70 to 75dB MC phono amp suggestions wanted

[tabarddn51]

Hi, I am currently running a Accupase AC-2 MC cartridge on my Temaad Titanium 12'' arm. The cart has an output of 0.18mv so is quite low. My current MC amp, (a AD797 phono amp from this very web site), can just handle that. But I have a chance to buy a Ortofon MC3000 at a very low price. The output of that is only 0.1mv, so I know my Phono amp will not be up to the task.
Can anyone recommend a MC phono amp that is up to the performance level of the AD797phono amp, but can output around 70 to 75dB.

Cheers & Keep Safe

 

[Mr Boochie]

What's your price range?

Maybe, Ortofon ST-70 or 80?

https://www.ortofon.com/st-80-se-mc-transformer-p-434

 

[rothwellaudio]

If that phonostage is a DIY kit you could perhaps increase the gain with a change of resistor value.
However, you're pushing the limits of what's possible in terms of a good signal-to-noise ratio. If you wanted to step up the cartridge's signal with a transformer it would be a good idea to use one with a turns ratio between 1:25 and 1:50. Some of the older Ortofon transformers would fit the bill.
A lower ratio transformer, say 1:20, would still give offer some benefit.

 

[totem]

Off the top Gold Note has a high output level 65 db, +6db -3 db and they note a 0.1mv level range.

 

[HalfApt]

Hi, I am currently running a Accupase AC-2 MC cartridge on my Temaad Titanium 12'' arm. The cart has an output of 0.18mv so is quite low. My current MC amp, (a AD797 phono amp from this very web site), can just handle that.

Which AD797 did you build? I'm guessing this one?

https://audiokarma.org/forums/index.php?threads/ad797-phono-stage-build-and-help-desk-thread.501186/

If so, changing to 47 ohm AD797 feedback resistor (R15/R16 I think) with a lower value will up the gain to the range you want. That would be the simplest & cheapest thing to try first.

eg, with the stock values (2k pot + 47r), nominal gain with pot at 1k mid-point is @60.6dB (adjustment range from 55 to 66dB). If my analysis is correct, the AD797 stage provides 25.6dB mid-gain, the RIAA stage provides the remaining 35dB.

With 47r changed to 15r the adjustment range is 64 to 76dB (70.3 w/pot at 1k mid-point).

But I have a chance to buy a Ortofon MC3000 at a very low price. The output of that is only 0.1mv, so I know my Phono amp will not be up to the task.

Personally, I don't think you'll need more than 70dB for the MC3000 (maybe less). I use an MC20 (0.07mV output) and a custom AD797 MC head amp (feeding a 36dB preamp MM stage). I only needed 34 dB from the AD797, for a total of 70dB (providing 3.5mV to the MM stage).

Try it and see if it works w/out undue noise.

 

[tabarddn51]

Hi Guys, Thanks for the replies,
The price range would be up the say $1500, but that would be a push.
Yes I have the AD797 that was linked to, interesting about the recommendation to change the resistor, I will give it a try as it s quick & easy to do.
Looked at head amps & tied a couple like the Boozhound, & a couple of SUTs but they just added noise.
I am build a head amp myself, am waiting for more AD797 op-amps to arrive. But just wondered if the was anything ease out there. Do not mind S/H as a path. HiFi Shark has quite a few listings for the Ortofon ST70/80 & even a 90 (balanced) in my price range. So I will do some more research around them.

Thanks again & keep safe.

 

[rothwellaudio]

Looked at head amps & tied a couple like the Boozhound, & a couple of SUTs but they just added noise.

The very low output of the cartridges you're using makes it a tough job for a headamp to give you a good S/N ratio. The Boozhound isn't a particularly low noise design. I'm very surprised that a SUT would add noise though. Certainly the hiss should be very low with a SUT. If there's any hum it should be possible to fix it with correct wiring and careful siting.
Having said all that, the easiest and cheapest way forward is increasing the gain of your existing phonostage.

 

[tabarddn51]

Hi again guy's, It is said (very truly) that it is easier to often solve a problem with more heads. So as far as I understand using a SUT would be preferable to pushing up the gain of my AD797 unit. However SUT are designed to mate with MM phono stages, (I knew I should have kept my Pearl 2 that I just sold!!)
However in browsing I stumbled upon a review of Jim's Piccolo battery powered (I like batter power). Reading one reviews put the Piccolo as preferred to the highly rated TX-103 SUT. Also as far as I understand the output impedance is 300 ohms, suitable for my MC phono amp.

I will investigate more.

Cheers & Keep Safe

 

[HalfApt]

.... So as far as I understand using a SUT would be preferable to pushing up the gain of my AD797 unit.

Not necessarily. It's more a matter of personal choice. There are many who swear by SUTs, and just as many who swear at them. Conversely, there are many who swear by head amps, and just as many who swear at them. The "debate" has been going on for as long as MC carts have existed, and will continue ad infinitum.

SUTs and head amps both have their pros and cons, so it's up to you to decide which is best for you, in your system.

While the AD797 board isn't SOTA, it's pretty good. What's to lose by swapping a couple of resistors, maybe $1.00? Why not try it first, it will boost your gain, and you may be pleasantly surprised.

