Tube Amp DIY'ers Club-DIY Bassman soundclips p.25!

[mugen]

Salamat din sir BAMF..

Ilang beses ko din tinanggal at kabit yung unang build ko hanggang luminis..

[BAMF]

Salamat din sir BAMF..

Ilang beses ko din tinanggal at kabit yung unang build ko hanggang luminis..

Yep. The lessons are more important than the amp itself.

[sd8450]

Honga ano. No, I didn't go tube rectifier on this one. Maybe on later projects, but I plan on going solid state rectifier for my next two projects (18 watt and spitfire). Perhaps when I do my MIG-50 (this seems to be a simple 50-watter build) I'll go tube rectifier. Pero I'm thinking, the tube sag of the rectifier can be replicated by series resistors in the power supply anyway. Whatdya think ?

I think I can manage a choke although it will have to be mounted inside the C-section, there's no more space topside. I was planning on  leaving that space between the tubes and the PT empty to minimize hum.

Some like tube rectifier sag and some like the stiff/fast response of ss rectifier, so it's a matter of taste.

I have not come across any reference about series resistors in the power supply replicating the sag of tube rectifier. AFAIK resistors in the power supply section are voltage dividers, providing different voltages required to various sections of the amp. Some resistors are wired in parallel to the big filter caps. I think they are put in there to "absorb" or "soak" the dangerous high voltages from the big filter caps after the power cable is unplugged. Without these the big filter caps will hold their charge for a long time even after the power cable is unplugged, a potentially dangerous condition.   

AFAIK chokes help to smooth out the ripples from the power supply and help reduce power supply induced hum. If you can get them cheap then it would be better to stick to the schematic and use one. In Fender amps the choke is placed close to the PT so topside next to the PT would be a better placement than inside the C section.

[BAMF]

Some like tube rectifier sag and some like the stiff/fast response of ss rectifier, so it's a matter of taste.

I have not come across any reference about series resistors in the power supply replicating the sag of tube rectifier. AFAIK resistors in the power supply section are voltage dividers, providing different voltages required to various sections of the amp. Some resistors are wired in parallel to the big filter caps. I think they are put in there to "absorb" or "soak" the dangerous high voltages from the big filter caps after the power cable is unplugged. Without these the big filter caps will hold their charge for a long time even after the power cable is unplugged, a potentially dangerous condition.   

AFAIK chokes help to smooth out the ripples from the power supply and help reduce power supply induced hum. If you can get them cheap then it would be better to stick to the schematic and use one. In Fender amps the choke is placed close to the PT so topside next to the PT would be a better placement than inside the C section.

That's great info ! Yes, chokes can be had for cheap...I got a 3.5H 2.5A choke from Amco-Raon. It was many years ago, cant remember how much for but I don't remember saying ouch over it . I stuck it into the SEL.  There was this company called Lion Transformers...sad they don't seem to be around anymore but that choke I got was a Lion. Anyway, I'm sure Mang JV can wind me one as well. Kaya lang baka parang yung PT, baka oversized na naman .

The series resistors thing, while yes they do drop the voltages to certain points, they also act as a current limiter, they reduce the current as more is being drawn by the amp, thus mimicking the sag of a rectifier tube. Anyway, I have to test that one...that came from my late older brother. . He was no fan of tubes and when I explained the warmth of tubes, he said "miller capacitance, stick a 10 pF across your base and ground on a transistor." When I said "sag" he said "put a resistor between your power supply and the B+ of the output section of your SS amp...  so...I'll just try all options  see what I like the most .

Anyway, an idea hit me...has anyone tried using a flourescent ballast as a choke ? Its a relatively large-value inductor. I mean those that are not solid-state.

[BAMF]

ngapala, before I forget, there are good news-bad news on the 6BQ5 (EL84). First good news, it only costs P300 per piece at Deeco. So if you guys wanna make a P1, this will cut your costs drastically. Bad news, it's out of stock as of now. I've been reading in some tube diy forums that matching tubes are artifacts from the hi-fi world, some diy'ers have said that non-matching tubes sound good on guitar tube amps.

Maybe a little more parts research and we'll find another source, hopefully as cheap as Deeco's.

