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dustbowl

Blues Custom 30 - volume and headroom

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Hi there,

 

I bought a Blues Custom about a year ago and I'm really happy I did although reading the thread about the BC 30 mods left me thinking there is still room for improvement, which is great.

Some of the comments that are often made about this amp surprise me though. For instance many people say it is "loud".

One of the reasons I got this amp is that I wanted an amp for home and band/live use. The option to switch from 15W to 30 seemed to be just what I needed. I expected 30W to be more than enough most of the time; I used to have a JCM 900 and it was so frustrating to be told to turn it down all the time! I don't know it this is the right term but I wanted an amp that I could "drive": whose tubes I could make "work".

Of course the BC 30 is loud for home but I can live with that. However the first time I took it to practice (just me and a drummer) I was disappointed: the amp had no headroom at all and just didn't keep up with the drums in terms of volume (at all, ended up diming all the knobs so I could hear what I was playing - I also raised the amp, to little avail).

I want to know if this could be related to the tubes or if I was simply expecting too much from 30W (although I've read somewhere that the amp is actually less than 30W technically). The reason I talk about lack of volume and headroom is that I feel these problems are probably related. Maybe I'm wrong.

 

Thanks a lot for your interest/help

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Might want to find that volume knob on your drummer and turn him down. :(

 

On a more serious note, if you don't already, you might want to tilt the amp back or put it on a tilting amp stand like any one of these:

http://www.americanmusical.com/Item--i-MUS-RS7000-LIST This is the one I use

http://www.americanmusical.com/Item--i-QUI-BS317-LIST

http://www.americanmusical.com/Item--i-TRI-STANDBACK

 

My BC30 is plenty loud for rehearsal with the full band (5 piece) and I run it on 15 watts. Lately I've been using my Bugera V22 for rehearsals because it's lighter to carry and I run that on the triode setting (~13 watts). The BC30 is great for gigs.

 

I don't play totally clean nor do I play totally dirty. It's mostly clean until I turn up my volume on the guitar so I can get the grit. Though I have a multiFX box I don't use it too often anymore. Just the reverb on the amp and wah pedal.

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I've used mine at pub jam sessions alongside a loud drummer, a 50W Marshall 2 x 12 Valve combo and a 150W 4 x 8 Bass combo. Never found any problems in cutting through without diming it - usually have both channels set at around 2 o'clock to 3 o'clock.

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Perhaps you could experiment with some different output tubes. I found the stock Sovtek 5881s and 6L6WXTs don't really put out the most harmonically rich or loudest sound with these amps. I personally like Reflektor marketed Svetlana 6L6GGCs - they certainly gave my BC30 a bit more oomph in the volume department - mainly because they seem to have more bottom end and a warmer midrange.

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[biggrin]: the drummer volume knob is certainly worth considering, Twanger I'll try that next time! As for a stand, the amp was raised: I put it on a box roughly at waist height which did improve things but didn't solve the problem.

I play reasonably loud post-rock-ish stuff, nothing extreme, really. I play mostly solo stuff at home at the moment so the problem is not urgent but I bought this amp hoping it would be "the one" and I want to know what I can do with it. It's funny because I remember the first amp I owned was a really trebly 20W solid state "Live" amp with which I never had a problem to cut through in a 5 piece band.

Twanger and Wiggy, your comments confirm my suspicion that it doesn't deliver what it should. Wildschwein262, I was thinking the issue might have something to do with tubes but I know very little about the effect they have on tone, volume, headroom and so on so I'm trying to find as much info as possible at the moment - I don't really want to change all the tubes if changing just one or two could do the trick.

I'd like to first determine whether retubing is worth considering, and which tubes have the most impact on tone, and then take it from there and maybe look at the mods that have been discussed on this forum if I'm not completely satisfied. It's true that the amp is bright but I've found that it's not too difficult to "tame" the brightness with the EQ.

