A simple question, I hope.
For a nominal 2.5mV rms input from a high output moving coil cartridge (Denon DL-110), what is my target output voltage? I would like the output from the phono stage to match the output from a CD or SACD player (2V rms for 0dBFS).
What makes this a potentially complicated question is that what I'd really like is for the subjective 'loudness' to be the same from my phono and my SACD/CD player.
I've read all sorts of contradictory things on the innerwebs.
For a standard 5mV rms input from a standard MM cartridge, some sources say that I want about 325mV rms output from the phono preamp. Is that correct? If so, that's only about 36dB gain. If so...
For a cartridge with a nominal 2.5mV output (HOMC), I'd want twice that gain, or 325mV/2.5mV = 130X or 42dB gain.
So, do I want 42dB gain for my DL-110 with nominal 2.5mV output, so that 2.5mV rms input to my preamp gives me 325mV rms out from my preamp?
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For a nominal 2.5mV rms input from a high output moving coil cartridge (Denon DL-110), what is my target output voltage? I would like the output from the phono stage to match the output from a CD or SACD player (2V rms for 0dBFS).
What makes this a potentially complicated question is that what I'd really like is for the subjective 'loudness' to be the same from my phono and my SACD/CD player.
I've read all sorts of contradictory things on the innerwebs.
For a standard 5mV rms input from a standard MM cartridge, some sources say that I want about 325mV rms output from the phono preamp. Is that correct? If so, that's only about 36dB gain. If so...
For a cartridge with a nominal 2.5mV output (HOMC), I'd want twice that gain, or 325mV/2.5mV = 130X or 42dB gain.
So, do I want 42dB gain for my DL-110 with nominal 2.5mV output, so that 2.5mV rms input to my preamp gives me 325mV rms out from my preamp?
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Some amps need as much as 1VRMS in to get full power out.
So that would mean a gain of about 400.
Depends how sensitive your amp is.
So that would mean a gain of about 400.
Depends how sensitive your amp is.
Yes, that's about the minimum gain you'd want for the Denon. A little more would be better.
You'd need 16dB more gain to get to 2V, though.
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Gain of 400 is 52dB. That's a lot.
I don't think you want the amp to reach full power from the nominal output level of the cartridge. For instance, if I had a typical MM cartridge that had a nominal level of 5mV RMS at 5cm/S, I would not want that to drive my power amp to full power, would I?
I think what you want is for the maximum level of a typical LP to yield about 2V RMS output from the phono preamp. So, if the nomimal level is 5mV, and the maximum recorded level on the LP is 20dB above that, that is 10X the 5mV level, or 50mV.
2000mV/50mV = 40X gain, or only 32dB gain. Add a few dB for good measure, and you get something like 36dB of gain. That's what Kevin at KAB recommends as a standard level of gain to shoot for.
If my cartridge has a nominal level of only 2mV at 5cm/S, then I need 100X gain, 2000mV/20mV = 100X, or 40dB gain. Add a few dB of gain for good measure and there I am at 43 to 45dB gain.
Is that what I want?
I don't think you want the amp to reach full power from the nominal output level of the cartridge. For instance, if I had a typical MM cartridge that had a nominal level of 5mV RMS at 5cm/S, I would not want that to drive my power amp to full power, would I?
I think what you want is for the maximum level of a typical LP to yield about 2V RMS output from the phono preamp. So, if the nomimal level is 5mV, and the maximum recorded level on the LP is 20dB above that, that is 10X the 5mV level, or 50mV.
2000mV/50mV = 40X gain, or only 32dB gain. Add a few dB for good measure, and you get something like 36dB of gain. That's what Kevin at KAB recommends as a standard level of gain to shoot for.
If my cartridge has a nominal level of only 2mV at 5cm/S, then I need 100X gain, 2000mV/20mV = 100X, or 40dB gain. Add a few dB of gain for good measure and there I am at 43 to 45dB gain.
Is that what I want?
So, maybe 6dB extra, for those quiet pressings? That would make 48dB gain, which is what I dialed in with the gain switches on my Schiit Mani. Or is 6dB of extra gain too much, do you think?
