Hi there,
I made a little 6C45 single stage SE amp the other day. It runs on about 186V on anode, 2V LED on cathode, sounds very good with airy openness & loads of details...
This flea amp is fed by an active xover, serves from 160Hz & up.
For the other end, below 160Hz, I've tried 300B SE (which was originally at the position of 6C45 SE now)
Mid to high from 6C45 is very good, despite the tiny power under 1w. However, 300B on bass somewhat disappoints me
My 300B amp is so-called DRD circuit, with the same 6C45 as driver loaded by choke & direct couples to 300B. 2 power supplies with individual LCLC, and the output is stacked on the driver. The 300B sees 427V on anode & 71V on cathode with 76mA DC current.
Bass sound from this 300B amp is not all that bad, but sometimes it's too soft I should say.
Even jazz piano trio can make it exhausted. Sometimes, overlapped notes from acoustic bass & kick drum are smeared when they are fast enough. Usually that's when the rhythm getting hot, but with the smeared bass notes, the motivation of the music is lost It became a noisy chaos
However, sometimes the bass solo can be good, with crisp snaps & good pitch definition.
I think it's OK in the mid-bass range, but looses control on the low end...
I've read an article on <Sound Practices> several years back, about the gapped output trany on SE amps. It says, SE amp can actually do better than PP on the bass region, unlike most people might think. That's because the gapped output trany is very linear so the low level details are well kept. This contributes to good bass response.
In my recent experience on this, I doubt.
Before this, I used a pair of antique Altec 1568A for bass. They were modified with 2 pairs of big chokes & more caps. And the original 6CA7 output tubes were swapped to 6L6GC. This amp is good on bass, at least better then 300B SE.
Before Altec, I used a sand amp, a good (& hot) one-- Kinergetics KBA75. It's, simply put, rock-solid. No wonder, it's a "solid" state amp...
Why don't I go back to sand? Maybe it's some kind of obsession with tubes... (and now, not only tube, but low watt and SE... )
Soooo....., what's next? Keep trying to squeeze out more potential from 300B? (until I kill it? I think I've been very close.)
Or, I got several 811A & SV-811-3 which can take high voltage or be driven into A2 to get bigger output.
( But, does more watt really means good bass? )
Or, I should try low-z tubes? I got several 6336....
Or, I should totally forget about SE for bass....
Any thoughts?
I made a little 6C45 single stage SE amp the other day. It runs on about 186V on anode, 2V LED on cathode, sounds very good with airy openness & loads of details...
This flea amp is fed by an active xover, serves from 160Hz & up.
For the other end, below 160Hz, I've tried 300B SE (which was originally at the position of 6C45 SE now)
Mid to high from 6C45 is very good, despite the tiny power under 1w. However, 300B on bass somewhat disappoints me
My 300B amp is so-called DRD circuit, with the same 6C45 as driver loaded by choke & direct couples to 300B. 2 power supplies with individual LCLC, and the output is stacked on the driver. The 300B sees 427V on anode & 71V on cathode with 76mA DC current.
Bass sound from this 300B amp is not all that bad, but sometimes it's too soft I should say.
Even jazz piano trio can make it exhausted. Sometimes, overlapped notes from acoustic bass & kick drum are smeared when they are fast enough. Usually that's when the rhythm getting hot, but with the smeared bass notes, the motivation of the music is lost
It became a noisy chaosHowever, sometimes the bass solo can be good, with crisp snaps & good pitch definition.
I think it's OK in the mid-bass range, but looses control on the low end...
I've read an article on <Sound Practices> several years back, about the gapped output trany on SE amps. It says, SE amp can actually do better than PP on the bass region, unlike most people might think. That's because the gapped output trany is very linear so the low level details are well kept. This contributes to good bass response.
In my recent experience on this, I doubt.
Before this, I used a pair of antique Altec 1568A for bass. They were modified with 2 pairs of big chokes & more caps. And the original 6CA7 output tubes were swapped to 6L6GC. This amp is good on bass, at least better then 300B SE.
