Show us your flea-watts amps!

[cary]

This is my favorite amplifier, Bottlehead's Single Ended Experimenter's better known as the SEX amp. It features a dual mono power supply, also works as a headphone amp and has two watts of flea power. I always demo this amp at audio meets and shows. It receives great reviews from everybody.

This photo is from a DIY show a couple of months ago in Davis, California.

Here's a review from the show:

Re: DIY Audio Show in Davis, California
« Reply #9 on: April 21, 2013, 09:50:20 AM »

* Quote

so i went to the show in davis yesterday and it was nice to meet fellow bottlehead, cary.
he brought his good old trusted s.e.x. amp and had two very small speakers with fostex drivers that looked similar in size to the orcas from blumenstein. although i could not stay to the end of the show and only got the chance to listen to a few tunes on caries setup, it was, to my ears, the best sounding setup of the show. although there were some very impressive diy speakers showcased ranging from small to enormous, cary had the only setup that was driven with a tube amp.
and maybe that made all the difference to me. and maybe i am just biased because i am a bottlehead fan. i do not have any audiophile words for it, i only know that caries tube setup sounded more natural and pleasing to the ear. there was an effortless quality to the music. i was not trying to analyze it and listen for the characteristic of the speakers the music just immediately sounded nice. its always impressive when 2 watts and tiny speakers can achieve that. this experience makes me very curious about what some of these single driver speakers can do. maybe that needs to be next on my list after i am done tweaking my original s.e.x amps that i am working on currently. thanks cary for bringing your gear, too bad i couldn't stay longer to listen more. best, stefan


Cary
Bottlehead Ambassador

 

[Alan Cohen]

300B OTL Monoblock. 1.5 most glorious watts:



This is a pretty trick amp. 300Bs don't lend themselves to OTL without a fight. "In an OTL, the cathode is connected to the speaker. A 300B triode has a directly heated cathode. That means the cathode is the filament. This places the filament in direct electrical contact with the speaker." Needless to say all kinds of hum issues are in play.

Due to some pretty clever design engineering (not mine), most of the hum is self cancelled. The rest is dealt with by a dedicated A/C power supply for the heaters (bottom box). This PSU converts 60Hz A/C to 25Hz A/C to heat the filaments, and effectively makes whatever hum is left virtually inaudible.



The circuit is so elegantly simple:



And the sound is to die for.

 

[buglegirl]

Hiya,

Transcendent makes some rather nice sounding and good looking equipment. Love the fact its also in kit form as well.

Someday when I move on to new production equipment I have these guys on my short list.

Frannie

 

[GAryB]

another 1.5W amplifier

About a decade ago, I picked up a kit from Sun Audio in Tokyo while on a business trip. It's their model VT-25, which unsurprisingly uses the VT25/10 tube for a surprisingly big sounding 1.5W. Not a lot of power but what is there sounds really good.
---Gary

 

[knockbill]

Heres my little Philco "suitcase phono amp" mods,,, It had a tube rectifier, and 35C5's ... I converted the PS to SS, with an isolation transformer, and 50C5 output tubes, and a center tapped 12AX7 to help lower heater hum,, (thanks wa2ise!!),,, I have a pair of new Sylvania 50C5's, and an Electro Harminix 12AX7, in it now,,,I also removed teh tone controls...
The OPT's have a separate feedback winding, and it's pushing a pair of 15" Magnavox console cabinets, and sounds pretty amazing to me...

Regards,
John

 

[Alan Cohen]

Transcendent makes some rather nice sounding and good looking equipment. Love the fact its also in kit form as well.

I don't know about "good looking", but nice sounding fits the bill.

I can't say enough about how grateful I am these are available in relatively affordable kit form. There would be know other way I could afford this level of performance.

 

[goldleaf]

About a decade ago, I picked up a kit from Sun Audio in Tokyo while on a business trip. It's their model VT-25, which unsurprisingly uses the VT25/10 tube for a surprisingly big sounding 1.5W. Not a lot of power but what is there sounds really good.
---Gary

That is lovely. Been thinking about a 10Y SET in the future...:yes:

 

[goldleaf]

nice. how do you like the Qinpu? I have it running speakers on desktop at my office.

That A3 is an under appreciated amp. It is dead quiet, deals with all headphones with aplomb and once you change those chinese furnished tubes, sounds quite excellent. The FET section does not pair very well with some of my speakers though (the ADS L810's for example). It appears to prefer a 4 to 6 ohm speaker impedance like the Canton's you see on the picture.

 

[GAryB]

DC double darling

It's sitting in the garage right now waiting to be rebuilt with better output transformers, but here is a DC double darling that I put together a few years ago. It's built on 2 hammond chassis, held together by a wooden frame that makes it seem like one big chassis. Power supply in the back and amp in the front. As shown in the pictures, it uses some inexpensive Hammond 125SE outputs which are good value but the amp is good enough that it would justify better iron.
---Gary

 

[davidro]

This is my favorite amplifier, Bottlehead's Single Ended Experimenter's better known as the SEX amp. It features a dual mono power supply, also works as a headphone amp and has two watts of flea power. I always demo this amp at audio meets and shows. It receives great reviews from everybody.

