[neobop]

Maybe I missed it, but I didn't see any mention of capacitance loading for MMs. I prefer 50pF for mine, but some people use 300pF or more.

Resistance loading options for both hi and low outputs would be a very desirable feature and attract many cart rollers (like myself) along with people who want to do whatever they can to optimise performance. Perhaps you could have something like 1 meg on the circuit board and 4 little sockets to insert any value desired. I'm not used to using a head amp, but going straight in, loads usually vary from around 20 ohms on up for MCs. I read about Herron infinite loading thing and figure it must have something to do with his circuit/tube configuration. Herron customers rave on and on about it.
neo

[Roger A. Modjeski]

Maybe I missed it, but I didn't see any mention of capacitance loading for MMs. I prefer 50pF for mine, but some people use 300pF or more.

Resistance loading options for both hi and low outputs would be a very desirable feature and attract many cart rollers (like myself) along with people who want to do whatever they can to optimise performance. Perhaps you could have something like 1 meg on the circuit board and 4 little sockets to insert any value desired. I'm not used to using a head amp, but going straight in, loads usually vary from around 20 ohms on up for MCs. I read about Herron infinite loading thing and figure it must have something to do with his circuit/tube configuration. Herron customers rave on and on about it.
neo

So far I have 12 positions of loading: 7 ranging from 10 to 1000 ohms and 5 ranging from 10K to no load at all. As to capacitance, it does make a difference and I can offer it as an option but most people have too much already when you add the cables and input capacitance of the preamp which is often not trivial and not stated. The popular 12AX7 has 85 pf miller capacitance internally. If there is just another 2 pf in the wiring from plate to grid you can multiply whatever that is by the tube gain which is typically 50.

What range of load capacitance would you like to see? How much cable capacitance are most people encountering? Keep in mind it just moves that electrical resonance down to a lower frequency where it is more audible.

[Clio09]

I put a volume control in for myself but I find that I am in the minority. Of course was in the minority about banana jacks 20 years ago and now people want them.

I have a lot of experience with LDR's I dont see any sonic advantage and I wonder how well the two channels stay in balance... how the heck do they do that?

Well I guess I'm in the minority with you. I see no need for an additional preamp in the chain when the gain of the phono stage in addition to what the amp provides should be sufficient for a MM or high output MC cartridge. Since I use MM only (actually moving iron) I guess I'm in the minority again.

As to LDRs, the manufacturer of mine has acknowledged the difficulty in matching them, but in 2 years I have not had any issues with the LDRs causing channel imbalance. As for sonic advantage this is what the Lightspeed manufacturer has to say:

"The best way to describe the Lightspeed Attenuator is that it is like just one fixed soldered resistor that is in the signal path between the source (cd) or phono stage, and the power amp. This resistor is soldered in place and has no contact points that potentiometers pots (potentiometers) or switched resistor (dact type) or TVC (Transformer) volume controls have. Now this resistor LDR (light dependent resistor) has the ability to change it's resistance according to how much light LED (light emitting diode) is shone on it, hence it can control the volume without any mechanical contacts needed in the signal path.

It is believed that any light weight contacts (switches and especially pots and their wipers) have a diode rectification effect on the AC music signal, trying to rectify it which is very bad. The Lightspeed Attenuator (LDR) system totally addresses is diode rectification effect. This is why it is so transparent and totally honest to the source, not adding any colorations or distortions to the source, it is just like being able to plug your cd players fixed output directly into your poweramp yet having control over the volume.

Ever wonder why when after having cleaned your RCA plugs and sockets on your interconnects, your system always sounds better. This is a similar type of contact albeit a much better one than the feather weight one inside a pot and the wiper contact of a switched resistor type control, because an RCA has a much larger and stronger pressure contact area, but still benefits by keeping it clean."

I would certainly be interested in your comments on this.

[neobop]

So far I have 12 positions of loading: 7 ranging from 10 to 1000 ohms and 5 ranging from 10K to no load at all. As to capacitance, it does make a difference and I can offer it as an option but most people have too much already when you add the cables and input capacitance of the preamp which is often not trivial and not stated. The popular 12AX7 has 85 pf miller capacitance internally. If there is just another 2 pf in the wiring from plate to grid you can multiply whatever that is by the tube gain which is typically 50.

