I am in my happy place - designing something new.  I have several MM cartridges with relatively low to modest output when compared to say a 2M Black at 5 mV.

You see, in the world of solid state phono stages you probably wouldn't notice because the gain of the stages are usually adjustable, but in my world where a tube phono stage has 43dB of gain, and able to handle nearly 20mV of input, I find that cartridges with higher output have more density and slam not to mention blacker backgrounds because you don't have to turn the preamp or amp up as loud, so any noise that is there, is basically unheard.

Even with solid state... just because you have enough or even more than enough gain... doesn't mean you have the ideal gain structure.  Let's say we compare a 5mv cartridge against a 3 mv cartridge.  The 3 mv cartridge is quieter.  We turn up the volume to make the music as loud as it was with the 5 mv cartridge and it sounds more like it.  That is until you realize the noise is 3 to 6 dB louder than it was, which basically means the dynamics are reduced by that same amount.  The sound is consequently less dense and not as engaging.

So what happens when we select a higher gain on the solid state phono stage?  Noise problem solved.  Dynamics are improved and everything sounds relatively great.  This is where most people quit.

But what would happen if we set the gain on the phono stage back to the lower setting and instead added another gain stage between the cartridge and the phono stage?

Lots.

Firstly, unlike the phono stage, this gain stage is linear.  It has no EQ.  Dynamics are the same from top to bottom.

Secondly by increasing the gain from the cartridge we also add an additional interconnect.  This would normally be a deal breaker.  The cable used between the cartridge and phono stage is a very real part of the sound because it has a given capacitance and the cartridge responds to if not depends on it to have the correct frequency balance. But, the game changes when the cable is used to store energy as pressure (voltage) and then release it through an orifice. (input voltage divider staged in front of a given impedance.)

Yes, that's going to need some explaining.  So we take a 3mV cartridge and we increase to to 12mv.  This travels through the cable to the input of the phono stage that in turn embellishes it like nourishment to the body and now highly energized and full of life it leaves the phono stage at a reference of 5 volts instead of 1 or 2 volts.  This in turn causes you to turn down the input control on the amplifier or preamp which then raises the pressure in the cable between the phono stage and the amp or preamp.  This tension is reflected back through the entire phono stage, the interconnect, the gain stage driving that, and the tonearm cable and cartridge.  That is the reality of it.  The result is a profound change in how the cartridge sounds.

Having the linear gain stage between the cartridge and phonostage gives more opportunity to voice things as well as dial it into the matrix.  The prototype I am presently using has an adjustable output level which basically means I can adjust the output of a 3mv cartridge anywhere from 0mv. to 12mv or more while I listen to find that magic balance of transparency and power that can only be found this way.  It is reserved for the the brave few who are still reading this.

This is the most critical part  -- the gain structure that you create for yourself starts here.  

The current prototype is battery driven solid state but I am in the process of building a zero feedback design using battery driven tubes, one per channel.  This should be so good it makes me wet myself.  We will see.

The batteries in both of these designs have a direct effect on the sound signature of the cartridge.  Alkaline do not sound the same a Lithium which do not sound the same a carbon.  You can voice your cartridge by rolling batteries.  Carbon is where it's at if you like vintage tone.

This is taking the performance of the London Decca to a new place.  Prior to this experiment, I used a step up cartridge for it that gave me 6dB of gain and it sounds great.  That is what I have been using to evaluate that cartridge for the majority of the time I've listened to it.  That said, I have not been able to get it as high as I would like to achieve the ideal gain structure and have never gotten it completely black as far as hum goes.  Listening to the cartridge by itself without the transformer into a ZP3 is a hum problem because the cartridge is only 3 poles instead of 4.  By the time I get the gain on the amp or preamp high enough to start smiling, the hum ruins it.  But just before I pull the plug hearing the cartridge with no transformer makes it even faster and accurate.

This is why a gain stage for the Decca and the other MM carts I use makes sense because it can be more neutral or less neutral than a transformer and ultimately have more drive and slam with less noise.  

The output level and slam we're trying to achieve is similar at the least to a FR7f with it's 30 to 1 transformer that has some serious slam and a bold presence that makes you look at records like some kind of magic pancake from heaven.

Hope to have something done by spring.  The solid state unit I did is so good, I have doubts that it can be topped.  But I also realize I might laugh at that statement once I hear the NFB triode model. That would be fun!

