I'm running older Sowter 7136x (9575) transformers, which are very good IMHO. Can't comment on the "shrinkage".
jeff
Can't comment on the "shrinkage".
Ha! Fair enough.
I'm thinking through how to resistor-tune potential SUTs, starting with the Sowter. Do I have the concepts and the math right?
Sowter 9580 -- 1:12.5
Denon DL-301ii -- 0.4mV, 33 ohm
The cart will want to "see" a 33 ohm load (is that right?).
So to obtain that, we first calculate the the impedance ratio resulting from the voltage gain. The impedance ratio will equal the voltage gain squared:
12.5^2 = 156.25
The input impedance of the phono stage will need to match the new impedance coming out of the SUT, so:
156.25 * 33 = 5156.25 ohm
So I would remove the existing input resistors from the phono pre (selectable 33K, 47k, and 68k) and replace them with a 5156.25 ohm or its closest equivalent.
Ah, I glossed over the advice at Rothwell, VTA, etc., which states that following an SUT, a load impedance should normally be ten times the source impedance.
So the DL-301ii will want to see a reflected load of 330 ohm.
If using the 9580, the input resistor on the PH16 would need to be 5156.25 * 10 = 51562.50 or something close like 52k.
Is that correct?
So the DL-301ii will want to see a reflected load of 330 ohm.
If using the 9580, the input resistor on the PH16 would need to be 5156.25 * 10 = 51562.50 or something close like 52k.
Is that correct?
Remember, the impedance ratio of a transformer is the square of the turns ratio. For a 1:10 turns ratio, the impedance ratio is 1:100. So, if the phono preamp has an I/P of 47 Kohms, the load presented to the cart. is 470 ohms. That is plenty. It will cost very little to use the 47 Kohm standard and retain MM level capability.
Given their rising HF response, LOMCs may benefit from resistive padding, on the primary side of the SUT. You can make your own padding kit from all metal, gold plated, "Y" connectors, RCA plugs, and low noise resistors. You experiment with various resistance values to determine what sounds "best", in your setup.
Given their rising HF response, LOMCs may benefit from resistive padding, on the primary side of the SUT. You can make your own padding kit from all metal, gold plated, "Y" connectors, RCA plugs, and low noise resistors. You experiment with various resistance values to determine what sounds "best", in your setup.
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OK, so in the case of the PH16, which comes with selectable 33k, 47k, and 68k input resistors, I could theoretically use the 33k (for a reflected 330 ohm load, exactly 10 times the internal impedance of the cart) or the 47k to start, and then fine tune by swapping in other values if desired.
Brian Sowter wrote back and is recommending the 9570 unless I really need the extra little gain of the 9580. I admit I'm concerned about having enough gain but, if I decide on the Sowters, will follow his recommendation.
So, now that we're talking 1:10 SUTs, the Jensen jt-44k-dx, recommended by merlin el mago is also in play at $104 ea., though I wouldn't really want to go more expensive than that. Anyone have experience to compare those with Lundahls or Sowters?
Brian Sowter wrote back and is recommending the 9570 unless I really need the extra little gain of the 9580. I admit I'm concerned about having enough gain but, if I decide on the Sowters, will follow his recommendation.
So, now that we're talking 1:10 SUTs, the Jensen jt-44k-dx, recommended by merlin el mago is also in play at $104 ea., though I wouldn't really want to go more expensive than that. Anyone have experience to compare those with Lundahls or Sowters?
I don't know the circuit, but for reference feedback is not always such a bad thing.
From what Roy describes on his website, it looks to be FET input. You usually have quite a wide degree of freedom to play with the input impedance when using a FET. This is good if you want to reflect the best load to your MC cartridge through your step-up.
I liked the Sowter and the Jensen's when I used Moving coil. My favourite was S&B TX103. They're somewhat pricy though.
Ian
What about the Lundahl LL1681? It's got a 1:13 option which puts the DL-301ii output to 5.2mV, which would probably be right around 5mV after internal impedance. Anyone have experience with the 1681?