[BAMF]

Bos Mel,

I tried what you said about separating preamp and power amp grounds. I couldn't find a 5 ohm 5 watt resistor so I used a 1.8 ohm instead. The reduction in hum is significant ! Meron pa din, but nothing unusual to tube amps. The SEL is soundclip-ready na ! Thanks !

[embot]

Bos Mel,

I tried what you said about separating preamp and power amp grounds. I couldn't find a 5 ohm 5 watt resistor so I used a 1.8 ohm instead. The reduction in hum is significant ! Meron pa din, but nothing unusual to tube amps. The SEL is soundclip-ready na ! Thanks !

Glad it worked for you Jobet.  That grounding scheme is very useful, especially sa mga high gain amps.

[mugen]

Marshall 1974x schem. (from 18W.com)


Layout (18W.com)


Board Layout(from 18W.com)


Chassis (from 18W.com)




sunod ko yung Face Plate & Cabinet.

[BAMF]

Cool Mugen !

Anyway, update...my Spitfire is alive and playing. However, I slapped on it the OT I got from the Fender Champ and it brought with it to the Spitfire the disease it gave the Champ: underpowered and weak. Guess I gotta get the OT I had made for it back from the SEL and slap back the original OT for it. Hindi pala putok ang windings nun...cool

[BAMF]

Picture posting time !

Tapos na yung Spitfire! Pinahirapan ako neto na tanggalin yung hum, pero nahuli din ang teknik. Ground lift on the filament artificial center tap lang pala ang solusyon. Meron pa din parang subsonic rumble. Buti na lang di pa ubos ang alas ko, I'll be picking up the 10H filter chokes I had made. Baka yun na ang last straw and it will be as quiet as a mouse na.
Post ko na lang yung "done" pics pagka-galing ko sa gig sa carbon tonight.


The "almost done" pics

[BAMF]

Rectifier tube "sag" emulation using a power resistor! Found it. Just when I thought it was an audio urban myth, it's actually practiced pala.

http://studentweb.eku.edu/justin_holton/sag.html

[sd8450]

Rectifier tube "sag" emulation using a power resistor! Found it. Just when I thought it was an audio urban myth, it's actually practiced pala.

http://studentweb.eku.edu/justin_holton/sag.html

Nice info!
Though personally I do not think it is worth the trouble doing.
I'd leave the ss rectifier as is. As I read it, the mod will put the performance of the amp in a limbo state between an ss and tube recto amp (sag-wise and even bias-and-plate-voltage-wise). 
If I will be doing an amp project that calls for a tube rectifier and I can get the PT with the 5V winding cheap, I would go for the tube rectifier. The additional cost would be the cost difference between the extra tube socket and the rectifier tube vs. the cost of diodes and the big wirewound resistor.
Then I would know that the project amp would perform and sound close if not exactly the same as the original amp being cloned. Otherwise there would always be a question in my mind about the amps sound and performance vs the orig. But that's just me.    

[mugen]

Picture posting time !
Meron pa din parang subsonic rumble. Buti na lang di pa ubos ang alas ko, I'll be picking up the 10H filter chokes I had made. Baka yun na ang last straw and it will be as quiet as a mouse na.
Post ko na lang yung "done" pics pagka-galing ko sa gig sa carbon tonight.

Sir BAMF try to use a shielded cable sa input jack to V1. Then ground the other end near the tube or near the jack. 

[BAMF]

True. And even that cost differential won't be much. Nice thing lang with solid states (assuming that the sag gets close enough to desired results) is that you can slap on lots of capacitance to the power supply without any negative effects.

Entiire SS-Tube recto thing will require adjustment anyway. When you use SS rectos, the voltage shoots up by 50 VDC from the schematic readout values so you'll have to readjust bias anyway (assuming we're still within safe limits). Then the resistor sag mod can be used to compensate for that voltage shoot-up. It's a balancing act.

