| Sch3mat1c |
6L6 PP (UL or pentode).
Tim |
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| Saurav |
| I have used an 8W amp on 87dB speakers (though my room is bigger than yours). I too mostly listen to rock. I don't think a 300B SE will produce satisfying sound. I currently listen to 96dB speakers on 3.5W amps (1/2 the power, 8 times the sensitivity), and I still wish sometimes that I had a more powerful amp (or higher sensitivity speakers). |
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| Kuei Yang Wang |
Konnichiwa,
First, from experience, with 87db/W/m you need as much power as you can get hold of. With 300B's this means PSE, BUT PSE Sounds MUCh, MUCH worse than SE and in fact, at that point you are better off going Push Pull (I am listening to Push-Pull 45's with 96db/1W/m sensitive open baffle speakers right now - sounds as great as anything i had in my system).
I remember this Amp well. It drove some Watt/Puppy Inspired Speakers (93db/1W/1m 4 Ohm) and mamanged a credible job, but tended to run out of steam when I had really big stuff (Mahler, Ravel/Mussorsky, St Saen) playing.
I think you would be better off with a well designed 2A3 PP Amp (which will cost a lot less than a decent 300B PSE Amp) using "any old EL34 PP Output transformer" and Sovtek 2A3's while spending your money on better (and thus invariably more sensitive) speakers.
If you must have loads of power, consider the 6S33, look here:
http://diyaudio.com/forums/showthre...5822#post285822
Sayonara |
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| Ysabban |
Thanks
if i remember correct
my target is to produce sound level 0f 100dB (which is very loud i guess (120db - jetplane)
and as i saw on other threads
87db - 1w
90db - 2w
93db - 4w
96db - 8w
99db - 16w
so getting a amplifier with 16w output is enough? and i right?
but i realy dont know what the 6 ohm means?
i saw amplifier with 4 ohm and 8 ohm,
if i connect my 6ohm speakers to an 8 ohm amplifier output' is it o.k?
and as for the 6l6pp do u have any source for schematics |
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| Ysabban |
| quote: | | I think you would be better off with a well designed 2A3 PP Amp (which will cost a lot less than a decent 300B PSE Amp) using "any old EL34 PP Output transformer" and Sovtek 2A3's while spending your money on better (and thus invariably more sensitive) speakers. |
for all the 2a3 Amplifiers i saw their output is between 3-6.5w
this is less then the 300b,
if you can direct me to a better schematics, it will be great!!
and for the 6L6 PP , what schematic you suggest?
i have found one schematics on
http://babelfish.altavista.com/babe...lp=fr_en&tt=url
(sorry for the long url but i translated from french to english using babelfish)
Thank you |
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| Sch3mat1c |
Search for some... thousands to chose from...
Tim |
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| fdegrove |
Hi,
| quote: | | I think you would be better off with a well designed 2A3 PP Amp |
Couldn't agree more...more than ample for my bedroom two way 88dB/W speakers.
Cheers,;) |
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| arnoldc |
| may i ask about your experiences between PSE 2A3 vs. PP 2A3? |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Ysabban
if i remember correct
my target is to produce sound level 0f 100dB (which is very loud i guess)
|
Hmmm. 100db WHAT?
100db short peaks or 100db sustained average SPL? At 1m Distance or where you are sitting? The Milkfloat Driver calculation you present is mathematically correct, but irelevant to the topic.
At a classic concert with large scale music I measured a highest AVERAGE Sound Level of around 90 - 92db on the climaxes. Knowing the ballistics of the meter used AND the dynamics of live music I expect at least 10db higher peaks. In recorded music I usually find a crest factor (peak to average ratio) of around 10db.
Further, each time you double the distance to the speaker you loose 6db SPL in normal free field conditions. Using a stereo pair of speakers in a room reduces the drop in SPL and boosts SPL, but it remains that with around 3m listening distance you need a 1m/SPL at least 6db higher than that desired at the listening position.