Update on my schematic from post #81:
It sounds absolutely killer. Some minor tweaks to the schematic as suggested throughout the thread. I built with AC heaters (CT referenced to ground) first and must have done something right because there is no hum at normal listening levels. It's there when cranked and I'll try referencing around 30V and then DC heaters if it still bothers me.
I owe everyone here a huge thank you. Especially you, Eli. There is very obvious MOSFET inspiration borrowed from your tweaked RCA design here.
It sounds absolutely killer. Some minor tweaks to the schematic as suggested throughout the thread. I built with AC heaters (CT referenced to ground) first and must have done something right because there is no hum at normal listening levels. It's there when cranked and I'll try referencing around 30V and then DC heaters if it still bothers me.
I owe everyone here a huge thank you. Especially you, Eli. There is very obvious MOSFET inspiration borrowed from your tweaked RCA design here.
Hi, I think Im confused about what must be the output level of a phono MM stage, in order to maintain the same "loudness" when You switch on it, coming from a CD source.
Im talking with standard mid priced MM carts: Shure, AT, Stanton and the genre, the same program in the vinyl as the CD.
This chart left me unsure about the whole issue:
I need 1Vrms or 2Vrms?
Im talking with standard mid priced MM carts: Shure, AT, Stanton and the genre, the same program in the vinyl as the CD.
This chart left me unsure about the whole issue:
I need 1Vrms or 2Vrms?
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I've asked myself that same question.
In the digital world, there is a standard. For 0dB Full Scale (0dBFS) from your source, the analog audio output signal should be 2V RMS (2.83V peak) into a standard load, usually 100k ohms, 47k ohms, or 10k ohms. That's the standard output level from a CD player, DVD, BD, etc.
Smartphones and other battery powered, portable players typically output only 1V RMS from 0dBFS input.
In the analog world, there is no standard. A typical MM phono cartridge will be specified to generate a certain signal output at 1kHz from a certain deflection of its needle, typically (but not necessarily) 5cm/second.
The specs for Shure M97xe cartridge say 4.0mV @ 5cm/sec.
They never state if that's RMS or peak signal level. Does anyone know? I'll assume peak.
I think that's supposed to be a typical 'average' signal level from an LP, not a peak level. Let's say the absolute peak level will be +10dB from that. That's roughly 3.16 times the level, so about 16mV absolute peak. Let's say we want 16mV from the cartridge to cause an output level of about 2.8V peak from the preamp.
2.8V peak / 0.012V peak = 175X gain, or 44.86dB gain
(I used Decibels to Voltage Gain and Loss convert calculation conversion amplification amplifier electronics - sengpielaudio Sengpiel Berlin)
I use a Denon DL110 cartridge, which is a high output moving coil that makes a bit less signal than a MM like a Shure. With the DL110 in mind, I aimed for 48dB gain from my phono preamp.
In my setup, 48dB gain from my phono preamp brings the level from my Denon DL110 to about even (subjectively) with the output from my CD player. But if I switch to a Shure (I have an SC35C) then the phono is subjectively just a hair louder than the CD.
I hope that helps.
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Thanks
So, a quick gross check can be: my phono got enough gain when, if feeded with a 1Khz, 1mV sine, it put out round 251mV..
I think (but I don't know) that with 1mV 1kHz sine wave input, anything from about 150mV to 250mV out should be OK.
The usual 12AX7 -> passive RIAA -> 12AX7 -> cathode or source follower should do it. Like Eli Duttman's RIAA Redux, or Sodacose's recent take on this from a few posts back.
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My experience mirrors yours, Rongon. I calculate the gain from the preamp I built to be around 47-48db. My cart is rated at 5mV (Ortofon 2M Blue). It is louder than my CD player at the same point on the volume knob (not hugely, but it is obvious).
I built this for someone with a cart that's rated at 2.5mV so it should be about right.
I built this for someone with a cart that's rated at 2.5mV so it should be about right.
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