Underperforming valve head

[razze06]

Some time ago I've acquired this home-brew fender bassman 100 clone head, and I love its tone. Fantastic clarity and all the rest.

Unfortunately, it is not very loud.

What do I mean by "not very loud"?

I have it plugged into my ashdown MAG 4x10, as my other more modern cabs didn't like it (TC RS212 and Tecamp s210), and I have to run it at full tilt (no clean headroom) to be able to practice with the (rock covers) band.

Given that this is nominally a 100W amp, I was expecting a bit more.
Now I knew it was a little underpowered when I got it, as the previous owner said that he had it checked, and it seemed to be putting out only around 60W.

My question here is quite simple: I would love to use it for live work, what do you recommend I do?

- Get a cab with higher sensitivity, more efficient, or with a shape and tuning more suitable to the head

- Get the amp serviced again, with a view to restoring its nominal power (or more)

- Sell it to someone who doesn't need the volume and get something else, maybe a real fender bassman 100 or 135

- More cabs is realy not an option, as I don't have the space or the inclination to use them.

[hubrad]

Any idea of the impedance of your cab? Most amps specify the output power RMS into 4 Ohms.
100W into 4 Ohms amp only gives about 2/3 of that, ie 60-odd Watts, into 8 Ohms. Not much power for a rock band bass.
Also, if that 100W is the Peak measurement, the RMS - this is the figure that most of us go by - will also be considerably less, prob about 60W.
If both those apply you might be putting as little as 40W into your cab, which will be a struggle in a rock band!
I used to struggle with a 100W into 2 x 15" cabs!

[vocrockguitars]

[quote name='razze06' post='1147322' date='Mar 2 2011, 04:34 PM']Some time ago I've acquired this home-brew fender bassman 100 clone head, and I love its tone. Fantastic clarity and all the rest.

Unfortunately, it is not very loud.

What do I mean by "not very loud"?

I have it plugged into my ashdown MAG 4x10, as my other more modern cabs didn't like it (TC RS212 and Tecamp s210), and I have to run it at full tilt (no clean headroom) to be able to practice with the (rock covers) band.

Given that this is nominally a 100W amp, I was expecting a bit more.
Now I knew it was a little underpowered when I got it, as the previous owner said that he had it checked, and it seemed to be putting out only around 60W.

My question here is quite simple: I would love to use it for live work, what do you recommend I do?

- Get a cab with higher sensitivity, more efficient, or with a shape and tuning more suitable to the head

- Get the amp serviced again, with a view to restoring its nominal power (or more)

- Sell it to someone who doesn't need the volume and get something else, maybe a real fender bassman 100 or 135

- More cabs is realy not an option, as I don't have the space or the inclination to use them.[/quote]
Hello, The original Bassman 100 had 4x6l6GC valves in the output section and was capable of at least 100W when set up correctly. Might be worth checking the Bias Current. You should be looking at a range of 30mA to 36mA per 6l6GC tube for optimum power and performance. Hope that helps, Regards Voc Rock.

[razze06]

[quote name='hubrad' post='1147349' date='Mar 2 2011, 05:00 PM']Any idea of the impedance of your cab? Most amps specify the output power RMS into 4 Ohms.
100W into 4 Ohms amp only gives about 2/3 of that, ie 60-odd Watts, into 8 Ohms. Not much power for a rock band bass.
Also, if that 100W is the Peak measurement, the RMS - this is the figure that most of us go by - will also be considerably less, prob about 60W.
If both those apply you might be putting as little as 40W into your cab, which will be a struggle in a rock band!
I used to struggle with a 100W into 2 x 15" cabs! [/quote]

The cab is 8ohm, but bear in mind that we are talking about a home made head here, so I don't know how the power output was measured. I see 4 power valves, I know it's a clone of the fender bassman 100, ergo I suspect the intended output power was 100W.

I've played it through an ampeg 8x10 wardrobe in a practice room, with a quieter band, and still had to go very close to full tilt to get the volume. Those cabs are 4ohm and loads of cone area...

