Joe19582001
Mcintosh lover and tube
any bgw stories 750 or 500
BGW amp 750B anyone familiar with it ?
- Thread starter hongyingdang
- Start date
W9TR
Super Member
When I worked for Harris Broadcast, I had the pleasure of meeting Brian many times. I ran the 750 through its paces and found it to be an exemplary performer. It was quiet, stable, and exceeded its power output and distortion numbers by a fair margin. An honest product from an honest man.
What happened to Brian? I gather he is no longer with us.
Tom
What happened to Brian? I gather he is no longer with us.
Tom
Godzilla525
New Member
I picked up a 750C about a month ago and just recently a 250D.
The 750, while functional, sounded awful-horrifically dirty midrange and very grainy treble. It came around full-circle with new electrolytics on the amp modules along with new 2.7 ohm flameproof industrial-grade resistors to replace the carbon-composition ones (one of the ones in the HF compensation circuit on the output had popcorned, but still measured good...)
I'm thinking at some time in the past someone either had a resistor in the feedback network fail open and had it repaired or else had a loose signal plug in the back.
Disconnecting the ground-bond jumper helped clear up the sound a lot also. It was the first thing I did. It would make popping noises at moderate volume levels.
I'm genuinely surprised that something this powerful can sound this delicate and refined.
Of course the power cord's been through hell and that's next on my list...
What has me somewhat confused is the 250D. From what I've gathered, it's supposed to be sonically better than the 750 although mine seems heavy on midrange and lacks any sort of imaging ability. It's decent enough to tell mono apart from stereo and that's about all. It hasn't responded to a capacitor refresh like the 750 did, and in fact the original caps are branded BGW. That's ...strange. It also needs a new relay since I have to tap it occasionally with the handle of a screwdriver and hasn't responded to reinstalling the socket in the PCB or cleaning the inside of the relay.
Whoever had it before didn't play it loudly enough to keep the contacts clean and only drove it slowly to the store on sundays. :twak:
I also noticed that the LM318s are from two different companies: TI and LT. It technically shouldn't make a difference, but I've ordered a couple National LM118H parts anyway. I'm going to try that and a few power resistors (doing the same functions as the ones I changed out in the 750) and then maybe look into replacing the main filter capacitors, and maybe try different output transistors (Right now it has 2N3773 NPN from GE/RCA and 2N6609 PNP from Motorola-the driver transistors are TO-66 and probably unobtanium). As it stands, it's pretty hard to listen to...I think it'll come around though.
The 750, while functional, sounded awful-horrifically dirty midrange and very grainy treble. It came around full-circle with new electrolytics on the amp modules along with new 2.7 ohm flameproof industrial-grade resistors to replace the carbon-composition ones (one of the ones in the HF compensation circuit on the output had popcorned, but still measured good...)
I'm thinking at some time in the past someone either had a resistor in the feedback network fail open and had it repaired or else had a loose signal plug in the back.
Disconnecting the ground-bond jumper helped clear up the sound a lot also. It was the first thing I did. It would make popping noises at moderate volume levels.
I'm genuinely surprised that something this powerful can sound this delicate and refined.
Of course the power cord's been through hell and that's next on my list...
What has me somewhat confused is the 250D. From what I've gathered, it's supposed to be sonically better than the 750 although mine seems heavy on midrange and lacks any sort of imaging ability. It's decent enough to tell mono apart from stereo and that's about all. It hasn't responded to a capacitor refresh like the 750 did, and in fact the original caps are branded BGW. That's ...strange. It also needs a new relay since I have to tap it occasionally with the handle of a screwdriver and hasn't responded to reinstalling the socket in the PCB or cleaning the inside of the relay.
Whoever had it before didn't play it loudly enough to keep the contacts clean and only drove it slowly to the store on sundays. :twak:
I also noticed that the LM318s are from two different companies: TI and LT. It technically shouldn't make a difference, but I've ordered a couple National LM118H parts anyway. I'm going to try that and a few power resistors (doing the same functions as the ones I changed out in the 750) and then maybe look into replacing the main filter capacitors, and maybe try different output transistors (Right now it has 2N3773 NPN from GE/RCA and 2N6609 PNP from Motorola-the driver transistors are TO-66 and probably unobtanium). As it stands, it's pretty hard to listen to...I think it'll come around though.