So, let's calculate what is needed for 100db at the listening position with a 10db crestfactor. First, peak power is 3db higher than the RMS power, so we need to reproduce 110db peaks but only 107db "RMS" at the listening position. In addition we need to account for the drop in SPL with Distance, so we add another 6db to give us an SPL requirement per stereo Speaker of 113db/1m at rated amplifier power. Assuming a 20W RMS Amplifier (or 13dbw) we require a Speaker pair with 100db/W/m sensitivity.
A Speaker with 87db/W/m would require an amplifier with 26dbw output power or 400 W RMS, assuming the speaker could handle this kind of power and/or would not alrady heavily compress.
If we relax our requirement to 92db at the listening position with 10db crest factor we still need 99db "RMS" at the listening position and around 105db/1m. This can be achieved by using for example a 95db/W/m Speaker and an amplifier with 10dbw Power (eg. 10W RMS) or an 87db Speaker with with 18dbw Power (eg. 65W RMS).
| quote: | Originally posted by Ysabban
so getting a amplifier with 16w output is enough?
|
MOST LIKELY, NO.
| quote: | Originally posted by Ysabban
but i realy dont know what the 6 ohm means?
i saw amplifier with 4 ohm and 8 ohm,
|
Would you feel it a good idea to put a 120W Lightbulb into a fitting rated at 80W? A Speaker with a nominal 6 Ohm Imepdance usually has impedance drops to below 4 Ohm and belongs really onto the 4 ohm Tap.
That said, sometimes the subjective percieved effect is better with a lower impedance speaker on the higher impedance tap. In most cases Valve Amplifiers are tolerant of even short circuited outputs and thus you cannot easily damage things by connecting the speaker with the wrong impedance, but the sound may not be good.
Are you sure that you should attempt to build a Valve Amplifier, with lethal voltages inside from scratch (as opposed to a kit) if you do not know the basics of electronics? I would advise against it. It may be better (and safer to you and your loved ones) to start with a kit.
Given your speakers, how about the DIY HiFiSupply "Ella" Amplifier? This will give 40W in Ultralinear mode and maybe 15 - 20W in triode connection and at a later stage, when you have more experience, you could convert the Amplifer to use 300B's in Push-Pull and hardwire the entire circuit for better performance.
http://www.diyhifisupply.com/diy_kits/the_ella.html
If you where to purchase better Speaker (better automatically means higher sensitivity, if you accept that lower distortion and compression mean "better") you might be able to use the "Joplin" 2A3 PP Amp from DIY HiFisupply, I use a modified version of this myself, currently with 45's but I can fit 2A3's and 300B's also.
http://www.diyhifisupply.com/diy_kits/the_joplin.html
My Joplin through the times and mods....
http://www.diyhifisupply.com/KYWJoplin/KYW.htm
| quote: | Originally posted by Ysabban
for all the 2a3 Amplifiers i saw their output is between 3-6.5w
this is less then the 300b,
|
With my own Joplin Amp I get around 10W RMS if fitted with 2A3's, 12W RMS if fitted with 300B's and around 6W RMS if fitted with 45's. Please also note that I recommended to use the 2A3 PP Amplifier in conjunction with better speakers. A 2A3 PP Amplifier is much cheaper to build than a 300B SE Amp and can sound very good.
| quote: | Originally posted by arnoldc
may i ask about your experiences between PSE 2A3 vs. PP 2A3? |
I have compared 300B PSE vs. SE (in the same Amp - I literally removed one valve and connected the 4 Ohm Speakers to the 2 Ohm Tap) and various SE vs PP (2A3, 45, 10/VT25, 300B, 845, 813).
Most PP Amplifier literally suck, not sure why. I found that certain direct and transformer coupled PP designs (like the Amity from Lynn Olson) have most of the positive attributes of SE Amp's with non or very little of the negative attributes of PP Amp's.
PSE Amp's can sound okay on some recordings, on others the loss of resolution and transparency is not small. Comparing the Audio Note Japan Baransu (300B SE) to the more expensive Kegon (300B PSE) on suitable speakers (like Avant garde Duo's) illustrates exactly what I mean.