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It's a trade-off between noise and hf overload. Experiment, but the high output mc mode
for the Mani is probably the best choice, unless you have lots of "hot" records. This will give
you a 14dB overload margin.
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> what I'd really like is for the subjective 'loudness' to be the same from my phono and my SACD/CD player.
Won't happen.
Digital MAX is a fixed known value. You can't have more than all-Ones.
There is no fixed maximum level on a phonograph cut. It is a 3-way compromise: peak levels, time per side, and engineer judgement.
I recall LPs varying 10dB average one to the next. I recall several outliers: a 4-min 10" 33 "DJ pressing" seemed 6dB hotter than any other, OTOH Todd Rundgren's A Wizard... ran 56 minutes and was cut far below average levels.
Won't happen.
Digital MAX is a fixed known value. You can't have more than all-Ones.
There is no fixed maximum level on a phonograph cut. It is a 3-way compromise: peak levels, time per side, and engineer judgement.
I recall LPs varying 10dB average one to the next. I recall several outliers: a 4-min 10" 33 "DJ pressing" seemed 6dB hotter than any other, OTOH Todd Rundgren's A Wizard... ran 56 minutes and was cut far below average levels.
I'm trying to decide on a tube phono preamp to make, and I think I want to have one optimized for the DL-110 and DL-160, since I like them a lot.
A preamp using two 12AX7 stages with an all-in-one-go passive EQ between them, with a cathode follower or source follower on the output, seems like it should work well. LTspice is saying I'll get about 48dB of gain. The high input C of the 12AX7 should not be an issue with HOMC's.
I was also toying with the idea of using a 6SN7-LSK170 cascode for the first stage (100X gain), with a 6SN7 (15X gain) and a source follower afterwards. But that will yield about 43dB gain, which may not be enough for the DL-110.
Hence the question.
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A preamp using two 12AX7 stages with an all-in-one-go passive EQ between them, with a cathode follower or source follower on the output, seems like it should work well. LTspice is saying I'll get about 48dB of gain. The high input C of the 12AX7 should not be an issue with HOMC's.
I was also toying with the idea of using a 6SN7-LSK170 cascode for the first stage (100X gain), with a 6SN7 (15X gain) and a source follower afterwards. But that will yield about 43dB gain, which may not be enough for the DL-110.
Hence the question.
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Sorry, I wasn't clear in my statement. I should have said 'roughly similar subjective loudness between phono and CD, in general.' In other words, I don't want to have to make large adjustments on my volume control every time I switch from a CD to an LP. I understand that LP's vary a lot in level between pressings. I have found that if you get the relative levels of CD vs LP playback pretty close, it's good enough. It doesn't have to be spot on.
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You are over-thinking it, as most people do.
40 dB for MM stage, 60 dB for an MC stage, go with that or a fraction less and you'll be fine.
40 dB for MM stage, 60 dB for an MC stage, go with that or a fraction less and you'll be fine.
I have 6 power amps. The least sensitive takes 1.6 VAC to reach maximum output. Another is similar. Some of the more modern ones have op amp input stages and an attenuator pot at the input, giving excess gain at full volume, but the 1961 and 1970 ones are fixed gain, 35 W/ch on the 1961 model and 25 on the 1970 one.
My CD player will put out 2 vac. I alternate between LP and CD when listening so my mixer is adjusted to have similar volume on each. I have a few properly recorded LP's and CD's that have a full range of volume, on say 1812 overture, so I like the volume peaks to reach 100 db in my music room when the cannon goes off. I like idle noise to be so low I have to stand next to the speaker to hear it. ATCO's and other highly compressed 45's are way too loud at normal volume, but that was the record company's fault, not my system's.
My mixer mm phono function has 50x gain, My CD function attenuates a little in normal use. However If I want to drive the 1.3 kw amp to full volume to play a crowd in a parking lot, my preamp has the gain to do it. It will go up to 6 vac output. That is on mm cartridge, a Shure M97EraIV. If I bought a mc cartridge, I'd have to fiddle with the resistors to get more gain. However, the RA88a is a "disco" mixer and dj rigs were all mm or ceramic IMHO. Stanton was the disco standard cartridge, in the US.