Joe19582001
Mcintosh lover and tube
great stories my 750a . i did a total cap rebuild what a difference the bass is solid it has that bgw sound that i remember from the 1970s tight and powerful
I still have a 500D that's had amp board caps and PS filter caps replaced. I installed a 12V fan & run it on 6V to minimize noise. I'm wondering about installing a socket where the LM318 op amp is in order to try some other options. As others have noted, these things produce some impressive bass!
Joe19582001
Mcintosh lover and tube
sfox52 interesting to see what results you get. i heard of someone changing the LM318 to a faster one but never heard if it is better. let us know......... bgw fans
Joe- I guess I need to work up the nerve first! I have the sockets and a few op-amps on hand, but someone cautioned about causing oscillation with the wrong ones. I'd hate to fry the old beast. It does seem to roll off the high freqs more than my other amps when using it full range.
Godzilla525
New Member
So far the only other op-amp I've come across that supports overcompensation on pin 1 like the LM318 is the AD744. It also has a similar slew rate, and at first glance appears to be a drop-in replacement but with FET inputs.
EDIT: Scratch that. I just checked again on the AD744 and pin 1 is decompensation.
Granted, I haven't been looking too hard since the '318 seems to be doing a good job in this circuit.
I'm genuinely scared to try it with either the 250D or 750C given the amount of power available to absolutely destroy something if it wasn't exactly right.
EDIT: Scratch that. I just checked again on the AD744 and pin 1 is decompensation.
Granted, I haven't been looking too hard since the '318 seems to be doing a good job in this circuit.
I'm genuinely scared to try it with either the 250D or 750C given the amount of power available to absolutely destroy something if it wasn't exactly right.
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Joe19582001
Mcintosh lover and tube
interesting if someone tried to change the op amp what sound it will produce?
Joe19582001
Mcintosh lover and tube
any bgw 750a stories
Joe19582001
Mcintosh lover and tube
any bgw 750 newbies
Joe19582001
Mcintosh lover and tube
any new bgw owners
BobbyBluz
Super Member
I'm an old BGW owner that recently moved my collection of them and powered them all up. Now I need to obtain some worthy speakers that won't vaporize when vintage BGW power is fed into them. I sold my huge PA because having to rent a truck to move the speakers had become a major inconvienence. From past experience a 750B can make short work of most voice coils at high volume levels.
That must have been an almost a back breaking exercise. The 750 and 600's almost feel like one solid lump of iron.
Joe19582001
Mcintosh lover and tube
still the bgw 750 is an unknown secret to many . massive power for little money. Any new bgw fans out there??????
beeker
New Member
howdy:yes:
this might be my first post i cant remember here. anyhow building onto my pro amp collection using at home and on dj rig possibly is my mint cond. rebuilt 750c. Im planning on running it on a woofer set at a gig or 2. at home im running it bridged to an achademy center and swtched to my big paradigm center. it hauls the mail with sound in center channel. I litterally hadnt stopped listening for days. its between 2 75lb klipsch towers ran by a crown xls 602 and a denon 160x2 on my surround boston a150's on sidewalls. this is the first iv actually pushed a center channel in a theater. also got 2 paradigm 12s and 10s fr&rr powered for subs.
a 50lb amp dont surprise me as im sure some others feel. even today if you put your hand on near to any high end home amp worth over $15k half will weigh at least 40lbs and some many more than that. there are amps that brake down into very similar pieces that weigh 128lbs made today, costing $20k and conservatively rate their watts at 200 watts per channel, dozens out there. comparing every aspect the bgw amps allow any man to get there hands on a great music and video audio reproducing machine.
i ran thru several pirs of high end floor monitors off this 750 and it produces rich clean power at 8/4 and nicely at 2 ohms for a short period of time(i didnt push it long). Reason for running it on center for now is cause it sounds awsome and its next use is on 2 pro 18's unless i can only afford 15's. I know it will run any pair well and all 4 good.
