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Blues Custom 30 "Reverb and 15w Class A mode"


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I recently acquired a BC 30 and noticed that when the reverb is set past 9 o'clock an auible howl starts to gradually build up. Below 9 o'clock where I would set the control it's fine. Any Ideas. Number 3 12ax7 seems to be quiet and not microphonic.

 

When switched to The class A mode a low frequency hum (60 to 100hz) is heard. The hum does not increase or decrease with amp or guitar volume. Although, it is not noticible when playing.

 

Final question : Is the fan supposed to be on at all times.

 

Other than the above the amp sounds great with my lespaul. I would definitely appreciate some feedback.

 

Thanks #-o

 

Gene

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I recently acquired a BC 30 and noticed that when the reverb is set past 9 o'clock an auible howl starts to gradually build up. Below 9 o'clock where I would set the control it's fine. Any Ideas. Number 3 12ax7 seems to be quiet and not microphonic.

 

When switched to The class A mode a low frequency hum (60 to 100hz) is heard. The hum does not increase or decrease with amp or guitar volume. Although, it is not noticible when playing.

 

Final question : Is the fan supposed to be on at all times.

 

Other than the above the amp sounds great with my lespaul. I would definitely appreciate some feedback.

 

Thanks #-o

 

Gene

Hi Gene,

I was just jammin on mine about an hour ago. I have never had any hum on mine as you described. One thing you might consider is doing a "Cap-Cut" mod as a lot of members here have done. Everyone seems to agree that the amp right out of the box had a "Ice Pick" Treble tone. Very easy. What you have to do is remove the back. (With power off), and remove the chassis. Before I go any further,you may want to read the thread I attached below. It made the amp very warm and fat sounding. I also swapped the stock tubes to Tungsol Reissues. These mods turned a great amp into a super amp. It really worked.The fan stays on all the time. Oh, and Congrats on your new BC30!!! B) Heres the link to the thread.

Regards,

Michael

 


http://forum.gibson.com/index.php?/topic/43505-blues-custom-mods/

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To answer your last question re the fan - Yep it's supposed to be on all the time, in fact if it isn't then turn off the amp straight away as it's wired into the circuitry and could cause damage (can't remember the exact reason why but a quick search on here should bring up the answer.)

 

The howl you're getting sounds like feedback so could be either of the reverb valves or the tank itself - more knowledgeable people will be able to confirm and suggest a solution.

 

The hum sounds like classic 60Hz interference.

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My BC30 hums in 15 watt mode - always has - so I just always set it in 30 watt mode where the hum is not present. I prefer the sound of it like that anyway; as there is more headroom and clarity. The reverb is funny on these - kind of weak but bloomy all at the same time. I think you should change out the valves and see what happens. Reverb is run by v3 and v5 from memory.

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  • 3 weeks later...

My BC30 hums in 15 watt mode - always has - so I just always set it in 30 watt mode where the hum is not present. I prefer the sound of it like that anyway; as there is more headroom and clarity. The reverb is funny on these - kind of weak but bloomy all at the same time. I think you should change out the valves and see what happens. Reverb is run by v3 and v5 from memory.

Thanks....for the input. Unfortunately I had to say goodbye to the BC30. UPS took it back. It seems that UPS

delivered the amp to me not in the best of shape. The top was split from front to back. The seller had the pkg insured.

 

too bad...but it would have cost a bunch to fix it and perhaps the circuit board could have had some damage. Guess I will start looking all over again

 

Gene [crying]

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Thanks....for the input. Unfortunately I had to say goodbye to the BC30. UPS took it back. It seems that UPS

delivered the amp to me not in the best of shape. The top was split from front to back. The seller had the pkg insured.

 

too bad...but it would have cost a bunch to fix it and perhaps the circuit board could have had some damage. Guess I will start looking all over again

 

Gene [crying]

Sorry to hear that...You may want to check out a Peavey Delta Blues. Super sweet amp. I've been thinking of getting one down the road. But the little lady wouldn't like it +:-@[biggrin]

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  • 2 weeks later...

I recently acquired a BC 30 and noticed that when the reverb is set past 9 o'clock an auible howl starts to gradually build up. Below 9 o'clock where I would set the control it's fine. Any Ideas. Number 3 12ax7 seems to be quiet and not microphonic.

 

When switched to The class A mode a low frequency hum (60 to 100hz) is heard. The hum does not increase or decrease with amp or guitar volume. Although, it is not noticible when playing.

 

Final question : Is the fan supposed to be on at all times.

 

Other than the above the amp sounds great with my lespaul. I would definitely appreciate some feedback.

 

Thanks #-o

 

Gene

 

The reverb is quite wet. You can get an acoustic feedback howl through the tank so make sure it is bagged and secured down.

 

The amp runs in triode or tetrode* mode, both are Class AB. Only a single-ended amp can be guaranteed to be Class A, you can build a Class A push-pull but they are low-output, little more than the SE job, and they require a /very/ large OP transformer. Depending on choice of output valve the tetrode may give 26-30+ watts at full chat. In triode mode it is likely to be over 15 watts. For some reason this is a very loud amp. This could be down to a good efficient output transformer, it is not always about watts. The OP valve bases are pre-wired for pin 1 to take an EL34 which is a pentode. Being cathode biased, you can swap different type octal bottles around with some impunity.

 

The amp hums. The layout design is poor. The various HT, heater and signal wires are bundled together, and it has earth grounding points all over the place.

 

The fan is supposed to be on all the time. It runs off the heater circuit and adds hum to the circuit. Anything noisy on the heater is added to the cathode. Mine was not connected from new and required poking with the soldering iron. Connecting the fan added noise. The amp gets /very/ hot without the fan.

 

If you want feedback then turn the volume up, crank up the gain of the drive channel and bring the Les Paul up real close to the speakers.slayer.gif

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  • 1 month later...

I had the same reverb problem, and it also seemed like the reverb went from zero to full without much nuance. I replaced both reverb tubes (12ax7) with lower-gain 12at7's and both problems went away. Sounds great now. I also tried the 12au7 with even lower gain...not so good. 12at7 is a classic reverb tube in old Fender amps, stick with that one.

I did notice that whoever posted the original message no longer has his BC30--decided to respond anyhow, hope someone else sees this and benefits as much as I did.

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Thank you all for the feedback...... [thumbup]

 

The new BC30 that I received arrived in 95% condition...nice. The drive channel 2 is "killer" with my lespaul in independent mode. To get output with a strat the interactive mode seems to crank it up good. I did notice that there is a "big" difference" in volume between channel 1 and channel 2. The tone on channel 1 seems less bright than channel 2. For my taste I use channel 2 backing off the highs. treble 8/9 oclock mids 9/10 oclock and bass 2/3 oclock.

I run the master between 3 oclock and full with the pre-gain set at 11/12 oclock. The mid control exclusive to channel 2 kind of gives me a voxy tone if set between 11 and 2 oclock. Set between 3 oclock and full and I am in the blues breaker / vintage modern / plexi area with a little more bass should I need it.

 

I was wondering if the cap cut/mod would help. I just want to take off some top giving the treble control more usable sweep and still get say 85% of the high freq's if needed.

 

Thanks again guy's B)

 

Gene

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