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Radial 500 Series Twin Servo Preamp
Old 16th September 2015
  #1
Gear Nut
Radial 500 Series Twin Servo Preamp

I just saw an ad for this in Recording mag. It looks like a 500 version of the John Hardy Twin Servo, which was announced several years ago but to my knowledge was never released. I wonder if they licensed the product from him....
Old 16th September 2015
  #2
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Jensen, of course... hope they don't make it all fugly like (not a fan of the Radial/Tonka-toy-truck look).

http://www.johnhardyco.com/pdf/Jense...reliminary.pdf
Old 19th September 2015
  #3
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ARIEL's Avatar
Yes I agree , I wish they would make their range with a consistent company colour rather than the lego / tonka toy scheme . I dig their products mind you . great stuff !
Old 19th September 2015
  #4
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Yes, that's the shame... if their products were bad, we wouldn't care.

Back to Hardy, if that's what it is or maybe they have a direct deal with Jensen?

Regardless, it should be a killer... we have two channels of Hardy M1 and the TS is supposed to be a couple steps up from that, with two 990 stages to the M1/M2's single, if I remember correctly.
Old 19th September 2015
  #5
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ARIEL's Avatar
Radial actually bought Jensen apparently
Old 19th September 2015
  #6
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Boom!
Old 19th September 2015
  #7
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From TapeOp:

Radial 500 Series Twin Servo Preamp-twin-servo.jpg
Attached Thumbnails
Radial 500 Series Twin Servo Preamp-twin-servo.jpg  
Old 19th September 2015
  #8
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Interesting... thanks for posting!

Not as classy as the proposed Hardy, but more dignified than the typical Radial offering (ad looks to be B&W, though).

I wonder if they're doing their own 990 variant.

Hardy's are 990c (through-hole and later, surface-mount, as I recall)... should sound great, regardless.
Old 19th September 2015
  #9
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superwack's Avatar
according to the info on John Hardy's site - the Twin Servo 990 preamp design is a circuit Dean Jensen published. I'm sure Hardy had a lot to do with refinements (especially with the 990c) but I'd imagine this new Radial will be pretty close and certainly should be great!
Old 20th September 2015
  #10
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cheu78's Avatar
Quote:
Originally Posted by ARIEL View Post
Radial actually bought Jensen apparently
Yes, radial bought Jensen transformers some time ago..
I hope John Hardy was involved in this project



Cheu
Old 22nd September 2015
  #11
Wondering as well with John was involved in the design
Old 22nd September 2015
  #12
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Paging Peter Bonemeister!

(like a porn name, no?)
Old 23rd September 2015
  #13
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ManMulcahy's Avatar
How much is this mamma jamma going to cost?
Old 30th September 2015
  #14
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ddageek's Avatar
 

Quote:
Originally Posted by Sean Sullivan View Post
Wondering as well with John was involved in the design
why the Pre and the 990 are Dean Jensen designs Radial now owns Jensen .
Hardy is the first to credit Jensen with both designs.
Old 30th September 2015
  #15
Quote:
Originally Posted by ddageek View Post
why the Pre and the 990 are Dean Jensen designs Radial now owns Jensen .
Hardy is the first to credit Jensen with both designs.
But Hardy manufactures the op amps. I suppose Radial could do their own
Old 30th September 2015
  #16
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ddageek's Avatar
 

Quote:
Originally Posted by Sean Sullivan View Post
But Hardy manufactures the op amps. I suppose Radial could do their own
There have been others and they do have the documents !
Old 30th September 2015
  #17
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cheu78's Avatar
Quote:
Originally Posted by ddageek View Post
why the Pre and the 990 are Dean Jensen designs Radial now owns Jensen .
Hardy is the first to credit Jensen with both designs.
You are right.. but Hardy was the guy who really brought those designs (Dean's) to "fame" somehow.. I credit his good implementation of the design, choice of materials and hard work..
He always wanted to make a 500 series preamp, therefore I think it could have been "right"..

Just my 0.02$,

Cheu
Old 30th September 2015
  #18
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superwack's Avatar
Here's the story of the Twin Servo from Mr. Hardy himself. Basic story: Dean Jensen invented the Twin Servo 990, contracted a company called Boulder to manufacture it, Hardy showed Dean his M1, Dean and Boulder had a falling out and ended their deal then he struck a deal with Hardy to build it. Dean Jensen designed the 990 Opamp and said anyone could build it - but Hardy has since made changes/improvements. As mentioned OTHERS make 990s including Hairball, Seventh Circle, and others

here's the video about the Twin https://www.youtube.com/watch?v=YR3_fJGlYzE
and the 990 https://www.youtube.com/watch?v=DPq89ne4OS8
Old 1st October 2015
  #19
Gear Maniac
 

Here is a look at board #1 of my Jensen Twin Servo 500 mic preamp card. I am performing final testing and tweaking.

You may need to click on a thumbnail to see it.

Thank you.