And there are things that can be done to further optimize that board, mostly covered in the original thread.

in browsing I stumbled upon a review of Jim's Piccolo battery powered (I like batter power). Reading one reviews put the Piccolo as preferred to the highly rated TX-103 SUT. Also as far as I understand the output impedance is 300 ohms, suitable for my MC phono amp.

??? What "Piccolo" are you referring to? This one?

https://hagerman-audio-labs.myshopify.com/products/piccolo2-mc-preamp

If so, you're confusing functionalities. The original Piccolo (& Piccolo-2) are just MC head amps, and need to feed into an MM Phono stage, which apparently you don't have? It serves the same function as an SUT.

Your AD797 is a combination of MC head amp + RIAA phono stage, and feeds in an AUX preamp input. You don't put head amps (or SUTs) in front of the AD797. The Piccolo won't replace your AD797, and can't be used in conjunction with it.

 

[wyn palmer]

Hi, I am currently running a Accupase AC-2 MC cartridge on my Temaad Titanium 12'' arm. The cart has an output of 0.18mv so is quite low. My current MC amp, (a AD797 phono amp from this very web site), can just handle that. But I have a chance to buy a Ortofon MC3000 at a very low price. The output of that is only 0.1mv, so I know my Phono amp will not be up to the task.
Can anyone recommend a MC phono amp that is up to the performance level of the AD797phono amp, but can output around 70 to 75dB.

Cheers & Keep Safe

There is a phono stage on this very site that can provide 69dB of gain, and can be easily configured for 73dB with a single R change.
https://audiokarma.org/forums/index...d-preamp-for-low-output-mc-cartridges.879145/
Extremely low noise. Unmeasurably low distortion. RIAA compliance to better than +/-0.1dB 20-20kHz (guaranteed by design), low output impedance, single ended or balanced output, user adjustable input loads. Internal SMPS. Extremely high overload characteristics. Dc coupled. Offset corrected.
What more could you want?
Oh, and many people claim that it subjectively sounds quite good.

 

[slippers-on]

Hi...I run a Denon DL-S1 cartridge and it 0.15mV...even lower than your cart. I have no issues using a Creek OBH-15 MK II and it can be configured up to 80db. I run the Denon at 70-73db. And no noise. The Creek only cost $595.00

 

[twiiii]

60 db would give 1 volt and 66 db would give you 2 volts and thats all you need. Most line inputs only need .25 volts you could get by with 60 db gain quite easily unless you are trying to drive an amp without a pre-amp. .

 

[wyn palmer]

60 db would give 1 volt and 66 db would give you 2 volts and thats all you need. Most line inputs only need .25 volts you could get by with 60 db gain quite easily unless you are trying to drive an amp without a pre-amp. .

With a cartridge output sensitivity of 0.1mv (presumably rms @5cm/sec. 1kHz) 60dB will give you 0.1v output. 66dB will give you 0.2v rms. Assuming 12dB until the cartridge miss-tracks- and the usual headroom on LPs, this would provide 0.8v rms. 69dB would give about 1.1v.
Even with 250mv sensitivity in the input of the preamp this would mean that you would have to operate the volume control at a pretty high level, and whether it was enough would depend on your PA sensitivity and the gain of your line stage.
70dB seems like a pretty typical pre amp gain number for a cartridge with this output.
In my opinion, you would need a gain stage with a S/N ratio at least 6dB better than the best peak S/N of an LP which is 70dB A weighted at the +12dB level- or 58dB+6= 64dB A weighted at the nominal output of 5cm/sec 1kHz.
Both the original AD797 based phono stage with mods and the suggested one at the link above will just satisfy this goal. The suggested one has other advantages, but if gain and S/N is all you want then just increase the gain in the input stage of your AD797 preamp by the appropriate amount.
Increasing the gain will not decrease the noise performance and will only degrade the distortion and the relatively poor RIAA compliance of the AD797 design by a bit.
The AD797 changes will be minimal cost. The suggested preamp would be c. $120 plus box.

 

[wyn palmer]

Not necessarily. It's more a matter of personal choice. There are many who swear by SUTs, and just as many who swear at them. Conversely, there are many who swear by head amps, and just as many who swear at them. The "debate" has been going on for as long as MC carts have existed, and will continue ad infinitum.

SUTs and head amps both have their pros and cons, so it's up to you to decide which is best for you, in your system.

While the AD797 board isn't SOTA, it's pretty good. What's to lose by swapping a couple of resistors, maybe $1.00? Why not try it first, it will boost your gain, and you may be pleasantly surprised.

And there are things that can be done to further optimize that board, mostly covered in the original thread.

??? What "Piccolo" are you referring to? This one?

https://hagerman-audio-labs.myshopify.com/products/piccolo2-mc-preamp

If so, you're confusing functionalities. The original Piccolo (& Piccolo-2) are just MC head amps, and need to feed into an MM Phono stage, which apparently you don't have? It serves the same function as an SUT.

Your AD797 is a combination of MC head amp + RIAA phono stage, and feeds in an AUX preamp input. You don't put head amps (or SUTs) in front of the AD797. The Piccolo won't replace your AD797, and can't be used in conjunction with it.