[razze06]

[quote name='vocrockguitars' post='1147369' date='Mar 2 2011, 05:18 PM']Hello, The original Bassman 100 had 4x6l6GC valves in the output section and was capable of at least 100W when set up correctly. Might be worth checking the Bias Current. You should be looking at a range of 30mA to 36mA per 6l6GC tube for optimum power and performance. Hope that helps, Regards Voc Rock.[/quote]

It does! I'm just hesitant to take it for an expensive rebias and service, when it may not be worth the effort in the end.

[hubrad]

[quote name='razze06' post='1147375' date='Mar 2 2011, 05:21 PM']The cab is 8ohm, but bear in mind that we are talking about a home made head here, so I don't know how the power output was measured. I see 4 power valves, I know it's a clone of the fender bassman 100, ergo I suspect the intended output power was 100W.

I've played it through an ampeg 8x10 wardrobe in a practice room, with a quieter band, and still had to go very close to full tilt to get the volume. Those cabs are 4ohm and loads of cone area...[/quote]
SOunds like it's just underpowered for your needs. I'd be more inclined to put potential setup money (and sale money) into something that will really do the job.
I couldn't help but spot this in the Marketplace:

[url="http://basschat.co.uk/index.php?showtopic=125209"]http://basschat.co.uk/index.php?showtopic=125209[/url]

recently. Plenty of power there; I have the AH250SMX myself, and have never needed more power than that, using various cabs from 1x10 to 2x10. These days I tend to carry a 1x10 and a 1x12 and still get asked to turn down!
Try a few different heads - Bass Bashes are often good for that, also there's a big show coming up in London - I'm sure others on here will have their favourites, but I once saw a top video explaing how Trace grow their Watts on local farms in Essex which is why their amplifiers are so loud!

[Bassnut62]

I used to have a Bassman 75 and it was easily loud enough to practice with. I now run a Bassman 135 into an 8ohm 1x15 or a 4ohm 2x15. It is comfortably loud enough to gig with in small to medium situations. So I don't think the original Fender design is a problem. Also don't forget these are valve watts not tranny watts, ie 135 is closer to 300w

[Subthumper]

I'd suggest getting it looked at. There's a number of things that could cause this problem. Get the valves tested-all of them, and as suggested get the bias checked and have the tech check out the power supply and smoothing caps. As said 100 watts of valves should be pretty loud even through very average cabs.
Good luck
Cheers Just

[Big_Stu]

[quote name='razze06' post='1147378' date='Mar 2 2011, 05:22 PM']It does! I'm just hesitant to take it for an expensive rebias and service, when it may not be worth the effort in the end.[/quote]
Phone Dennis Marshall, he's listed in the recommended amp techs pages for Edinburgh. NB. he's not in Bo'ness anymore so keep going till you get his Dunf address. He's an absolute master of valve heads, it's his life and hobby. He won't rip you off & he's a nice guy to deal with. Tell him I said hiya.

[Ancient Mariner]

And make sure you run it into the correct impedance cab. Valve amps are not like SS amps, that can cope happily with a range of impedances. They must only ever be run at the correct impedance (although you might get away with the wrong impedance for a while).

Since the previous owner suggested it was producing about 65 watts, I wonder if one pair of power valves is not working? Even so, a 65 watt valve bass amp should be pretty loud.

[icastle]

My understanding is that this is a home made amp reputed to be based on a Bassman 100.

I think you're going to find it very hard to find an amp tech willing to take on such an item.
Any that do will have a rather hefty bill for you at the end of it as they would have to unravel the build without the aid of known and accurate circuit diagrams.

[umph]

[quote name='razze06' post='1147322' date='Mar 2 2011, 04:34 PM']Some time ago I've acquired this home-brew fender bassman 100 clone head, and I love its tone. Fantastic clarity and all the rest.

Unfortunately, it is not very loud.

What do I mean by "not very loud"?

