Andy Bartha said:
That amp was created before all his Aikido stuffs surfaced. I think he will approve this amp.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=65708&highlight=
And now , is your mod worth the effort ? 
cheers , Pierre 77series, here is the link you asked for re WE91Clone
(still wired as a pentode... I will updated this thread one of these days)
http://www.diyaudio.com/forums/showthread.php?s=&threadid=109140
coresta, yes this was worth the effort.... I CAN hear the difference.
(still wired as a pentode... I will updated this thread one of these days)
http://www.diyaudio.com/forums/showthread.php?s=&threadid=109140
coresta, yes this was worth the effort.... I CAN hear the difference.
Thanks for the information on your 91A experiments. I like the idea of the 91A but I was thinking of using either the 6J7 for the classic route or the 12HG7 or D3a for the lean-n'-mean version. For just a slight increase in cost though I think the interstage coupled versions would be best. The choice now is between the all DHT, which seems like a very good choice, or the 417a or 12HG7 (triode strapped of course). The DRD is still on the table but recently I have been very interested in some of these "other" designs. I am planing in the very near future to build a Moebius SRPP line amplifier, I know some don't like it but I have read a lot recently about SRPP.
That is interesting though about your 91A, what do you feel...er...hear you gained from the change?
BTW yes I am planing on using a line amp, I am kind of on a line amp kick as of recent. I have built 3 in the past month or so and I have at least 4 lined up and ready to build. I actually have a lot of projects I would like to build but line amps, sand or hollow, are cheap and easy. Plus I like to listen, that is the name of the game, but I really love to build, it may be my favorite part.
That link to the Aikido 300B is interesting. I was never a big fan of the Aikido, though I don't really know why, then I tried one. I have built a JFET Aikido line amp, I must say that it is quite a little monster! It was mentioned in a thread on the Pass JFET Bride of Zen that I follow closely since I have a JFET BoZ. I built it in about 30 min since I had all the parts on hand and it was quite simple. I was very impressed with the sound to the point where I am rebuilding it with better JFET's and better passives. I really want to try the tube Aikido line amp, JFET's are close, but not quite hollow enough
.
I know you mentioned the 6SN7, unless it is a SRPP or paired with another stage I think that tube is out. From what I have read and heard from people it is a poor 300B driver. Check out the tests that Mr. Millett did with drivers, the 12HG7 could swing many more volts at way lower distortion than the 6SN7 both in pentode and triode mode.
Thanks too for another vote for Electra-Print iron. I am considering the cost for outputs, I will use their interstage and chokes though, both power and anode. I am thinking One Electon for the outputs if Electra's end up out of the budget.
Cheers
JD
That is interesting though about your 91A, what do you feel...er...hear you gained from the change?
BTW yes I am planing on using a line amp, I am kind of on a line amp kick as of recent. I have built 3 in the past month or so and I have at least 4 lined up and ready to build. I actually have a lot of projects I would like to build but line amps, sand or hollow, are cheap and easy. Plus I like to listen, that is the name of the game, but I really love to build, it may be my favorite part.
That link to the Aikido 300B is interesting. I was never a big fan of the Aikido, though I don't really know why, then I tried one. I have built a JFET Aikido line amp, I must say that it is quite a little monster! It was mentioned in a thread on the Pass JFET Bride of Zen that I follow closely since I have a JFET BoZ. I built it in about 30 min since I had all the parts on hand and it was quite simple. I was very impressed with the sound to the point where I am rebuilding it with better JFET's and better passives. I really want to try the tube Aikido line amp, JFET's are close, but not quite hollow enough
.I know you mentioned the 6SN7, unless it is a SRPP or paired with another stage I think that tube is out. From what I have read and heard from people it is a poor 300B driver. Check out the tests that Mr. Millett did with drivers, the 12HG7 could swing many more volts at way lower distortion than the 6SN7 both in pentode and triode mode.
Thanks too for another vote for Electra-Print iron. I am considering the cost for outputs, I will use their interstage and chokes though, both power and anode. I am thinking One Electon for the outputs if Electra's end up out of the budget.
Cheers
JD
Regarding Sgerus' bad experience with WE91 I'ld be inclined not to throw away the child with the bathwater (literal translation of a Flemish proverb ) and still consider a pentode (in pentode mode that is) that can pass lots of current and gets top reviews as driver for 300B. C3m is the most quoted as such; Thorsten Loesch has published one circuit and at diyparadiso.com there are several others. An aikido driver stage also sounds like a top solution to me.
Simon
) and still consider a pentode (in pentode mode that is) that can pass lots of current and gets top reviews as driver for 300B. C3m is the most quoted as such; Thorsten Loesch has published one circuit and at diyparadiso.com there are several others. An aikido driver stage also sounds like a top solution to me.Simon
coresta said:Amazing Simon, just exactly the same in wallon , french
Almost the same in English: Don't throw out the baby with the bath water..