As the one who suggested the changes to improving the original AD797 board I would say that there is only so much you can do. The basic architecture has flaws that only a significant redesign could correct.

 

[twiiii]

Well I see you caught my math foo-pah! Sorry about that. I'll stick with my high out put Dynavectors. Remember Signal to noise is always the most important parameter. I'll take a little higher distortion and a little bit of irregularity in frequency response, but the best signal to noise is what is important for me especially with efficient speakers. Remember you can't have great signal to noise with high distortion. After all distortion is noise.

 

[wyn palmer]

Well I see you caught my math foo-pah! Sorry about that. I'll stick with my high out put Dynavectors. Remember Signal to noise is always the most important parameter. I'll take a little higher distortion and a little bit of irregularity in frequency response, but the best signal to noise is what is important for me especially with efficient speakers. Remember you can't have great signal to noise with high distortion. After all distortion is noise.

What has the efficiency of your speakers to do with signal to noise? Volume control is usually provided after the source signal is gained up and the S/N etc. ratio is effectively set.
No, distortion isn't noise. Totally different types of characteristics, totally different types of generating mechanisms, totally different psycho-acoustic properties and consequences.
As far as irregularities in frequency response- anything more than +/-0.1dB or so variation from "nominal" over a broad frequency range is audibly different. That was demonstrated and proven quite some time ago. If the device doesn't have a response at least this tight over the audio band then it will have its own acoustic character- which is part of the reason why audio gear sounds different from one piece to another.
In addition- the LP/cartridge playback combo has really poor S/N ratios, and even worse SINADs.
Peak S/N is no better than about 70dBA, and SINAD can be much worse- 3% harmonic distortion on heavily modulated tracks is not unusual- having it as low as 1% is, which would make SINAD about 40dB under these circumstances and as bad as 30dB!
Heck, even 2 track 15IPS tape recorders "from the golden age" (no Dolby or similar) have weighted S/N ratios in the low to mid 60dBs and 1% harmonic distortion.
All you need is a phono stage with a S/N ratio c. 6dB or better than the LP/cartridge combo to make it effectively inaudible.
Having a high output cartridge doesn't materially change this fact.
In fact, many MM phono stages still use bipolar input devices (such as the AD797 and LT1115, for example) that cause the S/N ratio- the real S/N ratio- to be quite poor despite their "specs" because of the high input bias current noise of the input devices and the high source impedance - both resistance AND inductance- of the cartridge, which combine to produce high input noise.

 

[rothwellaudio]

It's refreshing to see someone who obviously understands noise talk about how much there is and how low it can be. I get fed up of seeing posts on AK where people claim their phonostage has "no noise" or is "dead silent".

 

[tabarddn51]

Hi, Well thanks for your suggestions again, Yes Wyn, I am well aware of your design, but have very limited electronic construction skills, so that will be out of the questions for me unless I could find one on the S/H market. I had a hard enough job getting my AD797 Phono to work properly!!
However today I had the opportunity to borrow a friend's Dynavector 75 mkIII, in set up in turbo mode. Very impressive & lots of gain, with a extremely quite background. Bass is a little bloated but still very good & even gave me chill's running down my back on a couple of LP's. Preamp is a Pass B1 Korg, (picked up a build up board, wonderful, wonderful Pre).
Yes, I am also aware that adding extra circuits will add noise but listening to the Dyna today certainly shows you can get adequate gain with minimum noise. I understand that there is now a mk IV, so it may well be possible to get a loaner for a trial

Cheers Derek

 

[wyn palmer]

Hi, Well thanks for your suggestions again, Yes Wyn, I am well aware of your design, but have very limited electronic construction skills, so that will be out of the questions for me unless I could find one on the S/H market. I had a hard enough job getting my AD797 Phono to work properly!!
However today I had the opportunity to borrow a friend's Dynavector 75 mkIII, in set up in turbo mode. Very impressive & lots of gain, with a extremely quite background. Bass is a little bloated but still very good & even gave me chill's running down my back on a couple of LP's. Preamp is a Pass B1 Korg, (picked up a build up board, wonderful, wonderful Pre).
Yes, I am also aware that adding extra circuits will add noise but listening to the Dyna today certainly shows you can get adequate gain with minimum noise. I understand that there is now a mk IV, so it may well be possible to get a loaner for a trial

Cheers Derek

Well, if all you want is more gain on the Hypnotoad board you just have to solder a resistor in parallel with the 47 ohm (if I remember correctly) resistor (R15) from the inverting input terminals of OA1 (and OA2) to ground and set the 2k gain pots to maximum. I'd use a 22 ohm. Then I'd reduce the gain pot to whatever was appropriate. This increases the gain by about 10dB max. Total cost- perhaps a few dollars if you don't have the Rs on hand.

 

[Nashou66]

It's refreshing to see someone who obviously understands noise talk about how much there is and how low it can be. I get fed up of seeing posts on AK where people claim their phonostage has "no noise" or is "dead silent".

I agree , but even I use that term " Dead Silent" but I figured most would understand its not really totally silent. Even a room has noise .

Athanasios