Are there any SET Amp users in the house?

My power amp is cracking the sads and seems to be in for repairs more often than its at home these days. l have started wondering what may be a good replacement. SE triode amps have always held my curiosity and now that l own highly efficient speakers (96db) l thought now's the time to jump in and try them. Problem is my speakers impedance dips to 2ohms and is generally in the 4-6 range.

Most SET's would clip badly into that load. However there is one amp, the Decware Zen that actually increses its output at lower impedance loads. The model l am curious about is the SV83M, all 4 watts of it!!

Anybody have any experiences with Decware or able to offer advice, their own experiences with SET, alternatives etc. All advice greatfully received

Cheers Mondie

 

Talk to SCIDB - he runs a Border Patrol 300B SET amp (not sure of the model name).

Michael.

 

There might be more to it than that though Chris, I am sure that with low feedback valve amps, driving loads of varying impedance can alter the amplifiers frequency response. I am sure someone more knowledgeable will be along soon to explain why.

 

Hi,

No, they would not. In fact, if you connect that speaker to the 4 Ohm Tap yopu should be okay, though you would be better off connecting it to a 2Ohm tap if present.

However, be aware that sensitivity and efficiency are NOT the same. With your speakers it would appear (from what you have written) that the sensitivity is 96db/2.83V, however with an average 4 Ohm Impedance this is in fact 93db/1W/1m as the speaker will require in fact 2" electrical power to be driven to 96db.

Actually ANY Amplifier will increase output into lower loads, at the cost of increased distortion. Any claims Decware makes that theirs is the only amplifier to do so are shall we say not entierly rooted in reality.

I had the Decware Zen (not the Mono's) Here, also the Bottlehaed Paraglow, and many others. The Decware Zen in absolute terms was poor sounding. Relative, for at the time $ 399 it would have been okayish for a secondary or bedroom system where sound quality is not of great concern. The Bottlehead Paraglow was much better IMNSHO, though even that was well out of it's depth when compared to what I had at the time (a copy of the Le Maison de l'Audiophile "Legacy" 300B Amplifier with EL84 Driver and valve regulated power supply).

With your speakers I think you will be at the absolute minimum need a 300B Amp on the slightly more powerfull side, something like the Broder Patrol mentioned in another post would do okay.

If money is a limiting factor, with current Dollar Course you can get the Lady Day Kit Amplifier from Hong Kong ASSEMBLED (this is pretty good one even stock) with the 91A Circuit Option pack, TJ Output Valves, Tent labs heater supply and Fed Ex airmail shipping for less than $ US 2,400, in English Money thanks top the good exchange rate this comes in at 1,250 Quid plus import duties/taxes (usually 10% and 17.5% Vishously Added tax) for a final landed cost of around £ 1,600 for a pair of Monoblock Amplifiers that are among the best available.

Lady Day 300B SE Amplifiers


If you ask nicely they can even supply the Amp wired for 3/6 Ohm Secondary impedances instead of 4/8 Ohm which would match your speakers better.

If you are getting these Amp's I would strongly suggest to pick up the "Django" Passive Preamp too, the combination will give an amplification chain that is nearly as good as it gets, regardless of cost, in my opinion at least...

Ciao T

PS, I am building up a pair of LDP 91 at the moment, I used to have a pair of the older "Billie" 300B Amp's from DIYHFS (and many other Amp's) and have the Music First Audio passive preamp which at the heart is similar to the Django, though it should be actually be a little better than the Django, but not that much. Speakers are Supravox Fieldcoil 8" Drivers on open baffles, these are actually genuinely 96db/1W/1m sensitive

 

Mondie,

Give Elson Silva from Single End Reserarch Tube Amp a call on 02 9789-3114 and ask about his new GM-70 based SET mono blocks cost around AUD$6000.00 pair with about 30 watts and enough glow & warmth to keep your room warm on Melbourne nights.

cheers

Alan

 

Yeah Robbo, thats what concerns me. l was led to believe most SETS act as unpredictable tone controls on speakers with peculiar impedance curves.

My budget is probably around US$4k; second hand definitley an option.

3DSonics > The Ladyday amp is something l have been curious about for a while and has a strong following. My speaker specs also quote 102dB @ 2.83V/1M so l guess they are even more efficent than l realsied. Never knew the significance of that measurement, thanks for explaining it. l think l will contct DIY HiFi as l wasnt aware they can wire for a 3ohm impedance, that could make all the difference. It would be the Zen signatures that l would go for if l was to buy through Decware. (US$2k)

AlanL > Will do, it amazes me how many little "one man shows" there are in the local industry. Do you have one of his amps?


