Need help with my EZ1290 Pre

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nano_lee

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Jun 30, 2021
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Hi Everyone

A few months back I completed my EZ1290 build. However, I did not go completely by Martin A's build guide. I designed my own simple linear power supply using an LT317 voltage regulator. It worked great. I also decided to replace all the Vishay electrolytic caps with the fancy Nichicon UKA "audio grade" caps. Other than that, all the components are exactly like everyone else's EZ1290. Also, I went with the MPSA18 transistors.

The preamp has amazing dynamic range, it has tones of headroom, and no grounding problems. However, it sounds a little bit "tinny". I can't say it's all the way "tinny" cause there is midrange and bass, but it's edging towards "tinny-ness". I can only imagine the new fancy Nichicon UKA caps might be opening up the top end too much? Is this the reason it's a little tinny?

I did not bias the big transistor with a scope, I just did it the sloppy way. I turned the screw thingy until the case of transistor measured 22.66 Volts.
Could it be this (bias without the scope) that makes it sound a little tinny?

Any suggestions guys?
 

Dualflip

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Nov 15, 2008
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Just saying that it sounds tiny does not offer any guidance on where to start helping you, could it just be that you don't like it?
 

Whoops

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I can only imagine the new fancy Nichicon UKA caps might be opening up the top end too much? Is this the reason it's a little tinny?

I highly doubt you or anyone notices any sound difference by using those Nichicon caps when compared to any other good brand capacitor (Panasonic, Vishay, etc)


I did not bias the big transistor with a scope, I just did it the sloppy way. I turned the screw thingy until the case of transistor measured 22.66 Volts.
Could it be this (bias without the scope) that makes it sound a little tinny?

The bias will set a symmetrical clipping point, I don't think that's the reason for your problem

First start by describing technically what you mean by "Tinny" as it's a subjective term and doesn't mean much technically and might mean different things for different people
 

nano_lee

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Sorry for not being more specific. By tinny, I just mean it sounds "bright". And by bright I mean it sounds like it has a bump in the frequency of about 6 Kilohertz that should not be there. It's just big enough to annoy me, but not enough to ruin the amp. I still like the sound of it better than the stock pres in my motu interface.

I noticed that the brent averill 1073 remake uses vishay electrolytics throughout the whole thing, and it sounds like a darker version of mine. But then again it uses polystyrene caps like the original. Would polystyrene sound brighter or darker than the Wima caps? It might be important to note that I did slightly damage the .01uF styrene cap that is connected between pin 8 and 5 of the output transformer, could that be the problem?

Maybe I'm just being too picky, I dunno. I was hoping to get some insight on how to make slight modifications to change the tone of it.
Maybe I should just take advantage of its brightness and use ribbon mics with it. Prolly balance out a dark ribbon very well.
 
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Whoops

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Sorry for not being more specific. By tinny, I just mean it sounds "bright". And by bright I mean it sounds like it has a bump in the frequency of about 6 Kilohertz that should not be there. It's just big enough to annoy me, but not enough to ruin the amp. I still like the sound of it better than the stock pres in my motu interface.

Do you have any other ez1290 build to compare your unit to?
That would be the best thing to do so that you could be certain if there's a problem in your unit or not


I noticed that the brent averill 1073 remake uses vishay electrolytics throughout the whole thing, and it sounds like a darker version of mine. But then again it uses polystyrene caps like the original. Would polystyrene sound brighter or darker than the Wima caps?

Forget about caps brands and types, it doesn't matter and if your unit has a problem in the frequency response is not due to a capacitor brand or dielectric. If the sound is off it's because you made a mistake somewhere in your build
 

lars on

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Joined
Nov 18, 2018
Messages
83
Hi everyone !

I just finished another ez1290 and I have a bad voltage on TR1 Emitter, I have ~360mV instead of 0,4 Volts.
BUT when I switch on the unit the voltage is good during 5 secondes.
Maybe a bad capacitor ?
Anyone have an idea for that ?
Thank's
 
Last edited:

lars on

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Nov 18, 2018
Messages
83
The unit seems to work correctly when I measure the frequency response.
Today I have adjusted the bias and I had this curve.
Did anyone had the same ?
 

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