John Hardy preamp question

[hollywood_steve]

I'm leaning towards the John Hardy M1 as my next mic preamp. They will be used almost exclusively for location use and transformer coupled I/O can really save your butt on location. But in order afford the Hardy (instead of cheaper brands), I'm going to probably buy the version without the output transformers. Do the base model Hardy preamps have unbalanced outputs or are they "active balanced"? And if I buy the base model without the output transformers, can they be easily added later?

steve
lex125@pacbell.net

[Frost]

I think you will end up using these preamps on much more than just location once you start using them. I believe the output is still balanced even without the transformer. I am sure you can add the transformer later and even add a switch to use it in the signal or not. This must be done by john but I have seen it done. You can also contact John directly. Most people I know in chicago just stop by his house to get more channels of preamp or get something fixed. He's a nice guy.
Frost

[paterno]

Originally posted by hollywood_steve
I'm leaning towards the John Hardy M1 as my next mic preamp. They will be used almost exclusively for location use and transformer coupled I/O can really save your butt on location. But in order afford the Hardy (instead of cheaper brands), I'm going to probably buy the version without the output transformers. Do the base model Hardy preamps have unbalanced outputs or are they "active balanced"? And if I buy the base model without the output transformers, can they be easily added later?

steve
lex125@pacbell.net

Steve --

Do yourself a favor - spend the extra cash and get the output transformers. Besides the the technical advantages (ie, running it into an unbalanced or otherwise questionable input), it sounds great. If you want to save a little money, maybe get the peak LED instead of the full blown meter option. I have never once in my years of owning the M1's wish I had the put the full metering on ...

Cheers,
John

[juniorhifikit]

I don't have the full metering on mine either - and don't miss it. Without the output transformer they're still balanced, and have no coupling caps in the signal chain - nice. He uses a DC null kind of thing to cancel out the DC on output. I don't have the output transformers, so I can't comment on the sound of them. Give John a call - he's a great guy: 847-864-8060

[MIKEHARRIS]

the transformer O part of the I/O cant save your butt if you delete it...get both

[PlugHead]

I'm with John on this one - get the XFRMR: it sounds really good, and will not act cranky (as some pre's do) patching anything into it. They are the very best transformers in the business. IMNSHO, the M1 without the iron doesn't sound as good - have listened to both side by side ( I own a pr w/ tranny's) and the Jensen's win every time...

YMMV,

[theom]

It's not much more, GET THE TRANNY.
I got mine from merc, It was so woth the extra $125 or whatever it was to get the x-former out and full metering.
I have one without meter and x former and one with, It depends on the source but, I alway use the tranny if it is an option, It's just plain smoooother.
And, one of these days I will send the one without to john so he can put the tranny in.

I love my great river and my calrec but in the end,... my john hardy M1 is the best all around pre I own.

[John Hardy]

Regarding the outputs of the M-1 and M-2 mic preamps, if you do not have the output transformers installed, the output is properly described as "Impedance balanced". The output of the 990 op-amp goes to pin #2 of the output XLR through an "output isolator", which is simply a 39.2 ohm resistor with a 3.6uH inductor in parallel with it. Pin #3 of the output XLR goes to ground through another output isolator. Therefore, both pin #2 and pin #3 present the same output impedance to the input of the next piece of equipment. This provides the ideal circumstance for common-mode rejection at the input of the next piece of gear.

The output isolator looks like zero-ohms from DC to well beyond the audio bandwidth because of the presence of the inductor. This provides full signal transfer. Well beyond the audio bandwidth where cable capacitance could become a problem for the 990, the impedance of the inductor has risen to the point where the 39.2 ohm resistor is the lower impedance. So, you get zero ohms of impedance in the audio bandwidth, 39.2 ohms at frequencies far above the audio bandwidth, isolating the cable capacitance from the output terminal of the 990 where it might otherwise cause instability.

Note that I added the 2nd isolator seven or eiight years ago. Earlier M-1 preamps have just one isolator, in series with the output of the 990.

If the output transformers are installed, the first isolator goes to the high side of the primary, the second goes to the low side.

