suggestions for a bass amp build?

[frpax]

I'm wanting to build a bass amp now. Any suggestions? I'm wanting something high wattage... not sure if i want a combo or head/cabinet. Help me out!

[sluckey]

Sunn 2000 or Model T. Ampeg SVT.

[SILVERGUN]

It helps me to have a clear goal early, so I'm suggesting that you forget about a combo for a high wattage bass amp. It would surely come out to over a hundred pounds with the 'right' speaker.
 
Also, I would suggest thinking about alternate methods for your power and output transformers.
If it was me, I'd get a dedicated filament transformer based off of how many and which type of output tubes I decided to use, and then look for a dedicated HV transformer to get B+ and tap bias off of it.
 
I'd also consider using 2 output transformers, rather than trying to source one that will handle the job at 200+ watts....(I'm assuming that by "high wattage" you're talking 200 watts min.)
*Hammond has one OT (1650W) that will handle 280watts output and it weighs 28lbs. and costs $300
 
I'd also consider just going on my local Craigslist and picking up a used amp and getting on with my life, cuz this is one huge, expensive project.
 

[Willabe]

so I'm suggesting that you forget about a combo for a high wattage bass amp. It would surely come out to over a hundred pounds with the 'right' speaker.

+1

Also, I would suggest thinking about alternate methods for your power and output transformers.
If it was me, I'd get a dedicated filament transformer based off of how many and which type of output tubes I decided to use, and then look for a dedicated HV transformer to get B+ and tap bias off of it.

Why?

It will cost more, weigh more and take up more space on the chassis. 

I'd also consider using 2 output transformers, rather than trying to source one that will handle the job at 200+ watts....(I'm assuming that by "high wattage" you're talking 200 watts min.)
*Hammond has one OT (1650W) that will handle 280watts output and it weighs 28lbs. and costs $300

Again, why?

It will cost more, weigh more and take up more space on the chassis.

[SILVERGUN]

Also, I would suggest thinking about alternate methods for your power and output transformers.
If it was me, I'd get a dedicated filament transformer based off of how many and which type of output tubes I decided to use, and then look for a dedicated HV transformer to get B+ and tap bias off of it.

Why?

It will cost more, weigh more and take up more space on the chassis.

I'm suggesting "free thought"...I see too many guys worried about trying to source the exact part # off of a schematic, when there are always other options.
If he's doing a head only, then I'm not really concerned about weight or space on the chassis.
Weight increase 'could be' marginal and space doesn't have to be an issue if you start with the right plan and chassis.
Cost is arguable, cuz if you can strap 2 smaller xfmrs in series to get to where you're going, they could be much less expensive than a dedicated all-in-one.
....or just using a repurposed toroid with one big 'linked' secondary is something I've been eyeing. (something I have laying around)
 
Let's say he wants to run 8 - 6550 output tubes....how many 'classic tube' PT's have a 13 amp filament winding, how much will it cost, and how heavy will it be?
Hammond 379wx would probably get him there, but 32 pounds later (and $463.00 from Newark) not sure it's a good idea.
 
 

I'd also consider using 2 output transformers, rather than trying to source one that will handle the job at 200+ watts....(I'm assuming that by "high wattage" you're talking 200 watts min.)
*Hammond has one OT (1650W) that will handle 280watts output and it weighs 28lbs. and costs $300

Again, why?

It will cost more, weigh more and take up more space on the chassis.

Again, free thought...
Bigger single unit aint' guaranteed better option, that's all
 
This is all subjective and based off of how high his "high output' pie in the sky is. 
 
Happy New Year!
Dave 

[frpax]

It helps me to have a clear goal early, so I'm suggesting that you forget about a combo for a high wattage bass amp. It would surely come out to over a hundred pounds with the 'right' speaker.
 
Also, I would suggest thinking about alternate methods for your power and output transformers.
If it was me, I'd get a dedicated filament transformer based off of how many and which type of output tubes I decided to use, and then look for a dedicated HV transformer to get B+ and tap bias off of it.
 
I'd also consider using 2 output transformers, rather than trying to source one that will handle the job at 200+ watts....(I'm assuming that by "high wattage" you're talking 200 watts min.)
*Hammond has one OT (1650W) that will handle 280watts output and it weighs 28lbs. and costs $300
 
I'd also consider just going on my local Craigslist and picking up a used amp and getting on with my life, cuz this is one huge, expensive project.

Thank you for your suggestions.

While Craigs List, eBay and Reverb are certainly options for buying used gear, I'm looking more for the personal satisfaction that I get from building one. Also, I'm not really looking for a kit, per se, but a prebuilt chassis would be a wonderful thing.

I agree about the weight of a combo, so I have ruled that out. Head and cabinet for sure.