What gets me excited is knowing that many people with MM cartridges will feel like they have never heard them once they add this head amp.  It will be like taking a $500 cartridge or a $300 cartridge and making it sound like a $1500 cartridge, as well it will be like taking a $5000 cartridge and making it sound like a 15,000 cartridge.

This is all based on the battery driven solid state model I have developed to sound like tubes.  As far as I am concerned it can go into production now.  However I have to pit it against a worthy contender the NFB battery driven triodes to find out which is actually going to be liked by those who would purchase it.

Hope you're having a great holiday and happy listening!  

Steve : )

Too soon to know anything.  But I can let you in on a secret -- the battery operated solid state unit is a Zen Head (ZH-1) repackaged in a larger chassis with RCA jacks.  It could be used as is with simple 3.5mm stereo to RCA adapters.

Steve

London Decca 101 Jubilee Cartridge  

It's tricky.  So far I have been using ultra low draw 1L4 tubes wired in triode.  A single D cell will power the heater for around 140 hours.  The 9 volt batteries take care of the high voltage (36-45vdc) and could last for 1000's of hours.  I don't frankly care if it only lasts 10 hours if I get something I'm happy with.  But why not start out with big plans : ).  

I'll post some prototype pics next time I have stuff apart.

An arm for everything...



The Fidelity Research is a medium mass arm, but can run different head shells. The Audio Craft and the Moarch arms both have different mass arm tubes that you can put on ranging from low to high mass. In the case of the Audio Craft, some arm tubes have fixed head shells and some have removable head shells. On the bottom side, I have a collection of step up transformers for moving magnet, moving coil, solid state head amps, and battery head amps, and a collection of tonearm cables each with a different capacitance. This is what it takes to accurately test a product that will be used for vinyl. You can't Spice model your way to fame on something like this, you have to put in the hours and listen.  You have to see how it responds to different cartridge and tonearm combinations or you're just guessing. : )

Steve…this is a very interesting thread and concept with adding a gain stage between the tonearm and the phono stage.  I have to admit that my ZRock2 is invaluable with vinyl playback.  It allows me to add some gain before my CSP2+, so I don’t have to push the CSP too high…essentially balancing out the gain.   Yes the ZROCK adds EQ..but I normally only run the ZRock2 at like 1 o’clock.   I know the new ZRock3 eliminated the front cut switch, but I find it useful too see the before and after with vinyl records.  There are some records where the increased gain is absolutely needed for that record and very noticeable, and there are others where the increased gain is not as big of a deal.  

I run an Amperex Holland Pinched waist D Getter 7062 tube in the ZROCK2 which puts out more gain than the 12 AU7.  When playing vinyl….the added gain of the 7062 tube is a welcome.  When playing digital through my system…..I dial back my ZBIT to 80% for the sweet spot when I run the SE84C+ Zen Monos.

To find a way to accommodate these 7 pin tubes, I made a circuit board that mounts on the center conductor of the RCA jacks.  As I was building it I  realized that the only way it was going to work is if I mounted the tube sockets to the wrong side of the board so I had to scrap it.  Sadly I didn't figure this out until it was done and wouldn't pass a signal.



So now we wait for a new board full of improvements so that I feel good about screwing up the first one.

Approach #2 would be to find a friendlier tube that is less microphonic, and ideally a dual triode to simplify the circuit not to mention make finding tubes twice as easy.

This would turn out to be an ECC86 / 6GM8 tube.  This tube has a 6.3v heater like any of the signal tubes we use, but other than that it is designed for low voltages and will work with as low as 6 volts on the plate and as high as 12 volts.  

Since it is a 9 pin tube, we could probably use our ZBOX/ZSTAGE chassis, so I have been working on that prototype the past couple days.  This one just dropped together like it was blessed, worked perfectly the first time, and took very little voicing to get right.  ZERO microphonics.




The simplicity of this and the performance make it seem like a giant step up.  The sound is so close I would have to A/B.  Suffice it to say it is extremely good and literally stone quiet.

Things are getting interesting : )

So far all three units that I have tried have the commonality of being the great leveler.  I am rotating between 7K, 5K, 700.00 cartridges at the moment, and enjoying them all equally.  Prior to this gain stage, that wasn't the case.  The $700 one was pleasant and ideal for casual listening to take some of the wear and tear off the more expensive units. The $7K one was not enjoyed as much as the 5K unit because it had 2mV less output so it didn't slam as hard or have as much presence.

Now I like the $7K better but just barely.  The $700.00 unit is dreamy good now, so it is getting more than double time compared to before the gain stage.