The Jensen JT-11-BMQ output transformer can be installed by the end user. First you bolt it in place. The four wires coming out of the transformer (two for the primary, two for the secondary) are terminated with a 4-position plug. Plug the 4-position plug into the 4-position receptacle on the main p.c. board. If you do not have the output transformer option, there is a 4-position jumper plug installed in the receptacle. I regularly offer to prospective customers to include the little plug-in jumpers so they can unplug the output transformer and install the jumper in its place for comparison purposes during the 15-day trial period. They can send the transformers (or the whole preamp) back for a refund if they wish. I've had dozens of customers take me up on that offer, and nobody has sent the transformers back.

Also note that I added the 4-position plug around the same time that I added the 2nd isolator. Earlier M-1 preamps were harder to deal with, using some insulation displacement terminals for the four wires of the output transformer and jumpers.

The JT-11-BMQ is Jensen's best output transformer. and the Jensen JT-16-B is Jensen's best mic-input transformer.

Thank you.

John Hardy
The John Hardy Co.

[subspace]

Originally posted by John Hardy

If the output transformers are installed, the first isolator goes to the high side of the primary, the second goes to the low side.

The Jensen JT-11-BMQ output transformer can be installed by the end user. First you bolt it in place. The four wires coming out of the transformer (two for the primary, two for the secondary) are terminated with a 4-position plug. Plug the 4-position plug into the 4-position receptacle on the main p.c. board. If you do not have the output transformer option, there is a 4-position jumper plug installed in the receptacle. I regularly offer to prospective customers to include the little plug-in jumpers so they can unplug the output transformer and install the jumper in its place for comparison purposes during the 15-day trial period. They can send the transformers (or the whole preamp) back for a refund if they wish. I've had dozens of customers take me up on that offer, and nobody has sent the transformers back.

Would it be possible to wire the isolators to drive an output directly, as well as drive the transformer in paralell to a second output? Would that affect the output stage's loading for the worse?

[John Hardy]

subspace;

Would it be possible to wire the isolators to drive an output directly, as well as drive the transformer in paralell to a second output? Would that affect the output stage's loading for the worse?

I contacted Bill Whitlock, President of Jensen Transformers, for the best advice. He informed me as follows:

"...simply connect the transformer primary to the preamp's direct outputs." Regarding the output isolators, he said: "...only one pair is necessary regardless of how many loads are driven, either direct or transformer coupled."

The presence of the output transformer should have no significant effect on the quality of the direct output. One of the great things about the 990 is its ability to drive loads as low as 75 ohms and still meet some fairly extreme performance specs. There is a standard test where the 990 must meet certain THD specs while operated at 40dB of gain with a +24dBu output level at 20kHz into a 75 ohm load. That is asking alot of an op-amp. The presence of the transformer does not load down the output of the 990 unless the transformer itself sees a low impedance load.

John Hardy
The John Hardy Co.

[toledo3]

Wow, what a great explanation John. I didn't ask the question, but thanks!

[John Hardy]

G-man;

Thanks for the compliment. The 990 is really quite a special op-amp. It has extremely low noise so it is great for a mic preamp and summing amp, and it has great output characteristics for driving very low impedances. It could almost be considered a power amp. It can put out over two WATTS of power. Plus, it sounds great!

John Hardy
The John Hardy Co.

[sonic dogg]

Welcome to the foray John and great info.

While I cant go downstairs to my studio and see ANY John Hardy pres at the present time, after much research and a quick hearing of the results from an M1, I can safely say that a 4-pack of these is on my 'to do' list.

Uncle Jules can we have this guy for a Guest Moderator???

John, one of my musical partners who is also an electronics genius says yer stuff looks 'real cool'........

This is a guy who builds class A amps out of gum wrappers and tissue rolls because..."he can"

[John Hardy]

sonic dogg;

Thanks for your compliments. Meanwhile, I'm in the middle of fixing a couple of power amps that were recommended by an old friend who worked at the power amp company back in 1994 (the company shall remain nameless). There are so many basic screw-ups in the design that I feel like I'm playing one of those "How many monkeys can you find in this picture?" games. Way too many problems to list here, but it is a reminder of how badly something can be built. The main problem though, is the use of electrolytic capacitors with a maximum temperature rating of 85 degrees Centigrade instead of the 105C versions that I always use. Many of the caps have failed in these amps. The 105C parts will last much longer and perform better than the 85C parts. I'll stop venting for now.