I hope this helps.
Sayonara |
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| PTSOUNDLAB |
Hi,
for Rock and 87db speakers, try World Audio Design KiT88 or Kit6550 40W class A , great amplifiers.
WAD don't make KiT88 anymore but you can see (and buy) the 6550 40W class A here http://www.worldaudiodesign.co.uk/
I have build a KiT88, with some modifications, the sound is great for a good price (you can see the schematic and building here http://ptsoundlab.free.fr/sectubes/...assakt8840w.htm sorry it's in french).
And the KT88 or 6550 have not the "too much medium and not enough bass" of a 300B, and Class A is the best (for me ;) )
Best Regards
Pascal. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by PTSOUNDLAB
And the KT88 or 6550 have not the "too much medium and not enough bass" of a 300B |
EXCUSE ME!? It is precisely the vastly superior Bass that struck me upon converting push pull Amplifiers from Pentodes (EL34/KT88/6550) to 300B. I think you heard Amplifiers incidentally fitted with 300B's that behaved like you describe, but under "all else sufficiently equal" conditions the 300B whups the butt of any KT88 or 6550 BIG TIME.
Sayonara |
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| dhaen |
Thorsten, I think you missed the double negative in his sentence...
These Romance languages...:xeye: |
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| PTSOUNDLAB |
Hi,
I have indicate that it is my opinion and not a generality ;)
After having building SE amplifiers (845, 300B, 2A3 and SE KT88) with good transformers, for me, the 300B have a fabulous medium, but just a little bit too much in front, 2A3, KT88 or 845 have more linear frenquency range.
I have 2 set of loudspeakers, more than 96db loudspeakers and 91 db loudspeaker, so I have try SE and PP.
For me and for a standard loudspeaker (not high efficiency), 300B are great but a little bit "too much" in medium, 2A3 have not enough power but it's like 300B with more basses, 845 is not cheap, KT88 Electro Harmonix sound great in SE or PP. But it's just my opinion.
"Cordialement" (in French)
Pascal. |
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| Ysabban |
thank you
right now i am more confused than before
but at least now i know why
right now i am trying to understand the info you gave me
looking for more web resources
| quote: | Originally posted by Kuei Yang Wang
Are you sure that you should attempt to build a Valve Amplifier, with lethal voltages inside from scratch (as opposed to a kit) if you do not know the basics of electronics? I would advise against it. It may be better (and safer to you and your loved ones) to start with a kit. |
i will not build this amplifier alone by myself, i will use the help of people i know that will guide me
i dont want to start with a simple kit because i don't want to build another amplifier again
i want to invest my money and efforts on one good amplifier
thank you
btw : i am still looking for schematics
i found this site with few amplifiers schematics, and i would be gratfull if you give your oppinion about them
thank you again
and a happy new year!!!
:joker: |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Ysabban
i dont want to start with a simple kit because i don't want to build another amplifier again
i want to invest my money and efforts on one good amplifier
|
In that case sort out your speakers first. Also, note that parts quality in such an amplifier is crucial.
My PERSONAL TAKE on a VERY GOOD Amplifier, suitable for speakers 95db/W/m or higher sensitivity would be:
WE 437A Driver Valve OR Russian 6S45-PE, operated at around 10mA/10k Anode Load
TJ Mesh Anode or WE 300B operated at 350V/60mA/3k5 Load probably Tamura F7002 or F5002 Output Transformer, any decent Gridchoke (Stevens & Billington, Magnequest etc.), Solen/Audyn/M-Cap/Angela Tinfoil coupling Cap 0.22uF/630V around the 300B.
Powersupply should use matching (the Output Transformer in looks) Tamura Mains Transformer Chokes equivalent to PC3004/3007. Rectify the PSU with TJ or WE 274A/B Valve or RCA brown Base 5R4GY, CLCLC Filtering with 4uF/8H/47uF+/8H/47uF+ for the 300B and RCRC filtering for the WE 437A with 6K8/22uF/6k8/47uF from the 300B Anode Supply.