Before Altec, I used a sand amp, a good (& hot) one-- Kinergetics KBA75. It's, simply put, rock-solid. No wonder, it's a "solid" state amp...
Why don't I go back to sand? Maybe it's some kind of obsession with tubes... (and now, not only tube, but low watt and SE... )
Soooo....., what's next? Keep trying to squeeze out more potential from 300B? (until I kill it? I think I've been very close.)
Or, I got several 811A & SV-811-3 which can take high voltage or be driven into A2 to get bigger output.
( But, does more watt really means good bass? )
Or, I should try low-z tubes? I got several 6336....
Or, I should totally forget about SE for bass....
Any thoughts?
Bass amps and SE can work well, but you have to be bold. Unlearn what you have learned from HiFi (and put the 300B in the power supply 
)
Breadboard this: 6L6GC SET and drive it with something insane, like a 6CB6. Listen to it (yeah 1 watt, but listen ) Quite the tonal quality and thump, eh? Now just find a more powerful tube.... transmitting tubes are good and don't overlook triode connected horizontal sweep pentodes.
Good luck!
)Breadboard this: 6L6GC SET and drive it with something insane, like a 6CB6. Listen to it (yeah 1 watt, but listen
) Quite the tonal quality and thump, eh? Now just find a more powerful tube.... transmitting tubes are good and don't overlook triode connected horizontal sweep pentodes.Good luck!
Hi CLS,
bass response with SE amps usually is limited by core saturation effects of under-dimensioned OPTs.
However, there is no reason you cannot get, say, 15Hz flat (at -1dB) at 15 Watts Po, at 165mA iddle current, w/o any sign of iron hysteresis, from say, a triple of paralleled triode strapped EL34 or something. Been there, done that. The problem is, you will need a core size of about EI126 with about 1,5-2kg of copper (for each OPT, of course).
Tom
bass response with SE amps usually is limited by core saturation effects of under-dimensioned OPTs.
However, there is no reason you cannot get, say, 15Hz flat (at -1dB) at 15 Watts Po, at 165mA iddle current, w/o any sign of iron hysteresis, from say, a triple of paralleled triode strapped EL34 or something. Been there, done that. The problem is, you will need a core size of about EI126 with about 1,5-2kg of copper (for each OPT, of course).
Tom
Simpleton said:
Still my best tube amp
I still love mine as well!
Because I can't leave well enough alone I'm thinking of replacing the 6N1P cathode resistor with a LM317-based CCS. I have a bunch of LM317s in my parts bin so the modification will cost me a resistor! I'll report back when I finally get around to soldering it in.
Geek,
This is my first post here on DIY I have been a member for some time but your post really hit a stimulating nerve with the debut of PP vs SET and the issue of quality bass from a SET people are not thinking out of the box!
by being bold for instance I use a very fast 200 Joule power supply for each one of my Monoblocks, I use a design that allows me to get the transparency of an all Polyprop based supply while using electrolytics for bulk I discovered this by looking to obtain speed in my supplys
Most people seem to make such an issue over going after noise and using really big chokes of high inductive values, when they should be doing just the opposite by using large cores with low inductive values which keeps the DCR low as well.
I once conducted a little experiment as you know many vintage push-pull amps used a 100 ohm resistor between the first cap that the rectifier uses and the second cap that feeds the output stage center taps.
The resulting music had a punch that was startling opening my eyes!!!
Tubes4e4,
You also hit it on the head! I use the Hammond 75 watt 5k SE for my 10 watt SET there surely is a greater sense of ease with with the larger core great space, supurb low end extension if fact my SET had no trouble at all beating out a Jollita 100 watt hybrid in virtually every area except in sheer volume the soundstage was also only half the size of my SET's alot of this I feel is contributed by the large core of the hammond I also realize that Hammond has not always lived up to their claims in their specs with the SE line but I can say the 75 watter is working for me!