I should give this a go one day. Is it the easiest to DIY among the BH amps?

wow 4 mothers and that's just 1.5w?
love the Altect speakers :drool:

About a decade ago, I picked up a kit from Sun Audio in Tokyo while on a business trip. It's their model VT-25, which unsurprisingly uses the VT25/10 tube for a surprisingly big sounding 1.5W. Not a lot of power but what is there sounds really good.
---Gary

I really like the look of this amp...

That A3 is an under appreciated amp. It is dead quiet, deals with all headphones with aplomb and once you change those chinese furnished tubes, sounds quite excellent. The FET section does not pair very well with some of my speakers though (the ADS L810's for example). It appears to prefer a 4 to 6 ohm speaker impedance like the Canton's you see on the picture.

I have a question...is this a tube-pre + FET-power amp or is the tube just a buffer?

 

[mhardy6647]

300B OTL Monoblock. 1.5 most glorious watts:



This is a pretty trick amp. 300Bs don't lend themselves to OTL without a fight. "In an OTL, the cathode is connected to the speaker. A 300B triode has a directly heated cathode. That means the cathode is the filament. This places the filament in direct electrical contact with the speaker." Needless to say all kinds of hum issues are in play.

Due to some pretty clever design engineering (not mine), most of the hum is self cancelled. The rest is dealt with by a dedicated A/C power supply for the heaters (bottom box). This PSU converts 60Hz A/C to 25Hz A/C to heat the filaments, and effectively makes whatever hum is left virtually inaudible.



The circuit is so elegantly simple:



And the sound is to die for.

Holy cow those are nice looking boxes the Duplexes are in!

Bruce certainly has an interesting perspective - I've been tempted to try that itty-bitty fleapowered OTL kit he has (although I don't know if it is still available, truth be told)... and also his Grounded Grid preamp.

 

[seanrr]

I see that little Altec badge in the corner of your cabs Alan - Are those the little brass reproduction ones somebody sold on that auction site awhile ago? If so, I got some of those for my Altecs too - they add a nice touch.

 

[GAryB]

I really like the look of this amp...

Me too. They use really good transformers from Tamura, which explains why they sound so good.

To get a feel for what a high end store in Tokyo's Akihibara district looks like, take a look at this youtube video: http://www.youtube.com/watch?v=Hl9w1aVVm30
The first part is a visit to Hino Audio, which carries a lot of kits and parts for DIY along with some finished goods. About 1:28 into the video they go upstairs to Sun Audio where you see the Sun amps briefly. All of these places are tiny with equipment jammed into every nook and cranny. A fun place to visit.

---Gary

 

[goldleaf]

Me too. They use really good transformers from Tamura, which explains why the sound so good.

To get a feel for what a high end store in Tokyo's Akihibara district looks like, take a look at this youtube video: http://www.youtube.com/watch?v=Hl9w1aVVm30
The first part is a visit to Hino Audio, which carries a lot of kits and parts for DIY along with some finished goods. About 1:28 into the video they go upstairs to Sun Audio where you see the Sun amps briefly. All of these places are tiny with equipment jammed into every nook and cranny. A fun place to visit.

---Gary

Found this http://www2.big.or.jp/~sunaudio/sv/svvt25_e.html

 

[goldleaf]

I have a question...is this a tube-pre + FET-power amp or is the tube just a buffer?

Been looking for a schematic of the A3 for ages with no luck. Based on similar designs elsewhere and the fact the 6n3p/2c51/5670/we396 is an excellent voltage gain stage, I'd speculate the 6n3p is not a buffer (ie, 1:1 gain) but a "pre".

 

[davidro]

Me too. They use really good transformers from Tamura, which explains why the sound so good.

To get a feel for what a high end store in Tokyo's Akihibara district looks like, take a look at this youtube video: http://www.youtube.com/watch?v=Hl9w1aVVm30
The first part is a visit to Hino Audio, which carries a lot of kits and parts for DIY along with some finished goods. About 1:28 into the video they go upstairs to Sun Audio where you see the Sun amps briefly. All of these places are tiny with equipment jammed into every nook and cranny. A fun place to visit.

---Gary

Found this http://www2.big.or.jp/~sunaudio/sv/svvt25_e.html

yes this amp was on my wishlist when I was looking for a SET. the price was outta range for me though, even for as a kit. There's a Chinese lookalike stuff on the Bay too: Bowei 2A3C.

 

[davidro]

Been looking for a schematic of the A3 for ages with no luck. Based on similar designs elsewhere and the fact the 6n3p/2c51/5670/we396 is an excellent voltage gain stage, I'd speculate the 6n3p is not a buffer (ie, 1:1 gain) but a "pre".

I think it runs a little too hot to be a mere buffer.

 

[GAryB]

yes this amp was on my wishlist when I was looking for a SET. the price was outta range for me though, even for as a kit. There's a Chinese lookalike stuff on the Bay too: Bowei 2A3C.

Prices have gone up a lot since I bought mine around 2000 - basically doubling between the rise in the cost of materials and the fact that the dollar has weakened against the yen. I think I paid $800 for the kit including NOS tubes back then, which now looks like a screaming deal but seemed expensive at the time.

---Gary

 

[jaymanaa]

Beautiful stuff guys, great thread idea. :thmbsp:

 

[MWalt]

Here's mine in 'flea' mode (45). Actually a better fit in my system when using 2A3s though.

Beautiful! Who makes that one?