I agree. A good carbon film or metal film resistor is just fine for that. The film resistors come very close to an ideal resistor. At least up to 100 MHz or so. Yaego makes a bunch that are pretty price competitive.
Carbon composite resistors on the other hand, are the old-fashioned resistors that tend to be rather noisy. In particular they have high 1/f noise.
~Tom
Hell all right! I'll draw the schematic.
Is there a good guide to follow for making my own schematic?
I will try to draw one, but really, by just looking at schematics in here, I'm lost, I don'T know what all the signs means.
thanks for your help.
Their also seems to be a more serious problem if I shall say: one amp play slightly louder then the other, ugh...
Is there a good guide to follow for making my own schematic?
I will try to draw one, but really, by just looking at schematics in here, I'm lost, I don'T know what all the signs means.
thanks for your help.
Their also seems to be a more serious problem if I shall say: one amp play slightly louder then the other, ugh...
Absolutely!
A bit of sense in a hobby plagued by 'Fashion'!
IMO--way too much emphisis is placed on component type, rather than the design and implementation!
A Cruddy design and layout will still be cruddy no matter how many boutique and stupidly expensive parts are used!
Get it as perfect as possible using the standard range resistors/caps --Then, and ONLY then, play with the exotic parts....
I'm always suspicious of designs Ive seen, that specify that you MUST use a certain boutique cap or resistor, as in the past Ive built the odd one like this, and found that the DESIGN was at fault in some way or other.....
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I think what you're referring to are carbon composite resistors not carbon film. Carbon film is a conductive film evaporated onto a ceramic tube and trimmed to get the desired resistance. Same process as with metal film. The carbon composite resistors are carbon molecules that are squished/sintered together to form the resistive element. They tend to have high 1/f noise, but supposedly have very low inductance.
~Tom
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I sense you are anxious to fix the amp but are held back because you aren't comfortable or confident about the technical aspects of it ? I think you will be vastly happier if you resolve yourself to take some effort to understand more of the technical aspects instead of relying on folklore about component choices. If you work out the schematic for yourself and read up a bit to see how others build DIY tube amps you will gain a lot.
The main thing - SAFETY first. These amps can kill. Never go inside it when it's plugged into the AC outlet, and make sure all capacitors are discharged. They should have resistors across them to ensure a safe and slow discharge on power-off. If not, there can be enough juice in the power supply caps to end your music days.
with a SET and no feedback the tubes can have different gains so the volume in one channel can be slightly higher than the other - that's normal.
I have a bag of 6B4G tubes waiting for a project, I bought them because I believe they are good tubes and capable of being used to make a nice sounding amp.
The main thing - SAFETY first. These amps can kill. Never go inside it when it's plugged into the AC outlet, and make sure all capacitors are discharged. They should have resistors across them to ensure a safe and slow discharge on power-off. If not, there can be enough juice in the power supply caps to end your music days.
with a SET and no feedback the tubes can have different gains so the volume in one channel can be slightly higher than the other - that's normal.
I have a bag of 6B4G tubes waiting for a project, I bought them because I believe they are good tubes and capable of being used to make a nice sounding amp.
I understand your reason for doubt, but I do mean carbon film. I find them to be more vibrant sounding than metal film, but less noisy than carbon comp (and don't have the drift problem either).
Interesting, to each their own I guess. Could be a system thing or design philosophy. (Different goals) I actually avoid them mostly because I have run across a few that seemed to have measurable linearity issues at least in the context of the designs I do.. Like CC they do have a significant voltage coefficient and generate a lot more 2nd harmonic than most metal films (have run into some bad ones here as well) - wonder if this characteristic warms the sound up a bit?
I'd put the Jensens back in, bypass them with a .1uf poly cap, if you have a cement resistor on your power output, change it with a non inductive resistor like is in speaker crossovers.
also, consider your input impedance. calculations worry about bias more than the input load. Start the grid to ground resistor at 1M and go down till the phasey sound is eliminated in the sound stage. you'll notice a gain increase as you reach the proper input impedance and as the total circuit becomes resonate, the white noise will go down.
I never liked any Russian caps as they are not consistent in quality ( esr fluctuates too much from cap to cap)
also, consider your input impedance. calculations worry about bias more than the input load. Start the grid to ground resistor at 1M and go down till the phasey sound is eliminated in the sound stage. you'll notice a gain increase as you reach the proper input impedance and as the total circuit becomes resonate, the white noise will go down.
I never liked any Russian caps as they are not consistent in quality ( esr fluctuates too much from cap to cap)
Just curious as to whether you have tried or measured the Russian FT-3? They seem very consistent in terms of tolerance and all other parameters I have measured. I have not measured their ESR, but would expect similar behavior.
I find the Jensens to be very colored, but that is just my set of preferences.
update: I'm making the schematics as we speak, will be done within 2 weeks or 2 months
Carry on at whatever pace you can manage!
Hmm--Strange. Perhaps you had a bad batch or something...
Ive got a box of 25, 0.1uf 1000V K40Y-9 and the capacitance tolerance is supposed to be 10%. Ive checked them all and found to my surprise, they are all under 3% tolerance....
The 0.22uf 1000V 10% tolerance were a little wider at 7%, but still under the maker's claims.
The 0.47 630V 10% were a little better at about 6% tolerance...
The couple Ive checked for ESR were also low and of the same order for each same value one, gave up testing after 4 or 5......
Must have been rejects or a bad batch.
The ones I had were in a sealed manufacturers box of 25 pieces, kulled off the 'bay....
Can you elaborate here? It's really interesting, but I'm really not enough confident or knowledgeable...
What should be the bias results?
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