What range of load capacitance would you like to see? How much cable capacitance are most people encountering? Keep in mind it just moves that electrical resonance down to a lower frequency where it is more audible.

That's way too much capacitance already for MMs. It will move the high frequency resonance way down into the midrange probably and roll off the high end severely. MMs like to see as little capacitance as possible. Sometimes C is used to make up for dips in the amplitude response or mechanical shortcomings. 600pF is the most total C recommended, that I know of. Most modern carts work best with 0 to 200pF preamp C. Typical arm wire + cables are around 100 to 150pF, but some people replace cables with Blue Jean which has around 12pF/foot.

Is there any way the circuit can be configured so the cart doesn't see all that tube C as shunt C?
neo

[neobop]

I checked the recommended shunt capacitance for a few popular brands of MM carts. These are recommended ranges for total capacitance:
Ortofon - 2M series - 150 to 300pF
Audio Technica 150MLX, 440MLa, 120E - 100 to 200pF
Goldring 1042 - 150 to 200pF

Another popular budget cart is the Shure M97. This cart needs around 250pF total shunt capacitance because of a treble dip around 6KHz. Some tweakers like to load this cart at 62K. Here's an interesting article about it, with measured response graphs.
http://www.tnt-audio.com/sorgenti/load_the_magnets_e.html

You can see how capacitance minimizes the dip, but limits high frequency extension. In this case there is a mechanical solution though. Users report that an aftermarket Jico SAS stylus (boron/microline) "cures" the dip and I'm sure it extends treble response. Those who load the stock cart at 62K, go back to 47K with this stylus.
neo

[IkeH]

About your comment from yoiur Japanese distributor... 

Being originally from Japan, lived in US and now in Europe, I can understand the looks of your proto type does not sell.  Some of my audiophile friends in Japan, would not buy an equipment because of their looks even if it sounds the best.  In my view, majority of audiophiles in Japan prefer refined or authoritative looks even if it means paying more for it looks.  More importantly, hi-end equipment needs to look expensive even to the eyes of non-audiophile!  Goldmund and Jeff Rowland Design are very popular there.
Personally, I don't care much the looks.  My wife would not embrace any stereo equipment because of the design except for that of B&O.  She tolerates my system because she can hear that it sound much better and much less expensive than B&Os 

As I really like the phono section of my RM-5, I would love to try your new phono-amp but due to recent relocation, I am bit strapped for cash:<   I wish the price would have been much lower and there would be an introductory offer 

Ike

PS:  Roger, excuse my ignorance (I am not technical) but wouldn’t a tube amplification state require high voltage? 

[Roger A. Modjeski]

About your comment from yoiur Japanese distributor... 

Being originally from Japan, lived in US and now in Europe, I can understand the looks of your proto type does not sell.  Some of my audiophile friends in Japan, would not buy an equipment because of their looks even if it sounds the best.  In my view, majority of audiophiles in Japan prefer refined or authoritative looks even if it means paying more for it looks.  More importantly, hi-end equipment needs to look expensive even to the eyes of non-audiophile!  Goldmund and Jeff Rowland Design are very popular there.
Personally, I don't care much the looks.  My wife would not embrace any stereo equipment because of the design except for that of B&O.  She tolerates my system because she can hear that it sound much better and much less expensive than B&Os 

As I really like the phono section of my RM-5, I would love to try your new phono-amp but due to recent relocation, I am bit strapped for cash:<   I wish the price would have been much lower and there would be an introductory offer 

Ike

PS:  Roger, excuse my ignorance (I am not technical) but wouldn’t a tube amplification state require high voltage?

My prototype is just something I did for myself. I was curious to see if there are any listeners out there who want something that looks really different.