FWIW: A 6SN7 SRPP running on a 400V supply at 9 - 10mA does a more than decent job driving the 300B. Source impedance well under 2K and >250Vpp swing open circuit. (It will drive a 300B into hard clipping.) The 300B is not generally intended to run into grid current so you are dealing with 100K grid circuit resistance and <100pF of cmiller and strays with good construction practices.. Measured bandwidth in this amp at the output is -3dB at around 80kHz with a Tamura FS-5002. (No feedback) Dominant distortion source is the output tube itself. I built a well regarded commercial series of amps in the late 90's and early 2000 based on this topology. I built my own in 2004. It has more than survived comparison with any other amplifier it has been A/B'd against in any system. I actually would not mind an IT coupled amplifier myself, just wanted to set the record straight.
It is true that I shouldn't let one bad experience ruin my foray into 300B power. I liked the pentode drive because of it's flexibility, ie: pentode mode, triode mode, triode DRD, IT coupled etc... I really am drawn to the IT coupled all DHT though that was discussed earlier. Regarding the Aikido, I think the design is interesting but it seems the main idea behind it is to use as a drive when a weaker tube not fully able to drive the 300B directly is employed. Personally I don't feel it is needed when there are so many other options out there, especially in the world of pentodes that would do the job just fine. I would like to hear one though .
Thanks for the information on the SRPP Kevin, I wasn't aware that the 6SN7 could swing that much in SRPP! When you built yours, and the commercial ones, was it based on the 6SN7? I have seen a few SRPP's that use the 6SL7 instead, or some other higher mu tube. Like I mentioned I have been reading a bit recently about SRPP. I am thinking that after this amp, and after enjoying/modding it for a little while, I may build the EL34 amp off of AudioTropic's site. I have considered his line amp for a while now, both the 6AQ5 version and the shrunken 6T4 version that is outlined in another thread. The EL34 uses a SRPP front end so I decided to learn a little about this arrangement. If I build this amp though I think I will mod it a bit to run 807's since I have a lot of them, and maybe use a 9-pin input for a broader range of SRPP options...but that is another thread!
I think the one thing I have grown to hate about the 300B is the massive amount of driver options, all with their ups and downs !
Cheers
James
.Thanks for the information on the SRPP Kevin, I wasn't aware that the 6SN7 could swing that much in SRPP! When you built yours, and the commercial ones, was it based on the 6SN7? I have seen a few SRPP's that use the 6SL7 instead, or some other higher mu tube. Like I mentioned I have been reading a bit recently about SRPP. I am thinking that after this amp, and after enjoying/modding it for a little while, I may build the EL34 amp off of AudioTropic's site. I have considered his line amp for a while now, both the 6AQ5 version and the shrunken 6T4 version that is outlined in another thread. The EL34 uses a SRPP front end so I decided to learn a little about this arrangement. If I build this amp though I think I will mod it a bit to run 807's since I have a lot of them, and maybe use a 9-pin input for a broader range of SRPP options...but that is another thread!
I think the one thing I have grown to hate about the 300B is the massive amount of driver options, all with their ups and downs
!Cheers
James
Guys,
Please don’t take my comments about the WE91 the wrong way, the circuit just wasn’t the best for MY needs. I’ve started several threads asking for the best was to drive a 2a3 or300B. The answers are all over the map, and some people have very strong opinions.
I’m just here to share information and try to learn something.
JD, I also tested the 6J7 as a pentode…. It’s interchangeable with the EF37A
Here is a good link for a 2A3 PSE amp that uses a D3A in triode mode for the input/driver.
http://www.audiodesignguide.com/New2A3/new2A3.html
I have attached the EF37A “As a Triode” circuit for reference
Simon, When my amp was in pentode mode, I tested all the ideas in Thorstens YAWE91 article. I was not able to get the same frequency response as Thorsten….
Kevin, With the 6SN7 in SRPP, what input voltage to you need to the 250V pp swing from the 6SN7?
Please don’t take my comments about the WE91 the wrong way, the circuit just wasn’t the best for MY needs. I’ve started several threads asking for the best was to drive a 2a3 or300B. The answers are all over the map, and some people have very strong opinions.
I’m just here to share information and try to learn something.
JD, I also tested the 6J7 as a pentode…. It’s interchangeable with the EF37A
Here is a good link for a 2A3 PSE amp that uses a D3A in triode mode for the input/driver.
http://www.audiodesignguide.com/New2A3/new2A3.html
I have attached the EF37A “As a Triode” circuit for reference
Simon, When my amp was in pentode mode, I tested all the ideas in Thorstens YAWE91 article. I was not able to get the same frequency response as Thorsten….
Kevin, With the 6SN7 in SRPP, what input voltage to you need to the 250V pp swing from the 6SN7?
sgerus said:
IIRC Something close to 15Vpp - 16Vpp, lower cathode must be bypassed, and literally right on the verge of clipping.. (400V plate voltage, 9 - 10mA, 820 ohm to 1K cathode resistors.) Note that I really don't recommend anyone design to those limits (and that wasn't clear in my post) - something just under 200Vpp is more realistic. My amplifier requires between 140Vpp - 180Vpp for full output depending on OP of the output stage. (I currently run unbypassed.)
I'm currently thinking about 6AH4 choke loaded to replace the SRPP based driver - mostly out of curiosity, and it would be easily reversible if I did not like the result.
