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Usher r1.5 mods


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I've come to a decision to modify my r1.5 amp that nelson path suggested.

I will be upgrading

the power supply caps from 6x 10000uf to 6x15000uf

Increasing the Class A bias to 50*C thermal temperature

Obviously there will or may be questionable reliability issues raised but I'm more curious to people's opinions and thoughts on what or if any differences to the sound will be. Guess I love this amps but may have grown bored of it but like anything can't bring myself to part with it

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Hmmm - any links to the mods that Nelson Pass has suggested would be greatly appreciated.

 

I have one of these lazy monsters and remain quite ambivalent about it.  Certainly, it's one of the coolest-running amps I've come across, suggesting the class A bias is minimal.  The owner's manual is written in extreme Chenglish and some of the quoted specs are clearly nonsense.

 

I understand the 2.5 model had a lot in common with one of NP's Stasis designs, but I didn't think the 1.5 shared that distinction.  So, I'd be fascinated to find out what Nelson Pass has to say about it.

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  • 4 years later...

Here is the circuit of the Usher 2.5 should you need it (note there are many more output transistors than shown),  Nelson Pass also suggested the heatsinks should be at or around 50-55c after a couple hours at idle, this will give most Class-A bang for buck with much heat stress to components. 

 

Cheers George

 

R2.5.thumb.JPG.cd5c4f0c6c74416e22e485dd404fa8e6.jpg

Edited by georgehifi
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Sorry to burst your bubble, the R1.5 a 150w Class-A/B amp with that amount of heat sinking, could only sustain up to a max of approx 10w of Class-A bias on it before it got so hot it would either shut down or go into thermal runaway.

 

To give an example here a pair of  ML2 monoblocks at 25w class-A each into 8ohm, (that's it there's no Class-B, which makes the Class-A heat go up exponentially the more Class-B there is)

  

Cheers George

 

c.jpg

 

Edited by georgehifi
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I have owned two Usher R 1.5s.The older one ran a lot hotter than the newer one to the point that the paint or anodising on the top cover has burnt off.I suspect Usher made the early ones with a lot more  Class A bias and then backed it off due to the heat generation.

If there was any difference in the sound I was battling to hear it.

Why you would would want to mess with a great sounding amp is beyond me.They are happy driving really difficult low impedance speakers as they are.

Using two did sound slightly better on some speakers but the difference was extremely slight and not worth the extra heat generation and power consumption.Which is why I sold one.

 

Edited by THOMO
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29 minutes ago, THOMO said:

I have owned two Usher R 1.5s.The older one ran a lot hotter than the newer one to the point that the paint or anodising on the top cover has burnt off.I suspect Usher made the early ones with a lot more  Class A bias and then backed it off due to the heat generation.

If there was any difference in the sound I was battling to hear it.

Why you would would want to mess with a great sounding amp is beyond me.They are happy driving really difficult low impedance speakers as they are.

Using two did sound slightly better on some speakers but the difference was extremely slight and not worth the extra heat generation and power consumption.Which is why I sold one.

 

Interesting, one thing I wonder about, is if the Usher 1.5 likes easy to drive speakers?

i don’t think my 5/9 go below 6ohm!

Read somewhere that it really likes tough to drive speakers, although in my mind it should maybe handle easier loads that better, but maybe someone with better understanding of these things would know better.

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I previously had a loan of an Usher R1.5 and found it to be grossly underpowered, and lacking in control and dynamics.  I think at 10 o'clock on the dial it was game over.   I used it with Gale 401s, KEF Reference 104/2, and Lenehan ML1 and ML3's.  

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9 hours ago, gryphongryph said:

Interesting, one thing I wonder about, is if the Usher 1.5 likes easy to drive speakers?

All amps as far as I'm aware prefer easy to drive speakers.

 

Cheers George

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12 hours ago, Peter_F said:

I previously had a loan of an Usher R1.5 and found it to be grossly underpowered, and lacking in control and dynamics.  I think at 10 o'clock on the dial it was game over.   I used it with Gale 401s, KEF Reference 104/2, and Lenehan ML1 and ML3's.  