All PSU filtering capacitors should be either MKP Metal Can encased (like "Motor Run" Capacitors) or if you must follow audiophool propaganda Black Gate, where you need to buy the most expensive series to get decent sound.
Resistors I'd recommend Mills Non Inductive Wirewound throughout and for the Chassis Monoblock, wood would be good as main material.
Budget at least around $ 3000 in parts ($ 5000 if you go for all WE valves) for this, to make sure you don't run out of money early.
The resulting Amplifier, if well build, should be among the best in the world, regardless of money etc, assuming that around 8 Watt power suffice.
Sayonara |
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| Ysabban |
| quote: | Originally posted by Ysabban
i dont want to start with a simple kit because i don't want to build another amplifier again
i want to invest my money and efforts on one good amplifier
|
Well , 5000 $ :faint: , i have limited my budget to 1500$
i am not looking for the best of the best
i just want to enjoy it, but i dont want to buy 300-4004 kit and them build a better one,
i guess 1500$ is small amount of money
but i am sure i will manage
thank you |
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| PTSOUNDLAB |
Ysabban, sorry if you are confused by what I say,
but don't forget one or two things when you try to find the "graal":
If you listen Rock like you say, it's certainly better to have a fast amplifier with good deep bass.
With Class A you have a real better medium with a real real good définition
With your 87db loudspeakers, try to find an amplifier with good power.
It is not because an amplifier or components have a high price that it is a high quality. The price don't make the quality. You have very good quality transformers like Audio Note, Lundahll,... for a good price. You can find so, some esoterics transformers made by little stores (we have some in France) and the quality could be better than others.
You can make a great amplifier for 1000 dollars or euros and you can make a great amplifier for 10 000$ or euros. In first, choose the price you can pay ;)
"Cordialement"
Happy new year to all !!!!
Pascal. |
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| fdegrove |
Hi,
| quote: | | Well , 5000 $ , i have limited my budget to 1500$ |
For USD 1500 I'd opt for a PP 2A3...
I can wake up everybody in a second even with my 88dB/W speakers...
| quote: | | Happy new year to all !!!! |
Ne pas si vite...On est que le 31...;)
A propos, "cordialement" en anglais c'est "cordially".
Cheers, |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Ysabban
i have limited my budget to 1500$ i am not looking for the best of the best, i just want to enjoy it, but i dont want to buy 300-4004 kit and them build a better one,
|
Well, you get kit's on any number of level.
Anyway, assuming you absolutely want to keep your speakers you are definitly in the territory for a Push-Pull Amplifier, probably parallel Push-Pull if it is supposed to be Class A and (maybe) triode Operation. A PPP (Parallel Push Pull) Amplifier using triode wired KT88/6550 should provide between 40 to 60W Output.
I would probably recommend a variation of the Quicksilver Circuit, such as used in the old Qicksilver Monoblocks but scaled up to use multiple parallel Output Valves. Among the PPP Amplifiers I came across the Quicksilver sounded rather good.
You should be able to google the needed info on the net.
One option would be to base your Amplifier on the Velleman Kit's:
http://www.velleman.be/common/product.Aspx?id=19149
http://www.velleman.be/common/product.Aspx?id=337980
They do benefit from improved passive components and/or circuit modifications, but they fairly closely match the Quicksilver Design and offer an excellent "High Power" Amplifier Platform. Or you could build somthing like it from scratch, likely with less ideal fit & finish.
Sayonara |
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| PTSOUNDLAB |
Hi,
thank you Franck ! "Cordialement" is more poetic than "cordially" ;) :) but I will try. Congratulations for your french.
PP 2A3 is very good, I have try a PP2A3 http://ptsoundlab.free.fr/sectubes/...2w/pp2a312w.htm (with Triangle 91db loudspeakers), great for under 1500$.