you can still have a new 750g built today at this link. http://www.bgw.com/amplifiers/professional/750.asp
this might be my first post i cant remember here. anyhow building onto my pro amp collection using at home and on dj rig possibly is my mint cond. rebuilt 750c. Im planning on running it on a woofer set at a gig or 2. at home im running it bridged to an achademy center and swtched to my big paradigm center. it hauls the mail with sound in center channel. I litterally hadnt stopped listening for days. its between 2 75lb klipsch towers ran by a crown xls 602 and a denon 160x2 on my surround boston a150's on sidewalls. this is the first iv actually pushed a center channel in a theater. also got 2 paradigm 12s and 10s fr&rr powered for subs.
a 50lb amp dont surprise me as im sure some others feel. even today if you put your hand on near to any high end home amp worth over $15k half will weigh at least 40lbs and some many more than that. there are amps that brake down into very similar pieces that weigh 128lbs made today, costing $20k and conservatively rate their watts at 200 watts per channel, dozens out there. comparing every aspect the bgw amps allow any man to get there hands on a great music and video audio reproducing machine.
i ran thru several pirs of high end floor monitors off this 750 and it produces rich clean power at 8/4 and nicely at 2 ohms for a short period of time(i didnt push it long). Reason for running it on center for now is cause it sounds awsome and its next use is on 2 pro 18's unless i can only afford 15's. I know it will run any pair well and all 4 good.
you can still have a new 750g built today at this link. http://www.bgw.com/amplifiers/professional/750.asp
BGW 750 series
I've read this entire thread and had to chime in. 1st of all the peavey cs-800 and the bgw 750 series amps are not the same. Yes they appear similar on the outside and have similar heatsinks under the cover, but that's about where the similarities end. I own both and with only basic knowledge of electronics it's more than obvious the two output stages are totally different. The main reason being the peavey used "stacked npn" output transistors on both rails, and the bgw is a true a/b amp with complimentary pnp/npn output transistors. The driver circuitry also appears to be nothing alike because the bgw uses a lot more semiconductors than the 800. I just got a hold of a broken 750B and don't know any of it's history. The two output modules look almost identical. One uses a couple heat sunk resistors? (in what I believe to be the bias compensation circuitry) that have 2 inch leads and go through holes in the board filled with white heatsink compound. The other module has fixed resistors but the holes are in the pc board for the heat sunk type. I acquired a complete brand new old stock module and it doesn't have these holes. Seems there are a number of different revisions to these boards and I'd like to find a breakdown of them and which amps they were used in. Anybody?
I've read this entire thread and had to chime in. 1st of all the peavey cs-800 and the bgw 750 series amps are not the same. Yes they appear similar on the outside and have similar heatsinks under the cover, but that's about where the similarities end. I own both and with only basic knowledge of electronics it's more than obvious the two output stages are totally different. The main reason being the peavey used "stacked npn" output transistors on both rails, and the bgw is a true a/b amp with complimentary pnp/npn output transistors. The driver circuitry also appears to be nothing alike because the bgw uses a lot more semiconductors than the 800. I just got a hold of a broken 750B and don't know any of it's history. The two output modules look almost identical. One uses a couple heat sunk resistors? (in what I believe to be the bias compensation circuitry) that have 2 inch leads and go through holes in the board filled with white heatsink compound. The other module has fixed resistors but the holes are in the pc board for the heat sunk type. I acquired a complete brand new old stock module and it doesn't have these holes. Seems there are a number of different revisions to these boards and I'd like to find a breakdown of them and which amps they were used in. Anybody?
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funllbb- can you post a picture of what you are describing? I have a BGW 500D that is very similar to the 750 A model, there are some metal can type driver transistors in wells with compound around them on my boards. I know later 750 models went to plastic body transistors. The outputs are metal TO-3 in all of them.
Spy-Fi
Member
Not sure if anyone already mentioned this site for manuals but I've been very pleased with "HiFi Engine" for sourcing hard to find manuals and literature. It's easy to use as well as free. Just sign up and go. No affiliation. Got a service manual for my 750B and I know they have other models manuals etc.