Hi Joe,
First things first; I'd highly recommend hooking up a "normal" preamp (read newer) for a while to make sure everything is working properly.
Both Chris and I have warned regarding the H/K until you've had a chance to go through it.
The lack of bass could also be caused by weak tubes or bad caps in the H/K.
I'd recommend a solid state preamp that you know for certain is working properly... If you don't currently have one, perhaps consider picking one up off Audiogon.
Let's limit the number of possible variables until we know for sure the amp is fixed.
If everything is right with the amp, you should detect a deeper soundstage. The higher bias tends to increase the width and primarily the perceived depth of the soundstage. Tonally, I would think that both amps should be very similar.
If I were you, I'd consider buying film caps for all of the locations on the driver boards if they will fit. Buy the Solen's from Parts Connexion in Canada as they're pretty cheap and sound much better than the electrolytics. Yeah, I know you've already changed some of them... Just make sure they will fit as they are substantially larger physically.
You were going to buy new input jacks anyway right?
Hopefully the thing is fixed and the problem is your preamp.
Keep us posted once you feel better and your hearing is back to normal.
First things first; I'd highly recommend hooking up a "normal" preamp (read newer) for a while to make sure everything is working properly.
Both Chris and I have warned regarding the H/K until you've had a chance to go through it.
The lack of bass could also be caused by weak tubes or bad caps in the H/K.I'd recommend a solid state preamp that you know for certain is working properly... If you don't currently have one, perhaps consider picking one up off Audiogon.
Let's limit the number of possible variables until we know for sure the amp is fixed.
If everything is right with the amp, you should detect a deeper soundstage. The higher bias tends to increase the width and primarily the perceived depth of the soundstage. Tonally, I would think that both amps should be very similar.
If I were you, I'd consider buying film caps for all of the locations on the driver boards if they will fit. Buy the Solen's from Parts Connexion in Canada as they're pretty cheap and sound much better than the electrolytics. Yeah, I know you've already changed some of them... Just make sure they will fit as they are substantially larger physically.
You were going to buy new input jacks anyway right?
Hopefully the thing is fixed and the problem is your preamp.
Keep us posted once you feel better and your hearing is back to normal.
Hi guys.. just thought I'd update you all.. Been talking to Steve quite a bit offline.. the 400a still has a few issues but all and all its a runner.. I just replaced the filter caps with a pair of 33k MfD caps and wired in fuses on the output just like my other 400a. I bought the limiters Mr. Pass recommended but it looks like with 5 amp fuses I dont need it.. seems to power up okay so far; though I havent tried with them fully bled yet. In the minimalist spirt I dont plan to solder one in unless it requires it. 
I still have a few more caps to replace as one channel is still quirky.. sometimes a "power cycle" clears it up (no audio, only happened once so far). But overall this project has been a success as I really have learned a TON.. and in fact I already used the knowledge.. in an automotive application which I wont go into..
I WAS going to build a Aleph 3 but found one so inexpensive I just went ahead and bought it. I plan to use it for the top end and one of the 400a's on the bottom of my Vandersteen 2ce's.. Should be a really fun experiment.. the interesting thing about that is that they are both perfect in capacity for each frequency range! I will need to build a limiter in the inputs of the 400a to balance them but I will ask for help with that in a different thread.
I have not received the Aleph yet.. but am excited to get it.
I still have a few more caps to replace as one channel is still quirky.. sometimes a "power cycle" clears it up (no audio, only happened once so far). But overall this project has been a success as I really have learned a TON.. and in fact I already used the knowledge.. in an automotive application which I wont go into..
I WAS going to build a Aleph 3 but found one so inexpensive I just went ahead and bought it. I plan to use it for the top end and one of the 400a's on the bottom of my Vandersteen 2ce's.. Should be a really fun experiment.. the interesting thing about that is that they are both perfect in capacity for each frequency range! I will need to build a limiter in the inputs of the 400a to balance them but I will ask for help with that in a different thread.
I have not received the Aleph yet.. but am excited to get it.
Hi,First post so ........ Very nice project you are doing with your 400A me i just bought this dude.
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1178558661 I own many amps DR-3 VHC , DR-3 and a Forté 4a ,and a lovey Bedini 100/100 .
Now i in waiting for my 400A to come to its new home, i do not do DIY but who knows one day maybe. With your help you members of this great forum.
Like my wellcome says Route 66 is back.
regards Daniel
Route 66 said:
First post so ........ Very nice project you are doing with your 400A me i just bought this dude.
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1178558661 I own many amps DR-3 VHC , DR-3 and a Forté 4a ,and a lovey Bedini 100/100 .
Now i in waiting for my 400A to come to its new home, i do not do DIY but who knows one day maybe. With your help you members of this great forum.
Like my wellcome says Route 66 is back.
regards Daniel
Be sure and and let us know how it sounds/runs. I am an EXPERT in biasing the 400a..
I have done it 12 times now I bet.. lolDo you know how old it is? If its early certainly should have the caps replaced.. I think any year of the 400a is old enough to need this done however.
EDIT: I am now looking at the pics.. Be adviced; the right channel was repaired.. all the emitter resistors were replaced which means it had a meltdown similar to mine.
The filter caps were replaced (expensive!).. Check to make sure they are at least 15kMFD and they did not skimp or your bass response will suffer.. mine were 9800mfd and I noticed a much nicer bass signal when I went with dual 33kmfd.
This is a mid-life unit similar to my 2nd 400a.. I believe its early enough to be non-cascoded.
It looks like the right input board may have had a cap replaced.. not sure. But several are original still.
Yes i know all that, the dude told me so i wll have the repair bill and i think i have enough parts here to do a nice job....... Realy hope it will sound like i expect .
I will be place in my reference système.......