I've also read that some BC30s owners have simply bypassed the standby button and put a master volume instead - I find this interesting, have any of you here done it?

 

Thanks a lot for your replies - any suggestions are welcome!

Cheers

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Have you re-valved the BC30 yet?

 

Changing the rectifier usually gives it more headroom, and a pair of 6L6GC or even EL34 in lieu of the 5881 opens it up.

 

Tilt back: I've fitted the long 19-in Fender tilt-back legs, and castors!

 

Volume: without the tilt-back the players invariably have it too loud: I went outside the hall whilst one guy was playing through it, with drummer, bass and another guitar (50W Marshall), and it was they only thing I could hear, and it was not cranked right up.

 

Clean headroom: the clean channel is not 100% clean at high volume.

 

Further mods: I've just made some more mods and am posting them on the mods thread...

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I find it very interesting that a lot of people advocate replacing the stock 5881's with 6L6's. Don't know whether it's a geographical or manufacture date thing but my BC30 came fitted with Sovtek 6L6WXT's as stock. AFAIK these are slightly lower output than 6L6GC's but are not the same as true 5881 valves.

 

Are people describing their 6L6WXT's as 5881's or are their amps fitted with different valves to those which mine came with as stock?

 

BTW Carverman if you read this - I know I asked this same question a while back but still trying to get a handle on what valves have been fitted to these amps as stock over time i.e genuine 5881's, 6L6WXT's, 6L6GC's? as it would be interesting to get a picture of people's opinion of the amp according to what was in it when they got it from stock.

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I'll keep an eye on this topic as I have a BC30 as well. I took it to the first rehearsal of my new band last night and it just sounded a bit 'mushy'. Could be the room we're playing in though as it was pretty small. I don't find the amp quiet at all, but it certainly loses definition at higher volumes. Next week I'm going to try out a few different things and see how it sounds. I didn't try the 30w mode last night for some reason.

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Hi there,

 

I'm realizing a lot of info has been made available on the BC30 and possible mods. Apart from the thread on this forum I found this thread (to which some people here have contributed) very interesting, with answers to questions I had on tube combinations, speaker/external speaker options and so on. I couldn't help but notice one BC30 owner also regrets the lack of clean headroom and volume.

 

On my amp the stock valves are

2 Sovtek 6L6WXT+

5 12AX7EH

1 Electron Tube 5AR4

 

I haven't retubed it yet. I'll start by changing the rectifier tube. I thought I'd change the power tubes, but I've read (jefrs) that swapping the EH12AX7s for ECC83s was a better idea so I might do that.

Although I don't have a proper amp stand I always tilt the amp back as I noticed it makes a difference.

 

Re clean headroom, when I played it at high volume, the amp was really overdriven on the "Clean" channel, not just "dirty" - in fact a bit like the B channel at lower volume with the drive setting cranked... Played with humbuckers (epi LP custom, stock) and single coils (Burns Trisonic): the single coils were cleaner but just. Hence my surprise to read

the clean is very clean to above '7' (ear-splitting)
!

 

Thank you for sharing your latest mods jefrs. Any thoughts on adding a Master volume?

 

Thanks!

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Regarding the stock valves, mine were

Sovtek "6L6WXT+"

Electro-Harmonix 12AX7EH

Electron Tube 5AR4 (made in China)

 

The Chinese 5AR4 is poor, very poor, try Sovtek. IMO this rectifier does make a lot of difference to the tone and feel of the amp.

 

The 12AX7EH are ok for the reverb. Suggest E83CC or other low-noise type in V1, a low-noise high-gain can go in V1 to over-drive a normal-gain V2, V4 the PI is 'balanced' normal-gain. There are too many ECC83/7025 types to suggest makes, some TAD are ok (they re-badge), Watford give good descriptions of wares.

 

The 6L6WXT+ are not too bad, but imo are not on par with Svetlana =C= 6L6GC.

