Zach's 700B Thread

[Zach C.]

Yay!

I am extremely happy to announce that this thing is up and running!

I couldn't sleep, so I'm working on it at this obscene hour. Even I don't get up this early.

Right now, I have Don's board installed as recommended in his instructions, and it's coming up fine. Since I did not check at every step along the way, I'm not 100% sure what made the difference, but I suspect either the AC rewire, or the bridge rectifier caps.

What I've done since starting this thread.

1) Replace Q4 in both channels due to having physically broken one leg in Q4 left channel. I'm positive this was fine before, and I broke it during this process. The amp had been running fine in stock config. DC offset was already low at around 15mV in both channels- now it's 7-10 or so.
2) Rewire AC as per Joe's recommendation, routing all A/C (including that for Don's board) along the top of the chassis.
3) Install 4 .01uF ceramic caps on the bridge (removing the original- C25)
Basic testing after this point revealed that the meter slam I have always had was now gone- not sure why other than improved stability.
4) Install 4 .33uF Poly Caps from DC rails to common at outputs as shown in mlucitt's drawing.

At this point, I checked to see if the amp would come up w/o the factory zobel- i.e. with the output open. It did.
I then reinstalled Don's board as per the provided instructions. The amp came up just fine, and the relays clicked in.

For what it's worth, the board I got from Don has the 4.7r resistors in it, though this seems irrelevant to anybody except possibly Don.

For now, I think I'm going to run this thing as is for a while to be sure everything continues to be cool, and the look at going to a star ground. If that proves out, I'll go ahead and install the White Oak driver board- it's all assembled and patiently waiting.

As soon as the wife wakes up, I'm hooking up speakers. Woot!

I owe a huge thanks to all who contributed to this repair!

THANKS!

Zach

 

[orange]

Dr. Lucitt?

Are congratulations in order?

Well, congratulations on a full career and upcoming RETIREMENT...

 

[Zach C.]

Well, congratulations on a full career and upcoming RETIREMENT...

That's odd. I thought he told me he was working on a graduate degree.

Perhaps I misunderstood, or maybe it's both?

Zach

 

[kevin]

Just what kind of speakers ya hooking up Zach ?????

 

[Zach C.]

Just what kind of speakers ya hooking up Zach ?????

lol, not those- at least, not yet. And, likely not for very long anyway. I definitely want to see what it will do when driving my arrays, but the Outlaw 7100 that's driving them now does just fine. With speakers that sensitive, you could drive them with a potato if you could figure out where to attach the wires.

This is likely more than you wanted to know, but this morning, I hooked it up to my desktop speakers. Those are a DIY Minimus upgrade using a 4" Tang Band midwoofer and TB tweeter. Sounded fine- for all those little guys could take.

It's long term home will probably be in my kitchen system driving some DIY MTM transmission line speakers (someone else's design) using two Dayton classic 6.5 and "silkie" tweeter. It might find it's way back into the main system later when I get my other speakers done. I'm going to need at least 8 channels for those, maybe 10 depending. We'll see.

It seems I'm not entirely out of the woods anyway. Mind you the face plate was still off, and I was driving it with an MP3 player, but I had some wicked 60Hz hum until I ran a jumper from the face plate to circuit common. Even them there was a little hum- not bothersome, but there.

Zach

 

[kevin]

Ok... Well... I was just wondering. But do yourself a favor and hook it to them.... See, I think just the opposite of them, after having a 700 on them I think they need tons of power..... Hook em to the 700..... You will see what im talking about. LOL... Real glad you about got it lined out !!!!

 

[Zach C.]

Just what kind of speakers ya hooking up Zach ?????

Oh yeah, have you ever checked what kind of SPL you can get without blowing anything up with your system?

I know it's room dependent, etc, etc. Just wondered what might be safe-ish. Usually I would say "until they distort" but we melted a couple of RS28F's in my buddies HT Sunday. They never did audibly distort- just hung in there until they smoked. Three of us were listening for distortion, just turning things up looking to find out where the limit was. We found out- about 105dB sustained at around 3 meters according to his SPL meter.

Those planar tweeters have gotten too expensive to buy a dozen at a time.

Zach

 

[Zach C.]

Ok... Well... I was just wondering. But do yourself a favor and hook it to them.... See, I think just the opposite of them, after having a 700 on them I think they need tons of power..... Hook em to the 700..... You will see what im talking about. LOL... Real glad you about got it lined out !!!!

Oh, you betcherass I'm gonna!

thanks.

Zach

 

[Gepetto]

lol, not those- at least, not yet. And, likely not for very long anyway. I definitely want to see what it will do when driving my arrays, but the Outlaw 7100 that's driving them now does just fine. With speakers that sensitive, you could drive them with a potato if you could figure out where to attach the wires.

This is likely more than you wanted to know, but this morning, I hooked it up to my desktop speakers. Those are a DIY Minimus upgrade using a 4" Tang Band midwoofer and TB tweeter. Sounded fine- for all those little guys could take.

It's long term home will probably be in my kitchen system driving some DIY MTM transmission line speakers (someone else's design) using two Dayton classic 6.5 and "silkie" tweeter. It might find it's way back into the main system later when I get my other speakers done. I'm going to need at least 8 channels for those, maybe 10 depending. We'll see.

