AX84 BBS

Amp Parts and Kits

Doberman Music Products, LLC offers a variety of parts and kits

RE: Best ss mini amps ...(by Dick J)

Sat, 31 Jul 2010 06:00:27 -0400

If you wanted to go solid state, you could build a small amp using an LM1875 from National semi as you're power amp. The chip will output up to 15W depending on transformer size/voltage and heatsinking. If you aimed for ~5W into a given load you could probably get away with some thick aluminum bolted too an aluminum case to act as a heat spreader for heatsinking. There are plenty of kits and PCB's around for the power amp section using these chips, you'd just need to figure out the preamp.

RE: Best ss mini amps ...(by DrHugenstein)

Sat, 31 Jul 2010 03:49:06 -0400

Not sure about the tube cricket at .5 watts. I want to be able to play clean as well. In fact most of my playing is relatively clean to on the edge of breakup. I also have a pedal for reverb and for overdrive so building a small approx 2 watt amp is probably where I will set the goal.

RE: EF86 High gain?(by Soundmasterg)

Sat, 31 Jul 2010 03:13:51 -0400

Pentodes function better as far as giving higher gain when they don't have a huge load on their output. Having a CF there and directly coupling them to the CF allows the pentode to get pretty much max gain. If you run a 1M grid leak on the stage after the pentode or a 1M volume control, then you lose some gain, but it can still work ok. You wouldn't want a 220k load after an EF86 though for example...it would bog itself down too much. Having a gain stage before the pentode as the others mentioned is a good way to get some juicy tones too. Greg

RE: Another question...(by Bonfire)

Sat, 31 Jul 2010 03:02:39 -0400

Yep - It works great, here is the current schematic: [link] I'm also still trying to find the optimal primary impedance for my pair of 6KV8's as I can't find any data that gives an indication of plate load in push pull... Any ideas? I'm using 8k plate to plate presently...

RE: Is this worth the effort?(by Alex G)

Sat, 31 Jul 2010 01:39:11 -0400

I'd say try the partially bypassed tonestack... if you have a tonestack, that is. It's easy to find a balance between the amount of boost, and range where the knobs still work. I'd need to see the rest of the circuit to recommend any other boost possibilities, although I'm sure you're looking pretty hard :)

RE: Is this worth the effort?(by Alex G)

Sat, 31 Jul 2010 01:36:05 -0400

On 07/29/2010 @ 11:56, Balijukka wrote : I have really no idea. it's about an inch of a felt tip pen tube with 3-4mm thick winding around it, and a M6 nut glued in one end. Then I screw in enough of a 40x6mm screw to tweak it where I like it. :) : : jukka --

I think I saw that on an episode of MacGyver!

RE: Cap coupled bias:(by Bonfire)

Sat, 31 Jul 2010 01:25:31 -0400

Ahhh, Merlin! Win! Yes, I am using a bridge rectifier! Could you explain why the extra resistor is necessary?

RE: Matt rocks!(by ogorir)

Sat, 31 Jul 2010 00:42:51 -0400

me, and I haven't decided yet. maybe a tube modular synth. anything other would be a waste of the massive heater current, plus it has that 25v winding :)

RE: Is this worth the effort?(by 3rdof3)

Fri, 30 Jul 2010 23:38:04 -0400

So I built the bootstrapped CF circuit and it makes a *little* difference in tone, but it's probably due to there only being one gain stage before it. I made it switchable along with the bypass cap and it works, just not as dramatically as I'd hoped. Let's try something else!

RE: A simpler way(by t mod)

Fri, 30 Jul 2010 21:10:00 -0400

On 07/30/2010 @ 21:05, t mod wrote :

On 07/30/2010 @ 14:15, Zoe N Iain wrote : : Wonder if there's a 4P4T rotary you can get at a reasonable price?? Can't see one with a quick Google, though there seem to be slide switches with 4P4T. Not as cool as another 'knob' though. ;-( : -- : :

: : Try eBay. There's a bunch of auctions selling NOS surplus soviet stuff. I've bought several sets of rotary switches when buying tubes for virtually nothing. Can't remermber if I have any 4d4t, but I'm sure they can be had for next to nothing. I'll look around tomorrow; if I find some I'll be happy to send you a couple... --

The results of a very quick search: [link] You'd have to live with made-for-pcb terminals, but seems ok otherwise. $3.33 shipped isn't too bad. Lots of surplus 4p5t from Eastern Europe for $1/each or less as well if you want to use the extra position for something... Will check my stash in the morning!

