anatech said:
Yes and manufactures spec is WAY hotter than I am running.. I can hold my heat sink fins indefinately without discomfort.. the spec is 5 seconds and then it should be uncomfortable..
I should not have said upgrade.. I meant simply to restore the rest of the electrolytics and then set the Bias per specs...
You dont think power cords will help? Neither do I.. but read this anyway.. its just too weird... this is not too far off topic.. its about the 400a and a power cord...
http://forum.audiogon.com/cgi-bin/fr.pl?rcabl&1136162727&read&keyw&zzthreshold=400a
Babowana said:
Sorry I do not know what this sentence means.. or is it two sentences.. ?? Maybe someone can explain. Whats a mods? And what does it mean to "well playing with"?
I did notice you had a message in Texas though.. maybe this is part of that message? I didnt read it.
barchetta said:
Mods are moderators.
My English is no good; I mean you are doing good with 400a 😉
Bias adjustment
Joe,
It'd be great if you'd post the spec and procedure that Jon shared with you so others have it for reference.
The five second finger burn test sounds about right. If your flesh stays stuck then it's perfect... (joke!)
For reference, you will find that increased bias increases the subjective depth of the sound stage. However, one needs to be careful with a bipolar amp as the transistors can't handle the heat that mosfets can.
That having been said, a little heat is definitely a very good thing 😉 Just make sure not to overdo it or you'll be buying more outputs and possibly speakers...
As Chris suggested, I'd start with factory spec and go from there.
Joe,
It'd be great if you'd post the spec and procedure that Jon shared with you so others have it for reference.
The five second finger burn test sounds about right. If your flesh stays stuck then it's perfect... (joke!)
For reference, you will find that increased bias increases the subjective depth of the sound stage. However, one needs to be careful with a bipolar amp as the transistors can't handle the heat that mosfets can.
That having been said, a little heat is definitely a very good thing 😉 Just make sure not to overdo it or you'll be buying more outputs and possibly speakers...
As Chris suggested, I'd start with factory spec and go from there.
Since he designed it, I consider him the manufacture spec:
quoted from this thread re: 400a
http://www.diyaudio.com/forums/showthread.php?s=&postid=465173&highlight=#post465173
"Nelson Pass []
The one and only
Simply replacing all the electrolytics is a good step, and none
of them are critical in value and none need more than 50 volts,
as I recall.
The bias should be set so that after the amp warms up the
heat sinks should be at a temperature where you can put your
hand on them for 5 seconds but not 10. (this, by the way, is the
standard formula I use for every amp)."
Jon didn't tell me this was the spec he simply agreed with me and then just mentioned as you get it hotter the high end becomes smoother.. and I think its well known and agree to that the 400a lacks on the high end.. this is of course why Mr. Pass did not stop designing amplifiers after he did the 400a. 😉
The cool thing about the 400a is if you want to upgrade you can use the 400a for your bass and a newer pass engineered amp for your highs.. 😉
Oh what Jon said was to check the voltage of an emitter.. pick ONE emitter and use it for testing.. then run the amp for 12 hours.. (I hope I am not messing something up here).. then, if its not hot enough or too hot, tweek the pot.. but now I forgot how many mv he said... damnit.. it was very small increments.. and then wait 3 hours for the adjustment.. this is with no input or output on the amp.. just sitting on the "bench" lol.. my bench is my dining room table.. 🙂
Can someone fine tune what I am trying to say here?
He also told me to replace the pots cuz they are too old to adjust now.. and I forgot to order.. double damnit! I will order some today.
Joe
P.S. I would love to hear comments from you guys regarding the power cord link I posted above while I am waiting for parts.. Love to know why you think it really made a difference or why this guy thought it did but it didn't..
My .02.. I think the guy is an extreme critical listener and I would never hear the difference he heard.
quoted from this thread re: 400a
http://www.diyaudio.com/forums/showthread.php?s=&postid=465173&highlight=#post465173
"Nelson Pass []
The one and only
Simply replacing all the electrolytics is a good step, and none
of them are critical in value and none need more than 50 volts,
as I recall.
The bias should be set so that after the amp warms up the
heat sinks should be at a temperature where you can put your
hand on them for 5 seconds but not 10. (this, by the way, is the
standard formula I use for every amp)."
