Suhr ISO box

psychodave

psychodave

Well-known member
I was moving stuff around and figured I take a few pics and share my Custom Suhr ISO boxes.

These were made around 20 years ago. A friend of mine had his made along with the other one (made for another friend). These were made before the standard ISO box was made. I mainly use the silver one since I use a mixer and can adjust the levels there. Both sound 99% the same… you damn well know I wasted several hours going back and fourth 🤣. I will say that they sound better than the mass produced version as I wasted several more hours comparing. Compared to the mass produced version, they have more clarity, texture and depth to the sound. As you can see, they are larger in size and a lot more heavy due to the ISO transformers.



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Found it..

It's a JT-11-BM

DKqGPQs.jpg


  • • Distortion 0.002% typ at 20 Hz and +4 dBu output level.
  • • Wide bandwidth: -3 dB at 0.15 Hz and 15 MHz.
  • • Drives 600 Ω loads to levels up to +27 dBu at 20 Hz.
  • • Excellent time domain performance: DLP 0.3° typ 20 Hz to 20 kHz.
  • • Insertion loss only 1.1 dB when driving 600 Ω load.
 
Arch Stanton said:
Found it..

It's a JT-11-BM

DKqGPQs.jpg


  • • Distortion 0.002% typ at 20 Hz and +4 dBu output level.
  • • Wide bandwidth: -3 dB at 0.15 Hz and 15 MHz.
  • • Drives 600 Ω loads to levels up to +27 dBu at 20 Hz.
  • • Excellent time domain performance: DLP 0.3° typ 20 Hz to 20 kHz.
  • • Insertion loss only 1.1 dB when driving 600 Ω load.
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No, it’s a JT-11-FL. Doesn’t look like they are made anymore, and I understand that these older transformers sound better than the new ones?

1707589907718.jpeg
 
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Arch Stanton said:
Ha! It's the exact same one I used in my reactive loadbox !

That one is the older version with the grayish tape over the windings.
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I’ve heard and read the older ones sound better than the newer ones? I’ve haven’t heard a newer one so it’s hearsay. Not sure why he blacked out the model number and parts in one and not the other.

I swear by these ISO boxes though. I’d never part with them.
 
psychodave said:
I’ve heard and read the older ones sound better than the newer ones? I’ve haven’t heard a newer one so it’s hearsay. Not sure why he blacked out the model number and parts in one and not the other.

I swear by these ISO boxes though. I’d never part with them.
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It's that thing where teh builders want to hide what they're doing.

🤷‍♂️
 
psychodave said:
I get it, but why one and not the other? 🤣 I do know they were not built at the same time… my friend sent the black one back to have the volume pot added.
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Prolly started seeing copycats.

🐈

I was running a different Jensen transformer in my reactive load, when the guys over at AmpGarage recommended that one, specifically.. now I know why.
 
harddriver said:
Thank goodness I never heard those bigger models with the fullsize Jensens X-formers...... I've been blissfully happy with my standard Iso Line outs for years now!:yes::scared::poke:

STOP IT DAVE...... JUST STOP IT!!!!!!!!:eek::eek::eek::eek::p:p:p:p
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I thought the same thing...then I thought wait, I just turned 60...and I'm deaf in my right ear...and it rings really loud. I could probably rig up a Victrola instead and not hear the difference.

So @harddriver ...you got that going for you.

FWIW, I have found the modern Suhr Iso Line Out to sound better than the internal Line Outs in certain load boxes. So I just just use the load box as a load and run a second speaker cable to the Suhr. Now Dave adds another level.
 
SpiderWars said:
I thought the same thing...then I thought wait, I just turned 60...and I'm deaf in my right ear...and it rings really loud. I could probably rig up a Victrola instead and not hear the difference.

So @harddriver ...you got that going for you.

FWIW, I have found the modern Suhr Iso Line Out to sound better than the internal Line Outs in certain load boxes. So I just just use the load box as a load and run a second speaker cable to the Suhr. Now Dave adds another level.
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I fully agree.... the Suhr Iso Line out just provides the most optimum sound/tone and feel when tapping a line out signal to another amp or power amp. I found exactly as you did with my attenuator built in line outs ( THD/Rivera Rockcrusher) leave alot to be desired when compared to the Suhr.:yes:
 
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Would the built in line out/slave out on many amps be even better?
 
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paulyc said:
No, usually not transformer isolated.
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I changed my post to include ‘slave out’. That feature is usually tapped right off the amp’s transformer. So a good line out box is still better than such a slave out?
 
No,
thegame said:
I changed my post to include ‘slave out’. That feature is usually tapped right off the amp’s transformer. So a good line out box is still better than such a slave out?
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That’s the amp’s output transformer, look at Dave’s pics above. Those boxes use a small Jensen isolation transformers and a few other passive components. If an amp company included an isolation transformer on their amp’s slave output, then it would be similar. The debate above is about even which Jensen transformer sounds better, and of course it’s the one that’s no longer made. The perpetual plight of guitar players. The technology gets “better” or more advanced and the tone suffers. Story of our lives.
 
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