Bass amp idea

Fender Amp Discussion

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martin manning
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Re: Bass amp idea

Post by martin manning »

M Fowler wrote:I agree Martin the amp should be able to see 150w-180w right?
Yes, I think 180 or so. The KT88 data sheets show a pair in typical operation with B+ at 560V putting out 100W in ultra linear, same for PP with 560 plate/300 screen.
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RWood
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Re: Bass amp idea

Post by RWood »

I gigged bass with a 50w Fender Bassman head/4x10 cab for years, most of the time with two guitar players going through Marshall plexi 100w superleads.

I must have been stupid for not realizing I needed 300w, even though no one ever complained about me not punching through.

I did mike it a few times, but only because everyone else at the venue were doing it.
matt h
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Re: Bass amp idea

Post by matt h »

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didit
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Re: Bass amp idea

Post by didit »

Watts only go so far. One of my favourite bass amps is the Ampeg b15, which is roughly 35W. You need a quiet drummer and sensible guitar volumes. And mike or line into PA for any larger venue.

Wondering out loud why this is posted in the Fender zone? The Dual Showman by most reckoning is the best out of a bunch not great real amps for bass.

On to how to get 150-200W. The Hammond iron proposed looks OK. You might think about 1650RA too. Push on the voltage vs current but you will get less overall power. You will need to borrow designs or think hard about driving a quad of output tubes at those voltages.

For guidance/inspiration you might want to look at the Traynor YBA3 custom special. It was actually built up around 1650T output transformer with just simplified secondary wiring and no UL connections. Or at least that's what Kevin O'Connor notes in his chapter on it.

http://www.0rigami.com/vb/models.html#c ... ecialyba-3
http://www.0rigami.com/vb/YBA3__cool-schematics.gif

And then there's the BTO bass from Garnet.

http://www.webphix.com/schematic%20heav ... o_bass.pdf

After all that I'd still encourage thinking about a 60W derivative off an early b15 preamp and a pair of KT88s into a beefy 5K primary OPT.

Best .. Ian

PS -- PM if you'd like a bit more detail from O'Connor's TUT-3 chapter on Traynor CS.
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tony hunt
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Re: Bass amp idea

Post by tony hunt »

For 4 x KT88 bass use, I'm thinking 200W OT like the large Partridge iron in the old HiWatt PA amps.

I'd like park a schematic here which I drew up a while back for Chief Mushroom Cloud. It is the 4 x KT77 Burman Pro 4000 bass amp from the late '70s.
Huge custom iron and tone stacks that actually work. These are derived from the Pro 2000 series which Tracy described as a cross between a rabid Twin and a HiWatt on steroids, or was it the other way around?

tony
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RWood
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Re: Bass amp idea

Post by RWood »

didit wrote:After all that I'd still encourage thinking about a 60W derivative off an early b15 preamp and a pair of KT88s into a beefy 5K primary OPT.
That sounds like good advice.

That's what I was eluding to earlier. 99% of all gigs I've played in 40 years didn't require over 50 watts, and when it did I miked or lined out to board or power amp.

I have also walked out of many clubs because the band was just too loud.

60 watts of pure tone can be driven to untold watts into clean power amp, but in my opinion (which ain't worth a hill of beans) pure tone is harder to achieve from huge amp if needed at lower volumes.
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Aurora
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Re: Bass amp idea

Post by Aurora »

A better-designed-than-most loudspeaker/cab combo should easily double the apparent wattage......
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M Fowler
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Re: Bass amp idea

Post by M Fowler »

Thanks for the replies.

Got my chassis and waiting on Transformers non-stock items. :)

Going to give O-netic's a call about their 280w transformers I read about.
Want to try a six tube 6550 bass amp too. Got the bug while working on an SVT Classic.
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briane
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Re: Bass amp idea

Post by briane »

Ive built a few tube - bass amps - over the years - yep power is a real problem at 50watts - 100 seems fine for most for recording/practice - more would be needed for a large venue as already said. Ive had good luck with a 6550x2 setup.

I dont think your PT is going to power a kt88x4 - that can be a real problem in big amps - just aint enough current for all of them.

I build off the marshall 1986 style - then add a SVT cathode follower and LNFB - sounds great - and those 2 extras really add to the clean headroom.

Ive learned over the years - Its just not economical to build bass heads - I think I would spend about 2-3 k juts in parts to build a 300 watter - and I can get a really nice svt for 950 or so - poor a bit over a k at most.

so in the end - cheaper to buy an svt is what I tell the bass guys that come a looking now.
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M Fowler
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Re: Bass amp idea

Post by M Fowler »

SVT amps suck because they're damn hard to work on.

What PT would you suggest?
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didit
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Re: Bass amp idea

Post by didit »

What PT would you suggest?
The 378CX mentioned at the start of the thread will be just fine. The Hammond 300 series is quite conservatively spec'ed. As I mentioned earlier Kevin O'Connor has a bass amp quad KT88 design based on it, which in turn is derived from Pete Traynor's YBA-3 custom special. This is an overgrown Bassman derivative so pretty much precisely what you've set out to build.

Just don't forget the fan.

Best .. Ian

ps -- again, PM and I'll happily pull details for you from K.O'C's "Generations of Tone"
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gui_tarzan
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Re: Bass amp idea

Post by gui_tarzan »

M Fowler wrote:SVT amps suck because they're damn hard to work on.
I'm glad I don't have to work on my SVT that often. ;)
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M Fowler
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Re: Bass amp idea

Post by M Fowler »

Oh I forgot one other thing I need a choke and do not have a lot of room for a very large frame choke and ideas?
boots
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Re: Bass amp idea

Post by boots »

FWIW when I was younger and playing bass in garage bands at outdoor kegger parties, I had a 300 watt SS Kustom bass amp with 2x 15's, and I was glad to have that much power. It was just perfect for playing with a full band, and I had a little reserve so the amp always sounded very rich and full.

Every other time I've used smaller bass amps (like in church), I always felt like 50 watts just got buried by the drums and other guitars.
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boots
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Re: Bass amp idea

Post by boots »

Mark, I've still got a PT from an old Drake power supply that might be good for a bass amp. I don't remember the specs on it but can look when I get home tonight. It is a pretty big chunk of iron and I remember it had a separate winding for a bias supply. Don't think it has a 5v winding though.
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