I am confused by your request to make something look very expensive and yet ask for it to cost even less. Rowland started out putting good stuff inside his "authoritative" looking equipment but soon found out that the buyers didn't care what went inside. At one point he was using National Semiconductor integrated circuit power amps as opposed to the discrete circuits he once used. Now I understand he is using class D modules. Is this what your audiophile friends want?

I will have an introductory offer for AC members as soon as I settle on the package. The circuitry is done, and yes there is a 100 volt B+ supply for the tubes which is powered by the battery.

[Roger A. Modjeski]

I checked the recommended shunt capacitance for a few popular brands of MM carts. These are recommended ranges for total capacitance:
Ortofon - 2M series - 150 to 300pF
Audio Technica 150MLX, 440MLa, 120E - 100 to 200pF
Goldring 1042 - 150 to 200pF

Another popular budget cart is the Shure M97. This cart needs around 250pF total shunt capacitance because of a treble dip around 6KHz. Some tweakers like to load this cart at 62K. Here's an interesting article about it, with measured response graphs.
http://www.tnt-audio.com/sorgenti/load_the_magnets_e.html


You can see how capacitance minimizes the dip, but limits high frequency extension. In this case there is a mechanical solution though. Users report that an aftermarket Jico SAS stylus (boron/microline) "cures" the dip and I'm sure it extends treble response. Those who load the stock cart at 62K, go back to 47K with this stylus.
neo

I already have the infinite (1 meg load) going, its no problem with a tube input stage. I also have the capacitance problem solved for the mm carts. I was pointing out the high capacitance of 12AX7 because of its popularity and wondering if those using it are stating their input capacitance.

Are there any preamp input capacitances you can quote for us.

[neobop]

Input capacitance seems to be the forgotten spec. It seems like 100pF is the new go-to value for high end units. It's interesting that the Steelhead has 10 step user selectable, from 10 to 1100pF. Why anyone would want to go to 1100 is beyond me. Anyway, the Graham Slee MM units seem to have 100pF. I'm pretty sure the Vacuum State JLTI is 100pF as is the Abbingdon PH-77 and the Herron VTPH-2 definitely is.

Good to hear that you have the infinite resistance thing going. That, along with an extra set of RCA jacks for loading, is extremely desirable feature. Anyone who wants more capacitance can load it in the extra jacks right along with their load resistors. Many of the top units are now doing this, including JLTI and Herron.

If I wanted to change capacitance in my phono pre, what kind of caps would you recommend? BTW, I've found that IRC RC55 series resistors seem to work out nicely. They're .1% metal film, 1/4 watt and seem clean and neutral.
neo

[Roger A. Modjeski]

I wonder how many phono preamps state the "intrinsic" capacitance that we are adding to with external capacitor and cable loading. It's all in parallel and adds up just like money. When someone says they have 100 pf load does that include the capacitance in the input tube which, as i previously stated, is not small? I get the feeling that these stated "loads" do not include what's already in the tube and wiring.

Let me arm you with a little information.

1. With a tube input infinite impedance (the resistive part) is not problem. The cartridge goes right to the grid and the grid is returned to ground through the cartridge whose resistance is rather small and makes a fine return.

2. Capacitance is another issue. I looked up the 12AX7 and 6DJ8 today. The grid to plate capacitance is the largest factor which is 1.7 pf and 1.4 respectively. Those numbers get multiplied by the tube gain along with any other grid to plate capacitance in the socket and wiring which can be large on a PCB or with poorly designed wire routing. Even if there is no additional wiring capacitance the 12AX7 input capacitance is 1.7 x 60 (it's typical gain) = 102 pf and the 6DJ8 is 1.4 x 25 (its typical gain) = 35 pf. If the tube sections are connected in parallel (and they sometimes are) double those numbers.

3. MC cartridges will be rather immune to capacitance in these ranges while MM, as pointed out in many posts are very much affected by them due to their high inductance.

[Roger A. Modjeski]

Input capacitance seems to be the forgotten spec. It seems like 100pF is the new go-to value for high end units. It's interesting that the Steelhead has 10 step user selectable, from 10 to 1100pF. Why anyone would want to go to 1100 is beyond me. Anyway, the Graham Slee MM units seem to have 100pF. I'm pretty sure the Vacuum State JLTI is 100pF as is the Abbingdon PH-77 and the Herron VTPH-2 definitely is.