SET12
This is my first post here on DIY I have been a member for some time but your post really hit a stimulating nerve with the debut of PP vs SET and the issue of quality bass from a SET people are not thinking out of the box!
by being bold for instance I use a very fast 200 Joule power supply for each one of my Monoblocks, I use a design that allows me to get the transparency of an all Polyprop based supply while using electrolytics for bulk I discovered this by looking to obtain speed in my supplysMost people seem to make such an issue over going after noise and using really big chokes of high inductive values, when they should be doing just the opposite by using large cores with low inductive values which keeps the DCR low as well.
I once conducted a little experiment as you know many vintage push-pull amps used a 100 ohm resistor between the first cap that the rectifier uses and the second cap that feeds the output stage center taps.
The resulting music had a punch that was startling opening my eyes!!!
Tubes4e4,
You also hit it on the head! I use the Hammond 75 watt 5k SE for my 10 watt SET there surely is a greater sense of ease with with the larger core great space, supurb low end extension if fact my SET had no trouble at all beating out a Jollita 100 watt hybrid in virtually every area except in sheer volume the soundstage was also only half the size of my SET's alot of this I feel is contributed by the large core of the hammond I also realize that Hammond has not always lived up to their claims in their specs with the SE line but I can say the 75 watter is working for me!
SET12
Hi SET12
Interesting point on the use of elco's...how did you compare both? Hvae you built a 200J supply and made AxB comparison? (Should be bij, 200J with poliprop..)
I think that noise is a big issue in SE designs...but you are using low inductance chokes, prefering low resistande in spite of the noise? Have you tried regulated supplies?
I don't understand what you did in your experiment...you talk about the resistor from 100R...but what did you do with it? Shorted, substituted for a choke (low DCR off course, otherwise it's bad).
I am curious - and all ears
Erik
Interesting point on the use of elco's...how did you compare both? Hvae you built a 200J supply and made AxB comparison? (Should be bij, 200J with poliprop..)
I think that noise is a big issue in SE designs...but you are using low inductance chokes, prefering low resistande in spite of the noise? Have you tried regulated supplies?
I don't understand what you did in your experiment...you talk about the resistor from 100R...but what did you do with it? Shorted, substituted for a choke (low DCR off course, otherwise it's bad).
I am curious - and all ears
Erik
Have you measured the high frequency response with this transformer? I need a big transformer for a big amp. I have asked on the forums before if anyone has any experience with them, and my questions went unanswered? I just got a pair of their 1628SE's and the response from 10 to 20KHz is poor.
Below that it is flat down to a -3db point at 14Hz. The bass is killer with a 10 watt SE amp in UL mode. I am also using a low impedance power supply with motor RUN caps for filtering. I can switch between SS and tube rectifers on the fly, and SS has better bass. A big toroidal power transformer and a 40 ohm choke help too.
ErikdeBest said:
Thank you! I use no chokes at all in my 811/572 class A2 amp Just some 1800uf+ in three sections plus the Props as a final cap!( just bypassing with a prop does not get you the transperancy of my supplies) driven by 6EM7 for gain and cathode drive which works very well although I'm sure the power drive would fair better!
If I were to use chokes I would use low DCR ones like Hammonds 1 henry 17lb unit with just 5 ohms I believe I picked this up from Herb Reicharts articles in the former Sound Pratices Magazine from his 300B amp "Flesh and Blood" and based on my experiance he is very correct in the whys he also uses very large Power Iron and bleeds some of it to get good regulation.
The resistor was shorted out!No chokes were added at all! the test was done on a hunch of mine and I never looked back after ward! this ment that the Rectifier was feeding the output stage directly instead of haveing 100 ohms in its path. The dynamic presentation was just a huge change The amp was a PP EL84 with a 12AX7 front end, Being push-pull is a plus here because of the noise cancellation of course when I did this I knew I maybe listening to more noise but that wasn't a concern it was dynamics or the punch as some would say that I wanted we were driving ProAc Response 2's with great delight from its 20 watts/channel.