RE: A simpler way(by t mod)

Fri, 30 Jul 2010 21:05:20 -0400

On 07/30/2010 @ 14:15, Zoe N Iain wrote : Wonder if there's a 4P4T rotary you can get at a reasonable price?? Can't see one with a quick Google, though there seem to be slide switches with 4P4T. Not as cool as another 'knob' though. ;-( --

Try eBay. There's a bunch of auctions selling NOS surplus soviet stuff. I've bought several sets of rotary switches when buying tubes for virtually nothing. Can't remermber if I have any 4d4t, but I'm sure they can be had for next to nothing. I'll look around tomorrow; if I find some I'll be happy to send you a couple...

RE: Tolex ?(by spud)

Fri, 30 Jul 2010 20:06:37 -0400

And another: [link] Jim

RE: Tolex ?(by spud)

Fri, 30 Jul 2010 16:31:07 -0400

Also found this thread on GearPage on re-tolexing a 4x12 cab. If you can wade through it all, he goes over corners in it too. [link] Jim

RE: 07/07 - 6AQ5 - 7 pin project - provisional preamp(by MasonAtom)

Fri, 30 Jul 2010 15:28:54 -0400

I've been working up a layout: [link] So far this only covers the preamp. I have a PA schematic and PSU drawn up by hand but haven't done the QCAD yet. I've changed my mind and will be using a 5k:8 ohm OT with UL screen taps. Why? Just because I have one sitting around... Mason

RE: UL wiring(by MasonAtom)

Fri, 30 Jul 2010 15:25:12 -0400

On 07/30/2010 @ 11:04, stringbend wrote : : I didn't mean if the corresponding UL tap went to the plate and vice versa - although that's an interesting quesion also. --

Umm, I accidentally did this once on a SE amp, and, umm... the result was not pleasant - very low volume with excessive fartiness. Of course it took me like a week to figure out what I had done wrong, being the dumbass that I am. Mason

RE: 50w PP - first attempt at PTP(by John Hynes)

Fri, 30 Jul 2010 15:13:46 -0400

I started to write up a simple whitepaper on my thoughts on layout some time ago. Guess I better finish and post it. Thanks for pimping ZUUL Jukka. -John

RE: A simpler way(by AdamM)

Fri, 30 Jul 2010 15:12:02 -0400

"Everything" would have to included a boostrapped gain stage /cathodyne for the highest gain option (~x95 with 12Ax7). We're gonna need a bigger switch...

RE: Tube mismatch by half?(by PhilS)

Fri, 30 Jul 2010 14:57:26 -0400

If it walks like a duck and quacks like a duck....

RE: 50w PP - first attempt at PTP(by GuiteLectrique)

Fri, 30 Jul 2010 14:33:48 -0400

Thanks John, These are exactly what I need! They will leave more room inside. What I meant actually was for the height of the lever (some are higher than others), but forget it, even the most common ones would fit. Gui

RE: 50w PP - first attempt at PTP(by GuiteLectrique)

Fri, 30 Jul 2010 14:29:39 -0400

Wow, those sure look nice! I've redrawn the whole thing with standard PS filter caps. So what do you think now? There ain't much room in there and with those flat mount trannies, it's gonna be a tight fit. [link] Thanks for your help, Gui

RE: A simpler way(by Zoe N Iain)

Fri, 30 Jul 2010 14:15:49 -0400

Wonder if there's a 4P4T rotary you can get at a reasonable price?? Can't see one with a quick Google, though there seem to be slide switches with 4P4T. Not as cool as another 'knob' though. ;-(

RE: Convertible Phase Inverter(by Zoe N Iain)

Fri, 30 Jul 2010 14:12:30 -0400

Works in an 18W, too, apparently... Lol. That was exactly what I built it into to test it, as it happens. I did a bog standard '18' without the tremolo and with 6V6 PA for a mate of mine, with the spare triode simply paralleled on the input stage. Just wondered how well the switchable PI would work, so I wired it up in true 'gash' fashion, just to see. Pretty cool, too, but noisy as all hell with flying leads running everywhere to make it work. Be great to see someone make a proper job of it, if you fancy taking it on, Phil??

RE: Matt rocks!(by yecrom)

Fri, 30 Jul 2010 14:01:10 -0400

I'll let the buyer reveal himself if he so desires. :)

RE: What are we doing anyway?(by Zaphod)

Fri, 30 Jul 2010 13:15:21 -0400

FYI Traynor amps have custom transformers made for them by Heyboer, which aren't the same as the ones the rest of us mere mortals can buy off the shelf. On 07/29/2010 @ 05:36, Tom Wettenhall wrote : : Traynors all use Hammond and it's not like every amp ever made has NFB. :

RE: Convertible Phase Inverter(by Zaphod)

Fri, 30 Jul 2010 13:11:43 -0400

That LTP/Paraphase PI is totally cool!