Good to hear that you have the infinite resistance thing going. That, along with an extra set of RCA jacks for loading, is extremely desirable feature. Anyone who wants more capacitance can load it in the extra jacks right along with their load resistors. Many of the top units are now doing this, including JLTI and Herron.

If I wanted to change capacitance in my phono pre, what kind of caps would you recommend? BTW, I've found that IRC RC55 series resistors seem to work out nicely. They're .1% metal film, 1/4 watt and seem clean and neutral.
neo

I would think the steelhead 1100 pf is for MC only. 10 pf seems very low considering there must be close to 100 pf in the preamp (see today's post). This capacitance issue is tricky business.

I would use mica caps as they all have silver electrodes and are available in small values. I would not use ceramic as they can be very microphonic.  RN-55 or carbon film resistors are fine. I don't think the resistor type has any sonic effect as the signal voltages are small and there is no DC across them.

[neobop]

I only saw 1 mention of circuit inherent capacitance, and it was in the 100pF range. I can't remember who it was. Most times I didn't even find the spec, although I didn't really pursue it. Somewhere else on a discussion, someone said that a pentode or cascade? circuit would get around the capacitance. I really don't know about this stuff. It also seems that a couple designers are using an FET input stage with tube gain stage.

Low output carts are said to be pretty much immune to capacitance effects. They have virtually no inductance. I have seen old Nagaoka tonearm cables that are low capacitance for MMs and another model that is low inductance for MCs. I never saw that before. I'm not sure exactly how inductance would effect the output of a MC. Sort of like a high pass filter, limiting the bass? I suspect it wouldn't do much at all. Capacitance doesn't seem to act like the classic filter, that effects a MM. Rather, it seems to lower the high frequency resonance. This augments the treble but rolls off the extreme high end.

Most of the more expensive stages are really designed for MCs, but there's a vocal minority that prefer MM/MI carts. Some of these guys have very expensive equipment and use classic TOTL carts usually. There's a very long ongoing thread on Audiogon forum about this.

Thanks for the cap recommendation. That's what I thought.
neo

[IkeH]

My prototype is just something I did for myself. I was curious to see if there are any listeners out there who want something that looks really different.

I am confused by your request to make something look very expensive and yet ask for it to cost even less. Rowland started out putting good stuff inside his "authoritative" looking equipment but soon found out that the buyers didn't care what went inside. At one point he was using National Semiconductor integrated circuit power amps as opposed to the discrete circuits he once used. Now I understand he is using class D modules. Is this what your audiophile friends want?

I will have an introductory offer for AC members as soon as I settle on the package. The circuitry is done, and yes there is a 100 volt B+ supply for the tubes which is powered by the battery.

Please don't get me wrong, I was just trying to explain about the peculiarity of Japanese audiophile market and not what I wanted...  So for you to sell to Japan, you would need to make different high priced versions for the Japanese market.  BTW, there is a small but enthusiastic following battery powered audiophile electronic in Japan.

I look forward to your special offer to AC members! 

[banquo446]

Poll answer: don't care about looks at all; sound is primary and price secondary (although obviously a constraint). Able to handle mc and mm carts is also important, as is adjustable loading. My Allnic h-1200 tube phono can't be adjusted and I'm regretting getting it for that reason.

[Waynefi]

Hello, I am reading this quite late. But something that allowed 4 ranges for MM would be nice as this is not available in most cases. 35K, 47K, 65K, 100K, and something also for the MC 70, 100, 230, 300, 1K (ohms of course). Capacitance- 0, 50, 100, 150, 220.

A lot of this is on my Jolida Hybrid, which maybe the most versatile out there, but has only the 47K ohm for MM. What many do is shut all the dip switches off and use external resistance plugs, to go above and below the 47K. It would be nice to have something like the above ranges above and below 47K, switches, jumpers or something like that.

It also has 8 gain levels, but I use 50db for mm.

Wayne