An other very good amplifier in class A for under 1500$ is a 6V6, 6v6 are very close to 300B. This is an exemple in double PP http://ptsoundlab.free.fr/sectubes/...v6gtclassea.htm
If you want a 300B, Audio Note Conquest 18W is very very good http://ptsoundlab.free.fr/sectubes/...b/audionote.htm
Ysabban, there is a lot of good amplifiers under 1500$, but for a more 15W PP under 1500$, I recommand WAD KIT88 or KIT6550 with KT88 valves 40W Class A, great for the price. You can buy it in kit at WAD or build one with schematic they give free.
I have build one KIT88 with some modifications like I have said, and some french and belgian people have do it to after me. If you can read a little bit french, you can find some informations on my forum's site http://ptsoundlab.jexiste.fr/forum/viewtopic.php?t=36 . If you choose KIT6550, wad have an english forum http://www.worldaudiodesign.co.uk/forum/index.php
Don't forget that for building an amplifier at a good price, you can find KT88,6550,2A3,6V6 very good valves for less than 300B or 845 very good valves.
I don't know if in your country you will find parts at the same price, but here in europe, for 1500$ or a little bit more, a great amplifier is a SE 18W 845 http://ptsoundlab.free.fr/sectubes/...alimseparee.htm . Certainly the best for this price.
Best Regards.
Cordially ;)
Pascal. |
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| Jaap |
| You can build a very decent en not too expensive amp that has tubes at the front and transistors and the back end. I once build an Italian kit with good result. If you don't want the best of the best and don't want to put fire on your wrong speakers......:smash: |
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| arnoldc |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
WE 437A Driver Valve OR Russian 6S45-PE, operated at around 10mA/10k Anode Load
TJ Mesh Anode or WE 300B operated at 350V/60mA/3k5 Load probably Tamura F7002 or F5002 Output Transformer, any decent Gridchoke (Stevens & Billington, Magnequest etc.), Solen/Audyn/M-Cap/Angela Tinfoil coupling Cap 0.22uF/630V around the 300B.
Powersupply should use matching (the Output Transformer in looks) Tamura Mains Transformer Chokes equivalent to PC3004/3007. Rectify the PSU with TJ or WE 274A/B Valve or RCA brown Base 5R4GY, CLCLC Filtering with 4uF/8H/47uF+/8H/47uF+ for the 300B and RCRC filtering for the WE 437A with 6K8/22uF/6k8/47uF from the 300B Anode Supply.
|
hi kuei yang wang,
where can i get pin configuration of the 437A (duncan's TDSL does not have those)? i believe i have stumbled upon these tubes from a friend of mine, but i picked up the 417As instead. i might just make one as my ultimate 300B.
edit: oh i found it Here |
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| agent.5 |
Hi kuei yang wang,
Just wondering if you have compare different WE pentode tube used as drivers? How does 437A compare to 310A (or 328A)? |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by agent.5
Just wondering if you have compare different WE pentode tube used as drivers? How does 437A compare to 310A (or 328A)? |
Well, the 437A is a Pentode, High Transconductance type. It sounds different to pentode drivers in general. It is best employed with CL coupling to the output Valve in a design meant to employ a little Class A2 for maximum power.
I will soon build another 300B Amp which will be based either on on the WECO 91A or maybe the Shindo 300B Limited, as I have WE 310A, WE 311B, WE 300B and WE 274A Valves at hand. I'll tell you about WE Pentodes then.
Sayonara |
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| RMS |
Hi Ysabban,
I have a similiar current post where I list a few links to schematics. I too am looking for suggestions mainly from people that have built an amp from a "Reliable/Tested" schematic. I also listen to rock. I get the feeling 300bs are for clasical music? Pluss the cost to build that type of amp seems like alot more than what we may want or need for Rock.
Have you ever built a tube amp before? I have only built one audio amp and two guitar amps.
