Netlist, Variac, thanks for the well wishes.. Steve pointed out that this was a team effort.. everyone helped out.. I feel very lucky this group is here and was willing to take on a guy with a bit of a "tude".. lol..
Hey.. I was also editing one I wonder if you missed.. my amp has .22ohm emitters.. which is not mentioned at all in any schematic.
Question: Is there a downside to this? Clearly he (Mr. Pass) ended up at .68ohm.. The bias chart posted here mentions 3: 1ohm; .68ohm and .33ohm.. Will these affect sound in any manner? I'm REALLY curious now since this seems to have been one of the components that changed over the years.. I realize some of these components may have changed for financial reasons rather than sound quality 😉 That's why I am curious as to what this component does I guess.. (no idea at all).
Steve: yes, I meant the filter caps.. and the one that looks like it was replaced is 9800MFD 100v.. Threshold does not show them on the schematic.. and the other has its skin removed.. I will follow your link but NO WAY IS A ADCOM COMPONENT GOING IN MY THRESHOLD. Well; unless I figure out who built it and I can remove the skin and write in the manufacture and part # on it 🙂
so Steve, Anatech... now you have me curious.. what artists are your favs??
Edit: Neil did have an amazing show.. it involved a stage to the right of actors the entire time he played.. weird/crazy/interesting.. I still dont like him. 🙂
Hey.. I was also editing one I wonder if you missed.. my amp has .22ohm emitters.. which is not mentioned at all in any schematic.
Question: Is there a downside to this? Clearly he (Mr. Pass) ended up at .68ohm.. The bias chart posted here mentions 3: 1ohm; .68ohm and .33ohm.. Will these affect sound in any manner? I'm REALLY curious now since this seems to have been one of the components that changed over the years.. I realize some of these components may have changed for financial reasons rather than sound quality 😉 That's why I am curious as to what this component does I guess.. (no idea at all).
Steve: yes, I meant the filter caps.. and the one that looks like it was replaced is 9800MFD 100v.. Threshold does not show them on the schematic.. and the other has its skin removed.. I will follow your link but NO WAY IS A ADCOM COMPONENT GOING IN MY THRESHOLD. Well; unless I figure out who built it and I can remove the skin and write in the manufacture and part # on it 🙂
so Steve, Anatech... now you have me curious.. what artists are your favs??
Edit: Neil did have an amazing show.. it involved a stage to the right of actors the entire time he played.. weird/crazy/interesting.. I still dont like him. 🙂
"I'm a bit puzzled why you powered it up when the seller told you that it needed the cap and bridge replaced.
"
NOW NOW Steve... 🙂 I'll tell you why he did it.. curiosty.. kinda like when I hooked up my preamp before it was really time.. 🙂
Hahah.. MJR sounds like he has even less knowledge then me.. which I thought was nearly impossible.. but he is learning much.. gotta keep reading... 🙂 He's taking the comments much better than I did though 🙂
"
NOW NOW Steve... 🙂 I'll tell you why he did it.. curiosty.. kinda like when I hooked up my preamp before it was really time.. 🙂
Hahah.. MJR sounds like he has even less knowledge then me.. which I thought was nearly impossible.. but he is learning much.. gotta keep reading... 🙂 He's taking the comments much better than I did though 🙂
Hi Joe,
I'll leave my musical tastes out of it for now. You know who I don't like.
I think Nelson really ought to be the one to comment on the emitter resistors and tradeoffs between them. Electronics and especially amplifier design is not always cut and dry. There are always trade offs and what Nelson intended is the most important thing second to how you like your amp.
With regard to your preamp, I am currently using a Fisher 400-C and an Eico HF-85. Both rebuilt. Do not continue using your Eico until you have rebuilt it. In case you are wondering what preamp is my favorite, that would be a Marantz SC-9 or 3650 (close in design). I have one of each with serious problems (switch contacts).
-Chris
I'll leave my musical tastes out of it for now. You know who I don't like.
I think Nelson really ought to be the one to comment on the emitter resistors and tradeoffs between them. Electronics and especially amplifier design is not always cut and dry. There are always trade offs and what Nelson intended is the most important thing second to how you like your amp.
Thanks, the entire forum is always here to help best they can.