I think that is what I am going to do. I still really like the all DHT design but I am afraid that cost may still be an issue. Way fewer passives compared to other designs, but they are outweighed by the cost of iron. Though I feel that $120 or so for an interstage from Electa-Print is quite reasonable. The biggest increase in cost though it is tubes, with the 91A I have plenty of the "classic" 6J7's. I also have a lot of other pentodes that could be tried. One day though hopefully soon a all DHT 300B will grace my home along with other designs.
Has anyone compared a 6J7 91A with one that uses the 310A or 6C6? I wouldn't expect much difference since these are all in the same breed more or less.
My next and biggest question is about iron, which I know that I have brought up before. I will start with the power supply side of things. I am considering a few different options for iron on this side. My main question is will it really matter much if I use Hammond power and chokes versus Electra, James, or One Electron? I may go all James though if I can order direct from them, though I don't have any price quotes.
On the amplifier side I am really considering James or One Electron. I would still like to get a quote from Electra-Print, but I may end up saving this cost for the all DHT or some other later design. I assume that both James or One Electron would be a step up from Hammonds. Out of these two does anyone have any opinions? At first I thought it would be fun to have a amp will all James iron, but at the same time I don't want to limit myself because I want a "theme amp".
I read a little something not to long ago about using a 0C3 on the screen of the pentode. I haven't seen this method used to often though, it the 0C3 to noisy? Along these lines would a zener be better than a couple resistors?
Last thing on iron, has anyone used Hasimoto's and how do they compare to some of the other high ends (Tango, Tumara, Electra, etc...)?
Back to hockey, Stanly Cup Game 5! Go Red Wings!!!
Cheers!
James
JPeitzman said:
I don't think so. For one project, I'm using a "Hammond Classic" power xfmr. Works great even though the current pull is a bit over the ratings (compensated by not using the heater windings so the primary VA is within ratings). I'm not having either excessive heating or noise problems with that.
For another project, I used an old Stancore power xfmr and OPT. Those might be 30 years old or older. Again, work just great. Indeed, the Stancore OPT measures better than a Hammond OPT, which is good since I couldn't tell if it came from a gee-tah amp or PA system.
Build it "stock" with the screen voltage divider resistors. Then try the OC3. I like the VR tube supply, but I think you should try it stock (use the Sound Practices or Angela Instruments circuit). I never had any noise issues with the VR tubes.
If you have excess gain with the stock resistor values try using a smaller plate resistor on the 6J7. Less top end roll-off and lower distortion. If you are comfortable with reworking the operating point on the 6J7, try to get it running at higher voltage and current.
Use carbon comp resistors and oil caps where you can. Then change them for other parts.
Nothing wrong with the James. I bought expensive Tamura OPTs for my build, but I wouldn't spend big money straight off if I had it to do over again. A friend of mine built an amazing sounding type 50 amp with Hammond OPTs. What's important is that you try things with the circuit and parts.
If you're thoughtful about layout and space, you can completely change the input stage in a couple of hours. A swap to 6SL7 SRPP would be easy. If you use separate top plates for each section, you can swap them out quickly.
If you have excess gain with the stock resistor values try using a smaller plate resistor on the 6J7. Less top end roll-off and lower distortion. If you are comfortable with reworking the operating point on the 6J7, try to get it running at higher voltage and current.
Use carbon comp resistors and oil caps where you can. Then change them for other parts.
Nothing wrong with the James. I bought expensive Tamura OPTs for my build, but I wouldn't spend big money straight off if I had it to do over again. A friend of mine built an amazing sounding type 50 amp with Hammond OPTs. What's important is that you try things with the circuit and parts.
If you're thoughtful about layout and space, you can completely change the input stage in a couple of hours. A swap to 6SL7 SRPP would be easy. If you use separate top plates for each section, you can swap them out quickly.
James,
You got me thinking about the 7193 > 6V6 > 300B setup. I am looking at the the two tubes (spec sheets) and am trying to figure out if they are drop in replacement capable. I know there are some differences between the two but are they close enough to try a simple plug and play without hardware changes? Sorry for the noob question but I might as well throw it out there to see what I get back and learn in the process.
Thanks
/e
You got me thinking about the 7193 > 6V6 > 300B setup. I am looking at the the two tubes (spec sheets) and am trying to figure out if they are drop in replacement capable. I know there are some differences between the two but are they close enough to try a simple plug and play without hardware changes? Sorry for the noob question but I might as well throw it out there to see what I get back and learn in the process.
Thanks
/e
You could also use the 6J5 or half of a 6SN7 in place of the 7193. The 7193 is basically a 6J5GT with anode and grid caps both. I think it is a very cool looking tube, I am not sure sound wise if it is much different than a 6J5GT. Though that combo with a triode-strapped 6V6 should REALLY drive 300B, choke or CCS load it for maximum swings! You could really go nuts and use a KT66 or KT88 in place of the 6V6, that is what I have thought about for a future GM70 amp. Though a KT88 is extreme overkill since it would drive a 833, but it sure would look cool. Though if you took out the 300B the 7193 > KT88 would give you more power .
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