200 Joules of Polyprop is very costly and not to mention very bulky! how do I know the differance? I removed the parts that allow the supply to sound like a polyprop based supply from my 900 Joule supply in my Phono Stage easy enough then put them back I don't want to discuss what I do exactly because I have never seen it done elsewhere and I have not looked into a possible Patent as of yet so on a classical note the low Inductance and low DCR is in the right direction but I bet that no choke is likely still better the way I implament my supplies
Yes noise is a big issue in SET's but when it is large enough like mine it is less than an issue and I have 98db/watt speakers I have some noise but not audiable with music, To many people make a fedral case out of it still I have my limits to!
You ask about Regulators I have not tackled that issue but J.C. Morrison once said they make the midrange is to barren for him I have work based on some of his Ideas as well and so I have not gone that path I will say and ACR path appears just as important! from my experiance. It is the ACR that the noise is droped across of course!
You should be able to duplicate my experiance even removeing a Dynaco st70's choke should be very audiable and that has a 60 ohm DCR if there is noise use more capacitance. And BTW I prefer pentode mode over Ultraliner reguardless of the extra distorion watch the dynamics go thru the roof with the stock st70 choke removed and the pentode mode!
I hope this helps
SET12
tubelab.com said:
I have followed your 833 work for awhile and have visited your web site and have had alot of entertainment from it! I look forward to conversing about the 833
I was sorry to here about the bad measurements I only hope that the 28lb SE1642 does better I have not measured it basicly my amp is a take off from the Glass Audio Project an 811 Amplifier and its only resemblance is the tubes that it uses other than that its a whole different animal.
Measureing it will be easy enough I own a signal generator and a decent Techtronix scope so when I can get my bench up I'll take those measurements hopefully soon. I have alot of stuff to organize as I recently moved.
The amp is not hurting for high frequency extension so I hope for the best anyway, The 1642SE only has a high pot rating of some 3500 volts so there are limits I have the understanding that you really don't want to use a B+ that is any higher than 1/4 of the hi pot rating I understand that Audio Note has a 5000 volt High Pot rating for their Iron and they have C-Cores available but they are pricy I paid just 450$ for the Hammonds a few yrs ago now I think they are 500$ or more I like them much BTW have you ever tried grounding the positive instead of the negative? I have done this with the Hammonds based on a review of a Hovland EL34 PP amp reviewed by Stereophile and the designer was asked why do you ground the positive instead of the negative of the OPT he said because it sounds better! Being single-ended I tried it easy enough to A-B sure enough it was an improvment in the sound stage size I have never gone back after several demonstrations to friends they all agreed it was better.
My education is 1/2 of an Associate Degree in Electronics enough for a 16 credit certificate in the principles of electronics basicly DC/AC theory and basic Digital I was at the top of my class but I had an advantage in that I was some what self taught I work for a Company called Plexus they are last I looked the 10th largest US electronics company I basicly do alot of functional work for them. I don't think that I will persue a Tech Degree because of my love of tube electronics.
I look forward again to much conversation!
I was born and grew up as a kid in North Miami.
SET12
So if I am following all this correctly, the answer would seem to be...
Conventional SET with relatively small iron optimized for great high frequency extension and clarity and a seperate sub amp with big hurky iron that is not expected to do anything over 150Hz and is optimized for the really low (even infrasonic) stuff. Any technical reason why this couldn't be done?
mike
Conventional SET with relatively small iron optimized for great high frequency extension and clarity and a seperate sub amp with big hurky iron that is not expected to do anything over 150Hz and is optimized for the really low (even infrasonic) stuff. Any technical reason why this couldn't be done?
mike
Are not choke input, or at least resonant choke input supplies, typically of lower output impedance than the capacitor input supplies discussed above?
If I was building an affordablish snazzy passive supply for 300B/EL34/6L6 SE etc amplifier in the US I would go with something like this:
1 500VA 480V xfmr $20, 1 Hammond 193J Choke 10H 82DCR 200ma $44, 24 100uF motor caps 232 Joules $264, 8 1000V UF diodes $3, 2 220nF caps $6 Total: $337 + a bunch of shipping.
Vout for this supply is around 440, ripple is negligible.