It seems I'm not entirely out of the woods anyway. Mind you the face plate was still off, and I was driving it with an MP3 player, but I had some wicked 60Hz hum until I ran a jumper from the face plate to circuit common. Even them there was a little hum- not bothersome, but there.

Zach

Hi Zach
Greetings from Shanghai.

You still have a problem then Zach, it should not require the faceplate to be tied to the chassis ground to be quiet with the faceplate off. The recent 700B that I fixed had this artifact before the repair. After the repair, dead quiet. The primary culprit in this is that the input jacks MUST be isolated from the chassis using the normal fiber washers AND there can be NO connection between these RCA input jack grounds and chassis ground other than through the connection to, and only to the control board.

The star point ground scheme honors this method.

Joe

 

[Zach C.]

...You still have a problem then Zach...The star point ground scheme honors this method.

Joe

Right on. I suspected the star ground might help with that. It's on the to do list for sure.

Thanks for the tip.

getting real close.

Zach

 

[kevin]

Nope.... Just usually do like you all did.... Sit listen and hope ya don't smell smoke.... I have blown a bunch of tweets in my time but knock on wood never one of the Planer tweets.... Yea.... they have gone out of site on price...

 

[laatsch55]

105db, damn, that's conversation level around here. The K's can get incredibly loud, and clear....

 

[laatsch55]

Dr. Lucitt?

Are congratulations in order?

I believe it is very close.....

 

[Zach C.]

105db, damn, that's conversation level around here. The K's can get incredibly loud, and clear....

What can I say...sissy dome tweeters? They're not even crossed that low.

I'd call 105 my conservative estimate. The preamp said 70dB the last time anybody had the SPL meter and it was hovering around 100-105. We'd had the pre up around 80dB when the tweeters went. Not sure what SPL that was, and I'm guessing my buddy isn't itching to recreate the experiment. That said, it was only a $50 boo boo, since replacement diaphragms were available.

One day, I'll try some compression driver w/ folded horns. Never can remember what they are called, but I love look of the klipsch (?) built into a credenza. Gotta build one some day.

Good stuff!

Zach

 

[laatsch55]

I have pegged out a 120db meter with a WOPL 1000 driving the Kornerhorns. The Al Klappenberger Universal Slope crossovers didn't like it and spit out a resistor and cap. 20.00 repair, was lucky.

 

[Gibsonian]

Hi Zach
Greetings from Shanghai.

You still have a problem then Zach, it should not require the faceplate to be tied to the chassis ground to be quiet with the faceplate off. The recent 700B that I fixed had this artifact before the repair. After the repair, dead quiet. The primary culprit in this is that the input jacks MUST be isolated from the chassis using the normal fiber washers AND there can be NO connection between these RCA input jack grounds and chassis ground other than through the connection to, and only to the control board.

The star point ground scheme honors this method.

Joe

Joe,

Where do you stay at while in Shanghai? I am a semi-regular traveler there as well. Was there in January and the pollution levels are defintely not getting any better. Other than that, not a bad city at all.

 

[Zach C.]

I have pegged out a 120db meter with a WOPL 1000 driving the Kornerhorns. The Al Klappenberger Universal Slope crossovers didn't like it and spit out a resistor and cap. 20.00 repair, was lucky.

According to the documentation I got from Jim Griffin when I got my Linus Arrays, they will do 115dB peaks cleanly, but oddly enough, I don't have an SPL meter (just never cared that much) so I can't really say. I use Sound Easy for speaker design, but it's not calibrated for absolute SPL. You can measure a known reference, on a large baffle to somewhat calibrate temporarily, but that's more trouble than it's worth.

I just say, "Damn, that was loud." It's funny how loud you can play low a distortion system without realizing it. It only becomes obvious when you turn it off and discover that you've been yelling at the guy next to you.

I only learned the other day that my buddy had one. I'm gonna find out at some point...Soon!

Zach

 

[laatsch55]

A stock Kornerhorn is said to be 108db at one watt at one meter.That's the official efficiency rating. A stock K-Horn is rated at 100 watts RMS continous at 8 ohms. I have blown those specs out of the water for at least twenty years. The K's I have will do at least 300 continuous with peaks to 700 or 800. And they will get loud if it's clean......when I'm getting radical I have to let the voice coils cool down for 10 minutes between songs, which is probably why I can still hear today.

 

[kevin]

LMAO... I going to say.... You cant even spell STOCK !!!! Why would you be talking about it !!!! Your speakers should be called Lee-horns.

 

[Fairchild]

A stock Kornerhorn is said to be 108db at one watt at one meter.That's the official efficiency rating. A stock K-Horn is rated at 100 watts RMS continous at 8 ohms. I have blown those specs out of the water for at least twenty years. The K's I have will do at least 300 continuous with peaks to 700 or 800. And they will get loud if it's clean......when I'm getting radical I have to let the voice coils cool down for 10 minutes between songs, which is probably why I can still hear today.

Lee, if you're like me hearing means something loud enough to block out some of the loud ringing that is always present. lol

Jim