Nice info!
Though personally I do not think it is worth the trouble doing.
I'd leave the ss rectifier as is. As I read it, the mod will put the performance of the amp in a limbo state between an ss and tube recto amp (sag-wise and even bias-and-plate-voltage-wise). 
If I will be doing an amp project that calls for a tube rectifier and I can get the PT with the 5V winding cheap, I would go for the tube rectifier. The additional cost would be the cost difference between the extra tube socket and the rectifier tube vs. the cost of diodes and the big wirewound resistor.
Then I would know that the project amp would perform and sound close if not exactly the same as the original amp being cloned. Otherwise there would always be a question in my mind about the amps sound and performance vs the orig. But that's just me.    

[qwixzh]

eto yung ginamit kong reference nung first power-up ko ng 18watts clone ko

PaulRuby

ok na guide. guided me alot. hope this helps you also. 

[BAMF]

Aight thanks hehehe.

Starting my next project using 2 X EL84's. And as I promised ke mugen, I'll try to catch up on his workmanship.

So...even if it feels like being thrust back to the time when I wasn't even a dirty thought in my father's mind...I decided to go point to point wiring from here onwards. So I'll need a proper point-to-point board. Inatake naman ako ng tamad masyado to do acrylic and turrets, so I did the next best thing. I found a perfboard/veroboard/donut board (dunno what the americans really call it) and two bags of terminal connectors. I then crimped those to the veroboard, and for extra strength, I soldered them to the underside.


I started installing components from my stash. Unfortunately, I don't have all the values needed, so I guess I have to stop my OC for now and get the components needed. Mukhang pwede ang back to back na power transformer dito, the 18 watt only needs 220VAC HVAC connection. And I have a spare output tranny, so I guess this one will finish faster than the time needed to finish the Spitfire.

Funny lang, when you're following plans to the letter, things do seem to go faster.

Cabinets naman pagtapos.

[BAMF]

Guys question:

I started with a 50-watter about 2 years ago but I chickened out. I thought to myself I better start on something smaller or do a hybrid.

One of the projects I thought of was making a firefly (1.5w push-pull), put an inductive load on it or a real small speaker, then put a line-out on it powering a powerful solid-state amp.

This way, you get power tube saturation sound without getting too loud, but still have the option of getting it louder. Best of both worlds...power tube sound, solid state power and efficiency.

Opinions ? Pros and cons ? Or does it sound like a perfect plan ? Coz I've already collected the parts for the firefly and when I get my filter chokes, I'll have the OT of this made already. Anubayan...kaka-adik. Hulog ng langit talga si Mang JV, I can make tube projects with impunity. Ganito lang malamang ang idea for the Zvex nano head. Baka nga rebranded Firefly lang yun. Now this is something I'd gladly mass-produce . After the 18 watt and firefly, I'll be doing smaller projects naman like the Real McTube then  tube mike preamps for the new PIMP recording studio that I'll be setting up. Tapos talon na sa malaki...maybe a Hoffman Super 50

[BAMF]

I hate to play favorites, but this is my bunso...the newest member of the BAMF Amf family . My newly finished Marshall 18 watter.

I mean, the Spitfire was great...fat sweet tone and all, but maybe I'm truly a Marshall tone guy at heart. This here baby sings. I didn't faithfully follow the circuit, I inserted that "Marshall" coupling stage...the 470pf in parallel with the 470 kohm. Delicious. Grabe ang bias nya, almost to saturation. Wala na syang clean pag sinagad mo ang volume. But the crunch is juuussst right. Gorgeous. I'll be waiting for the wooden cabinets for this and the Spitfire, they should arrive tonight.


I think I did a better job this time than the P1 and the Spitfire. Point to point wiring, point to point board all planned out before implementation. I guess I could use a little more improvement in my wire dress, but for all practical purposes I think my tube amp building has become quite...satisfactory (?).

Next na kaya...a 50 watter na para magamit ko na yung OPT na bigay ni embot ehehehe....

Ang mura na ng tubo...yung mga shuagang from China. Parang 10 dollars na lang ang isang EL34. A 100 watter is not out of reach any more . Actually, ang target ko talagang endpoint...the point where I stop making or stop going for higher power is a 200-watt Marshall Major. Parang apat na KT88 lang yun kaya umabot ng 200 watts yun . Oh well...bahala na. Next project will be finished in two weeks siguro.


