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Old 27th March 2002, 02:10 PM   #1
protos is offline protos  Greece
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Default Difference btw SE and PSE.

I want to build a good quality hi-end tube amp able to drive 90db 4ohm speakers in an average size room. It seems that I will need at least 15-20 watts and was looking at some PSE 300B kits as the possible solution. I was wondering how much of the SE magic you lose if it is PSE. Since I am looking for a reasonably powerful amp I was also wondering about finding a 845 kit but they don't seem to be available or are not so popular in kit form. Being a newcomer to DIY valves I am still confused about the relative merits in terms of sound quality regarding different tubes. Do DIY kits compare favourably to hi-end products like Jadis,Cary etc?
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Old 27th March 2002, 10:56 PM   #2
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Protos,

It is indeed a widespread notion that DIY is “Cheap and Nasty”. This has been the tradition. This is not always true.

There are a growing number of audiophiles, who resort to DIY because they have sampled many of the so called high end (“Reviewed, Respected and Glorified with glossy ads in leading underground magazines”) products and are not satisfied with them. I have been on that road and so I set out to design my own since the eighties.

Most commercially available power amps (including AudioNote, Audion, Audio Research, Carey, Jadis, Marantz…..) are made to be “Compatible” with generally available speakers. These are not dedicated products to suit your system. So if you wish to create what you can live with, then, you should “roll your own” amps and preamps.

If you are looking at 20W Single Ended, then you are going to have to deal with voltages approaching four figures. If you think that you can handle this, then by all means try building a kit. This is a starting point and it is the easiest way to learn, if you are technically inclined.

As to Single Ended or Parallel Single Ended, I quote from one of my earlier notes on this forum discussing the merits of SE vs PP.

SE vs PP

Single Ended amps are for those who are pure in heart and mind. For they shall listen to heavenly music.

A properly designed and built SE amp will be more musical than a Class A PP amp.
The difference to my ears is mainly in terms of tonal purity, real dynamics as opposed to the ‘slam’ of most PP amps and the ability to present a wealth of low level information that is simply not there with PP amps.

To enjoy the maximum benefits that Single Ended amps are capable of, we need speakers without crossovers. This means that the voice coil of the driver should be connected to the output transformer. In the old days, Philips made 600 ohm voice coils to suit their OTL amps. I wish a few of the present manufacturers would consider making full range (well, almost full range should be adequate for 90% of recorded music) drivers with 600 ohm voice coils. Some 5 years ago, I did take up the matter with Lowther and when I replied that I am willing to purchase 10 pairs, there was a brief silence at the other end of the telephone line and the discussion topic changed!

A less puristic approach will be to engineer the front end and output transformers of SE amps to roll off at frequencies appropriate for a selected driver. This means that we need separate amps for each driver and the drivers should be capable of operating over a wide frequency range to suit 6dB/octave roll off. This is going to be an expensive affair and could be outside the domain of most DIY enthusiasts. Besides, the wife would not like all those wires and ugly cases taking up more than their deserving share of the room. I hope that I have not offended some of our members.

Yes, paralleling output tubes and increasing the current drive to these tubes is an option to increase power output at the expense of loosing a puristic approach. Bottom line is that no two tubes would act alike. Full stop. We will need to match the tubes regularly and adjust the bias at each listening session. This is the story of PP amps.

Yes, there are ways of forcing the tubes (shared cathode resistors is a simplistic and effective approach) to be more consistent and follow each other more closely under signal conditions. The tubes then become rather restricted in their voltage and current swings because one tube may not exactly like what its neighbour is forcing it to do. The net result is somewhat diminished transient response (pulse rise time) than otherwise would have been possible with a single tube.

My opinion is that SE is for purists and single driver systems. PP is a more practical approach for systems with multiple drive unit systems. Yet again, some of my friends with ESL 57 say that parallel SE is more musically satisfying than their PP amps.

Mohan
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Old 28th March 2002, 08:38 AM   #3
argo is offline argo  Estonia
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protos

You could try A 15W SE POWER AMPLIFIER WITH 6C33C-B from Borbelyaudio http://www.borbelyaudio.com/15wse.pdf

B+ is less than 400V (three-digit figure)
The amp can pushed even to 18 - 20 W, according to designer.

I haven’t built nor heard this amp but as Mr. Borbely is reputed to be very talented designer in audio electronics and I have listened some other 6C33C-B SE amps, I can still recommend building this amp.