Nothing wrong with Adcom parts. They used very good parts in their products. Ceramic capacitors are a rare sight for example. At the end of the day, parts is parts. 😉
With regard to your preamp, I am currently using a Fisher 400-C and an Eico HF-85. Both rebuilt. Do not continue using your Eico until you have rebuilt it. In case you are wondering what preamp is my favorite, that would be a Marantz SC-9 or 3650 (close in design). I have one of each with serious problems (switch contacts).
-Chris
Anatech: the adcom comment was one of pure emotion..
Okay on the music.. but I will say its a bit wimpy 🙂
I'm all over the place.. but will admit I am a Ozzy fan.. which will kill any musical taste credibility I might have had.. I also love Bonnie Raitt, an old band called Sweet; Flim and the BB's; Dave Grusin; Lee Ritenour; The Tubes and here is the one that will nail the coffin.. HUGE David Lee Roth fan.
You guys will probably not speak to me now and have probably written all this work off as a waste of time.. lol.
MJR quote:
"If the fix/rebuild works, I will have spent $140 to fix the broken amp having replaced both filter caps, new bridge rectifiers in BOTH amps, and new electrolytic capacitors all around.
I am cautiously optimistic ... and to think that a repair shop quoted the previous owner $400 to fix the unit. "
I can't believe you guys let him get away with this comment!! I was KILLED when I suggested $480 for the power transistors was high! LOL!!!!!!!!!!! 🙂 This is purely sarcastic.. please lets not start this up again.. 🙂 thanks!
I still havent figured out which caps he ordered but my MFD value is WAY lower than his... I gotta figureout what the spec is on mine for the filter caps..
Okay on the music.. but I will say its a bit wimpy 🙂
I'm all over the place.. but will admit I am a Ozzy fan.. which will kill any musical taste credibility I might have had.. I also love Bonnie Raitt, an old band called Sweet; Flim and the BB's; Dave Grusin; Lee Ritenour; The Tubes and here is the one that will nail the coffin.. HUGE David Lee Roth fan.
You guys will probably not speak to me now and have probably written all this work off as a waste of time.. lol.
MJR quote:
"If the fix/rebuild works, I will have spent $140 to fix the broken amp having replaced both filter caps, new bridge rectifiers in BOTH amps, and new electrolytic capacitors all around.
I am cautiously optimistic ... and to think that a repair shop quoted the previous owner $400 to fix the unit. "
I can't believe you guys let him get away with this comment!! I was KILLED when I suggested $480 for the power transistors was high! LOL!!!!!!!!!!! 🙂 This is purely sarcastic.. please lets not start this up again.. 🙂 thanks!
I still havent figured out which caps he ordered but my MFD value is WAY lower than his... I gotta figureout what the spec is on mine for the filter caps..
Babowana said:
MJRAUDIO is the username.. he has a thread here on repairing his Adcom.. he was much quicker at fixing his then I was though!
Umm.. to quote one of my favorite movies "High Fidelity".. "Music is a state of PREFERENCE"... so no artist is bad in my opinion.. I just dont like him much.. MY preference. But then again you have seen what I like in a previous post.. lol.
Anatech: I've been playing my HF-85 for over 2 yrs now.. I dont thinkits going to bite it anytime soon.. hehehe I picked it up for $2.00 at a garage sale.
Although it recently got sidelined for a Harmon Kardon I bought on ebay which is a nice unit. I should post a pic of the Eico.. youd be blown away by its stock condition I bet.. maybe not. I bet it would be my main preamp though if I did the caps..
Although it recently got sidelined for a Harmon Kardon I bought on ebay which is a nice unit. I should post a pic of the Eico.. youd be blown away by its stock condition I bet.. maybe not. I bet it would be my main preamp though if I did the caps..
Couple of shots of my Eico HF-85 preamp for Anatech..
I have never checked for DC output (never knew how until now..) I'll have to do that.. but it plays nice 🙂
I think its original? It looks original ???
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I have never checked for DC output (never knew how until now..) I'll have to do that.. but it plays nice 🙂
I think its original? It looks original ???
Hi Joe,
It's not a question of if, it's when. You may already be getting short tube life and higher distortion than you should.
Now, before you lose the power transformer (you will not like the cost of a replacement), you'd better fix it. It can be a very nice little pre amp. I doubt you've actually heard it yet.
I had a pair of these, traded one for a copy of RDH4 (well worn). I'd like to get the bigger brother to this one only for the cosmetics if nothing else. 😉
-Chris
It's not a question of if, it's when. You may already be getting short tube life and higher distortion than you should.