John Hardy
The John Hardy Co.

[subspace]

Originally posted by John Hardy
subspace;



I contacted Bill Whitlock, President of Jensen Transformers, for the best advice. He informed me as follows:

"...simply connect the transformer primary to the preamp's direct outputs." Regarding the output isolators, he said: "...only one pair is necessary regardless of how many loads are driven, either direct or transformer coupled."

The presence of the output transformer should have no significant effect on the quality of the direct output. One of the great things about the 990 is its ability to drive loads as low as 75 ohms and still meet some fairly extreme performance specs. There is a standard test where the 990 must meet certain THD specs while operated at 40dB of gain with a +24dBu output level at 20kHz into a 75 ohm load. That is asking alot of an op-amp. The presence of the transformer does not load down the output of the 990 unless the transformer itself sees a low impedance load.

Thanks a lot for looking into that! Having both output flavors available at the same time seems like a workable option. Dan Kennedy had a similar option available for his first Great River preamp.
Another question, apologies if I'm overindulging on this opportunity to ask, but... What kind of performance difference is there between your outboard M-1 preamps running from their 24 volt supplies and your MXP-3000 replacement preamps, running off the consoles 18 volt rails? Is the output stage feeding the console a simple unbalanced direct out, or is it servoed?
Inquiring minds and all...

[John Hardy]

subspace;

What kind of performance difference is there between your outboard M-1 preamps running from their 24 volt supplies and your MXP-3000 replacement preamps, running off the consoles 18 volt rails? Is the output stage feeding the console a simple unbalanced direct out, or is it servoed?

My MPC-3000 card is very similar to the M-1, using the same Jensen JT-16-B input transformer, the 990C discrete class-A op-amp, input bias current compensation circuitry and DC-servo circuitry to eliminate coupling capacitors. There are minor differences in how those last two items are accomplished, but the same basic result.

The output of the MPC-3000 card comes from the 990 op-amp and passes through one "output isolator" (39.2 ohm resistor with a 3.6uH inductor in parallel with it). This "isolator" provides zero ohms of impedance from DC to well beyond the audio bandwidth (thanks to the inductor) for maximum signal transfer, and essentially 39.2 ohms of impedance at several hundred kHz and beyond to isolate cable capacitance from the output terminal of the 990.

So the main differences are:

1 The +/-18VDC supplies in the MXP-3000 console vs. the +/-24VDC supplies in the M-1, for a difference of about 2 or 3dB of maximum output level.

2. The MPC-3000 card does not have a "Polarity Reverse" switch. The M-1, M-2 and Jensen Twin Servo mic preamps do.

3. There are no meters on the MPC-3000 card, vs. the VU-1 option on the M-1, etc.

4. You are also perhaps limited by the quality of the power supplies (including the Phantom supply), the quality of grounding and the addition of connectors and cables inside the MXP-3000 consoles.

5. The M-1 has two output isolators, one that is in series with the 990 output going to pin #2 of the output XLR, the other isolator from pin #3 of the output XLR to ground to provide the "balanced impedance" capability. The MPC-3000 has only one isolator since it is only dealing with a single output terminal at its interface connector, not an XLR.

On the other hand, the MXP-3000 card is a direct plug-in card, and at $325 is a fairly economical way to quickly make a big difference in an MXP-3000 console. Both the MPC-3000 card and the MPC-600 card (for MCI 600-series consoles) have been updated within the last couple of years.

John Hardy
The John Hardy Co.

[subspace]

Thanks again! I'm going to have to budget for a couple MPC-3000 cards in the future...

[Joel Hamilton]

Seeing these posts by John Hardy makes me glad I chose the 990 for a custom console. Great product. Nice guy.


-joel

[John Hardy]

Joel;

Thank you.

John Hardy
The John Hardy Co.

[Remoteness]

John,

Have you considered manufacturing a multichannel (8 channel) mic pre based on your M-1 and/or M-2 designs?

Thanks...

[John Hardy]

Originally Posted by Remoteness

John,

Have you considered manufacturing a multichannel (8 channel) mic pre based on your M-1 and/or M-2 designs?

Thanks...

Yes, I have considered it. Beyond that I won't say without having to swear you to secrecy. But I am always open to suggestions. The more suggestions I get from you folks the better. Tell me what you want. Thank you.

