Vintage tube Bass amp Question

[stubbyfex]

Thanks all for the kind words!

Doctord02: Are you hooking up your OT with the screen taps? I think it adds a little more power. I read in the "Audio Cylopedia", (one of the Best tube books), that the UL taps are somewhere in between a triode hookup and a pentode hookup in terms of power and tone. I used them on my build, and couldn't be happier with the sound.

[doctord02]

My OT does not have ultralinear screen taps like that massive Hammond. I'm pretty much just wiring up a knockoff of the Hiwatt DR201 circuit - but adapted to the components I had or could get easily.

[koffee_iv]

A while back I built a "monster bass" head. I used four KT88's for about 200 watts of pure tone. The output transformer was a behemoth 30 pound Hammond Hi-Fi transformer that could go down to 20 hz at full power! I also used a toroid power transformer. The front end was similar to a Marshall super bass model. Wow, that thing would shake the walls! I put it in a Marshall sized head box. The weight wasn't too bad, about 50 lbs. I also added a line out jack so if more was wanted, the pa could be utilized.

Very cool! I saw the pic's. You say the front end was similar to a super bass. Did you modify or use another schem? What was your cost on this? Unfortunately I'm cost concious, thats why I was considering the 1/2 SS route. The iron is so pricy in big watt amps. Did you design your power section or use an existing schem?

I have a 69 B-25 (OT is toast) that is 50 watt. When jamming you had to sit in front of the speaker to hear yourself. I don't know if it was because the OT was already going out. I ended up using the pre out to the board and power my JBL mains to record off the woofer of the mains... not bad.... sample: http://www.electricchurch.net/music/IfY ... elieve.mp3 Compression and eq during master. Yes I would eq this a little different now. I'm still learning. I prefer the writing aranging and making music than the technical engineering aspects of the equipment. But I'm all I got right now. Kids are not interested in the tech part. The guitar amp is a P1ex design my 13 year old son built. He is the one who builds and repairs our vintage type stuff. I just come up with the ideas.

I had thought to build a four channel line level pre-amp with an SVT, Super Bass, Sunn, and Messa pre hooked to the SS power and an A/B box for channel selection or combining.

I guess thats kinda the long and the short of it. I really like the looks of your SS (Super Stubbyfex). Do you have any clips?

What thinkest thou?


.

[stubbyfex]

Hello! Well, the front end of my bass amp is from a Marshall Model 1987, up to the phase splitter. It has a "treble" sounding channel, great for the pop/slap bass parts, and it has a "bass" channel for the thunder! The power amp is very similar to the Marshall 1986, Super bass. Theirs uses (2) EL34's, and mine uses (4) KT88's. I had to up the bias supply, and I added larger filter caps, and I used a toroid power transformer that will supply lots of current, both fils and high voltage. I think it is good for 450ma. I think the choke is 40 henry. I used Sozo caps, regular carbon composition resistors, CTS brass shaft pots and Switchcraft jacks. Cost, well the chassis was custom made, the toroid was custom wound, and the massive Hammond output was over $200 by itself. I think I have just over $1000 in the chassis and parts alone. With our dollar dwindling, the Hammond transformers are getting more and more expensive, because they are made in Canada. This design was fun, I more or less took two different amps and combined them into one. As far as the preamp goes, I've done that also, I made the front end of a Fender 6G6 amp, and mounted it in a 1 space rack box, and then used it to drive a SS power amp. I had a custom toroid power transformer wound for it too. They are somewhat "self shielding" so the noise and hum were next to nothing. I put stereo output jacks so it could drive a stereo power amp. It sounded great.
I'll be able to post some clips before too long. With work, family, band and church, I stay busy. Thanks for the questions.

[koffee_iv]

I'll be able to post some clips before too long. With work, family, band and church, I stay busy.

Thanks Stubby. I understand on the responsibilities. I'll not be able to check replies till the end of the week since I'll be gone working. Are you in a church band? My family plays in churches wherever we are invited. We play for free so we can't get confused about why we are doing it. Our band website is on the bottom of the posts.

