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.

[Caucasian Blackplate]

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

[jrebman]

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