John Hardy
The John Hardy Co.
The John Hardy Co. Home
Attached Thumbnails
Radial 500 Series Twin Servo Preamp-img_2454-40.jpg  
Old 1st October 2015
  #20
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cheu78's Avatar
Quote:
Originally Posted by John Hardy View Post
Here is a look at board #1 of my Jensen Twin Servo 500 mic preamp card. I am performing final testing and tweaking.

You may need to click on a thumbnail to see it.

Thank you.

John Hardy
The John Hardy Co.
The John Hardy Co. Home
That looks stellar John!

Are you going to show it at AES 2015? When will it ship?... price?

Thank you!



Cheu
Old 6th October 2015
  #21
Gear Maniac
 

Cheu (and all);

Quote:
Are you going to show it at AES 2015? When will it ship?... price?

Thank you!
I will not be exhibiting at AES 2015. I had other urgent priorities. I am planning on exhibiting at AES 2016 though.

My Jensen Twin Servo 500 will have a retail price of $995. It will begin shipping in about 30 days.

I had no knowledge of the Radial product until I saw this discussion. So I have no idea of what is going on inside the Radial box. However, I DO know what is going on in MY product, and the photo that I posted earlier should make that clear. I took the original and official schematic of the Jensen Twin Servo that I started manufacturing for Deane Jensen in 1988 and adapted it for power supplies of +/-15VDC, changing component values only if necessary to accommodate the lower supply voltages. The original Jensen Twin Servo uses +/-24VDC supplies. All changes were approved at the highest levels at Jensen.

I use the very same input transformer in the 500 series version as the original version, the Jensen JT-16-B. In 1988 it was known as the Jensen JE-16-B. Around 1992 it was updated to the JT-16-B after a design refresh (that's the short story).

For the output transformer I use the Jensen JT-11-DM. The original Jensen Twin Servo uses the JT-11-BMQ (JE-11-BMQ) which is one size larger than the JT-11-DM, but that would have been overkill for the +/-15V supply limits of the 500 series. It would not fit in the 1.5" module width of the 500 series either. The original Twin Servo uses +/-24VDC supplies, therefore it has a higher maximum output level than the 500 series. The higher output level is better matched to the larger "BM" size. The "DM" size is ideal for the lower power supplies.

Radial is probably making their own 990 op-amps. They are not getting them from me. I have had 36 years of experience making the 990!

Thank you all very much.

John Hardy
The John Hardy Co.
The John Hardy Co. Home
Old 12th October 2015
  #22
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elambo's Avatar
That's great news, John! As a Twin Servo owner I've had my eye on the 550 version since it was first mentioned, and I just happen to have a free space in my lunchbox...
Old 20th October 2015
  #23
Gear Nut
 

Jensen Twin Servo 500 series

Hi All;

Yes, Radial invested in Jensen... not to change the company, but to secure manufacturing and ensure Jensen quality would not suffer if it got moved from its California home to someplace like China. Since then, Jensen's OEM customers have enjoyed the benefits without any change in price. Jensen is run independently.

John Hardy has been a staunch supporter of Jensen and the two companies have enjoyed many years of working together. The Deane Jensen 990 circuit was given to the world (public domain) after the original announcement and Hardy has kept this amazing design alive. There is good reason for this. When using two 990s (original design) Deane eliminated all capacitors in the signal path - replacing them with servos. He then put his two best transformers at the input and output to deliver a frequency response that extends from about 1Hz to 100kHz. I can tell you without any reservation that when I first heard the new Twin Servo 500, I was astonished at the bottom end. We spend hours and sometimes days listening to circuits and transformers. This is the most impressive preamp I have ever heard.

As for the design, yes... we worked with the Jensen engineering team to ensure the circuit is 100% faithful to the original. As John Hardy correctly points out, Deane Jensen actually made the design so that it could work with various voltages including the +/-24VDC that was used in the original Jensen 19" rack version and the +/-15VDC version that Jensen/Radial and Hardy have in their designs.

As you well know, Radial has been a staunch supporter of the 500 series with over 20 modules and a half-dozen Workhorse racks. Over the years, we have come to understand both the capabilities and the restrictions of this wonderful format. In producing the Twin Servo 500, two restrictions had to be addressed. The first was the +/-16VDC voltage which (as mentioned above) was actually quite easy as Deane had already done the work. The second was the limited space.

To address these issues, instead of using 'plug in' 990 op-amps, we went 100% discrete and placed all of the components directly onto the circuit board. There are no surface mount parts in the Jensen Twin Servo 500. Next, due to the limited width of the module, we worked with Jensen to find an alternate transformer that would deliver the same frequency response. The slightly smaller transformer allows us to put a cover onto the module which helps reduce electro-magnetic pollution from other modules. On the down side, instead of delivering a full +26dB, this will be reduced to about +24dB. It is worth noting that since all of the other modules in the 500 series format are also working with the same +/-16VDC rails, it is unlikely any module will be able to handle more than +22dB without severe distortion. The old 24dB broadcast standard was abandoned years ago when +4dB took over. We compared the two and could not measure or hear a difference.