Thanks for all the replies

Cheers Simon

 

Simon,

I use Elson's amp's they are 4 x 300B's per mono block in single ended mode 45 watts. I have had a listen to his GM-70 amp and would change but I love the 300B sound. A very good friend has Halcro DM-68 & a pair of elson's GM-70's and he tends to use the GM-70 over the Halcro amp's, speakers are Wilson watt puppy 6 cd player is linn cd-12.

Elson is a one man show but has been making amp for many years under the brand cymer and has just change the name due to the chance of moving to the USA with backing to move to the next level.

I would say that the only tube amp's that are on par with elson's amp are border patrol. Elson makes his own transformer or has bruce make them for the amp no off the shelf transformers.

If you do call elson make sure you have an hour or two free as he can talk the ear off anything.

cheers

Alan

inside elson's amp

 

Simon,

I've just ordered a Canary Audio 301 MK2. Now I know it's a PP design, but complete with a full set of new WE 300B's and a three year warranty, this cost me just $3,100 + taxes. With 22wpc it should drive those speakers with alacrity. Definately worth considering IMO.

 

Hi,

SE Amplifiers do that, but you need to understand exactly how "bad" (or not) this is.

Let us take a speaker from a recent Soundstage review that is a fairly difficult load, nomainally a 4 Ohm Speaker, the PSB Platinum T6 and assume a 300B operated at the standard WE condition of 350V/80mA with a 3K load matched to a bona fide 4 Ohm Tap.

Here the impedance curve of the PT6:



We find the minimum impedance to be around 2.5 Ohm around 2.5KHz and the Maximum impedance is 12R @ 50Hz.

Now taking a competently made 300B Output Transformer the insertion loss in Ohm on the 4 Ohm Tap will amount to around 0.25 Ohm. The 300B will have an anode impedance of around 625 Ohm, stepped down by a factor of 750, so the output impedance of the Amplifier will be around 1.1 Ohm.

How much deviation in terms of output level will we find between the highest impedance peak and the lowest drop? The response at 50Hz will be boosted around 1.35db and the response at 2.5KHz will be attenuated by around 1.05db. While this will probably be audible, the effect should be subtle.

Further, pulling the speakers a few inch away from the rear wall will probably flatten out the LF Lift. What is further noteworthy, if we look at the speakers frequency response...



...we find that the speaker has a Response lift in the region where the impedance drop resides and the bass output at 50Hz is already a good deal down, so the frequency response "distortion" caused by the SE Amplifier will end up at least partially fixing errors commisioned by the speaker. This is not always the case, but I have seen similar beavious (impedance drop co-incides with a boost in the overall response) many times.

Further, if the speaker is correctly matched and has an impedance that does not drop more than to 1/2 of the nominal impedance the worst case response deviation is still limited to +2.1db/-1.7db which wile notable is still a lot less than what the room will do.

So I would not worry too much about the Amplifier being an "unpredictable tone control", certainly not next to room acoustics.

The one thing to pay attention to however is that the Amplifiers do not produce above average power levels for their output valves (examples Cary's Amplifiers with a claimed 15W from a standard 300B compared to the common 7 - 9 Watt) because they achieve this by using very low load impedance, increasing the Amplifiers output Impedance. I would personally say that such "specmanship" borders on cheating, but it'#s legal so you need to read carefully between the lines....

Care to name your speakers? 102db @ 2.83V/1m would suggest serious Pro-Audio stuff or at least Semi-Pro....

Talk to Brian. Getting an Output Transformer with a modified secondary impedance wound will take some time, but it has been done. I recently worked wioth Brian on Prototypes of the new "universal" Output Transformers and mains transformers (I believe they are now standard) and turn around time was around 1 Month for the Outputs, the mains transformers where turned around quicker.

But in principle they can get the transformers made for any secondary impedance, even to drive 1 Ohm Apogee Ribbons (not the most sensible thing of course). When I build my next set of Speakers which will have a ribbon tweeter I'll probably have another pair and get them to make me a "ribbon only" output transformer to drive 0.05 Ohm....

Ciao T

 

Thor..how does the new 91 compare to the reg. lady days with mu?

And what about getting the 310....any chance of valve art making them and a 437, how come the Valve art 274 has one plate?

Any isight into the output tx's now in? cheers...

 

Ive had good experience of DIY hifi supply amps. They are also branded in some shops with the brand name ''Consonance''.

My pre-amp is a Consonance pre.

The amps are available as a kit, or made up for you if you want.

They do a lot of options on the componentry, and it really is worth digging deep and splashing out on better resistors, caps, wiring and valves. The free valves you get are ok, but not brilliant.