I have it plugged into my ashdown MAG 4x10, as my other more modern cabs didn't like it (TC RS212 and Tecamp s210), and I have to run it at full tilt (no clean headroom) to be able to practice with the (rock covers) band.

Given that this is nominally a 100W amp, I was expecting a bit more.
Now I knew it was a little underpowered when I got it, as the previous owner said that he had it checked, and it seemed to be putting out only around 60W.

My question here is quite simple: I would love to use it for live work, what do you recommend I do?

- Get a cab with higher sensitivity, more efficient, or with a shape and tuning more suitable to the head

- Get the amp serviced again, with a view to restoring its nominal power (or more)

- Sell it to someone who doesn't need the volume and get something else, maybe a real fender bassman 100 or 135

- More cabs is realy not an option, as I don't have the space or the inclination to use them.[/quote]

get it to a decent tech is all i can say, getting 60W out of 4 6l6's sounds like something is very wrong to me. How does it sound when you crank it?

[dincz]

If you manage to get its output up from 60W to 100W, you probably won't hear a great difference. A little over 2dB in fact - barely noticeable.

[hubrad]

It just occurred to me.. does it actually have a preamp section?

[razze06]

Thanks for the replies.

- I have another couple of amps and cabs that I regularly use for gigs and practice, so I don't really need another amp. I like the tone to bits though, and I'd love to use it more.

- According the notes scribbled on the backplate, the amp is designed to take 4 or 8 ohm loads. I never put more or less, or even in between (mixing 4 and 8 ohms)

- I would have thought that 100W would be plenty loud. For a couple of years I gigged and practiced with a 120W hartke kickback combo, so I think i'm entitled to expecting more sound out of this setup. We're not THAT loud...

- It does have a preamp section, and if I crank both pre and power section to full I get overdrive from hell. Actually, you get Motorhead Lemmy's tone by cranking the power section to full whack and about 1/3 of the way up on the preamp gain. Don't know it the pots are linear, i suspect not...

- Maybe i'll phone up Dennis Marshall, or some other tech. Big_stu, what's you real name, so that I can say hi on your behalf?

Keep them coming, I'd love to get this monster to its full potential!

[razze06]

[quote name='dincz' post='1148058' date='Mar 3 2011, 09:43 AM']If you manage to get its output up from 60W to 100W, you probably won't hear a great difference. A little over 2dB in fact - barely noticeable.[/quote]

True, I'm just suspicious of the quoted 60W.
Ultimately, I want to know if it can give enough for me to use in a regular band situation.

[Big_Stu]

[quote name='razze06' post='1148112' date='Mar 3 2011, 10:28 AM']- Maybe i'll phone up Dennis Marshall, or some other tech. Big_stu, what's you real name, so that I can say hi on your behalf? [/quote]
Strangely enough it's Stu If you mention my ex-Noddy Holder Hiwatt that he serviced for me he'll remember. He's a guru of valve amps, he's worked for some major league acts & while it was in he was getting offers from visitors for it. Great guy!

[umph]

[quote name='razze06' post='1148115' date='Mar 3 2011, 10:30 AM']True, I'm just suspicious of the quoted 60W.
Ultimately, I want to know if it can give enough for me to use in a regular band situation.[/quote]

So the distortion sounds like it should? no strange artifacts?

[razze06]

[quote name='umph' post='1148305' date='Mar 3 2011, 01:06 PM']So the distortion sounds like it should? no strange artifacts?[/quote]

It starts to distort heavily a little early IMO. Now that you mention it, sometimes it does strange, almost howling sound for a few moments. I thought that was just an artefact of the distortion, but maybe you can tell me more...

[umph]

[quote name='razze06' post='1148342' date='Mar 3 2011, 01:30 PM']It starts to distort heavily a little early IMO. Now that you mention it, sometimes it does strange, almost howling sound for a few moments. I thought that was just an artefact of the distortion, but maybe you can tell me more...[/quote]

I'd recomend getting it looked at, as with these homemade heads, you could have parasitic oscilation or any number of problems. Open it up and take some pictures of the guts.