Rob |
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| RMS |
| Sorry about the double post my mistake. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by RMS
I have a similiar current post where I list a few links to schematics. I too am looking for suggestions mainly from people that have built an amp from a "Reliable/Tested" schematic.
|
Well, I have build quite a few Amp's myself, plus helped many friends with theirs. I am familiar with Kit's from WAD, Bottlehead, DIY HiFisupply, Audio Note and Edison/Audion, plus many a scratch build unit. My tastes in sound and music seem less catholic than most, so my comments need to be seen in context.
I would suggest to avoid public endless flames from those who react badly to having their favourite 300B SE Amp (and co-incidentally also the only they build) criticised, you can send me a direct mail if you want comments from my viewpoint.
| quote: | Originally posted by RMS
I also listen to rock. I get the feeling 300bs are for clasical music?
|
Absolutely not. They do great on Rock, Pop, Rap and all sorts, given suitable speakers.
A pair of 15" Tannoy Coaxials in suitable large (230 litre) corner cabinets (97db/1W/1m, 16 Ohm, appx. 30Hz - 18KHz +/-6db 1/3rd ocatve pink noise in room) do great with all kind of music, driven by 300B's.
| quote: | Originally posted by RMS
Pluss the cost to build that type of amp seems like alot more than what we may want or need for Rock.
|
You can build an amplifier on any sort of Cost level. You can build the basic Kit from DIY HiFisupply with Valve Art or Sovtek 300B's for a little over $ 1,000. But in this form the Amplifier is okay comapred to other affordable Kit's although it knocks the stuffing out of some of the less expensive commercial 300B SE Amplifier, BUT it is far from the best sound you can get from a 300B, be the music Rock, Pop or classical.
Sayonara |
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| barretter |
| Wei thinggywotsit is quite wrong : the 437A is a very high transconductance triode , similar to the British 3A/167M but with a different base (magnoval, I beleive). As to how it sounds...I've never been able to afford one! |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Ysabban
right now i have few choices
|
Just to be sure, you are aware that all your "choices" will sound drastically different to each other?
And I hope you do not mind me saying that non of the choices you list strike me as having the potential for particulary good/outstanding sound either. Of the whole lot I'd probably choose the AN PSE Amp if I absolutely HAD TO CHOOSE one of these.
But even then I think you would be miles better of building a copy of the design by Simon Shilton (SJS) PSE Amp, this is easily adapted to PSE 300B, simply change Bias and +B Voltages to suit...
To make this schematic suitable to 300B's you simply add a moderate value Input Capacitor to the two +C Supplies, to bring the +B up to 350V under load, try 2u2 for starters. Equally a small value input Capacitor would likely be apropriate for the -B voltage to bring this up so 300B Valves can be biased correctly.
However, even the designer of the above prefers an amplifer much along the lines of my own preference, as shown below:
If you cannot find the WE 437A or think it too expensive, the E810F or E55L Triode wired works great too in the same circuit, maybe with a slight adjustment of the cathode resistor. Of course, now you are down to 8..10W Output Power.
My own implementation of a similar style amplifier looks like this:
This BTW was build on the Chassis and using the main components of the Kit from DIY HiFisupply.
My personal favourite for your direct situation keeping your existing Speakers, would likely be the circuit attached below, but the output stage changed to Parallel Push-Pull with 2 or 3 Pairs of Valves Ultralinear or even better Triode, you can use both EL34 and KT88/6550 as long as you bias them right.
http://www.bonavolta.ch/hobby/images/audio/8417a.gif
Original Power Supply:
http://www.bonavolta.ch/hobby/images/audio/8417p.gif
You would have to scale the Supply up to provide sufficient current for 2 or 3 Pairs output Valves and you need the change some desgin items to provide for the use of KT88 instead of the originally used valves, described here:
http://www.triodeel.com/8417.htm
The result would give you a "Homebrew" Quicksilver M135 Amplifier, one of my favourite "normal" Push-Pull Valve Amp's for "normal" Speakers. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by barretter
Wei thinggywotsit is quite wrong : the 437A is a very high transconductance triode |
My bad, I meant TRIODE, but somehow wrote Pentode, as the discussion was about them. Anyway, my usual lysdexia.
