poynton said:
Hey Andy, Thanks for the complement! Here is a link to some early construction photos! I really need to bring the amp home and shoot a few more completed (relative 🙂 ) pictures.
My 6AQ5 amp.
Hope this helps!
dg
Hundred volts, 4mA. Constraints of the resistive plate loading. I'd like to go up to 4.5mA, but then the voltage is so low I might get unacceptable distortion on max swing.
Interesting thing; I load the common tail with the IXYS chip CCS to minimize heat inside the chassis. It works a treat (very quiet, and dynamic resistance of the tail up in the hundreds of kilohms), and with a serendipitous side effect; I can reach into the space between the OTs and adjust the OP of the front end with the twist of a screwdriver on the pot. Less current, sound a little brighter. More current, sound fuller. At least in this situation. In the EL34 amp, I'll have another hundred volts of PS to work with, and so can explore this further. So far though, very succesful breadboard; I can't go back to the old amp, the sound is just too, um, opaque.
Aloha,
Poinz
Interesting thing; I load the common tail with the IXYS chip CCS to minimize heat inside the chassis. It works a treat (very quiet, and dynamic resistance of the tail up in the hundreds of kilohms), and with a serendipitous side effect; I can reach into the space between the OTs and adjust the OP of the front end with the twist of a screwdriver on the pot. Less current, sound a little brighter. More current, sound fuller. At least in this situation. In the EL34 amp, I'll have another hundred volts of PS to work with, and so can explore this further. So far though, very succesful breadboard; I can't go back to the old amp, the sound is just too, um, opaque.
Aloha,
Poinz
Looking at the plate curves, it seems you are using plate resistors around 47k. Personally, I would have been tempted to go for something a lot lower (say 22k) and shoot for around 110Vp at 7.5mA, letting any additional H2 cancel. Ri is around 7K2 here, so 22k Rp appears ok.
You have got me tempted to break out my stash of 4GK5s and start breadboarding LTPs. I currently use them as the second tube in my phono amp, where they work well in a grid leak config fed by a 2.5mA CCS.
BTW: your breadboards are better finished than my amps.
pm
found a full carton (24 or so) ck5073 triodes at a milsurp store, dirt cheap. these are submini tubes about 1.5 inch L x 0.3 inch dia. electronics guy at the milsurp store said they have more cartons of them in the attic. looks like it would make a nice project, such as a guitar preamp or tube fuzz......... also saw a radiosonde module using 5073's as a UHF oscillator and RF amp..... downloaded the spec sheet on them, and they have very low Cgp (1.2pf). i plan on assembling a tube op amp with them to test with....
I have a bunch of 12at6 tubes:
An externally hosted image should be here but it was not working when we last tested it.
Eli Duttman said:
What do you people think about the negative feedback in this circuit (using the 6AU6)?
http://www.tuberadios.com/temp/headphone1.jpg
From this thread:
http://www.diyaudio.com/forums/showthread.php?postid=1169738
Hi,
My site lists two circuits (click on the amp), one using Hashimoto iron and the other circuit from an old RadioTronics article. I believe I followed the older article and omited the tone control and NFB circuit. Not 100%, I would have to open it up and see exactly what I did.. However, I must say this is a very sweet sounding amp I use in the office.
Kind regards,
Danny
My Site
My site lists two circuits (click on the amp), one using Hashimoto iron and the other circuit from an old RadioTronics article. I believe I followed the older article and omited the tone control and NFB circuit. Not 100%, I would have to open it up and see exactly what I did.. However, I must say this is a very sweet sounding amp I use in the office.
Kind regards,
Danny
My Site
Very nice! I still have my meters. How do/did you plan on hooking them into the circuit? Any shots of the underside?
Regards,
Danny
Regards,
Danny
It isn't wired yet, but I'm using the output trannies from the recorder. I plan to wire them to the 600 ohm outputs with 10K pots as voltage dividers and a 100K pot in series just like it was in the recorder schematic.
Cool! I am using the 8 ohm for speakers and had thought about using the 600 ohm connections for driving a sub but have not hooked it up as of yet. Keep us posted of your progress..
Thanks,
ck
Thanks,
ck
An excellent 7-pin valve is GEC's A2134.