Do you sell amps or just repair? Is this your day job or moonlight job?

[dr. who]

so do you get the correct amount of low end with punch if you have a 4x8" cab coupled with a 1x15" or 2x15"? I like the old 8x8" cabs that are almost as tall as I am for their punch, but the low end of a loaded hard truckers 2x15" will almost make you shart yourself if you hit a low B and are too close. I am interested in the 300w dumbleland style bass amp, so using the SSS style filter controls you have an eq to adjust the high and low after the tonestack.

[stubbyfex]

koffee_IV:
I play cello and bass in a church band, and in a rock band.
I've owned/operated a tube amp repair business for over 25 years. I also build custom tube gear too, but repairs have always been my "bread and butter".

dr. who:
Hey! I'm a total doctor who fan, in fact I've named my two kids after characters. I love to use a 15" speaker. I recently changed the one in my combo amp to a 15" Jensen Neo, and the one in my single 15" extension cab to a Eminence Kappa Light 15". I really like the tone of each. The Jensen is better for guitar/cello, and the Kappa Light is better for bass. The Eminence one actually comes in two flavors, one a PA style speaker, and one a Woofer style that doesn't go as high. I'm using the woofer style one with bass. The tone is there, and my back is thanking me for doing it too!

[koffee_iv]

so do you get the correct amount of low end with punch if you have a 4x8" cab coupled with a 1x15" or 2x15"?

koffee_IV:
I play cello and bass in a church band, and in a rock band.
I've owned/operated a tube amp repair business for over 25 years. I also build custom tube gear too, but repairs have always been my "bread and butter".

dr. who:
I love to use a 15" speaker. The Eminence one actually comes in two flavors, one a PA style speaker, and one a Woofer style that doesn't go as high. I'm using the woofer style one with bass. The tone is there, and my back is thanking me for doing it too!

dr. who, Thats what I was thinking. I plugged my bass into my 65wattx2 (12in speakers) Peavey stereo chorus and it was so punchy but not bright (we're not into slap) and the overdrive was real tight. I've considered getting a cheap beringer combo to mate with this to get the lows but the peavey guitar amp would be more of the out front sound.... trying to stay cheap. I know you get what you pay for, but I'm trying to get more portable for small rooms. (don't need a 2000watt PA) I guess if I built a cab I'd put 2x10 on top and a 15 or 18 below and let my boys haul it around

Stubbyfex, have you ever put a spectrum analyzer on your super bass to see how low it goes?

My daughters would love a cello! we have a little of everything around here but no serious orchestra instruments... just violins. Right now the serious wish list is for a flute and bagpipes. we just bought a 88 key midi controller and the IK philharmonic software for our orchestra instruments on recorded tracts.

We have no amp or tube repair people here. My son and I have chatted up the local tv repair guy. He has a large room full of tubes (old ham). he has been helpful. I have a 1969 Ampeg B-25. The OT is shot. The Iron is $130.00. I don't want to repair it if it's not worth much more than the price of the OT. It wasn't loud enough anyway. It could have been it was going out when I got it....

[stubbyfex]

I have swept several amps that I used the Hammond 1600 series output transformers in. They are wonderful! Below is a link to their specs. It seems to me that the 3db down point is below 20 hz. It will even pass 10 hz with a fairly respectable waveform, but with lower volume. The high end is maybe up to 10Khz, mainly due to the large coupling caps in the amp. For a bass, there is very little energy up there anyway.

http://www.hammondmfg.com/1608A.htm

[koffee_iv]

I have swept several amps that I used the Hammond 1600 series output transformers in. They are wonderful! Below is a link to their specs. It seems to me that the 3db down point is below 20 hz. It will even pass 10 hz with a fairly respectable waveform, but with lower volume. The high end is maybe up to 10Khz, mainly due to the large coupling caps in the amp. For a bass, there is very little energy up there anyway.

http://www.hammondmfg.com/1608A.htm

Great! Thanks!