My CD player will put out 2 vac. I alternate between LP and CD when listening so my mixer is adjusted to have similar volume on each. I have a few properly recorded LP's and CD's that have a full range of volume, on say 1812 overture, so I like the volume peaks to reach 100 db in my music room when the cannon goes off. I like idle noise to be so low I have to stand next to the speaker to hear it. ATCO's and other highly compressed 45's are way too loud at normal volume, but that was the record company's fault, not my system's.
My mixer mm phono function has 50x gain, My CD function attenuates a little in normal use. However If I want to drive the 1.3 kw amp to full volume to play a crowd in a parking lot, my preamp has the gain to do it. It will go up to 6 vac output. That is on mm cartridge, a Shure M97EraIV. If I bought a mc cartridge, I'd have to fiddle with the resistors to get more gain. However, the RA88a is a "disco" mixer and dj rigs were all mm or ceramic IMHO. Stanton was the disco standard cartridge, in the US.
I have a similar problem with a design i try to finish. I have a turntable (Dual 601) with an element (orthofon 2M RED) that gives 5.5mV and an other turntable (technics SL1200, because i used to dj) with a Shure 44-7 that gives 9.5mV output. Would it not be possible to have this gain adjusted with a pot or a varistor at the last amplifier stage till the right output voltage? or is that a stupid id.
And if it's a good id, what kind of potentiometer should i use a 100K linear like you use in an amplifier on the input?
And if it's a good id, what kind of potentiometer should i use a 100K linear like you use in an amplifier on the input?
I don't need *exact* gain matching, but I would like it to be in the ballpark when I switch from my CD player to the phono.
indianajo, I don't need to think this through as far as you did, as I will never be moving my system out of my living room.
That said, using my favorite Denon DL-110 or DL-160 cartridges (2.5mV nominal output), when I set my phono preamp to 48dB gain it seems like a good match to the output from (unattenuated) CD output. If I set the phono preamp to the more normal 42dB gain, all LP's are noticeably quieter than their equivalent CD's.
I've also been experimenting with a Shure M35X (6mV nominal), which has noticeably higher output. That one matches up to the output from CD's with only 42dB gain.
My phono preamp also has a setting for 30dB gain. That setting results in too low a level from any of my cartridges.
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indianajo, I don't need to think this through as far as you did, as I will never be moving my system out of my living room.
That said, using my favorite Denon DL-110 or DL-160 cartridges (2.5mV nominal output), when I set my phono preamp to 48dB gain it seems like a good match to the output from (unattenuated) CD output. If I set the phono preamp to the more normal 42dB gain, all LP's are noticeably quieter than their equivalent CD's.
I've also been experimenting with a Shure M35X (6mV nominal), which has noticeably higher output. That one matches up to the output from CD's with only 42dB gain.
My phono preamp also has a setting for 30dB gain. That setting results in too low a level from any of my cartridges.
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You can put a pot on the output of your phono stage. What value the pot should be depends on the output impedance of your phono stage, and the input impedance of your preamp or amplifier.
For instance, a 100k pot will result in a maximum output impedance of 25k ohms when the pot is set to its electrical center (50k on either side of the wiper). If the input impedance of your amplifier is low, let's say 47k (many solid state amps are that low) then this will not be a good match (only ~2:1 out:in). If you're using a tube phono preamp with a very high output impedance, then you'll need to be very careful about this. You might want to start a new thread with this question if you're serious about trying this.
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I tend to design my phono stages for about 2 - 3Vrms out from a 5mV @ 5cm/sec cartridge, this equates to 52 - 56dB of gain @ 1kHz. I find this works very well with the low gain line stages I tend to favor. Good match in general with my two digital sources.
Several of my designs are here in analogue source and have gains in this region, but they are tube based. (Good for use with HOMC, MM or LOMC with transformers)
Several of my designs are here in analogue source and have gains in this region, but they are tube based. (Good for use with HOMC, MM or LOMC with transformers)
Hey Kevin, thanks for your input. I think I agree with you. I do not find that 48dB of gain is too much with the Denon DL-110, or 42dB with the 6mV@5cm/S Shure cartridge. Another few dB of gain wouldn't change things much.
