4 x KT88 Bass amp ?

[Smokebreak]

Traditional tube amp line-out is usually taken from the OT secondaries and will require 1. Power tubes operating 2. A load as you mentioned.

Ok I'm starting to get it.So for this^^^, what are the output options? Would you go straight to the board? DI box inbetween? What options would balanced vs. unbalanced give you? i guess you could go to another power amp, but you're getting output tubes sent, as well

An alternative would be a line-out pre-PI. Some modern tube amps turns the preamp tubes on in Standby, allowing for a preamp line-out signal to be sent to PA/Slave power amp. The power tubes turns on when you switch out of Standby. Or add a separate switch that cuts the cathode connection to ground for all power tubes, that will turn them off.

So even if I switch the outputs section's cathodes, I'll still need a load, correct?(without the standby switching)

[Reeltarded]

With guitar I have control issues to deal with that a bassist wouldn't normally encounter, but I use Palmer PGAs to attenuate and then something complicated happens and then a 2000w stereo power amp.

I have been getting the Palmers for less than half price on Ebay. They work as intended for a 40-50w amp but even though they say it can do 100watter with no problem.. Uhh.. that last attenuate light comes on at about 60w..

Tungsten bulb attenuation. Very groovy. Not at all like those hard assed silent speakers I threw away.

Palmer plug. If you look at what the PGA-04 does, that is what you'll need that amp to do. A couple other things..

I say 40-50w is perfect for the general machine because it can do smaller without the attenuation and 'reamp'. With a large cab, a power amp, and attenuation it becomes the monster. The 50w rig would still be a serious amp, not a toy.

[gui_tarzan]

I'm all for tubes, but I'm also financially challenged so having a full-tube bass amp is out of the question for me. My rig is an Ampeg SVT-III rack-mount head (non-pro) with a tube pre-amp and a solid-state power amp that gives me all the volume I need in small venues and works great through the PA in bigger venues and outside.

If it's a project amp he wants, An Ampeg or Sunn clone would be my choice. Otherwise a tube pre with a solid state power amp would be far more economical. KT88s aren't cheap! And I get 200w at 8 ohms (single EV SRO 15" in my case) or 350 with 4 ohms (two EV SRO 15s) and it does everything I need it to do.

[KellyBass]

Bass players speak out!!

A 2 kt88 Ampeg or Sunn-ish amp is definitely the way to go. The Hiwatt tone stack works great for bass as well. I fact, got a 2 KT88 build planned for the winter. It'll be based on a Sunn 200S. I'll be using some of the great Dynaco clone iron that's out there. It's going to be SS rectified and I've got 2 giant mallory 800uf can caps set aside for PS of this project. I'll also be attempting to make some changes in the driver tube area. The stock setup is the weak point of this amp, IMHO. Otherwise, the 200s amps sounded great back in the day. I've got a schematic and layout ready to go and I'd be more than happy to share what info I've gathered.

[jazbo8]

[img::]http://www.diyaudio.com/forums/attachme ... 60071p.jpg[/img]

More here.

[bb5000]

Ok I'm starting to get it.So for this^^^, what are the output options? Would you go straight to the board? DI box inbetween? What options would balanced vs. unbalanced give you? i guess you could go to another power amp, but you're getting output tubes sent, as well

If the line-out has the proper level, it could go directly to the board. You could have a "Line-Out level" pot for fine adjustment. A balanced output allows for longer cables.

I have built a Weber AB200, this one has an effect loop, so on that one I can connect a DI box in the loop and use the amp's Master Vol as stage volume control, while the preamp goes through the PA.

So even if I switch the outputs section's cathodes, I'll still need a load, correct?(without the standby switching)

When the power tube's cathode connection is broken, the tube is turned off, so in that state you won't need a load. If someone should happen to switch on the power tubes by mistake you're in trouble though..

[JazzGuitarGimp]

If someone should happen to switch on the power tubes by mistake you're in trouble though..

Key switch.

[Smokebreak]

Thanks a bunch for all the input, and for helping explore all the options. I'll let you know what the verdict is.

[roberto]

I've done some hybrid bass amps, some with just one 12ax7 for a clean preamp plus a mosfet CF, some with a PI and a PPIMV to include that sound. Then going into a class D power amp.

I have to say that in both cases the sound is very tubey and there's no need for a tube power amp. I can say I prefer class D over tubes for bass amps, as they handle better all the kinds of cabs.

In case of PI saturation, I've sometimes included a switch to change the tail resistor of the PI.

I think I've posted something about the modded baxandall I've used in some amps.

[roberto]

If a power tube is absolutely needed, I'm with xtian for a SE with an internal dummy load and a line out after the OT with just a level control to load an exterrnal SS power amp.

[RCGPNY1]

I am also of the opinion that a hybrid is the way to go. I remember breaking my back over the years carrying my freinds SVT, Sunn 2000S, and 200 watt Hiwatts. Check out Andy Fuch's "Bruiser Jr". A very amgegish(is that a word...anyway)
front end with a 500 watt class D poweramp. It sounds amazing! It has all the facility one could need.....

[M Fowler]

This follows along with the same idea Smokebreak had.

I finally got started on my four KT88 bass project I've been wanting to build for quite a while now. Chassis donated by Jana, thank you Jana.

Jelle suggested these transformers and they are huge. 378CX PT and 1650TA OT. Need to get a choke yet.

Beasley food server tray for board.

[Smokebreak]

That's what I'm talkin about Mark! Those were the trannies I was looking at. I'll be looking forward to your build. Turns out my guy found a cheap used Mesa, so I'm outta business for now.
Hopefully I'll get to build one soon.

[M Fowler]

That's what I'm talkin about Mark! Those were the trannies I was looking at. I'll be looking forward to your build. Turns out my guy found a cheap used Mesa, so I'm outta business for now.
Hopefully I'll get to build one soon.

I'll try do it right.

[beasleybodyshop]

looks good Mark! I see my lunch trays are going to good use