Sayonara |
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| Ysabban |
Hi Kuei Yang Wang and Ptsoundlab
thank you for you help (and everybody else)
i will now take you advice, and read more learn the schematics
and when i iwll start to build my project i will post picture and some building log about it
thank again |
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| Jaap |
For somebody starting with building amps and with the wrong speakers a hybrid amp could be the answer. What is your opinion on this one (GY 50). I build it as a starter some years ago and it was a satisfying experience, except that it uses PCB's which are not good for changing and experimenting after building.
You can find the kit at: http://www.audiodesignguide.com/ba/index.html
There is also the proposed parallel PP amp in kit form.
Those Italians are good in tube-amps
:bigeyes:
Pipo |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Jaap
For somebody starting with building amps and with the wrong speakers a hybrid amp could be the answer. What is your opinion on this one (GY 50). I build it as a starter some years ago and it was a satisfying experience, except that it uses PCB's which are not good for changing and experimenting after building.
|
Well, IF for arguments sake, you'd ask what I'd recommend as beginners Amp, hybrid and all, look at the attched. I think the resulting Amp would sound not halve bad.
Op-Amp chip of course National Semi LM3875 and yes, the whole shebang on the positive input can be replaced by a wire, if you are not worried about offset and the Amp may sound better that way. Also, you COULD return the positive input (with or without RC combo) to the 1 Ohm Resistor (negative speaker terminal) instead of ground, achieving thus not a positive output impedance of around 3R but a negative one of around 0.6 Ohm.
Or shortcircuit the 1 R resistor for a "low output impedance" option. One could fit a switch to select between -0.6R (return Op-Amp positive input to 1R resistor), appx. 0R (shortcircuit 1R), appx. 3R (schematic as shown) or appx. 6R5 (switch 1R to 2R2), depending upon speaker needs or listeners desires.
Sayonara |
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| shermanr |
Hello Schematic Seeker!
After reading through so many interesting follow-ups, I have my 2 cents worth (yup, another opinion!)
If you want the most neutral SE output transformers available today, choose the one's from UK's Audio Note. This iron gets the best reviews as compared to other esoteric types.
Money-no-object, then the venerable Tamura iron is the de-facto choice for success, as is the Magnequest transformers Mike LaFevre is winding.
As far as topology and power for a given speaker, you will need to know if your particular speaker is 'tube-friendly'.
Efficiency alone is not the holy-grail for good low power SE sound. A particular speaker must exhibit a benign Phase and Impedance characteristic. Just because a speaker puts out 100 dB at 1m/1w does not imply single ended success.
The whole subject of single ended low power has ended up as a hype driven subject with people who recommend stuff they truly know will only work after being tested, not because a specification implies a good match.
My recommendation is to buy the best SE output transformers, Choke and Power Transformer possible, then you begin to develop your design around these parts.
The 30 dollar coupling caps mean nothing is the circuit is not up to par. I see so many DIY aficionados spending hundreds on esoteric parts for equipment which inherently will never see the likes of a Stereophile Testing review. One will really only know if the design stands up when 0.90 cent NTE coupling caps sound about as good as 30 dollar Copper Foil Paper-in-oil.
Start cheap, listen, then upgrade.
To spend allot on parts is not the best for DIY. Get the amp built with the best transformers and you will the be rewarded with 98% of the sound. The other 2% will be in that 30 dollar capacitor.
As far as NFB designs are concerned, they never measure well, but can sound great with the right speakers.
If you are worried about a good 6 Ohm match, simply have your transformers wound with a 6 Ohm and 8 Ohm set of taps. That way you can be sure about your experiment with what sounds best.
I like the PSE 2A3 schematic, this looks like a promising design.
Myself, I built the original Kismet 2A3 and with some tweaks have an amp that some say rivals OEM designs in sound quality.
BR/
Rich |
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