Jon didn't tell me this was the spec he simply agreed with me and then just mentioned as you get it hotter the high end becomes smoother.. and I think its well known and agree to that the 400a lacks on the high end.. this is of course why Mr. Pass did not stop designing amplifiers after he did the 400a. 😉
The cool thing about the 400a is if you want to upgrade you can use the 400a for your bass and a newer pass engineered amp for your highs.. 😉
Oh what Jon said was to check the voltage of an emitter.. pick ONE emitter and use it for testing.. then run the amp for 12 hours.. (I hope I am not messing something up here).. then, if its not hot enough or too hot, tweek the pot.. but now I forgot how many mv he said... damnit.. it was very small increments.. and then wait 3 hours for the adjustment.. this is with no input or output on the amp.. just sitting on the "bench" lol.. my bench is my dining room table.. 🙂
Can someone fine tune what I am trying to say here?
He also told me to replace the pots cuz they are too old to adjust now.. and I forgot to order.. double damnit! I will order some today.
Joe
P.S. I would love to hear comments from you guys regarding the power cord link I posted above while I am waiting for parts.. Love to know why you think it really made a difference or why this guy thought it did but it didn't..
My .02.. I think the guy is an extreme critical listener and I would never hear the difference he heard.
barchetta said:
Ha, ha, like we didn't have enough excitment in this tread. That is controversal topic and what I've seen here on the board doesn't go well together with magical oils, special wood or stones to put under or on your equipment. So, if you want to finish your amp...
AR2 said:
Ha, ha, like we didn't have enough excitment in this tread. That is controversal topic and what I've seen here on the board doesn't go well together with magical oils, special wood or stones to put under or on your equipment. So, if you want to finish your amp...
That's a shame what you just said.. doesn't speak well of the members.. but okay if thats the consensus.
Lets not talk about it because I just want to finsh my amp. Thanks.
EDIT: After reading several threads on debating power cords here I am asking, no, pleading please do NOT comment on my link. thanks.. lets keep this thread on track.. MY ERROR.
You could always start new tread on the topic, or just make search and you will find a lot.
I see it quite differently: if you would like to learn stuff that matters such as circuit design, measurement, quality components, theory, crafting... than this is best place to be. There were a lots of conversations on cables, oils, accessories, naked caps... and a lots of heated opinions. You could certainly discuss that, but it will derail your original tread.
I see it quite differently: if you would like to learn stuff that matters such as circuit design, measurement, quality components, theory, crafting... than this is best place to be. There were a lots of conversations on cables, oils, accessories, naked caps... and a lots of heated opinions. You could certainly discuss that, but it will derail your original tread.
AR2 said:
See above.. I edited.. NONONONONO.. I am painfully reading threads now.. Starting another one would be like forum suicide. 🙂
AR2 said:
And mine does not change. 🙂
In all seriousness I am glad you said what you said.. I feel like I just dodged a bullet!
Babowana said:
I do not know what the letter O with a question mark next to it means.. but I guess its funny. 🙂
I apologize; you have to read the whole thread to know who Jon is; and I should have reasserted who I was speaking of.. Jon Soderberg from Vintage Amp Repair (http://www.vintageamprepair.net/).
Thanks for bringing that up.
And I apologize if I botched what he told me on the phone.. its to the best of my recollection..
O? = short form of "I did not know it" in my way.
I read English very slow.
Thanks to you, I don't need to read the whole thread from the beginning. Understood about Jon 🙂
I read English very slow.
Thanks to you, I don't need to read the whole thread from the beginning. Understood about Jon 🙂
Goodies have arrived...
First question.. does the MJ15003 replace the 2n5878 and the MJ15004 replace the 2n5876?
I'll try and figure it out by looking at the specs.. but to be sure... if someone can verify I can start soldering.
Edit: Had them backwards.. the 2n5876 is pnp and the mj15004 is pnp.. so I fixed the above.. But still would like verification.
An externally hosted image should be here but it was not working when we last tested it.
First question.. does the MJ15003 replace the 2n5878 and the MJ15004 replace the 2n5876?
I'll try and figure it out by looking at the specs.. but to be sure... if someone can verify I can start soldering.
Edit: Had them backwards.. the 2n5876 is pnp and the mj15004 is pnp.. so I fixed the above.. But still would like verification.
Also.. when a cap is not marked with a + sign or - sign for that matter its non polarized right? I should have asked this before.. there was only one cap out of all of them that had a + sign so I assumed the others were all non-polar and as a result that is what I ordered.
Thanks.. yeah was just hoping someone might confirm to put me at ease.. I have no schematic.. the pass schematic is WAY newer than my old 400a..
Question: do I put the grease on moth sides of the insulator? Is it okay if grease touches the leads of the transistor.. this is "silicon" grease so I assume its non-conductive?
Question: do I put the grease on moth sides of the insulator? Is it okay if grease touches the leads of the transistor.. this is "silicon" grease so I assume its non-conductive?