RIAA eq (94.5K and 90.9K) that would need small value adjustments to correct for the change in source impedance. I would have probably used significantly lower values of series resistance (maybe 1/3rd - but this makes the circuit more sensitive to parametric variations that affect the rp of the preceding stage) in the RIAA networks as those highish values contribute considerable johnson noise to the pre amplifier's total noise floor.
I had considerable success paralleling both 12AX7A/ECC83 or 5751 (up to 4 triodes) but they were not close to equivalent in noise performance (or anything else) to a single D3A or 5842/417A. Each triode section had its own cathode resistor and bypass cap, current sharing was much better this way than just paralleling them as the local dc current feedback resulted in similar operating points.
First, SUT = step up transformer, LOMC = low output moving coil.
OK, let's see what the 22R bypass could get you. The plate resistance of the 417 is about 1k6, so the gain with bypassed cathode (ignoring RIAA) is 5k/6k6 times the mu = 0.76 times mu. With the resistor not bypassed, the gain is 5k/(7k5) = 0.66 times mu. Gain difference is 0.76/0.66 = 1.15 = 1.22 dB. Not much!
The bypass would have to be pretty large. The effective impedance at the cathode is 22R in parallel with 175R (the cathode "looking in" impedance). That will be slightly under 20R. For an f3 of 5Hz, the capacitance would need to be 1/(2pi*20*5) = 1600 uF. And you've now degraded the first stage's overload recovery.
Seems hardly worth it.
LOW NOISE AND HUM MC PRE
Hi to all!
I can see that you have gone quite far and "semi-technical" with the thread, it is becoming difficult to follow
I would like to comment on transformers: while some would be inclined to use a transformer as first stage, bringing the MC level to MM levels to put it plainly, the rest of the preamp still needs to be able to "sing". Furthermore, the mentioned transformer has to be very expensive if you want to obtain high class results (unfortunately). It is by far easier to build an active stage based on some good schematics (maybe design it) than to go around shopping for good sounding MC/MM transformers.
Well, maybe not that easy having in mind the usual simple/simplish schematics garbled with hard to find tubes and mumbo-jumbo caps that can only be sourced here and there. I am always incline to critisize that attitude.
To me, it is as artful as possible to make it all vacuum tube and free of noise and hum (as much as humanly possible -- meaning "from not getting in the way of sound to virtually inaudible"). The sticker "use a transistor - go to jail" should apply here
On the other hand, prior to vacuum tubes, I used to design with OP amps. I still have (has not been dismantled, but I actually do not use it) my first "standalone" preamp for MC, which housed in a common plastic box I call "the ugly duckling". Well, the ugly duckling is dual mono (each channel on a separate circuit board) with hand selected (and huge size) polystyrene foil caps (low voltage, obviously) RIAA plus "audio grade" OP amps (like BB OPA134 and similia placed on sockets so you can change them like tubes... the PS is obviously solid state regulated, power being drawn from a "wall socket plastic housing", something like the one on your router or similar piece of IT equipment...
To cut a long story short, this preamp sounds IMPRESSIVE, while the noise and hum are MORE THAN VIRTUALLY INADUIBLE i.e. you have to play some music in order to hear that it is ON. Frankly, not because I built and designed it, very few commercial products in the highest league come close (like the various Rowlands, Krells, and similia in the behemoth class).
BUT, and that is a big BUT, the tube preamp mentioned above in the thread sounds way better, in spite of having (obviously) more noise and hum (but not that much, because if it was much than it would not be interesting). A good idea to try is calibrating important parameters of your arm-cartridge alignment (providing your arm lets you do that) like VTA and bias. With the ugly duckling, that is easy to do (not so with some xxx commercial phono preamp) but with the tube preamp it becomes a straight-forward-easy-to-do-in-a-few-steps thing to do, since you hear extremely well all the differences in nuance between the various settings you try.
Thanks for your patience in reading this.
Regards,
Alex
Hi to all!
I can see that you have gone quite far and "semi-technical" with the thread, it is becoming difficult to follow
I would like to comment on transformers: while some would be inclined to use a transformer as first stage, bringing the MC level to MM levels to put it plainly, the rest of the preamp still needs to be able to "sing". Furthermore, the mentioned transformer has to be very expensive if you want to obtain high class results (unfortunately). It is by far easier to build an active stage based on some good schematics (maybe design it) than to go around shopping for good sounding MC/MM transformers.
Well, maybe not that easy having in mind the usual simple/simplish schematics garbled with hard to find tubes and mumbo-jumbo caps that can only be sourced here and there. I am always incline to critisize that attitude.
To me, it is as artful as possible to make it all vacuum tube and free of noise and hum (as much as humanly possible -- meaning "from not getting in the way of sound to virtually inaudible"). The sticker "use a transistor - go to jail" should apply here
On the other hand, prior to vacuum tubes, I used to design with OP amps. I still have (has not been dismantled, but I actually do not use it) my first "standalone" preamp for MC, which housed in a common plastic box I call "the ugly duckling". Well, the ugly duckling is dual mono (each channel on a separate circuit board) with hand selected (and huge size) polystyrene foil caps (low voltage, obviously) RIAA plus "audio grade" OP amps (like BB OPA134 and similia placed on sockets so you can change them like tubes... the PS is obviously solid state regulated, power being drawn from a "wall socket plastic housing", something like the one on your router or similar piece of IT equipment...
To cut a long story short, this preamp sounds IMPRESSIVE, while the noise and hum are MORE THAN VIRTUALLY INADUIBLE i.e. you have to play some music in order to hear that it is ON. Frankly, not because I built and designed it, very few commercial products in the highest league come close (like the various Rowlands, Krells, and similia in the behemoth class).
BUT, and that is a big BUT, the tube preamp mentioned above in the thread sounds way better, in spite of having (obviously) more noise and hum (but not that much, because if it was much than it would not be interesting). A good idea to try is calibrating important parameters of your arm-cartridge alignment (providing your arm lets you do that) like VTA and bias. With the ugly duckling, that is easy to do (not so with some xxx commercial phono preamp) but with the tube preamp it becomes a straight-forward-easy-to-do-in-a-few-steps thing to do, since you hear extremely well all the differences in nuance between the various settings you try.
Thanks for your patience
in reading this.Regards,
Alex
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