These babies are the reason why nothing gets done in the past 3 weeks (except them). Haay. Thank goodness I'm a bum and can afford the time.
Haay. 1 amp assembly per week. That's a lot...sabagay kasama na shopping time dun. It's really meticulous pala to go point to point. But it was worth it.

[BAMF]

Gawa nga tayo ng BOM :

18 watt:

Chassis : 500 (actually 400+)
Veroboard- P50
Terminal strip connectors, 1 bag - P100
Sockets @ 30 each - 120
Switches @15 each - 30
All other electronics (deeco-class) - 400
Transformer set, including choke - P 1,000
12ax7's, 2 @ 300ea - P600
EL84's (got them for 1.5k matched quad bnew cond) - P750
Wooden cabinet est 700 including labor and vinyl covering

Lessee...the things only cost me...4,250 . Less pa for the Spitfire coz the chassis for that is just an aluminum C-section from a glass supply store

[embot]

Mukhang busing busy ka Jobet.  Nice amp.  Ako rin I'm working on an el84 amp.  Medyo malayo pa ako from completion pero I'll post pictures pag na completo ko na.

[Phil]

Mukhang busing busy ka Jobet.  Nice amp.  Ako rin I'm working on an el84 amp.  Medyo malayo pa ako from completion pero I'll post pictures pag na completo ko na.

Mel....what can you say about this......I'm attracted to this.

http://www.twisteramps.com/DUSTDEVIL.html

[embot]

Mel....what can you say about this......I'm attracted to this.

http://www.twisteramps.com/DUSTDEVIL.html

Looks good and sounds good Phil.  Lots of nice single ended amps in this price range though.  Before you buy check out Bad Cat Mini Cat II, Fuchs Lucky 7, DR Z Mini Z and Victoria 5112.  In the used amp market you can probably buy these amps for less than $500.  More expensive but the Fargen Miniplex II and the Cornford Harlequin are very nice too. If you wait you can probably buy a used one for about a grand.

I'd say play them all and buy the one that you like the most.

[BAMF]

Aasar na nga ako sa sarili ko. Para akong adik. Sabi ko pa sabbatical muna ako and pickup ko ulit sya in 2 weeks. Pero eto na naman ako, inumpisahan ko na yung board para dito :
http://www.schematicheaven.com/dumbleamps/97fullschem.pdf

Actually tapos ko na yung board para sa power supply section, so preamp section na lang. Mga tira-tira lang nung previous projects ko...sa Deeco kasi kahit isa lang kelangan mong piraso, isang buong supot ang mabibili mo .

Madami nang galit sa kin. Wala na ko inatupag kungdi eto. hay. Pati yung P1 kinalas ko tapos gumawa ako ng bagong power supply board nya para tumino ang loob. Ayun...malakas pa din ang hum. Teka...kelangan ko nga pala subukan yung 10H na choke. Napatahimik ko na to e...kaka-kalas lang kaya nagkakaganito Interesting...pag malaki ang core ng transformer kahit for the same wattage, lumalakas ang tunog . Nagiging believer ata ako ng oversized OPT a.

Mukhang busing busy ka Jobet.  Nice amp.  Ako rin I'm working on an el84 amp.  Medyo malayo pa ako from completion pero I'll post pictures pag na completo ko na.

[BAMF]

La lang. Update.

I'm doing two boards right now. Almost simultaneously. Wala lang naman...para akong nagni-knitting...doing this while watching TV. The bigger board is the Dumble ODS clone. The longer board is what will become a 50 or 100 watt marshall master volume (JMP100-2203).



Nice thing about these...you can decide later what wattage they will take. Just have the power tranny ready for 100 watts, and you can then slap on either a 50 watter 3200 ohm primary or a 100 watter 1700 ohm primary and two extra tubes.

I already ordered my EL34 matched quad. Tamang tama lang, when they arrive in about 2 or 3 weeks, the boards and trannies and chassis should be ready by then.

[tapslore]

newbie question for the tube diy'ers here: if i were to get a 5F6A '59 bassman clone made, would it totally ruin the legendary dynamics of the amp if i had it modified with an effects loop and a master volume?