The fact that slam and density is now adjustable for all three cartridges in my opinion doubles or triples their enjoyment.  I notice, I have the gain set different every night which is another unexpected discovery.

That means I am adjusting the cartridge to change its sound, nightly.  All of them.  The only way you could normally accomplish that would be to have many different cartridges for each tonearm.

It's a value multiplier -- which is why I am so excited about designing this.

I've been reticent to jump into MC carts and step up transformers, this might be my answer. Looking forward to seeing what comes of this.
Great work Steve.

JD

In a sense this reminds me of working with the 3S4 tube used in a simple preamp circuit. Despite the fact that it is microphonic, almost every facet of the sound improved with this simple design. So that is what reminds me of this approach to phono pre-pre stage. The fact that looks to be adjustable is the answer here. Each cartridge is going to change the setting. The tube phono pre that I built sounds wonderful, but just as you stated, the gain is somewhere in the 40 Db range. So then for a preamp that had too much gain for other sources, it became almost the opposite problem with phono. Ugh.

Have you thought about a rechargeable scheme? It could be set up to run on battery power only when being used, then when idle charge with a linear supply.

The DJ system was set up with auto amps that were powered with 4 jell cells that had enough amp hours to run for an hour or so. It sounded clean for that hour. Then the regulated power supplies would be switched on for the remainder of the session. Still sounded very good as long as it was switched on before the voltage dropped to low from the batteries. The batteries would act as capacitors and charge at that point. Got a lot of good comments with that system...especially when outdoors.

I am A) increasing to C cells and probably D cells.  That will make a huge difference.  Also, I am looking at an analog volt meter that goes from 0 to 2 volts.  I don't want to get gooned in the middle of a session by seeing the dreaded LED come on.  I need an analog dial that is big and easy to see so I know where I'm actually at.

Rechargeable batteries are always an option.  They sound different than Carbon and Lithium and Alkaline.  

Steve

Going to dispatch the new ZenHead build as a preamp booster for the Cambridge in loop C feeding the whole house and tech shop systems while waiting to see how this thread plays out.
Listened to the systems yesterday and the ZenHead really made very good improvements in sound. The volume was reduced on the JVC amp feeding the eight transformer coupled pots which took a strain from it creating better results all the way around.
Going to stick with an alkaline 9v battery hooked in series with relay contacts energized from switched outlets on the back of the of the JVC amp. Don't want to even attempt using a power supply like one of those that can be had on Amazon billed as battery replacements. Energized by what was heard yesterday I do not want to fool with it. I may use rechargeable batteries giving easy access to it. Whole house amp can be turned on/off remotely with Harmony app and the Cambridge with its app. Cell phones have become indispensable these days!    

A ZenHead hanging out in the shop. After building this little amp, I am really stoked on the possibilities with the tube model.
Hope all is proceeding well.

As far as more exotic batteries, I decided to keep it simple where even a quick trip to the dollar store can get you back online. It also offers many more variations/brands to try, and while most won't go there a few people will listen to every battery they can find.  

Here are some pics of the final result.

This is an upside down shot of the rear.  The silver jacks are the inputs for 3 tonearms, the gold jacks are the outputs that go to the phono stage.

Here is a picture of the top showing the battery meter and the 9 volt battery holders.

This is what it looks like when it is turned ON and with a fresh D-Cell battery.  The heater is looking for 1.4 volts and it works well down to 1.2 volts and probably becomes unusable by the time it hits .6 volts.

After trying many different internal battery holders for the 4 - 9 volt batteries, I spent $50 on a pair of these dual 9 volt battery holders.  Despite the possibility that you may never have to change the 9 volt batteries, depending on how much you listen, no one is going to enjoy removing the bottom cover every time they want to roll batteries to see how they sound.  

So long as it is 1.5 volts, the D-Cell doesn't seem to make any difference to the sound, but the 36 volts from the 9 volt batteries will change the sound from battery type to battery type so it needs to be easy and these are easy.  I find them actually worth the money.

Nice assembly. I like the convenience of battery change and analog gauge.

I found in the ZenHead that sound degradation starts to occur just under 6v. Also when setting idle it does not drain the battery as much as when being fed with a signal. Found that out when forgetting to turn it off! So....

I did find an isolated 110v ac to 9 volt dc card that fits nicely in the the space provided for a battery in my build. Works well in my use of the ZenHead. I could not see ripple in the oscilloscope trace from the output of the card.