[the_equalizer]

Quote:

Originally Posted by BoogieWoogie /img/forum/go_quote.gif <snip> Dam what now I have no idea how to configure this, how do I check the voltage with the voltmeter ? (yeah don't laugh)

This seems like a nice tutorial on multimeter use.

After that you'd want to go to the setup section in the MiniMax website to see how to bias the tubes.

cheers!

 

[Beefy]

Quote:

Originally Posted by BoogieWoogie /img/forum/go_quote.gif 1- Luckily my home town electronic store had a 24vac ac-ac 1A with the same output size =D

Didn't I tell you?

Quote:

2. You mean one tube is configured for the left and other to the right ? No he dint tell me I just plugged them without knowing would make any difference. Dam what now I have no idea how to configure this, how do I check the voltage with the voltmeter ? (yeah don't laugh)

Don't worry, it won't break anything if the tubes aren't properly biased. Absolute worst case scenario, you get slightly higher distortion in one channel, or one channel clips earlier than the other at very high volumes.

the_equalizer's advice is good. But don't obsess over it.

 

[BoogieWoogie]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Didn't I tell you? Don't worry, it won't break anything if the tubes aren't properly biased. Absolute worst case scenario, you get slightly higher distortion in one channel, or one channel clips earlier than the other at very high volumes. the_equalizer's advice is good. But don't obsess over it.

You sure ? I though it would fry the amp then I'm going to give it a listen immediately !

 

[Beefy]

So long as the power going in is 24VAC, and nothing broke during shipping, there isn't anything that should fry. Fire it up!

 

[BoogieWoogie]

I just tested the multimeter and its 25.5v coming from the transformer no biggy ?

 

[Beefy]

Nup, that's fine, so long as it is AC.

 

[tomb]

Beefy is correct in everything he's told you.

However, don't get upset if the sound is horrible in one channel or another - or even missing. Sometimes the bias can be that different. Either swap the tubes around or realize that all it takes is a turn of a screw while you are measuring with your meter at the tip jacks in back. Very simple stuff, but if the bias is way off, you may think the amp is broken. It would be a shame to jump to conclusions - so please keep that in mind.

 

[BoogieWoogie]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Beefy is correct in everything he's told you. However, don't get upset if the sound is horrible in one channel or another - or even missing. Sometimes the bias can be that different. Either swap the tubes around or realize that all it takes is a turn of a screw while you are measuring with your meter at the tip jacks in back. Very simple stuff, but if the bias is way off, you may think the amp is broken. It would be a shame to jump to conclusions - so please keep that in mind.

I checked with the previous owner and he said the 2 have the same bias setup and after 50hours playing he checked and were no changes.

Well it sounds terrible but because I have plug it to my first cheapest dvd I got when they came out, still waiting for the dac...

 

[wierddemon]

I have a Millet Hybrid Max that I got second hand about a week ago. This is my first time with tubes and so I know very little. When I was attempting to bias the tubes I noticed that they were close to 21mV each when (if I have been reading correctly) they should be at 13.5mV each since the power supply is at 27mV. Given that the tubes were biased incorrectly (to my understanding), I wanted to check to make sure the DB biasing was done correctly. How do I do this and what should the voltage be set to for the left and right DB?

 

[tomb]

Quote:

Originally Posted by wierddemon /img/forum/go_quote.gif I have a Millet Hybrid Max that I got second hand about a week ago. This is my first time with tubes and so I know very little. When I was attempting to bias the tubes I noticed that they were close to 21mV each when (if I have been reading correctly) they should be at 13.5mV each since the power supply is at 27mV. Given that the tubes were biased incorrectly (to my understanding), I wanted to check to make sure the DB biasing was done correctly. How do I do this and what should the voltage be set to for the left and right DB?

I would recommend that you not mess with the DB's. No offense, but if you have trouble keeping mV straight from V, you could fry the amp in no time.

Seriously (not that the above was a total joke), practice a little more taking readings, swapping tubes and adjusting the tubes until you are completely confident what you are reading and how the changes occur relative to adjusting the trimmers.

 

[moonboy403]

On my MiniMax, there's a little bit of hissing with my JH13 Pro even with the lowest gain tube and regardless of volume level even with the 12FK6 tubes.

1) Is it safe to assume that the gain of the MiniMax is still too high for the JH13?
2) Is there any way to lower the gain further?

Thanks.

 

[gspence2000]

Sounds like the pot needs grounding. See this post.

 

[moonboy403]

Quote:

Originally Posted by gspence2000 /img/forum/go_quote.gif Sounds like the pot needs grounding. See this post.

I'm not getting any hum, just plain hiss as the JH13 is pretty sensitive at 119db @ 1mw and 28 ohms.

With the use of an impedance adapter solved this problem but if I could, I would rather mod the MiniMax so I wouldn't have to use the impedance adapter which IMO degrades the SQ a bit.

 

[tomb]

Quote:

Originally Posted by moonboy403 /img/forum/go_quote.gif I'm not getting any hum, just plain hiss as the JH13 is pretty sensitive at 119db @ 1mw and 28 ohms. With the use of an impedance adapter solved this problem but if I could, I would rather mod the MiniMax so I wouldn't have to use the impedance adapter which IMO degrades the SQ a bit.

Yes, there are some low impedance/high efficiency phones that may exhibit hiss. You control this with the output resistors - anything from a jumper to 100ohms. Most find 10 or 22 ohms are enough, but there are exceptions that may need more output resistance. I think Beefy used much higher values for some AT headphones, but I'm not exactly sure what they were.

 

[Beefy]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Yes, there are some low impedance/high efficiency phones that may exhibit hiss. You control this with the output resistors - anything from a jumper to 100ohms. Most find 10 or 22 ohms are enough, but there are exceptions that may need more output resistance. I think Beefy used much higher values for some AT headphones, but I'm not exactly sure what they were.

I used 33 ohm output resistors for 32 ohms AT-ESW9s. Works great as a balance between noise/gain reduction and damping for these sensitive phones.

But in all honesty, as much as I love the MiniMax I don't think that it is even remotely suitable for IEMs. Too high a gain, too high a noise floor. Even higher resistances or impedance adapters might help with IEMs, but your damping factor will drop off a cliff.

Quote:

Originally Posted by gspence2000 /img/forum/go_quote.gif Sounds like the pot needs grounding. See this post.

No, I really doubt that is all it is.