They also have a kit available (does not include box though)

Argo
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Old 28th March 2002, 10:30 AM   #4
griff is offline griff  Australia
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alright, i listen to a fair bit of rock, alt, etc, influences including Superheist, Slipknot, Fuel, Silverchair, Incubus, its all hard hitting music, what kind of amp would best suit me, i like it loud but i also like it accurate, meaty and dynamics i feel is the heart of all music.
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Old 28th March 2002, 09:01 PM   #5
dice45 is offline dice45  Germany
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Griff,


the rock music you mentioned demands a high average power output and this is a weak point of SE amps. They do not excel in pressing on and pressing on and pressing on, they excel in an extremely wide dynamic range where occasional power peaks are few and occasional (very soft) clipping does not hurt.



For rock music i would prefer a well-built PP tube amp to any SE amp.

Technical background : a class-A PP amp is a constant load for its PS.



Mohan,

may i slighly disagree with you?

Let's not compare a medium quality PP amp with a 1st class quality SE amp. Allen Wright's fully differntial PP amp was equalling this wonderful Border Patrol WE 300B amp, except in the bass, there it was easliy shouldering it.

Parallel SE however is better than its rep. I too would prefer a good parallel SE amp to an inferior PP amp. My friend Hartmut built such an amp, one 300B *replaced* by 3 EL84 in parallel. He prefered it. I cannot tell how the amp sounded with 300B, but i truly like it with 3x EL84. Same OPT.

What i prefer more is Allen Wright's PP amp, using noname EL34.



argo and protos,

if anyone tames the 6C33, then Mr Borbely. But it is a hard-to-tame tube, it is thermally so unstable! The tube runs very hot on 500mA, it gets hotter, its plate resistnace changes due to this, applied bias is not enough, os plate current increases further. I hope Mr Borbely's kit has a bias regulator. Compared with this sort of thermal instability, power bipolars are a kid's toy. As my friend Bernhard B. can tell from own hurtful experience . The kit of challenges is not yet complete; the 6C33 is super high transconductant so that tiny variation in supply voltage yield considerable changes in quiescent current. And an OPT with 300 Ohm primary @ 500mA is needed which does not yet faint at 50 Hz.



THe 6C33 is often preferred to 211 and 845 because of its low plate voltage; people tend to avoid 1000V DC. That's wrong IMO, 90mA @ 1000V are much easier to tame than 500mA @ 200V.



I would not be as bold as tinkering with the 6C33, i would do my 1st steps on a good old 211 or 845. THe 845 is for the a bit more bold people, it wants to see about 300V p2p at its grid. But yes, it is possible to achieve this without using a 2A3 and an interstage trannie. My buddy Peter Hartmann built such a thing, sonics just gorgeous, using 6SL7, 6SN7 and 845. He might volunteer the schematic, but i have to ask him for that.



The 211 is good for 20 watts and the 845 for 25-30 watts in SE mode.
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Old 29th March 2002, 10:09 PM   #6
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Griff,

We cannot have everything we want and all at the same time. Do you have Klipshorns or Altec Voice Of the Theatre?
If you do not have high sensitivity speakers, then, I cannot add anything more to Bernhard’s advice.

Mohan
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Old 29th March 2002, 10:11 PM   #7
griff is offline griff  Australia
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so high power amp with any sensitivity speakers would be more adept then low power tube/valve with high sensitivity speakers?
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Old 29th March 2002, 11:50 PM   #8
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Griff,

Conceptually you are quite correct. However, the difficulty arises in finding or building a good high power amp. Over the years, I have auditioned many so called State of the Art high power amps (both solid state and tube kinds) and found none to my liking. The only amp that came close was the Stax DA300 Class A-PP.

Mohan
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Old 10th June 2002, 04:19 PM   #9
A'af is offline A'af  Indonesia
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Exclamation Stadium V

Hey, music lover

When you getting involved in single ended area (tubes or solid state) with preffered single driver (efficient one), becareful cause now you're in Stadium V like Cancer disease (if you're still live you're became maniac, ooopps) so we are gonna meet in Heaven.

End of Sermon


Best Regards,

Goodfella,
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Old 14th June 2002, 12:03 AM   #10
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For the rockers that have less than 92db efficiency speakers a good place to look would be 6550/KT-88 Ultralinear PP. A good simple example of this is the Dynaco Mark III. I like rock from my teens & 20s all those years ago and truthfully PP does a good job. PP does a good job with all types of music, but when I want to seriously listen nothing beats SE. And all SE is not created equal. I listened to a pair of C. Johnson SE 845s. Good amps with lots of power for SE but 845s do not compare to 300Bs. Watts are relative. Sound quality is not.
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