30ish watt bass amp

[Beezerboy]

I want to build a bass amp for a friend. looking for something in the 30-40 watt range. probably a combo, and as light as is realistic. I search for demos on tube bass amps and mostly I get guitar guys playing through bass amps. this is for a bass... for a guy that can really play the bass.... for the last 50 years.... play the bass, for a living... its all he does

what else is there besides the 5F6A?    and, I would prefer single channel, single input.... straight up fat tube amp

[Latole]

 5F6A  Fender Bassman is a good choice . Layout and schematic are available.

[tubenit]

Bobby Vega talks Fender P Bass and Ampeg B-15 on EMGtv - YouTube


Ampeg_b15n68_portaflex.pdf (el34world.com

Ampeg_sb127868_portaflex.pdf (el34world.com)

[tdvt]

Speaking as a bass player myself, the B-15 is a great suggestion. An iconic bass amp.

Further, a single-channel version, in a combo with a NEO speaker, would make a killer portable set-up.

I am surprised that configuration isn't already a thing out there (unless it is & I haven't heard of it..)

I was always a 15" guy but currently, & happily, play through a 12" KAPPALITE 3012LF. Sometimes X 2, but usually just one.

Less heavy, sounds great.

[tdvt]

If your friend is full-time, it wouldn't surprise me if he already had some iteration of a B-15.


But you have me pondering a new project....

[Beezerboy]

He's got a Hartke rig for his main amp. he always talked about some cabinet with 4 tens that he liked. I'm thinking maybe 2 tens in a combo. 25-35 watts is plenty for the small venues we have around here. I made him a lightweight (hollow) P bass last year because his 5 string Smith is just too heavy for an old man

yeah.... the B-15 deserves a look. thanks

[mresistor]

I vote for a B15 Porta flex  and older one ..   they are outstanding.. and very portable.


Or even something like this..    https://reverb.com/item/62570898-ampeg-sb-12-portaflex-2-channel-25-watt-1x12-fliptop-guitar-combo-1965-1971-black

[Beezerboy]

look what I found....

https://www.talkbass.com/threads/b-15-clone-build.1185039/


I wouldn't be building it to look like the original, so the trannys only need to match the circuit. the OT he uses is a Hammond 1650HA because he says that the one that matches... can't seem to find that one

[sluckey]

Look here...

https://www.hawkusa.com/search?search=1650ha&field_current_stock=All&field_rohs_compliant=All&items_per_page=10

[Beezerboy]

thanks! I forget about those Hawk guys. they have the stuff, and seem to have the good prices.

[AmberB]

You could use the transformers from a Bogan CHB-35A and change the tubes from 7868s to 7591s, same out put transformer spec for both tubes.  Ampeg used the 7591s in a few of their amps.
I can't say how available those Bogan tube PA amps are these days, but I've converted several of them to guitar amps.
A B-15 clone would be a pretty good small bass amp.
I played bass through a Fender silverface Bassman 50 for a lot of years.  I also had a Bassman 100, but it had more power than needed for the size of most of the venues that we played in.  I used the 50 watt amp with a 1-15 Musicman cabinet, it did the job.

[Lectroid]

@AmberB,

I'm wondering about a Bogen CHB-20B to be a donor patient.  With the ECL86, it looks to put out  around 8-10W.  Any experience with one of those?

No, cancel that.  Once I searched here, I found lots of Bogen threads.  Price is right so it might be worth the gamble.

[mresistor]

Interestingly  in the CTG parts list they reference Weber Transformers and of course they are less expensive
http://ctgelectronics.weebly.com/custom-amplifier---fcbn-51b.html

PTW022798
WOT45

[AmberB]

@AmberB,

I'm wondering about a Bogen CHB-20B to be a donor patient.  With the ECL86, it looks to put out  around 8-10W.  Any experience with one of those?

No, cancel that.  Once I searched here, I found lots of Bogen threads.  Price is right so it might be worth the gamble.

The ECL86 tube can put out 18 to 20 watts in push pull.  I modified A CHB-20 to guitar amp configuration and it sounded good and got pretty loud through a 12 inch speaker.  I have another CHB-20 chassis that needs a proper power transformer.  The PT had been replaced before I got it and the voltage was too high for the ECL86 tubes.

[Lectroid]

Did your guitar conversion run the B+ at about the same levels  (A = 400V, B=375, etc?)  as the stock PA amp?

Did you add grid blocking and/or screen blocking resistors to the power tubes?

[AmberB]

Did your guitar conversion run the B+ at about the same levels  (A = 400V, B=375, etc?)  as the stock PA amp?

Did you add grid blocking and/or screen blocking resistors to the power tubes?

I used the stock voltages for the amp.  I don't remember if I put in any grid or screen resistors.
I modified the preamp section to approximate the Ampeg Gemini II preamp.  I know there's a couple of threads on this forum about the CHB-20, one of them being the thread that I started.

[Lectroid]

I'll look for those.  Thanks!