I will let you know about all the issue when i have it in my hands.
Regards Route 66
Hi,I need advise, when i recieve it, i plug it and i had no mids and bass.... ? Then told the seller about it, then took it to one of my friend who is a Hi End Gourou....in electronics.
Took it back home and now its working metters and in all range High mids and bottom
Without doing anytihng... Just cheak it on his machine!What kind of problem happen to it! I dont know if i will keep it it scared me , when i saw the lights meters not going a the sounds that i was hearing!
Also Dos it run hot this beast? For A Class A it run cool . I know that i have Suparvox O.B. 97 db. My Pass 30 runs hot like hell , not this dude.
Thanks in adavnce for your answer
Oh i forgot its super clean , for the bias tell me how i will ask my friend, do you have the schematics? Sorry for my english . I am from a French dude from Quebec City. Regards Route 66 time for bed. 3H20 am
Route 66 said:
I need advise, when i recieve it, i plug it and i had no mids and bass.... ? Then told the seller about it, then took it to one of my friend who is a Hi End Gourou....in electronics.
Took it back home and now its working metters and in all range High mids and bottom
What kind of problem happen to it! I dont know if i will keep it it scared me , when i saw the lights meters not going a the sounds that i was hearing!
Also Dos it run hot this beast? For A Class A it run cool . I know that i have Suparvox O.B. 97 db. My Pass 30 runs hot like hell , not this dude.
Thanks in adavnce for your answer
Regards Route 66 time for bed. 3H20 am
The issue with no mids and no bass. If it was both channels then I would not suspect the amplifier but whatever was attached to it.. but maybe somebody else knows something.
After 1 hr of operation hold your hand on the heatsink on each side.. after 5-10 seconds you should want to pull your hand off. If not your bias is off.
There is a link to the schematics very early on in this thread.
The bias is a easy adjustment... I will give you step by step if you want.. you need a multimeter and 2 alligator clips for the ends of the multimeter. and in your case you will need a large 10k or so resistor to bleed off the filter caps so you can reach inside without hurting yourself.
Let me know if/when you are ready.
Joe
Hi ,
We suspected that the bias was out, and also the can are not the right one, very small ones to compares a the originals!
No it is very cool i could sit on it for hours and not get burned , but my as.... would suffer from the heat sink wings Ok i will look back to see what you talk about,
A can also if you email me, i will send you a copy of the work done on the service.
Thanks for helping me in this matter , P.S. it runs more like a big Class A/B Sound stage very up front and no détails
Regards Route 66
We suspected that the bias was out, and also the can are not the right one, very small ones to compares a the originals!
No it is very cool i could sit on it for hours and not get burned , but my as.... would suffer from the heat sink wings
Ok i will look back to see what you talk about,A can also if you email me, i will send you a copy of the work done on the service.
Thanks for helping me in this matter , P.S. it runs more like a big Class A/B Sound stage very up front and no détails
Regards Route 66
Route 66 said:Hi ,
We suspected that the bias was out, and also the can are not the right one, very small ones to compares a the originals!
No it is very cool i could sit on it for hours and not get burned , but my as.... would suffer from the heat sink wings
A can also if you email me, i will send you a copy of the work done on the service.
Thanks for helping me in this matter , P.S. it runs more like a big Class A/B Sound stage very up front and no détails
Regards Route 66
Someone correct me if I am wrong but the detail should improve as you get the bias higher. As Mr. Pass has pointed out; this is where people screw amps up.. be very careful to get the bias right. There is a document in this thread that explains the values; but patience is required between adjustments..
If you have the .27 emitters like I did (I think it was .27 .2something anyway) I can give you a ballpark.. BUT you have to move to the value SLOWLY.. the # is 75 millivolts. but if you are REALLY cold you will need to start a little higher.. as the temp increases the voltage decreases slightly... when I turn my amp on I see about 120mv... as it warms it arrives at 75mv @ abt 45degrees Celsius.
Hi Joe,
This is how myths start. For this amp, I'd say you were right. Nelson would be the final word as far as I'm concerned and I believe he mentioned this.
-Chris
Not always. It depends greatly on the design of the amp and how well the components are matched (again, depending on the amp design).
This is how myths start. For this amp, I'd say you were right. Nelson would be the final word as far as I'm concerned and I believe he mentioned this.
-Chris
anatech said:
No biggie.. I just dont remember him saying how it might affect the sound.. He just explained his bias method by feel.
Anyway.. maybe we can help get another 400a working correctly.. MIne btw has been used daily and I left it on overnight by mistake the other day.. I was afraid to go check on it in the morning.. but it was fine! So I am guessing its gonna continue working great..
Also.. picked up a Aleph 3 last night! Can't wait to listen.
I have about five degrees Celsius........,
Hi Joe,
I'm pretty sure you've done a good job on it. Way to go!
Hi Daniel,
It's a restoration, not a repair.
-Chris
I'm pretty sure you've done a good job on it. Way to go!
You're going to be spoiled. Just think what the bulk of the population is listening to!
Hi Daniel,
Keep in mind how old these are. Once you get it running properly you'll be fine. It just will not work perfectly first time out. It's old enough to have a personallity.
It's a restoration, not a repair.-Chris
anatech said:Hi Joe,
I'm pretty sure you've done a good job on it. Way to go!
You're going to be spoiled. Just think what the bulk of the population is listening to!
Hi Daniel,
Keep in mind how old these are. Once you get it running properly you'll be fine. It just will not work perfectly first time out. It's old enough to have a personallity.
-Chris
I know that its old, But it was suppose to be ok and repaired. Not default.
Or esle i would have not bought it! When i buy and the guy says it need repair ok but not the contraire.
i will see later what i will do with it, with a little help from my friend.......... lets sing along.
Route 66 The Raod of blues and jazz