[ssoaos]

Hi, I have noise issue with my Minimax and hope someone has seen it and could help.

I just finished building the Minimax and put in Tom's custom case. After two days the bias is stabilized. But there is a audible ground hum. It is not related to volume level.
1. The pot is grounded.
2. When I touch the case, the noise is gone.
3. I swapped the tube(They are 12AE6s from Beezar), the noise is lowered.
4. I thought it was ground loop, so I took the board out from the case, the noise was still there.
5. I disconnected the RCAs from the board, but it did not help.
6. If I touch any electrolytic cap, the noise it gone.
Any suggestion would be appreciated.

Stanley

 

[Beefy]

Is the amp actually hooked up to a source? Is the incoming ground wiring properly connected?

 

[ssoaos]

Hi, No source. I started by disconnected the source. Took the board out from the case with back panel connected. The disconnected the RCA.

Stanley

 

[ssoaos]

Hi Beefy, I just tried with only one tube installed. I noise goes away. It does not matter which channel.

 

[cetoole]

Sorry to say, that doesnt actually help you any. With either tube out, the heaters on both wont light, so the tubes dont function and buffers dont bias. How about you post some pics here? It sounds to me like a grounding issue.

 

[Beefy]

Try connecting it to a source and listening to it, rather than just sitting it on a desk and burning it in

 

[ssoaos]

Thank you Colin and Beefy,
Tom reminded me if I pulled out one tube, the series supply to the filament was broken and so my other channel is obviously quiet. Silly me! I did more tests last night by swapping the tube and the noise followed the tube to that channel, so Tom believes it is the tube and he is sending me a replacement to try. I did resoldered the whole board so the chance of having a cold solder is probably zero. I disconnect the input wire and the only wires to the board are the two AC wires.
Any suggestion is appreciated.
Thank you all!
Stanley

 

[oneplustwo]

Hey folks,

Just wanted to share some brief impressions of how my minimax compares to the active ground beta 22 I just built.

In short, the mini holds its own quite well! If I was to quantify SQ where my receiver headphone jack is 70, the mini max would rate at about a 91, and the beta would be a 97.

There's definitely more "color" in the minimax due to the tubes but I find the power and detail available is very good. This is in contrast to the beta where the sound is more clean/analytical for lack of a better word, but the power is awesome! Transient response seems instantaneous and even the softer sections are detailed and clear.

Is it worth the added cost? There is no right answer, obviously, but I didn't spend that much more on the beta than the mini since I went super cheap on the case work. So the price comparison for me isn't really apples to apples. For what it's worth, I'm glad I built the beta and love the quirky result.

Should I keep both? I'm not really that excited about selling the mini even though I told myself I would to justify the cost of the beta. For the moment, I'll keep them both. But after a few months, if I find I'm not listening to the mini any more I may sell it. I hate selling stuff I made though...

 

[tomb]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif Hey folks, Just wanted to share some brief impressions of how my minimax compares to the active ground beta 22 I just built. In short, the mini holds its own quite well! If I was to quantify SQ where my receiver headphone jack is 70, the mini max would rate at about a 91, and the beta would be a 97. There's definitely more "color" in the minimax due to the tubes but I find the power and detail available is very good. This is in contrast to the beta where the sound is more clean/analytical for lack of a better word, but the power is awesome! Transient response seems instantaneous and even the softer sections are detailed and clear. Is it worth the added cost? There is no right answer, obviously, but I didn't spend that much more on the beta than the mini since I went super cheap on the case work. So the price comparison for me isn't really apples to apples. For what it's worth, I'm glad I built the beta and love the quirky result. Should I keep both? I'm not really that excited about selling the mini even though I told myself I would to justify the cost of the beta. For the moment, I'll keep them both. But after a few months, if I find I'm not listening to the mini any more I may sell it. I hate selling stuff I made though...

I never thought I'd see someone compare the MiniMAX to the B22, but thanks for the report.

If anything, it confirms the thoughts that we've had: the changes to the power supply, the parts selection, the board layout, etc - it's pretty much as good as it gets when coming to the BJT version of a MAX/Millett Hybrid. When you factor in the case - despite the higher cost over a run-of-the-mill Hammond/Lansing - the result is even more satisfying.

 

[THE_SOURCE41]

I have life and sound in my amp! I just want to say thank you to tomb and everyone who has helped me with this.
I will post pics once it is enclosed and completely set up.

Sam

 

[Beefy]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif Just wanted to share some brief impressions of how my minimax compares to the active ground beta 22 I just built. In short, the mini holds its own quite well! If I was to quantify SQ where my receiver headphone jack is 70, the mini max would rate at about a 91, and the beta would be a 97.

I think that sometimes people forget how little 'real' difference there is between well designed amps. Sure, if you sit a couple of amps you are familiar with side by side, listen to tracks you have listened to for years, in an ideal environment with a complete lack of distractions...... then the potential for differences is there.

But when I am just kicking back and listening to the music, that really doesn't matter to me. I still maintain that my MMM is a better amp than any of the Maxes that I have built; that doesn't take away from the fact that I thoroughly enjoyed building and listening to every one of those amps.

 

[oneplustwo]

Agreed! Now that you mention it, I am curious how the MMM sounds having built the mini3 and the beta now. I'll have to use all my will power to NOT find out for myself.

 

[tomb]

Quote:

Originally Posted by THE_SOURCE41 /img/forum/go_quote.gif I have life and sound in my amp! I just want to say thank you to tomb and everyone who has helped me with this. I will post pics once it is enclosed and completely set up. Sam

Glad to hear it! ... and thank you for not giving up.

We've had one or two that did that when they realized a mistake with the output transistors. Hopefully, it wasn't that hard for you. Bring on the pics!!

 

[aphexii]

Just curious, what gauge wire are you guys using for your hookups? I have 18 or 20 gauge stranded in there right now but its a bit less flexible than I would prefer and have been thinking of maybe picking up some thinner wire.

 

[TimJo]

Quite a few of us use the 22 ga. Navships silver/teflon wire...

http://www.head-fi.org/forums/f6/hoo...dation-404921/