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Old 7th October 2011, 09:39 AM   #1
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Default Best tube combo for an electric bass..

Hi everyone. I am currently looking for suggestions to complete a preamp + amp stage single channel to amplify the output of an electric bass.

I currently have some parts at my disposal which are...

1 a brand new ECOR XPWR139 EDCOR Electronics Corporation. XPWR139-120/240

4x 6JM6
8x 6FG5
2x 12AT7
3x 12AX7

I will obviously buy the rest....

output should be around 30/40w

Any suggestions would be welcome.....

Thanks
Alex
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Old 7th October 2011, 09:48 AM   #2
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I'm a bass player, and I'd like a combo amp+speaker to carry in one hand so in my case I'd want a solid state output stage and tube inputs - a hybrid amp. I'm not sure of what kind of size and weight the OP is thinking of! 40 watts of tube outputs is heavy!

Andy
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Old 7th October 2011, 10:03 AM   #3
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The amp is intended to be used in the house for practice only...Comfort of use is not essential...

I have built a very nice millet enginner's amp which we use with a DAC for music playback. I was hoping to build an all tube amp (preamp and power amp) designed solely for bass. To some extent the aestethics of tubes is a welcome bonus to this project so I'd rather stay all tube


Alex
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Old 7th October 2011, 07:57 PM   #4
kevinkr is offline kevinkr  United States
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Per FORUM policy this belongs in I&A - moved.
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Old 7th October 2011, 08:26 PM   #5
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by Alexontherocks View Post
The amp is intended to be used in the house for practice only...Comfort of use is not essential...

I have built a very nice millet enginner's amp which we use with a DAC for music playback. I was hoping to build an all tube amp (preamp and power amp) designed solely for bass. To some extent the aestethics of tubes is a welcome bonus to this project so I'd rather stay all tube


Alex
Your transformer, I think is slightly under powered fora a 40W bass amp. As a rule of thumb a PT needs about twice the VA rating at the final output power of the amp. So I think you are looking to build 25W bass amp with that transformer. It will do OK for home practice if you are by your self

But really even a bass practice wit others the amp needs 60 to 100 watts especially if you've got a five string that goes lower than low-E. Even a standard tuning 4 string goes to 41Hz. You need power because human hearing is not so good at 40Hz so the bass is "felt" rather than heard. But it it is just you in a quiet room 25W is more than enough.

That said the "standard" would be a pair of 6L6 in push-pull with a good "HiFi" type output transformer. Then a moderate amount of NFB. That would give you the clean bass sound most want. With more power available you could go with a pair of KT88. I think all tubes in that family (6l6, 6550, KTxx) have the same sound. For a preamp I'd keep it simple. A triode grain stage, catode folloer then simple one knob tone stack, master volume then long tailed pair phase splitter and then the two 6L6. Shoud give a solid 25W
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Old 8th October 2011, 12:29 AM   #6
tinitus is offline tinitus  Europe
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if it were me, I'd use the PT for a tube pre, and use a classD or SS power amp

but mostly because I would find it very impractical to use tube amp for practicing

I'm simply swithing on and off way too often
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Old 8th October 2011, 01:56 AM   #7
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Can't go wrong copying a classic. Based on what you said you were looking for I would recommend copying a Bassman 5F6A circuit with your 3 12AX7's and 4 6JN6's http://drtube.com/schematics/fender/...-schematic.gif
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