I also am using a line amp with not much gain. I'm using one of Dave Slagle's inductive volume controls, and I think that has a bit of insertion loss. But since the outputs from all my sources go through the volume control, that shouldn't make a difference in relative levels of phono vs. digital sources.
Does your cascode 6N23P preamp have 52+dB of gain?
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if you stress the gain to much at 1khz, bass response will fall off as it needs 20 -25 db more gain from the preamp to reach 1khz output levels.
this is why op-amps provide good bass response with 100db open loop gain at 50hz.
this is why op-amps provide good bass response with 100db open loop gain at 50hz.
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I think there are ways around that problem, such as splitting the EQ sections, with the 2122Hz pole between the first two stages, and the 50Hz - 500Hz shelf between the 2nd and 3rd stages. You'd have two stages supplying the gain at 50Hz. T. Loesch's Toccata preamp is an example of that approach, but I would remove the first stage cascode and use the 5842 as a plain old common cathode amplifier. Or maybe use a 2SK170 under a 12AU7A.
I'd delete the selector switch and other controls, and I'd change tube types to keep the gain down to about 50dB in total. I'd also use LEDs to bias the tubes instead of battery bias. Maybe 2SK170-12AU7 cascode > 6SN7 > 6SN7 with a MOSFET source follower on the output, or something along those lines.
Any ideas how I can use LTspice to predict headroom at 50Hz?
I'd delete the selector switch and other controls, and I'd change tube types to keep the gain down to about 50dB in total. I'd also use LEDs to bias the tubes instead of battery bias. Maybe 2SK170-12AU7 cascode > 6SN7 > 6SN7 with a MOSFET source follower on the output, or something along those lines.
Any ideas how I can use LTspice to predict headroom at 50Hz?
I usually have twice the gain available than the book figures suggests. Recently I built an ultra simple phono stage for an unused radio input of a Quad 33 preamp. This input has never really suited any source and could said to sound awful. Looking at the circuit it shouldn't be so bad. It seems to be rather sensetive and runs from a low voltage. The result is a very closed in sound.
How this project really started is making the gain of the Quad 33 M1 phono card suit the Denon DL110. For a week or two I was really happy with that. Then I noticed a blandness that seemed strongly related to the facts of the measured results. A vinyl sound typical of the 1960's of which Quad was not the best. If asking my Armstrong 600 is far better and of the same school of design.
The idea I used was based on a Tobey and Dinsdale design of 1965. I quickly found that impractical. I retained the simplicity and used an MC33078 op amp that was in the draw ( NE5532 also, again rejected for having slight blandness and edge ). By getting the gain exactly right by ear ( about as loud as most radio via a Quad FM3 ) the results are stunning. I learnt a very big lesson from this. Exact gain really is important. One thing I have from this is the simplest possible signal path with ideal EQ for my 1950's style baffle speakers. The open sound of the baffles makes up for anything bad the Quad does. To be honest when understood the Quad is second to none compared with live classical music. Where is is not the best nor is real music.
How this project really started is making the gain of the Quad 33 M1 phono card suit the Denon DL110. For a week or two I was really happy with that. Then I noticed a blandness that seemed strongly related to the facts of the measured results. A vinyl sound typical of the 1960's of which Quad was not the best. If asking my Armstrong 600 is far better and of the same school of design.
The idea I used was based on a Tobey and Dinsdale design of 1965. I quickly found that impractical. I retained the simplicity and used an MC33078 op amp that was in the draw ( NE5532 also, again rejected for having slight blandness and edge ). By getting the gain exactly right by ear ( about as loud as most radio via a Quad FM3 ) the results are stunning. I learnt a very big lesson from this. Exact gain really is important. One thing I have from this is the simplest possible signal path with ideal EQ for my 1950's style baffle speakers. The open sound of the baffles makes up for anything bad the Quad does. To be honest when understood the Quad is second to none compared with live classical music. Where is is not the best nor is real music.
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