Greetings,
I am fooling around with a blue tooth module and wanting to install it inside a BGW 150. It sounds pretty good, but it doesn't have the gain required to drive the BGW to clipping. Was wondering how to modify the BGW to increase the gain.
Thanks!
Barry
I am fooling around with a blue tooth module and wanting to install it inside a BGW 150. It sounds pretty good, but it doesn't have the gain required to drive the BGW to clipping. Was wondering how to modify the BGW to increase the gain.
Thanks!
Barry
increase the value of the feedback resistor to the input op amp. On the BG250 schematic it is R6 a 7.2 Kohm resistor.
Hi barrybreaux
Be very careful when changing the LOOP GAIN as it will change the stability and may OSCILLATE & FAIL. I designed this amplifier @ BGW.
I don't remember where I put the pole?
Duke
Be very careful when changing the LOOP GAIN as it will change the stability and may OSCILLATE & FAIL. I designed this amplifier @ BGW.
I don't remember where I put the pole?
Duke
In principle increasing the CLG will also increase stability of an amp, if it s otherwise then it means that the design is somewhat flawed.
Not necessarily.
Design is always a compromise, you don't know which tradeoffs were accepted here.
Kudos to the original designer for chiming in.
Design is always a compromise, you don't know which tradeoffs were accepted here.
Kudos to the original designer for chiming in.
The higher the CLG the lower the loop gain and the more the stability, that s straightfoward, generaly people implement low CLG gains to have output noise and THD as low as possible, that please the specs readers, personaly i dont like lazy amps that require big amount of input voltage, i prefer amps with at least a 40 gain since you can generaly drive them with a PC soundcard easily.
Those asking for help must supply all necessary data.
Besides answering for free, should we also start hunting for schematics and manuals?
Why not post the necessary pages here?
Why go through ekektrotanya approval for download process, search for whatever the OP is asking, etc.?
Besides, often there are different versions of the same schematic, who guarantees we are all referring to the same one?
There is only one protection from that, posting it (or one) here, which then becomes the common reference.
The version of bgw125 manual on electrotanya the feedback resistor to the input op amp is R103 a 47.5 Kohm 1% resistor. I would try a 56k. To forestall destructive oscillation I would increase the bypass cap C104 from 30 pf to 56 or 62 pf. I cannot calculate stability, I presume the O.P. cannot either. A 60 w tungsten bulb series the AC input will light up if the amp is oscillating ultrasonically.
When I was 35, paying a car payment and rent on an apartment, I bought an old burnt up transistor amp and repaired it badly without a schematic. Vacuum tubes for the ST70 had become unavailable to those without secret knowledge. I listened to 8 watts per channel instead of the nameplate 60 for about 8 years before access to the internet became affordable. Some kind person on diyaudio pointed out an obscure website that had the schematic and theory of the output limiter. Two of my high school friends that always had all the best hobby toys those days are still working at age 73.
Diyaudio forum has or had a limit on how much data a member can post. Electrotanya is a site that requires no membership for fees. It does take some careful reading to find the actual download button instead of the huge "DOWNLOAD" ad that drives one to a pay site. Same misleading ad appears on another free site eserviceinfo.
When I was 35, paying a car payment and rent on an apartment, I bought an old burnt up transistor amp and repaired it badly without a schematic. Vacuum tubes for the ST70 had become unavailable to those without secret knowledge. I listened to 8 watts per channel instead of the nameplate 60 for about 8 years before access to the internet became affordable. Some kind person on diyaudio pointed out an obscure website that had the schematic and theory of the output limiter. Two of my high school friends that always had all the best hobby toys those days are still working at age 73.
Diyaudio forum has or had a limit on how much data a member can post. Electrotanya is a site that requires no membership for fees. It does take some careful reading to find the actual download button instead of the huge "DOWNLOAD" ad that drives one to a pay site. Same misleading ad appears on another free site eserviceinfo.
Thanks for all the replies! Sounds like the only answer so far is to modify the feedback divider on the input opamp.
For those who wants to see the schematic: https://audiocircuit.dk/downloads/bgw/BGW-150-pwr-sm.pdf.
i don’t expect Anyone to do a redesign for me.
Thanks for the replies!
For those who wants to see the schematic: https://audiocircuit.dk/downloads/bgw/BGW-150-pwr-sm.pdf.
i don’t expect Anyone to do a redesign for me.
Thanks for the replies!
Decrease R106 (2.49k) and increase C105 (47uF) in proportion, for instance if you reduce R106 down to 1.2k, wich will
increase the gain by about 2x then increase C105 to 100uF.
R103 (47.5k) shouldnt be modded because there s a capacitor in parralel and this would require to compute a new value
for this component as well and it not as easily computable because there s no proportionality in this case.
The other solution is to insert at the input of the amplifier a basic preamp using a NE5532 with the necessary gain.
increase the gain by about 2x then increase C105 to 100uF.
R103 (47.5k) shouldnt be modded because there s a capacitor in parralel and this would require to compute a new value
for this component as well and it not as easily computable because there s no proportionality in this case.
The other solution is to insert at the input of the amplifier a basic preamp using a NE5532 with the necessary gain.
Wahab, thanks for the insight Into the divider + the option of adding an additional opamp. I won’t be able to work on this for a few weeks.
I had configured a 5532 preamp external to the amp and that worked, but it would not fit inside and requires power. There is a 15 volt source on the output module, the opamp might be a solution. I have been collecting and restoring BGW amps for quite a while. My wife let me know 20 was enough.
I had configured a 5532 preamp external to the amp and that worked, but it would not fit inside and requires power. There is a 15 volt source on the output module, the opamp might be a solution. I have been collecting and restoring BGW amps for quite a while. My wife let me know 20 was enough.
If you want to power it from the internal supply, you don’t really need a 5532. You could use something a little less hungry, as you don’t need a lot of drive capability.