John Hardy
The John Hardy Co.

[estudiohighend]

Hi John, a good friend of mine recomendedme your preamps as the best and quiet mic preamp for recording clasical and choral music.
so.
first of all i'd like to know, which one of your models do you recomendme? M1, M2 or Tween Servo?
im planning to use a pair of Josephson 617 with Geffel omni capsule, or schoeps... im not deciding yet.

in second. i'd like to know g¡a generaly take of view of the diferences...

Best Regards.
Marcelo

[GoldMember]

Originally Posted by John Hardy

Yes, I have considered it. Beyond that I won't say without having to swear you to secrecy. But I am always open to suggestions. The more suggestions I get from you folks the better. Tell me what you want. Thank you.

John Hardy
The John Hardy Co.

500 series ?

[RobAnderson]

I keep meaning to give Mr. hardy a call about this one:

What I would give for a passive mixer with simple pan and level controls on the M-2...

I know - where do you put it?

Maybe instead of the meter card option?

[John Hardy]

first of all i'd like to know, which one of your models do you recomendme? M1, M2 or Tween Servo?
im planning to use a pair of Josephson 617 with Geffel omni capsule, or schoeps... im not deciding yet.

Any of the preamps will do a great job with any of those mics. The Jensen Twin Servo is a two-stage design that can be an advantage if you need very high gain all or most of the time. The two-stage design splits the gain equally between the two 990C op-amps rather than have one op-amp (M-1 or M-2) provide all of the gain. This can provide a little less distortion and wider bandwidth because each of the two op-amps is working at a more relaxed gain than a single op-amp would otherwise have to do. But the M-1 and M-2 do a fine job at high gains.

500 series ?

I am putting the finishing touches on my first 500-series card, the Jensen Twin Servo 500. I am determined to have a finished card for AES in October. The Jensen Twin Servo is the most complex, so I thought I would get the hardest one out of the way first. The easier ones (M-1 and M-2 versions) can easily follow the form-factor dictated by the Twin Servo.

What I would give for a passive mixer with simple pan and level controls on the M-2...

I know - where do you put it?

Maybe instead of the meter card option?

That would have to be a new product to do it properly. Maybe some day.

Thank you.

John Hardy
The John Hardy Co.
The John Hardy Co. Home

[estudiohighend]

John, once again, I have other quiestion about your M2 option button for 20 ohm microphones, i dont understand this, because i knew the conflictive ones are the ribbons, but the ribbons have higger than 20ohm,
ribbon 300-600ohm
condenser 30-60ohm aprox....
so, the condenser mics are the problem? i didnt know. why?
please i appreciate your explaind, i dont know how affect the impedance on this.
best regards
Marcelo

[kafka]

Originally Posted by John Hardy

I am putting the finishing touches on my first 500-series card, the Jensen Twin Servo 500. I am determined to have a finished card for AES in October. The Jensen Twin Servo is the most complex, so I thought I would get the hardest one out of the way first.
...
John Hardy
The John Hardy Co.
The John Hardy Co. Home

I'm not buying another preamp until I can get a pair of these ...

[supo]

Originally Posted by John Hardy

Yes, I have considered it. Beyond that I won't say without having to swear you to secrecy. But I am always open to suggestions. The more suggestions I get from you folks the better. Tell me what you want. Thank you.

John Hardy
The John Hardy Co.

While you're at it - add a recorder to it for over the shoulder and a battery and I'll be a loyal customer for life.

[rcrowley]

Since that discussion of the 8-channel product was 8 years ago, it seems reasonable to assume it isn't likely to show up under the Christmas tree anytime soon. I am seriously considering getting eight of the MPC-3000 modules and DIYing the mechanical and power portions of the project. In the absence of MPC-3000, what are the physical dimensions? Can I fit eight of them in 3.5 x 17 inches (2 rack spaces)?

[John Hardy]

In the absence of MPC-3000, what are the physical dimensions? Can I fit eight of them in 3.5 x 17 inches (2 rack spaces)?

The MPC-3000 front panel is 2.4" x 1.8". Circuit board is 5.5" x 2". The right-angle header pins at the bottom of the board add about .282" to the overall length. That header connector is somewhat offset (not centered) at the end of the board.

John Hardy