Whether you invest in a Hardy or a Jensen/Radial, one thing is sure: you will never experience an extended response like the 990 Twin Servo. It truly is remarkable.

Peter
Old 22nd October 2015
  #24
Gear Maniac
 

Hi Peter;

Quote:
Next, due to the limited width of the module, we worked with Jensen to find an alternate transformer that would deliver the same frequency response. The slightly smaller transformer allows us to put a cover onto the module which helps reduce electro-magnetic pollution from other modules.
When you mention “an alternative transformer”, are you referring to the input transformer, or the output transformer, or both? More specifically, which model of mic-input transformer are you using, and which model of line-output transformer are you using in your TS-500 card?

Thank you.

John Hardy
The John Hardy Co.
The John Hardy Co. Home
Old 22nd October 2015
  #25
Gear Nut
 

Jensen / Radial Twin Servo 500

Hi John;

We have the following transformers in the Jensen Twin Servo.

Input = JT-16
Output = JT-11-EM

Peter
Old 23rd October 2015
  #26
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elambo's Avatar
Quote:
Originally Posted by John Hardy View Post
I use the very same input transformer in the 500 series version as the original version, the Jensen JT-16-B.

...

For the output transformer I use the Jensen JT-11-DM.
Quote:
Originally Posted by Bonemeister View Post
We have the following transformers in the Jensen Twin Servo.

Input = JT-16
Output = JT-11-EM
Is there an appreciable difference between the JT-16-B and JT-16?

Is there an appreciable difference between the JT-11-DM and JT-11-EM?
Old 23rd October 2015
  #27
Gear Nut
 

Radial 500 series - Jensen Twin Servo

With Jensen, the part number extension generally describes the signal handling and/or the type of connection (wire mount versus PCB mount). You can view the specs for each transformer used in the Jensen Twin Servo 500 here and then download the other specs if you like.

http://www.jensen-transformers.com/w...8/jt-16-a1.pdf
http://www.jensen-transformers.com/w...jt-11-emcf.pdf

As a rule, the larger the transformer, the lower the bottom end response and higher the signal handling capacity. The challenge, as stated above is the limited physical size available with the 500 series format and the +/-16VDC rails. Using an over-sized transformer is kind of like having a small hose feeding a big water pipe. It will work perfectly well, but it will not produce more water than the small pipe that is feeding it. The JT-11-EM will handle less signal than the larger JT-11DM. Both have the same frequency response that nearly extends from DC to light! The JT-16 is the same in either case.

Have fun!
Old 24th October 2015
  #28
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elambo's Avatar
Thanks Peter!

So, all other things being equal, we'd not likely hear a difference between those transformers?
Old 24th October 2015
  #29
Gear Maniac
 

Hi Peter;

Quote:
With Jensen, the part number extension generally describes the signal handling and/or the type of connection (wire mount versus PCB mount).
You mentioned the “JT-16” a couple of times as the input transformer that you are using in your Jensen Twin Servo 500. Without a part number extension, it is still not clear which input transformer you are using. The Jensen web site shows the JT-16-A and the JT-16-ATB, basically the same transformer except for the configuration of the end-cap of the 1.32" diameter round shield can. The “A” version has four holes at the end of the can. Two of the holes are for the wires to exit, the other two holes are mounting holes. The “ATB” version is likely a special-order “bushing-mount” version using a 3/8” threaded bushing in the end cap for the wires to exit and for attaching the transformer to a chassis.

I am using the JT-16-B, which is identical to the JT-16-A except for the shape of the shield can. The “A” version has a round can (1.32"D), the “B” version has what appears to be a square can, but it is actually rectangular. A data sheet from 1995 shows the dimensions of the JT-16-B as 1.20” x 1.17” x 1.63” (LWH).

The data sheet that you linked to as the input transformer for your Jensen Twin Servo 500 is for the JT-16-A.

So the question remains, are you using the JT-16-A, JT-16-ATB, JT-16-B, or some other “JT-16” variant that is not listed on the Jensen site? A photo of your Jensen Twin Servo 500 without the cover would be cool!

As a foot note, I am at least partly responsible for the existence of the “B” version. Back in 1981 I was designing a mic preamp card for the MCI 500C series of consoles. The 1.32” diameter of the round can of the JE-16-A was too large to fit in the space available. The bobbin and “EI” laminations of this type of transformer are relatively squarish, so it seemed to me that if Deane Jensen could put the “A” windings in a square can, the overall package would be smaller. The resulting JE-16-B allowed me to put the 1.17” dimension where the 1.32” diameter dimension of the “A” version would otherwise be, a reduction of 0.15”. Enough of a reduction to make my MPC-500C card and other mic preamp cards possible.

Thank you.

John Hardy
The John Hardy Co.
The John Hardy Co. Home
Old 25th October 2015
  #30
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Petermix's Avatar
Quote:
Originally Posted by John Hardy View Post

My Jensen Twin Servo 500 will have a retail price of $995. It will begin shipping in about 30 days.
Soooo 2 weeks away now? Will it be direct from the website? #justasking
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