This paragraph is applicable IMO to most kit/built kit amps. Its almost always worth maxing out the componentry, and upgrading the free valves to something better from the off.

I think Border Patrol amps are excellent, and they have a choice of selection of taps on the back.

I really also like Glasshouse 300B amps (www.hificollective.co.uk). I think these are even better value for money than the DIYhifisupply, and are more attractive. The 300B power amp they do also comes with the option of a passive volume control giving you the option of using it source-direct if you have one source. Im sure you could pay a little more for a few more inputs and a selector.

Also worth a look are the evergreen WAD 300B kits. WAD also make kits for you if you dont fancy the DIY. www.worldaudiodesign.co.uk

Your maximum budget of UK 2,500 pounds would get you a second hand Border Patrol 300B SE, but not much change.

The hificollective amp built up will be around 900-950 pounds (bargain!)
LadyDay - ooh about 1200 ish
WAD 300B monos - about 1300 ish.

IMHO Id pick a second hand border patrol above the others, and then wouldnt find much to choose soundwise between the bottom 3.

I havent heard Mikes new Cary (although it looks to be a bargain - and would be a good choice if you want something that will work with less efficient speakers too) or an Elson amp - which I dont think is available in the UK (?).

Chris

 

Thanks for the great post mate, very informative.

My speakers are Australian made and use the now discontinued Audax Aerogel drivers, link here.Note the specs are revised since the new version uses different drivers to mine.

If your interested there is a little review here also.

Does anyone have any experince with these Consonance Cyber amps, look to be great value for money and getting some good press;

Cyber 211/845

These can be had in Australia for around US$2400. Unbelievably in the UK they are 3000 pounds! Talk about rip off Britain.

Cheers Simon

 

Hi,

Not myself, overwork at work, a spot of heath bother and too much commercial work has delayed my build. According to Brian, who has by now had a few of them assembled they sound great and he likes them better than the 6SL7 versions.

There is NOS stock around still, also of russian made copies. They do tend to cost real money though.

Valve Art? Not bleedin likely. TJ Might, but they have been rather coy about it so far as well.

???!!!???



The 274A is the one on the right, it definitly has two anodes.

Yes, they are basically the same as before, though aparently somewhat improved lamination material. Primary inductance stays exactly as was, the secondary has been provided with additional taps to allow "mismatching" of the primary, basically in the same sort of style as the Tango/Iso XE20S. Primary inductance is a little higher than the tango part, topend response is a little worse, nothing to loose over.

Ciao T

 

Hi,

Ahh. Looks capable, but I think the 102db/2.83V/1m may still be a little optimistic. If they used the 5" Aerogel Midrange the two midrange drivers would have produced 99db/2.83V/1m.

Still, quite nice and above average sensitivity, if your room is not huge you will be able to make do with a 300B.

The operat Suff is not bad, a friend of mine used to import them. He seemed to quite like 845 Amp. I did n't as much care for it. You might want to consider the 300B PSE Version of the Cyber as well.

Ciao T

 

get well soon,T, thanks

any idea on the no. of primary turns? circt 2-2500?

and inductance? at what conditions?

says on the diyhifi site that the 274 is one anode somewhere.
gonna get me some in that case

 

Consonance amps appear to be available in 3 ways -

1) In kit form from DIY hifisupply (very cheap)
2) Built up for you by DIY hifisupply (still quite cheap)
3) Built up for you through a distributor/dealership chain (bloody expensive)

(option 4/5 - buy directly from the factory, or from the country of origin?)

Ive noticed the dealerships offer slightly different Consonance models. Im guessing this is the work of the distributor, who may be trying to prevent customers buying the product for less elsewhere.

My guess is that Brian at DIY hifisupply goes directly to the factory for his kits.

DIYhifisupply has a forum, and if you're considering any Consonance amp, thats another good place to ask questions.

 

Hi,

DIY HiFisupply started out with products that where Kit Versions of Opera/Consonance (specifically one preamp and the EL34 PP Amp plus the 300B SE). This has been changed more and more over the years, both due a wish of Consonance to distinguish their products and the interest of Brian at DIYHFS to improve his DIY Products well past what Consonance manufacturers, in both circuit design and passive components.

Thus you will not find any Consonance product as DIYHFS Kit and you cannot get any of the Kits assembled from Opera/Consonance. Opera still manufacturers the metalwork and most transformers are sources from the suppliers Opera uses, however specifications tend to differ between DIYHFS Transformers and those used by Opera as well.

So, nowadays Opera and DIYHFS products are not all that similar.

Ciao T