[Roland Rock]

I had a very similar problem with my 100W valve head. Not loud enough for a rock band situation.
I took it in to my local guy (I'm lucky enough to live very near a very good valve guy, John Chambers). Here's the Techy bit from John's post mortem:

"This unit had been sold to Chris as a 100 watt head, but even with the 560 volts HT potential and tetrode connected, they were in cathode (self) bias. Running them like this as a pair, there is absolutely no chance of getting 100 watts! Once I had got the amp back to life, she was doing exactly 50 watts RMS, which is absolutely correct and spot-on with the original GEC specifications for running them under these conditions. I now phoned Chris and brought him right-up-to-date. I told him I could make the amp better by running the KT88’s in fixed bias and with a few tweaks. He gave me a free hand to do whatever was necessary"

"After all the work and modifications, and with all the conditions and specifications being within the original GEC data sheets for 100 watts from two tubes, she is now doing exactly 96 watts RMS"

As previous posts have stated, the result is not an enormous boost to the volume, but without doubt noticable, and it now can sit nicely with the rest of the band, and cope with medium venues (I mike up or DI for bigger venues)

Also, I had always thought that my bass had low output, not hot enough to really drive the preamp, and this didn't help with the volume issue. Got myself some new cables (OBBM) and the signal from the bass has boosted considerably. Just a related issue, although I understand that you have no problems pushing the amp into overdrive.

Edited March 5, 2011 by Roland Rock

[umph]

[quote name='Roland Rock' post='1150285' date='Mar 5 2011, 08:52 AM']I had a very similar problem with my 100W valve head. Not loud enough for a rock band situation.
I took it in to my local guy (I'm lucky enough to live very near a very good valve guy, John Chambers). Here's the Techy bit from John's post mortem:

"This unit had been sold to Chris as a 100 watt head, but even with the 560 volts HT potential and tetrode connected, they were in cathode (self) bias. Running them like this as a pair, there is absolutely no chance of getting 100 watts! Once I had got the amp back to life, she was doing exactly 50 watts RMS, which is absolutely correct and spot-on with the original GEC specifications for running them under these conditions. I now phoned Chris and brought him right-up-to-date. I told him I could make the amp better by running the KT88’s in fixed bias and with a few tweaks. He gave me a free hand to do whatever was necessary"

"After all the work and modifications, and with all the conditions and specifications being within the original GEC data sheets for 100 watts from two tubes, she is now doing exactly 96 watts RMS"

As previous posts have stated, the result is not an enormous boost to the volume, but without doubt noticable, and it now can sit nicely with the rest of the band, and cope with medium venues (I mike up or DI for bigger venues)

Also, I had always thought that my bass had low output, not hot enough to really drive the preamp, and this didn't help with the volume issue. Got myself some new cables (OBBM) and the signal from the bass has boosted considerably. Just a related issue, although I understand that you have no problems pushing the amp into overdrive.[/quote]


It's a bassman clone they wern't run in cathode bias like the linears etc.

[razze06]

[quote name='umph' post='1149017' date='Mar 3 2011, 10:38 PM']I'd recomend getting it looked at, as with these homemade heads, you could have parasitic oscilation or any number of problems. Open it up and take some pictures of the guts.[/quote]

I'll pick it up from the practice room on tuesday, I'll take some pics of the guts if I can

[Bassnut62]

Bassman amps are reknowned for great tone and incredible clean all the way to 11 on the dial. I don't reckon your amp should be distorting at all unless you put a dirt box in front of it. I guess there could be lots of reasons for your probs; but I think only a tech will be able to tell if there is a valve, component or clone-design fault with the amp.

I absolutely know what you mean about Bassman tone too - it's a thing of great beauty.
So worth persuing; but maybe you would be better to sell this clone and one of your other amps and go out and buy a real Bassman and go for the 135 this time.

[Roland Rock]

[quote name='umph' post='1151943' date='Mar 6 2011, 10:02 PM']It's a bassman clone they wern't run in cathode bias like the linears etc.[/quote]


Sorry, not added much value then!