How does "Sex" amp compare to other single ended tube amp out there

[tubtub]

Need opinion on how "Sex" amp compare to other amp out there.  I've already have a couple of James Burgess Single Ended 45 but want to build something on my own hence the question.  Thanks.

[Mudhiker]

The S.E.X. is easy to build.  It sounds good out of the box and can be modded quite easily.  It works quite well as a Headphone Amp.  The online support community (and support from bottlehead) is quite useful.  The Iron upgrades are fantastic.  If you have efficient speakers and a small to medium sized listening room you will be amazed at how much fantastic low-noise-floor great-bass sound can come out of a measly number of watts.

[Grainger49]

There are a number of DIY SET amps out there that are comparable to the SEX amp in simplicity, I have heard none of them.  One example is the SPUD amp that I have heard nice things about but can't say anything concrete because I haven't heard it.

The advantage I see in the SEX is that the SEX has an upgrade path that is supported by the maker and the community.  The stock amp has dual mono power supplies and is a headphone amp.  Both are above the average in the price range.  Then you can add the C4S constant current sources and upgrade the iron with Magnequest iron.  These upgrades are all supported by Bottlehead and the community.  After that you can upgrade parts as you see fit.

There is a good thread in the SEX amp file asking about upgrading different parts.  You should check there.

[tubtub]

Thank you all for the info. 

[Paul Joppa]

There are a few 6EM7 amps in the market currently; you can check what others have to say about them. It's a similar tube. The SEX amp can be converted to use the 6EM7, but we think the 6DN7 sound better.

[tubtub]

Thanks Paul.  I was told that I won't hear any better sound by going from a 45 to 6DN7 or 6EM7.  I guess I will just watch and learn for a while.

[Paul Joppa]

Well, I tend to thing of the SEX amp as the "poor man's 45" - similar power, and surprisingly good sound, at a fraction of the cost. But no, you won't equal a good 45 amp with any indirectly heated tube I know of.

[Doc B.]

I agree with PJ in general about this, but one must remember that the driver tube has a huge influence on the sound too. I don't know what tube is used (or how it is set up) in the Burgess amps and I haven't heard them - they are probably very nice sounding amps. But a crappy driver stage implementation in another amp could make even a 45 sound bad. I think that the reason the 6DN7 sounds better than the 6EM7 is that the driver stage triode is better suited to that job in the 6DN7.

[Dr. Toobz]

I agree with PJ in general about this, but one must remember that the driver tube has a huge influence on the sound too. I don't know what tube is used (or how it is set up) in the Burgess amps and I haven't heard them - they are probably very nice sounding amps. But a crappy driver stage implementation in another amp could make even a 45 sound bad. I think that the reason the 6DN7 sounds better than the 6EM7 is that the driver stage triode is better suited to that job in the 6DN7.

Is that also true of the driver-side of the 6EM7 when loaded with a CCS instead of a plate resistor? Does the CSS help even out the difference between the two tubes?

[Paul Joppa]

The CCS reduces distortion, extra necessary because the 'EM7 needs 3 times as much drive voltage. It does not reduce the high plate impedance of the driver triode, however.

[Paul Birkeland]

I will have to throw in those 90k:10k interstage transformers I have into one of my EM7 amps...

[Jim R.]

I think the Burgess amps use a small pentode (ef86?) driving a 12b4a, in turn driving the 45/2a3.  Supposedly a very nice arrangement, and I think using an IT between the 12b4a and 45.

Never heard one myself either, but am certainly curious.

-- Jim

[tuffy_puppy]

several months ago i took a chance and bought a sex 2.1 amp off audiogon.  within 5 minutes i knew that the decware amps and preamp i was using were out the door.  since then i have had some changes take place and some work done by the bottlehead tech shawn.  never been happier with my audio setup.  the whole process has been akin to removing several quilts from over my speakers,  12" audio nirvanas with a sensitivity of 95 db.  don

[jamestw]

Since I built my SEX2.1 at the end of last year, I'm still surprising its good sounding this small amp is. I don't have any tube power amp before so have no experiences to compare with other type of tube amps. But I like it more than my other SS amps - yamaha RX661 receiver and mcintosh mc352 . I was thinking there might has "The builder's proud" and "A fresh impress of new sounding" factors to affect my judgement.

From last 4 months, I switched my amps ; speakers to have certain comparisons - a lot, and I can still say I like SEX2.1 than my other amps. The speakers I have JBL 4425 (91dB, 8-Ohm) and diy Frugel horn MK3 (with Fostex fe-126en drivers, 93dB, 8-Ohm).

I've switched caps many times, just for fun, to get different hearing experiences, include change 0.1uf caps to orange drops, then russian oil caps, then mundorf caps. Also coupled 0.1uf russian teflon caps with output caps then put it out later. Changed 1000uf/35V caps to black gate caps.....
I found to change the volume pot made a huge difference, from original pot that came with kit to diy a 100k series type with China made 24-step rotary switches, then change to diy a SMD resistors-pot , then change to diy a ladder type (L-pad) pot, then change the pot to a Shallco.....
I got a lot of fun with this little amp and it sounds so good to my ears ! Even the C4S kit for 2.1 has not release yet.

Oh yeah, the quiet backgound noise was the first impress when the very first time I fired it up, surprising me :-)

james

[bainjs]

James,

It sounds like you have definitely been busy!  If you ever become satisfied with your cap changes, please post your final list.  A photo would also be helpful.

Thanks for sharing.

Joel