That has not been my experience.I wonder if the preamp you used had enough gain?

The Ushers do seem to need  high gain preamp like a Supratek .Even the matching Usher preamp seems to lack enough gain and sounds flat and lifeless when used with the Usher power amp and yet I have heard it sounding very good with other power amps.To the point that you would not believe you were listening to the same preamp.The importance of preamp/power amp synergy can be grossly undervalued.

I  have used some massively powerful amps including one that was 800 watts into four ohms and I would not say my Usher sounds like it lacks power or dynamics by comparison.

Having said that the appeal of the Usher lies in ts tonality /timbre  and organic sort of sound rather than its clout .In many ways it does sound more like a good valve amp rather than a typical SS powerhouse amp and you need to listen in that sort of way to appreciate it.Not one for headbangers and it does sound a bit laid back I suppose but I prefer that to the coarse and mechanical sort of sound you get from the vast majority of SS amps.

The closest sounding amp to the Usher I have heard is the Audio Flight Strumento 4 power amp [about $35,000 worth and yes it is better but has a similar sort of presentation].That also sounds superb with the Supratek preamp.

 

Edited by THOMO
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On 22/06/2019 at 8:11 AM, THOMO said:

Even the matching Usher preamp seems to lack enough gain and sounds flat and lifeless when used with the Usher power amp and yet I have heard it sounding very good with other power amps.

"flat and lifeless" that's not a factor of gain, if there was enough volume level then the gain is fine, it was probably more to do with the different amps used. The R1.5 only needs 1.6v in to give full output 150w, a Redbook CD has a min of 2v so in theory even a passive pre should do. The Usher pre has up to 15v out!!! with 2.3v input.

 

Cheers George 

Edited by georgehifi
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On 21/06/2019 at 12:17 AM, georgehifi said:

Sorry to burst your bubble, the R1.5 a 150w Class-A/B amp with that amount of heat sinking, could only sustain up to a max of approx 10w of Class-A bias on it before it got so hot it would either shut down or go into thermal runaway.

 

To give an example here a pair of  ML2 monoblocks at 25w class-A each into 8ohm, (that's it there's no Class-B, which makes the Class-A heat go up exponentially the more Class-B there is)

  

Cheers George

 

c.jpg

 

Maybe the difference is sliding biasing ! Like the Luxman 590ii 30w class A then goes into a/b power, same with Accuphase.

 

Got e-mail from Usher again, here is what the guy wrote.

“The R1.5 is in class A 50 watts. I have no idea what forums say. As it is measured and the reading is 50 watts.”
 
 
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7 hours ago, gryphongryph said:

Maybe the difference is sliding biasing !

 

All the Ushers amps use technician adjustable fixed biasing, none use Plateau (sliding) bias.

 

I've circled the bias adjusting pot for you in red in the circuit I posted up last week. All the Usher models amps use this circuit with varying amounts of output transistors and rail voltages 

R2.5.thumb.JPG.cd5c4f0c6c74416e22e485dd404fa8e6.jpg.eb0c53c8392f554cbab61e1f8bbe6724.jpg

 

BTW: And for those that haven't spotted it, the speakers are collector driven, just like Nelson Pass's Classics, the "Threshold Stasis models S150, 200, 300, 500", which if you didn't know the Ushers are a clone of. 

Also our very own "original" Australian made ME's amps use collector driven speaker outputs.

 

Cheers George

  

1044770241_StasisThresholdS300-2-optoxx.jpg.4c32883bb822ab5c3041011e0c95a7eb.jpg

 

 

Edited by georgehifi
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With bi-polar output transistors in push/pull amps you "normally" have

A "base" which is the input

Then the "collector" which usually goes to the power supply rail

And the "emitter" which usually goes to the speaker via a low impedance "emitter resistor".

 

But in the Pass, Usher, and Me cases, the "collector" goes to the speaker and the "emitter" with "emitter resistor" goes to the power supply rail. "Said" to sound better if you listen to their propaganda spiels. But Gryphon's big beasts, one of the best Bi-Polar amps around use the "normal" above.

 

Cheers George 

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