If I was building an affordablish snazzy passive supply for 300B/EL34/6L6 SE etc amplifier in the US I would go with something like this:
1 500VA 480V xfmr $20, 1 Hammond 193J Choke 10H 82DCR 200ma $44, 24 100uF motor caps 232 Joules $264, 8 1000V UF diodes $3, 2 220nF caps $6 Total: $337 + a bunch of shipping.
Vout for this supply is around 440, ripple is negligible.
My suggestion for an SE bass amp would be something like this:
Low Rp triodes, two or more in // to allow for a low ratio OPT.
A (big, obviously) custom made OPT with a CFB winding.
I´ve performed som testing on this subject (in small scale though)
and cathode feedback (CFB) seems to be the way to go if you want good bass response from SET´s.
Low Rp triodes, two or more in // to allow for a low ratio OPT.
A (big, obviously) custom made OPT with a CFB winding.
I´ve performed som testing on this subject (in small scale though)
and cathode feedback (CFB) seems to be the way to go if you want good bass response from SET´s.
Hi there,
I'm so happy to see all your informative replies.
SET12,
Big caps without chokes, your comments on tube amp power supply are revolutionary to me! (And I have to give up tube rectifier if I choose to follow)
A while ago, the power supply (for output stage) of my 300B amp was:
5R4GY -> 3u -> 8H/60R -> 100u -> 8H/60R -> 220u (430V)
I remember once I tried keeping the CD playing when power off the amp. And it kept singing for another 20second or so, not loud though.
I'm not sure if this mean good energy storage.
And what's your opinions on voltage regulation?
I'm so happy to see all your informative replies.
SET12,
Big caps without chokes, your comments on tube amp power supply are revolutionary to me! (And I have to give up tube rectifier if I choose to follow)
A while ago, the power supply (for output stage) of my 300B amp was:
5R4GY -> 3u -> 8H/60R -> 100u -> 8H/60R -> 220u (430V)
I remember once I tried keeping the CD playing when power off the amp. And it kept singing for another 20second or so, not loud though.
I'm not sure if this mean good energy storage.
And what's your opinions on voltage regulation?
Cool, I am in no hurry, since I don't have time to build "the big one" in the near future, but I do have a bunch of 833A's that need to be kept warm.
I got about that far at Miami Dade Jr. College before leaving to get a job for the big electronics company where I still work. After 20 years there, they paid for me to go to college and get a couple of engineering degrees. I was fortunate enough to go to a technical high school during the vacuum tube era. I have been tinkering with them ever since.
I have come to the same conclusion. Except that I have been searching for an off the shelf transformer (possibly mis-applied) that will work with CFB (not all will) and present a flat response across the entire audio band AND make good sound.
I have a similar design (using a 12AT7 driver) I have tried several transformers (with more comming) and several different tubes (the KT-88 produces the best bass). CFB helps the bass and lowers the distortion.
No this is done all of the time. For a low cost SE OPT that is good to 45 KHz at 10+ watts, look at the $18 Edcors. The bass amp could be push pull with feedback or even SS, but it is possible to build an SE amp for this purpose.
OK that would be a monster, but effective. I am constantly searching for the low buck approach. Here is my choice:
Big toroid AnTek AN-4T360 (720VCT @ 500mA, 2 X 6.3V @ 5A) $59 on Ebay, 2 FREDs $5, 3 100uF motor RUN caps (Ebay) $33, Choke 1.5 H 300mA 40 ohms, $16 bleeder resistors and small caps $7. The total is $120. I also get about 440 volts with enough current to arc weld, and very fast recovery.
ErikdeBest said:
When the supply gets up to about 6-700uf any noise is gone in my experiance a great sounding tube I'll try and post a pic of mine! I think you'll love it's looks you can then connect the output transformer center taps direct to the rectifiers cap the 6-700uf you can use 5-10 K to feed another 50-100uf and be set! I use only about 5 to 6db feedback in mine! A slow turn on rectifier like a 5AR4 works good or GZ37 that I use with the 1800 UF in my SET
I will limited the next couple of weeks for posting due to my daughter being with me for a couple of weeks.
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