Triad HSM-181 output transformer

[AardvarkBry]

I picked up this old hifi mono block with a gigantic Triad output transformer. It’s at least as big as my Ampeg B15 output transformer. I was thinking this thing would make an amazing bass amp, but it’s only rated for 15 watts. Is the wattage so low because that’s what it takes to stay “ultra linear?” How much do you think I could push that wattage? Could I possibly drive 2 6L6s? I know that’s around double the wattage rating. It’s also rated for 100ma, 535 volts. 8k ohm primary. I think my b15 is 6.6k.

 

[dmp]

The ultra-linear is the additional taps on the primary that is used in the 'ultra-linear' circuit I think
Though a larger core may be intended to avoid any saturation causing transformer non-linearities.
You could just ignore those taps for a B15 style bass amp
It's a guess how conservative they were when the rated it at 15 W

 

[CJ]

Those guys are rated at 7 to 50 kc, you need a lot of iron for 7 hz.

Made for el84, 6v6 and 2A3 , the 2A3 is listed for 3 k push pull primary z on the transformer. So 7 hz and 2A3 are the main reasons for the size.

I thought it might be large because of possible SE use. But it is only rated for 2.5 ma unbal DC so flush that idea down the toilet.

 

[AardvarkBry]

Those guys are rated at 7 to 50 kc, you need a lot of iron for 7 hz.

Made for el84, 6v6 and 2A3 , the 2A3 is listed for 3 k push pull primary z on the transformer. So 7 hz and 2A3 are the main reasons for the size.

I thought it might be large because of possible SE use. But it is only rated for 2.5 ma unbal DC so flush that idea down the toilet.

The mono block itself has 2 6V6s, and a pretty low current, fairly low voltage power transformer, 525v (263-0-263) 90ma. It’s also got what appears to be a solid state rectifier in a can.

 

[AardvarkBry]

Those guys are rated at 7 to 50 kc, you need a lot of iron for 7 hz.

Made for el84, 6v6 and 2A3 , the 2A3 is listed for 3 k push pull primary z on the transformer. So 7 hz and 2A3 are the main reasons for the size.

I thought it might be large because of possible SE use. But it is only rated for 2.5 ma unbal DC so flush that idea down the toilet.

 

[emrr]

It's total overkill for a bass amp in terms of response, and is worth so much to the hifi people you should let them have it, get a half dozen of whatever ideal bass transformer you want.

 

[AardvarkBry]

It's total overkill for a bass amp in terms of response, and is worth so much to the hifi people you should let them have it, get a half dozen of whatever ideal bass transformer you want.

Sounds like good advice. I got this whole thing for like half of what one of those Heyboer b15 output transformer clones cost. Maybe I could put in some new filter caps, a grounded 3 prong plug, flip this, and get a few of those.

 

[CJ]

I would try it first,
Could have amazing sound.
Half the fun is finding out.
Somebody gave me an obscure western electric 5214 military output , 4400 p to p to 4 ohms. Paired that up with four 6384 Bendix red bank output tubes and it is the best bass amp I have ever heard. Used the portaflex preamp circuit.

There is a teardown thread around here on the opt and the amp.

 

[AardvarkBry]

I am tempted to do it. I’ve been playing upright bass for 25+ years, and I have bought every state of the art upright bass amp on the market over the years, and hated every one of them. I built this flip top clone a couple of years ago, for my p-bass, and plugged my upright into it, not expecting much, and it completely changed my life. I have modded this thing every way I could find, and it sounds absolutely phenomenal. Most of the gigs I play are small jazz combos, and the 6L6s are way more power than I usually ever need. I don’t usually turn the volume up more than 1/3 of the way. I wonder if I slap the portaflex preamp section in front of these 2 6V6s, if it’ll be enough power? The solid state rectifier might even help? The upright is even deeper in the sub frequencies than electric, so it might sound spectacular, or it might be too much low end, and make the bass resonate out of control?

 

[soapfoot]

Sounds like you like tube amps.

I bet you don’t need this unobtanium, highly-valuable transformer to make a great sounding bass amp

 

[AardvarkBry]

Yeah, I am obsessed with tubes. They do something special to the bass frequencies. It just hits me right in the feels. Maybe first order of business is make sure this thing is safe, and not gonna zap me. One of the can caps has a broken base, and is flopping around. Then maybe just plug my bass into a preamp and into this as is, just to satisfy my morbid curiosity.

 

[CJ]

Who makes that upright that breaks down into a suitcase?

The guy in The Mavericks plays one. Not Robert Reynolds but the new guy.

 

[mad.ax]

When CBS took over Fender they went the ultralinear route and designed some 135W chassis... Didn't sound good for the guitarists because the 'improved' amps sounded too 'hi-fi'... But the Bassman 135 works really well for bass guitar for those who want a more defined low octave...
So imho, an ultralinear OT can be a really good choice for a bass amp.

Axel

 

[AardvarkBry]

Who makes that upright that breaks down into a suitcase?

The guy in The Mavericks plays one. Not Robert Reynolds but the new guy.

There are a lot of portable travel basses. The old school “baby bass,” that all the salsa guys play, Stagg. Eminence makes one that looks like a long skinny upright violin. David gage, and Upton make my favorite version, which is like a full upright, cut in half, without the bottom half. Something gaining a lot of popularity is taking the neck off, and mounting it with a bolt system, so it’s removable, and it fits in a trunk the size that airlines are ok with.

 

[AardvarkBry]

When CBS took over Fender they went the ultralinear route and designed some 135W chassis... Didn't sound good for the guitarists because the 'improved' amps sounded too 'hi-fi'... But the Bassman 135 works really well for bass guitar for those who want a more defined low octave...
So imho, an ultralinear OT can be a really good choice for a bass amp.

Axel

That’s interesting. I’ve read that Leo Fender purposely often used under sized transformers to add more saturation, and get more break up. Even with my b15, most guitarists aren’t crazy about it because it doesn’t break up enough.

 

[AardvarkBry]

Who makes that upright that breaks down into a suitcase?

The guy in The Mavericks plays one. Not Robert Reynolds but the new guy.

I just looked up their bass player Ed Friedland, and found a picture of him playing one of those “bb4 baby basses,” which are made by Ampeg. Ampeg has a long history in the upright bass game. The name Ampeg comes from their first idea/invention which was an upright bass end pin (peg) that had a pickup built into it, ala “amplified peg.” Those old SB12 amps, SB stood for standup bass.

 

[AardvarkBry]

I did my best to draw out the schematic from looking at the circuit.