 

The 6L6WXT+ appear to be a high-voltage 5881/6L6WGB type, but then so do JJ/Tesla 6V6GTS (JJ 6V6S). Of those tried the =C= 6L6GC give a rich full sound with plenty of bottom-end, the JJ 6V6S (note it can handle the 425V HT [uK=245VAC]) is very crisp and clear. It is hard to choose between the Sovtek 6L6WXT+ and the Philips/JAN 6L6WGB(5881), which speaks well for the 6L6WXT+.

 

Changing the output bottles does not automatically alter the power, that is changed by the bias, grid, HT and load, what is does do is alter the tone and power handling capability: the 6V6S were not noticeably quieter than the 6L6GC. The BC30 is cathode biased (self-biased), this allows a variety of valves to be used, provided they can handle the HT e.g. some 6V6, 5881 and 6L6GC (not 6L6), EL34, etc.

 

Regarding the master volume, I posted on this thread before: just before the phase inverter, replace the 220k R39 with a 220k or 250k potentiometer with the wiper onto C27, I tried a 500k pot but now use a Linear B220k. The pot is mounted on large washers in the hole left by the self-destruct standby switch which is not needed at all with a valve rectifier. Two-wire shielded co-ax is used (microphone cable), note it is only grounded at the board to avoid hum.

 

The MV allows the Beastly30 to be used at parlour level. It does not sound they same as at full gig level but it is nice and it is usable. The 6V6S can be over-driven to some extent but the 6L6GC just seem to get louder and increase bottom-end roar in a nice way, no lack of headroom at all, but it is not an entirely clean amp.

 

Regarding cleanliness: the clean channel does dirty up at high volume i.e. above '7' (ear splitting). The MV allows me to crank the clean volume up to max but imo the drive channel sounds better for this job (plus I've got a boost switch on the cathode resistor of V1b). Plus I can switch channels without having to dive for the MV.

 

Maybe another thing to observe is that I've got a pair of 8ohm Celestion Classic G12M-25 Greenback 75Hz 98dB in there, not the most efficient but nice and creamy. Now that R5 and R6 are now both about 45k, I'm getting a rich bluesy tone from the amp. I am close to getting it to emulate my original Mullard valved WEM Dominator "25", the Dominator is the one the 18W Marshall is a direct copy of...

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I would recommend you look at the biasing, could be running a little out. My stock valves are Sovtek 5881/6L6WGC, I'm back using these now. At some point this week I'll be trying different cathode resistors. When biasing my Tung-Sol 6V6GT's, I ended up with a 600ohm cathode resistor to stop red plating, this caused the negative side of the signal to clip heavily. Now back with 6L6WGC/250ohm the negative side is fine while the positive side clips a fair bit. I suspect a ~300ohm cathode resistor would balance things out and increase headroom.

 

I would like to work the biasing out properly but I can't find a datasheet for my valves and I don't know anything about the OP tranny.

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I find it very interesting that a lot of people advocate replacing the stock 5881's with 6L6's. Don't know whether it's a geographical or manufacture date thing but my BC30 came fitted with Sovtek 6L6WXT's as stock. AFAIK these are slightly lower output than 6L6GC's but are not the same as true 5881 valves.

 

Are people describing their 6L6WXT's as 5881's or are their amps fitted with different valves to those which mine came with as stock?

 

BTW Carverman if you read this - I know I asked this same question a while back but still trying to get a handle on what valves have been fitted to these amps as stock over time i.e genuine 5881's' date=' 6L6WXT's, 6L6GC's? as it would be interesting to get a picture of people's opinion of the amp according to what was in it when they got it from stock.

 

 

[/quote']

The earlier models shipped with Sovtek 5881/6L6WGC which are a Russian Military tube used for servomotors. They are in fact not true 5881s or 6L6s - those are US names - but they are close enough in specs to be used in place of 6L6GC/5881 tubes in many cases. Later BC30s shipped with Sovtek 6L6WXT+s which are a marginally better tube. Messing around with the power tubes in the BC30 does yield pretty different sounding results.