Now, before you lose the power transformer (you will not like the cost of a replacement), you'd better fix it. It can be a very nice little pre amp. I doubt you've actually heard it yet.
I had a pair of these, traded one for a copy of RDH4 (well worn). I'd like to get the bigger brother to this one only for the cosmetics if nothing else. 😉
-Chris
Nelson????
Hi Joe,
I'd have to agree with Anatech regarding your preamp. It's not if it's when... Order some nice film and mylar caps from Parts Connexion while you're at it...
Regarding the purpose of the emitter resistors, I tracked down this tutorial for you:
http://www.allaboutcircuits.com/vol_3/chpt_4/10.html
Also, I went back and read all of the pdf's regarding biasing proceedures from Threshold. Interesting...
We will need some input from Nelson regarding the "best" values for the emitter resistors and how he'd like you to set the bias.
From the schematics, it appears they eventually settled on .68 in the later versions. I don't know if this change will affect sound quality or not or what else you'd need to change at the same time...
Only the Master knows...
Nelson, for reference:
http://www.diyaudio.com/forums/showthread.php?postid=1132553#post1132553
Also:
http://www.diyaudio.com/forums/attachment.php?s=&postid=934892&stamp=1149673195
Hi Joe,
I'd have to agree with Anatech regarding your preamp. It's not if it's when... Order some nice film and mylar caps from Parts Connexion while you're at it...
Regarding the purpose of the emitter resistors, I tracked down this tutorial for you:
http://www.allaboutcircuits.com/vol_3/chpt_4/10.html
Also, I went back and read all of the pdf's regarding biasing proceedures from Threshold. Interesting...
We will need some input from Nelson regarding the "best" values for the emitter resistors and how he'd like you to set the bias.
From the schematics, it appears they eventually settled on .68 in the later versions. I don't know if this change will affect sound quality or not or what else you'd need to change at the same time...
Only the Master knows...
Nelson, for reference:
http://www.diyaudio.com/forums/showthread.php?postid=1132553#post1132553
Also:
http://www.diyaudio.com/forums/attachment.php?s=&postid=934892&stamp=1149673195
"Regarding the purpose of the emitter resistors, I tracked down this tutorial for you:
http://www.allaboutcircuits.com/vol_3/chpt_4/10.html"
Uh boy.. something tells me I am going to be spending a few hours on this site.. its got a lot of terrific onfo..
Anatech: Yeah.. cosmetically the HF-85 kinda sucks.. BUT.. let me know you how it can look in a stand aganst some more modern components.. I'll take a pic and see what you think..
OKAY! I will see about rebuilding! 🙂
http://www.allaboutcircuits.com/vol_3/chpt_4/10.html"
Uh boy.. something tells me I am going to be spending a few hours on this site.. its got a lot of terrific onfo..
Anatech: Yeah.. cosmetically the HF-85 kinda sucks.. BUT.. let me know you how it can look in a stand aganst some more modern components.. I'll take a pic and see what you think..
OKAY! I will see about rebuilding! 🙂
Hi Joe,
I hear enough bad news from people. Being the repair guy, most people will not bring anything in until the unit ceases to function completely and their friend's repair efforts have failed. I do therefore see a few write-offs. It's very sad when the original fault was much smaller.
The Eico looks okay around some modern gear. My decorating style is more Art Decco. Therefore, I can get away with using older equipment sometimes (there is always some new stuff hanging around too).
-Chris
Cool!
I hear enough bad news from people. Being the repair guy, most people will not bring anything in until the unit ceases to function completely and their friend's repair efforts have failed. I do therefore see a few write-offs. It's very sad when the original fault was much smaller.
The Eico looks okay around some modern gear. My decorating style is more Art Decco. Therefore, I can get away with using older equipment sometimes (there is always some new stuff hanging around too).
-Chris
Yeah, I think it looks damn cool if its kept in a real open space and all by itself.. and then with modern gear near it.. I'll take a pic of my stand when I get a chance.. And yeah, I know.. I really need to rebuild it before she blows... when I switched to the HK I noticed more detail.. so thats why it got sidelined.. and the phono section is really bad on my Eico.. and I think they are all bad.. but I could just get a RIAA preamp and run it into the aux. You advice is understood however.. I just printed the schematic so I can try and put an order together.
