My first post here, and my first DIY, dont be too hard on me... 
I got bored, no euros to upgrade my system, so I started playing with my amplifier...
1. replaced all tubes with Siemens NOS...
2. removed uneccessary gadgets, inputs and selector, volume control, usage timmer, relays, etc...
3. removed global negative feedback
4. replaced 12AT7 with E80CC, replaced R28 on the power supply to cope with extra current of this babies, and removed cathode CAP to decrease gain further...
5. rewired input stage point-to-point with Allen-Bradley resistors and replaced WIMA coupling capacitors with Russian PIOs...
I got bored, no euros to upgrade my system, so I started playing with my amplifier...
1. replaced all tubes with Siemens NOS...
2. removed uneccessary gadgets, inputs and selector, volume control, usage timmer, relays, etc...
3. removed global negative feedback
4. replaced 12AT7 with E80CC, replaced R28 on the power supply to cope with extra current of this babies, and removed cathode CAP to decrease gain further...
5. rewired input stage point-to-point with Allen-Bradley resistors and replaced WIMA coupling capacitors with Russian PIOs...
An externally hosted image should be here but it was not working when we last tested it.
TugaTweaker said:
Thanks, it doesnt look as good with enough resolution photo...
I did remove 20 components and 2 meters wire from the signal path, plus some not needed accessories...
It looks fuller because of the size of the Russion PIOs...
What else do you suggest, simple enough for me to do...
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Sorry i meant "good tube circuitry at best...".In my personal
experience , rectifying the filament supply of preamp and driver tubes is a good shoot . I like Black Gate electrolytics, Auricap props , and high voltage SiC Schottkys as rectifiers . Here , [urlhttp://www.tentlabs.com/Products/page6.html[/url] you can find more interesting matter to go further , as in my point of view an upgrade is never finnished .
Tugat
experience , rectifying the filament supply of preamp and driver tubes is a good shoot . I like Black Gate electrolytics, Auricap props , and high voltage SiC Schottkys as rectifiers . Here , [urlhttp://www.tentlabs.com/Products/page6.html[/url] you can find more interesting matter to go further , as in my point of view an upgrade is never finnished .
Tugat
Modding/replacing/removing can be quite addicting and I agree with tugat on the simpler the better. But I think it's important to know when to stop. I've built an amp over a year ago and it's been modded so many times that it's now a completely different beast. The sad part of it is, I really not convinced that it sounds better than it did last year! Sound is so damned subjective!
~~~John~~~
~~~John~~~
AndreasS said:
TugaTweaker said:
The components in "red" where removed, no global negative feedback...
Maybe there is more distortion, but it sounds much better now, particularly, more real, more lively, nicer mids and highs...
Tube_Dude said:Hi Lowrider
It seams that exist an error in your schematic.
R18 and R19 must be connected between the pin 8 of the EL34 ( cathode ) and ground.
It is used to measure bias.
Maybe the error is only in the schematic and not in the implementation...
Welcome!!
Hello Jorge,
Nice to meet you again, had to get into DIY for it...
Maybe the schema is wrong, I didnt change anything there, if I have time, I will open it on the weekend and test how it is really connected...
http://www.tentlabs.com/Products/Tubeamp/Tubeheater/index.html
Interesting, but I need higher output current to be able to use existing connections...
Interesting, but I need higher output current to be able to use existing connections...
There are options to cope , two E80 plus two 6SN7 heaters, not a big current problem as you will see consulting specific tubedata . But you said nothing about the feedback mod . You removed R6 and C3 , any subsequent mod is unnefecttive then , unless you have connected the wire to the next component in the circuit .
Tugat
Tugat
TugaTweaker said:
Good morning,
I need 4 x .6 A = 2.4A, Tentalabs modules are 1.5A maximum, Machmat needs at least 10V input, my transformer tap is 6.3V, of course, what would you suggest...
Anyway, I dont hear any hum, even with my ear against the speaker, it was one more experiment...
I broke the global feedback loop, no global NFB in my amplifier now, also hardwired triode mode...
I know the majority use and recommend global NFB, I tried both options, and preferred the sound in my system without...
I am very sensitive to crossover distortion, only like first order, or none, maybe NFB has a similar effect on sound, besides the known benefits...
An externally hosted image should be here but it was not working when we last tested it.
Tube_Dude,
Verified, and the schema corresponds to the circuit, 0 ohms between cathode, point 8, and ground, 10 ohms between supressor, point 1, and ground, or cathode, of course...
Maybe the Chinese do things different, but it works...
I replaced a couple more CAPs with Nichicons, aligned the PIOs on the right, and took a better picture, see first post...
The power supply schema is already updated with some more mods I am going to do next weekend, ordered a bunch of Philips 0.13 uF 1600V, to apply all over...
Verified, and the schema corresponds to the circuit, 0 ohms between cathode, point 8, and ground, 10 ohms between supressor, point 1, and ground, or cathode, of course...
Maybe the Chinese do things different, but it works...
I replaced a couple more CAPs with Nichicons, aligned the PIOs on the right, and took a better picture, see first post...
The power supply schema is already updated with some more mods I am going to do next weekend, ordered a bunch of Philips 0.13 uF 1600V, to apply all over...
Lowrider said:Next weekend I open it again to install all the bypass CAPs, I will try to do that, the problem is that I have to remove the EL34 to put it upside down, to open...
You don't need to open the amp to do that experience.
Take out one EL34, and measure the resistance between pin 8 and ground ( the outer part of the RCA inputs are a good ground).
Then , see if rotating the switch for that tube position , change the reading...
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