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My Mileage Varied on the phase inverter tube. Every tube I tried sucked until I put in a Groove Tubes 12ax7 SAG (Special Applications Group) which is tested for balanced output. It greatly (read: GREATLY) improved the amp. It did NOT increase clean headroom but the cleans sounded like cleans.

 

A lot of the BC30 owners have done the tube thing and have managed to get the most out of this amp. Better tubes to replace the stock tubes are pretty much a necessity. For more headroom/cleaner cleans or whatever you're looking for along those lines, at this point I really think that the only thing that would "open up" this amp any more would be to replace the output tranny and maybe even the power tranny.

 

Mercury Magnetics offers replacement trannies for power/output/choke. http://www.mercurymagnetics.com/pages/mainframe.htm

Just the power and output trannies are $440 for the pair. I love my BC30, however, I'm not willing to drop that kind of dough at this point in time. I'm sure the new trannies would get the BC30 up to it's maximum potential but, I have to ask... why? It meets my needs for the gigs I use it on. If I feel the need to inflict pain on my ears or if I want to hurt the audience I can use the Boogie.

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Hi there,

 

Thank you all for the info. I'll soon be ordering new tubes for my BC30, I'll share my impressions once the new valves are in. Sorry jfrs I missed what you had previously posted on the MV mod. I think it would be very useful for me but I'll wait to give it a go.

Tranny replacement is an interesting option but beyond my technical abilities and considering the cost I think I might as well buy another amp altogether. Although if I really felt this amp had it all except the loudness why not. Judging by what most people say though it may well be that this amp is simply in dire need of good tubes.

 

Cheers!

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Oh' date=' BTW jefrs. I think using a balanced PI is a little futile as the circuit itself is unbalanced. Check out valve wizards explanation of phase inverter circuits.

 

http://www.freewebs.com/valvewizard/acltp.html[/quote']

 

I agree.

 

Some advocate an slightly unbalanced output stage for guitar as it does give a gentle warble to the note. One of my WEM Dominators used to do that nicely until those valves died.

 

But as I had a balanced normal gain Harma Retro (Mullard re-build), I used that. It doesn't hurt. The output valves =C= 6L6GC-SVT are also balanced for gain. These are excellent sounding current build and imo better NOS Philips. I went this way because the BC30 is rather noisy electronically and was reducing the hum and buzz (messy wiring and grounding also sorted).

 

regarding: The Tung-Sol 6V6 - they will tend to red plate because they are not up to handling the HT, it does have to be re-biased for these. Whereas the JJ Tesla 6V6-S are more like 5881 with low current heaters, they can take over 500VDC and did not show any sign of red-plating when I thrashed them with stock cathode bias.

 

The output transformer appears to be or be based on the "SL60A" Soldano 60 (60W 2x6L6 4/8/16). [TAD €130] The 22000-0-22000 ohm marking appears to be pure BS, I measure 48 ohm DC across the primary which is consistent with correct for 6L6 etc. It's not bad but should not be bolted straight down to the chassis, there should be a dielectric insulator, raise it (and the power transformer) off the deck on a sheet of paxolin (pcb) to break the electro-magnetic coupling, it will still be earthed by its bolts.

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Oops!

 

I've maybe advocated modifying the cathode resistor on V2A elsewhere but the switch may actually be on V1B. I have modified both at some time and I'm afraid that my diagram has so much scribble on it now that it is hard to tell. The mod gives far more crunch and roar to Ch2. When I look under the hood next I'll sort that out and re-post into BC30 mods. See also mods there to R5 and R6 to give more clarity and depth. I shunted these to 470k from 1Meg and this really opens up the voice of the Beastly30, which is what this thread is about - see BC30 Mods thread for details

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