A 9W pentode with good gm, it makes a super driver when triode-strapped and indeed might make an interesting small p-p amplifier. Usually found as CV2179 and (I think) CV 4062.
Why two CV numbers? All CV 4xxx types are ruggedised for the military.
7N7
A 9W pentode with good gm, it makes a super driver when triode-strapped and indeed might make an interesting small p-p amplifier. Usually found as CV2179 and (I think) CV 4062.
Why two CV numbers? All CV 4xxx types are ruggedised for the military.
7N7
I ever built 2 6AQ5 PP AMP for my friends
only 2 6J6 and 4 6AQ5
P out= 10W+ 10W
sounds quite well
only 2 6J6 and 4 6AQ5
P out= 10W+ 10W
sounds quite well
6J6 5844 is a quite well and cheap tube
low plate resiste, mod mu
u can pall them works like 5842
low plate resiste, mod mu
u can pall them works like 5842
Hi,
Re 7N7's comments re A2134 ~
An excellent tube with the classical oval-anode structure. This is perhaps more available as the N78 or CV2179. Data via Franks site is astonishing - a PP pair as triodes can achieve 6 watts output when provided with HT of 350v - that's better than EL84s and lower distortion too. (See MJ -III - page 395) Generally GEC branded, but I have examples branded- Mullard.
EF91 - RF pentode, sharp-cut-off, high conductance. (Seek labels as 6AM6, 6064, M8083, CV4014....located by sleuthing Avionic-repair depots. Provides a useful triode-connection with mu around 70......
M8082. (CV4063) A darling oval-anode SQ output pentode by Mullard. In 6AU6-size glass and a Pa figure of 4.75 watt. Curves via Franks site reveal a very linear triode connection with a mu ~ 12. There's been many an application running through my mind - pre and line-amp output stages, differential driver stages, and even a sardine-can sized power amplifier.....Yes, I scored heavily at the same Avionic repair shop..........
Poinz.....
You're breaking my heart!! I have just bought all these 7062/E180CC tubes and here you are galloping off in another direction. I am still sticking with the 7236 for the output tube, despite the increased drive swing....no thread-break intended.
Regards,
Graeme
Re 7N7's comments re A2134 ~
An excellent tube with the classical oval-anode structure. This is perhaps more available as the N78 or CV2179. Data via Franks site is astonishing - a PP pair as triodes can achieve 6 watts output when provided with HT of 350v - that's better than EL84s and lower distortion too. (See MJ -III - page 395) Generally GEC branded, but I have examples branded- Mullard.
EF91 - RF pentode, sharp-cut-off, high conductance. (Seek labels as 6AM6, 6064, M8083, CV4014....located by sleuthing Avionic-repair depots. Provides a useful triode-connection with mu around 70......
M8082. (CV4063) A darling oval-anode SQ output pentode by Mullard. In 6AU6-size glass and a Pa figure of 4.75 watt. Curves via Franks site reveal a very linear triode connection with a mu ~ 12. There's been many an application running through my mind - pre and line-amp output stages, differential driver stages, and even a sardine-can sized power amplifier.....Yes, I scored heavily at the same Avionic repair shop..........
Poinz.....
You're breaking my heart!! I have just bought all these 7062/E180CC tubes and here you are galloping off in another direction. I am still sticking with the 7236 for the output tube, despite the increased drive swing....no thread-break intended.
Regards,
Graeme
7N7,
Sorry about that!!
The Marconi data sheets are confusing. Sheet for A2134 states this is commercial equivalent to CV2179. Visually, construction appears identical to the N78.......
Confusion abounds - you say the A2134 enjoys a higher voltage to that for the N78 - yet triode curves for the former are provided to 300v, whilst for the latter they are provided to 500v....Bias values are very different - the N78 figures are significantly lower.
Both very interesting tubes nevertheless.
Regards,
Graeme
Sorry about that!!
The Marconi data sheets are confusing. Sheet for A2134 states this is commercial equivalent to CV2179. Visually, construction appears identical to the N78.......
Confusion abounds - you say the A2134 enjoys a higher voltage to that for the N78 - yet triode curves for the former are provided to 300v, whilst for the latter they are provided to 500v....Bias values are very different - the N78 figures are significantly lower.
Both very interesting tubes nevertheless.
Regards,
Graeme