As for wattage, I was thinking at least 100w, but more might be nicer. In my tube inventory, I have 4 EL34's and 3 12AX7's and a 12AU7 (I think). So, I'd like to use those if at all possible.

Also, I'm not looking for anything super elaborate to build. Just a nice bass amp that I can gig with. (although an XLR out would be nice to have in certain situations)

[SILVERGUN]

As for wattage, I was thinking at least 100w, but more might be nicer
 
Then my initial answer was an over-reach.
We DO like to see people build amps around here so please do not lable me the "fun police".
 
It has been discussed a lot that 100 watts is usually not enough for a stage bass rig, but it all depends on the stage, player, band, type of music, etc.
 
4- EL34s is a very common platform for 100 watt amps, so your current tube stock can get you where you want to be. If you're OK with a 100 watt bass amp, then so are we, and you can get there.
 
Take a look at sluckey's suggestions in Reply#1
You 'could' amend any of those schematics to utilize your EL quad, and you will probably be sacrificing some headroom in the process.
 
You are 100% correct in wanting a pre-punched chassis because it will speed your process by limiting choices/decisions. If you are going to stick with a 4 - EL34 platform then there is no reason you cant use one of these and just reposition some holes as needed.
http://www.ebay.com/itm/100-watt-plexi-style-Tube-Amp-Chassis-/322114620940?hash=item4aff870e0c:g:DxYAAOSwstxU7AGX

[Willabe]

If he's doing a head only, then I'm not really concerned about weight or space on the chassis.
Weight increase 'could be' marginal and space doesn't have to be an issue if you start with the right plan and chassis.
Cost is arguable, cuz if you can strap 2 smaller xfmrs in series to get to where you're going, they could be much less expensive than a dedicated all-in-one.

Agree to disagree.

No way I'd start a new build for a BIG amp (maybe on a small amp, 20w and under) based on using 2 x PT and 2 x OT. To me it's just asking for trouble, longer wire runs inside the now larger chassis, orienting the iron for best noise rejection.

Cost is arguable, cuz if you can strap 2 smaller xfmrs in series to get to where you're going, they could be much less expensive than a dedicated all-in-one.

We know Sears Silvertone had a few amps with 2 x OT strapped together but they probably bought those on a close out and their not great amps anyway.

If it had cost savings, Fender and others would have done it on a regular basis.     

Let's say he wants to run 8 - 6550 output tubes....how many 'classic tube' PT's have a 13 amp filament winding, how much will it cost, and how heavy will it be?
Hammond 379wx would probably get him there, but 32 pounds later (and $463.00 from Newark) not sure it's a good idea.

With 8 x 6550 = ~~300w to ~~400w, it's gonna be heavy and expensive.

Going with a torid PT, like you said, might be the best option, for the PT.

Most companies that currently make BIG bass amps use torids for the PT.

[ampedup]

I built a sunn 2000s and really like it. It has not been used in a really loud band situation so I can't comment on if 120 watts is enough. It is a very simple amp, but gets great tone without the need for a lot of tone shaping options.

[frpax]

It has been discussed a lot that 100 watts is usually not enough for a stage bass rig, but it all depends on the stage, player, band, type of music, etc.
 
4- EL34s is a very common platform for 100 watt amps, so your current tube stock can get you where you want to be. If you're OK with a 100 watt bass amp, then so are we, and you can get there.

100w is about my minimum. If I go that route, I'd for want and XLR out so that I can run from amp to mixing board. That's my thinking anyway, until someone changes my mind!

[6G6]

I am a bass player.
These days 100 watts isn't going to cut it.
The Sunn 2000S is simple and Dynaco transformers are easy enough to find.
Use  SS recto for cooler operation, simplicity and higher voltage and out put.
Even though it's rate at 120 watts, that is a very conservative rating.
It can be pushed to more like 200 before you can hear distortion.

[MFowler]

I built a 200w bass recently running 4 KT88's.


Hammond 1650TA OT 1k9
Hammond 378CX PT
Hammond 194F choke 5h 120mA 115R
Filament transformer


These transformers do not cost $300 from Digi-key.
reused chassis from friend, board made from food serving tray and I had all the other parts on hand.

[John]

Just because I'm curious, about how much does it weigh?


And I like that serving tray thing!

[sluckey]

That's a powerful looking amp. But I'm surprised the OT is not bigger for a 200W amp.

[MFowler]

Not sure how much is weights the owner uses it every weekend.


Slucky, before I started I asked some professional amp builders for transformer recommendations for 180-200w bass amp and everyone was in agreement these are the transformer I should use.  That 120w OT is capable of more I was told.  I have two 150w transformers on the bench that are not nearly as large.


Mark