yes indeed, this is a spin off the Marantz7 and or SP3 that has quite a following....
Broskie has shown how to do a non global feedback and very simple line amp and yet.....
I have no money, to buy an new one, and very little knowledge of tubes and electronics. so the beste way is to send me a drawing to do that.
i help me a lot....
thanks forum
You are drawing in circles. Don't swap tubes, the design needs the dedicated tubes. Attenuation at the input must solve your gain and distortion problem. I don't understand what you mean with loosing "drive"? Too less gain? Well...
There is actually no more that you can do with your limited skills. Remember, this is a DIY forum, some basic knowledge is required to be able to work on electronics and to get good results. Please find a friend that can help you on the job at your location. Or accept it is not what you like and put it away for another 7 years.
There is actually no more that you can do with your limited skills. Remember, this is a DIY forum, some basic knowledge is required to be able to work on electronics and to get good results. Please find a friend that can help you on the job at your location. Or accept it is not what you like and put it away for another 7 years.
look at the Broskie CCDA, very simple to make, fewer parts, cost much lower and sonics are superb....CCDA: constant-current-draw amplifier
The original design uses the 12AU7 / ECC82. The amplification factor (mu) of the 12AU7 is 20.
Instead of sticking with the original tube, you have substituted the 12AX7 / ECC83. The amplification factor (mu) of the 12AX7 is 100. So it has more gain.
If the preamp has too much gain using a 12AU7 (mu 20), it doesn't make any sense to substitute a 12AX7 (mu 100). You are just making the problem worse by doing that.
It would be helpful if you could post some pictures and more information about it. I asked this earlier but got no response.
I would have assumed that the stock preamp had a volume control. Does it? If it does and you find that the level is hard to adjust properly - meaning that it's either too soft or too loud - there are a couple of ways to deal with that.
One, which was suggested 7 years ago, is to eliminate this preamp from the system and substitute a "passive preamp", which is just a simple volume control.
Perhaps there are reasons why you want to keep it in your system, though. Does this preamp also allow you to switch between different inputs? Does it have tone controls? Again, you haven't supplied this information.
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Don't use a ECC82, it will not work properly and can cause distortion. Use a ECC83 and then check again using the potmeter. If it still distorts then there is a problem somewhere else.
OK, I was confused. Totally my fault for not reading the whole thread more carefully.
The schematic shows two tubes, a 6N4 and a 12AU7. I'm unfamiliar with the 6N4 and when you posted about trying both 12AU7 and 12AX7s, I assumed that you were using these in the second part of the circuit, which calls for a 12AU7.
And I didn't look at the schematic closely enough. I now see that the 12AU7 is a cathode follower, which does not provide any gain.
Apparently, you are subbing them for the 6N4. To further confuse things, the tube used is a Chinese 6N4, which is not the same tube as an American 6N4. And there don't seem to be data sheets for the Chinese version.
Searching elsewhere, I found that the Chinese 6N4 is supposedly similar to a 12AX7, but not necessarily exactly the same. Since the Chinese also sell tubes labelled 12AX7, I would assume that they are not exactly the same as a 6N4. It's possible that the 6N4 has less gain than the 12AX7. But it may not matter much. Either tube probably has too much gain simply because you don't need any gain at all.
Now that I'm slightly less confused I'll point out and suggest a few things.
First, much earlier in the thread, a few people described flaws in the design. So fixing the gain problem likely involves more than simply trying different tube types.
I asked this previously, but you didn't answer so I'll ask again . . . did you build this from a kit or from scratch? Or is this a commercially sold product? If so, what brand and model is it? Does it use a circuit board or is it wired point to point? Please answer these basic questions.
One earlier suggestion was to modify the negative feedback loop to produce lower gain. Did you try that?
In Post #18 @Merlinb pointed out an error in the schematic. He knows a thing or two about circuit design. He is the person behind the Valve Wizard site.
How to design valve guitar amplifiers
I know nothing about cathode followers but it occurs to me that your preamp may have a design issue that's causing problems. Or, it's possible that the schematic is not accurate, which is always possible when it comes to cheap Chinese gear.
My point is that, if this uses a circuit board and the design flaw he mentions is creating a problem, it might be difficult to fix since this requires rewiring the circuit and it's often difficult to modify a circuit board. If it's wired point to point, it's easy.
Second, according to the schematic, it looks like there is a 100k volume pot on the input and also a volume pot on the output. The one on the output seems to be an odd value - 22k. This makes me wonder if the schematic is accurate.
Someone mentioned this earlier and commented that it is not a good design.
Is there either a volume pot (with a knob) on the output or perhaps it's some type of trimmer pot that's inside and needs to be adjusted with a screwdriver?
A pic of the preamp might clear up this question. You've been asked to post pics of the preamp but you haven't. Again, please post some pics of the preamp or a link that has pics.
Please explain further. It seems like it operates without distortion at times. Are you doing something, like turning up the volume, that makes it start to distort?
Is the volume control acting like it's too sensitive - either too soft or too loud and when it's too loud it's distorted. This is a symptom of having too much gain when you don't actually need any at all.
If that is the situation, a pot on the output may not be ideal but, from a purely functional standpoint, it could solve your problem. If you have a pot on the output, it can be adjusted lower and this will allow the pot on the input to have a wider, more usable, range.
Now, if you turn the volume down and it sounds good for a while and then it starts getting distorted, you've got other problems.
Third, it's been suggested several times over a period of 7 years that you eliminate the preamp and try a "passive preamp", which is just a simple volume pot without any circuitry attached.
Have you tried this? If not, why not?
It's clear that your amp can be driven to full power without the use of a preamp. If the preamp allows you to switch inputs or has remote control, I can see why you'd want to keep it in the system. If it doesn't offer such features, try a passive preamp.
If it does have features you can't live without, try adjusting or adding a volume control on the output.
Flacharlie,
Thanks for your info.
Its a Chinees preamp with pcb, I dont see any brand it looks like music angle.
I have change the 100k and also the feedback 23.5k but you hear a crack in the tweeter when playing a song with
with trumpet. Not always. Is not the cd player and not the cd.
I have try an other preamp also tube no problems
I try to make a picture. Dont know how to and this on this forum.
Thanks for your info.
Its a Chinees preamp with pcb, I dont see any brand it looks like music angle.
I have change the 100k and also the feedback 23.5k but you hear a crack in the tweeter when playing a song with
with trumpet. Not always. Is not the cd player and not the cd.
I have try an other preamp also tube no problems
I try to make a picture. Dont know how to and this on this forum.
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