Back to the 400a:
So I have both channels fired up now.. unfortunately it looks like the right meter is broken.. if you recall there is a peek and average for each side.. well the average is flashing like its a really sensitive peek.. so it is very busy.. I guess I will switch the wires around and make sure its not the channel itself.. doubtful I should think.. I will leave this be for another thread.. actually; I thought I might try and tackle this myself.. I think I saw a schematic somewhere.. or maybe Mr. Pass has seen this before and will chime in with a quick analysis.
But; I was really curious how the channels might compare.. with different power transistors and all.. at the moment I cant hear the difference.. and the HF-85 has that cool "reverse" switch on it to reverse the channels.. and I used it quite a bit with nothing noticed from side to side. BTW.. I hear lots of complaints about the large input switch being an issue on this oldies.. mine is perfect.. knock on wood. Boy thats a BIG switch assembly.. must be like 12 switches all on one knob.
Anyway.. on topic.. both channels playing.. just curious.. just wanted to listen before I rebuilt the other side.
And the heat sinks feel equal 20 minutes in.. but an hour in will be the indicator.. I will wait until then; again just out of curiosity.. sounds wonderful even thru the sort of brutal JBL's of old. I forget what they called those tweeters.. but I dont like em'.. they have that shhhh shhh shhh shhh sound too em... I know lots love em'..
Oh and its Steely Dan Aja.. I hope no one can have an issue there! Other than they were a bit commercial.
j
Back to the 400a:
So I have both channels fired up now.. unfortunately it looks like the right meter is broken.. if you recall there is a peek and average for each side.. well the average is flashing like its a really sensitive peek.. so it is very busy.. I guess I will switch the wires around and make sure its not the channel itself.. doubtful I should think.. I will leave this be for another thread.. actually; I thought I might try and tackle this myself.. I think I saw a schematic somewhere.. or maybe Mr. Pass has seen this before and will chime in with a quick analysis.
But; I was really curious how the channels might compare.. with different power transistors and all.. at the moment I cant hear the difference.. and the HF-85 has that cool "reverse" switch on it to reverse the channels.. and I used it quite a bit with nothing noticed from side to side. BTW.. I hear lots of complaints about the large input switch being an issue on this oldies.. mine is perfect.. knock on wood. Boy thats a BIG switch assembly.. must be like 12 switches all on one knob.
Anyway.. on topic.. both channels playing.. just curious.. just wanted to listen before I rebuilt the other side.
And the heat sinks feel equal 20 minutes in.. but an hour in will be the indicator.. I will wait until then; again just out of curiosity.. sounds wonderful even thru the sort of brutal JBL's of old. I forget what they called those tweeters.. but I dont like em'.. they have that shhhh shhh shhh shhh sound too em... I know lots love em'..
Oh and its Steely Dan Aja.. I hope no one can have an issue there! Other than they were a bit commercial.
j
Update: its the meter thats malfunctioning.. I swapped the inputs and it stayed on the same side...
There is a schematic at http://www.passlabs.com/np/led disp.tif but I have no idea if the 400a makes use of that concept.
/Hugo
/Hugo
Netlist said:
I knew I saw that somewhere.. thanks I was just looking for that.. gave up, came back here and whalla!
Yeah thats it.. but its the peak side.. my problem is on the average side.. I'm cosuming it now; maybe will offer some hint.. I guess I could start by testing all the caps and resistors then the transistors and then.. well; start replacing IC's.. But since the IC's seem to be drivers for the LED's I am guessing its not them.. something before them.. is my logic logical?
EDIT: On second look maybe it is both peak and avg.. the left and right inputs are confusing me.. I thought they were channel left and right but the meters are different.. so... okay.. I gotta Unglue mine and take a look.. I just glued it back on too.. doggone it. 🙂
anatech said:
Thanks! I will start checking caps immediately.. awesome... maybe just replace em.. 🙂 THANKS!
Hi Joe,
"average is flashing like its a really sensitive peek."
Makes me wonder if the right channel blew up at some point and a couple of resistors at the input of the circuit got hot from the DC surge and changed (decreased) resistance.
Otherwise, agreed, the caps are a good bet...
Might be worth checking.
"average is flashing like its a really sensitive peek."
Makes me wonder if the right channel blew up at some point and a couple of resistors at the input of the circuit got hot from the DC surge and changed (decreased) resistance.
Otherwise, agreed, the caps are a good bet...
Might be worth checking.