Bass Amp

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crgfrench
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Bass Amp

Post by crgfrench »

What is the best tube amp (to build) for bass that would be along the lines of an 18W or 36W? one that would pair well in a band with a bluesbreaker being used by the strat guitarist? I'm thinking of a cathode biased 5F6-A variant...
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Re: Bass Amp

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crgfrench wrote:
Sun 10/04/20 9:13 pm
What is the best tube amp (to build) for bass that would be along the lines of an 18W or 36W? one that would pair well in a band with a bluesbreaker being used by the strat guitarist? I'm thinking of a cathode biased 5F6-A variant...
Hmm, a 2x12 Bluesbreaker (and with a Strat) is going to be pretty loud. I'm not sure a 36W (EL84s?) as a bass amp is going to be able to compete? Maybe with a pair of EVs or other very efficient speakers? To me, bass and guitar sound best and complimentary where each is in its own frequency range and there is sufficient headroom to where each amp isn't collapsing into blocking distortion. Otherwise it can turn into a muddy mess with no definition or dynamics. I know guitar amps can certainly be bass amps, but a bass amp would need to be able to deliver enough power in the low frequencies to keep the sound coherent and cut through, unless distortion is desired. I think the choice of amp would also depend on how heavy-handed or controlled the drummer is. I am building a friend a 140Wrms 4xKT88 ultralinear bass amp. He likes a good clean and punchy sound. The power supply will be choked (the whole amp, not just the screens) and well-filtered. Speaker cabs will be a pair of Thiele TL606s with EVs or Eminence speakers. He also plays with a very good, but fairly heavy handed drummer.
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Re: Bass Amp

Post by ViperDoc »

colossal wrote:
Mon 10/05/20 8:06 am
crgfrench wrote:
Sun 10/04/20 9:13 pm
What is the best tube amp (to build) for bass that would be along the lines of an 18W or 36W? one that would pair well in a band with a bluesbreaker being used by the strat guitarist? I'm thinking of a cathode biased 5F6-A variant...
Hmm, a 2x12 Bluesbreaker (and with a Strat) is going to be pretty loud. I'm not sure a 36W (EL84s?) as a bass amp is going to be able to compete? Maybe with a pair of EVs or other very efficient speakers? To me, bass and guitar sound best and complimentary where each is in his own frequency range and there is sufficient headroom to where each amp isn't collapsing into blocking distortion. Otherwise it can turn into a muddy mess with no definition or dynamics. I know guitar amps can certainly be bass amps, but a bass amp would need to be able to deliver enough power in the low frequencies to keep the sound coherent and cut through, unless distortion is desired. I think the choice of amp would also depend on how heavy-handed or controlled the drummer is. I am building a friend a 140Wrms 4xKT88 ultralinear bass amp. He likes a good clean and punchy sound. The power supply will be choked (the whole amp, not just the screens) and well-filtered. Speaker cabs will be a pair of Thiele TL606s with EVs or Eminence speakers. He also plays with a very good, but fairly heavy handed drummer.
Putting it out there if you ever want to share that schematic. Sounds awesome! No pressure.
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Re: Bass Amp

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ViperDoc wrote:
Mon 10/05/20 4:13 pm
Putting it out there if you ever want to share that schematic. Sounds awesome! No pressure.
I may when I get it finished. The phase inverter will be a 6SL7 long tailed pair, followed by a 12AU7 cathode follower driver, into a 4 x 6550/KT88 power section running in ultralinear. I am still working on the preamp section but will be 6SL7 as well. The transformers were custom wound by Heyboer and the choke is as big as a 50W Plexi OT :lol: The output transformer is a clone of a Dynaco A451 and it and the PT are each the size of a small pumpkin. Totally ridiculous, but it should sound pretty killer. I got some barely used KT88 pulls out of an old Macintosh stereo. My buddy is having two 1x15 Thiele design TL606 cabs built. The tonal goal is Geddy Lee circa 1981.
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Re: Bass Amp

Post by ViperDoc »

Sounds like a decent "Caress of Iron". WOW. Can't wait to hear more about that!
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Re: Bass Amp

Post by crgfrench »

I was thinking of a pair of 6L6s but maybe it would need a quad...
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Re: Bass Amp

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ViperDoc wrote:
Mon 10/05/20 5:44 pm
Sounds like a decent "Caress of Iron". WOW. Can't wait to hear more about that!
Yes!! \m/ 8) \m/
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Re: Bass Amp

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crgfrench wrote:
Mon 10/05/20 5:55 pm
I was thinking of a pair of 6L6s but maybe it would need a quad...
I think it all depends on the situation, whether the group plays at reasonable/moderate levels, or, it's about moving serious air and making pant legs flap!
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Re: Bass Amp

Post by crgfrench »

I dont believe I've seen a design where a gain stage (the CF) follows a PI. Usually the PI is the last thing before the output tubes.
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Re: Bass Amp

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crgfrench wrote:
Mon 10/05/20 6:05 pm
I dont believe I've seen a design where a gain stage (the CF) follows a PI. Usually the PI is the last thing before the output tubes.
Check out this SVT power amp schematic. The driver supplies grid current when the power tubes are driven to AB2. I am using a dedicated +/-160VDC rail to supply the follower and two bias circuits, one for each pair of KT88s.
svt6550-jp.gif
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Re: Bass Amp

Post by colossal »

Oh, and the cathode follower is directly coupled to the grid, no coupling cap, so no blocking distortion.
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