another Jonokuchi lives.
this in still on the construction chassis and i will have to decide how to case it
sound is very clean and a little bassy. i would like a touch more gain as i am running the volume wide open (or almost) with both my grados and senn's
this in still on the construction chassis and i will have to decide how to case it
sound is very clean and a little bassy. i would like a touch more gain as i am running the volume wide open (or almost) with both my grados and senn's
Attachments
About the only thing you can check without tubes is the B+ voltage and the heater voltage (AC). The B+ voltage will be higher than what is on the schematic, since without the tubes there is no load on it.
Pete
i have 2 problems to solve before casing up.
1- there is a buzz that changes with volume if there is no load on the amp.
2- i have tested this with 8 sets of headphones. on 6, there is no hum. on 2 sets there is a low hum that does not change with volume. this is not audible when playing music.
the only difference seems to be the impedance of the phones. the 6 with no hum are 32r or 300r. the 2 with hum are both 60r.
any ideas?
1- there is a buzz that changes with volume if there is no load on the amp.
2- i have tested this with 8 sets of headphones. on 6, there is no hum. on 2 sets there is a low hum that does not change with volume. this is not audible when playing music.
the only difference seems to be the impedance of the phones. the 6 with no hum are 32r or 300r. the 2 with hum are both 60r.
any ideas?
yup. i did the low hum mod when i built it. i also have it on a temporary chassis with the transformers spread apart
A couple of things...
You may need to ground the volume control bushing. If it is installed in a grounded metal chassis, that will do it.
It looks like you have the ground loop breaker D1 installed, and no jumper on JP1. You can try shorting JP1 to connect AC ground to audio ground. That removes some noise for most people.
For the low level hum, try moving the transformers even farther apart, to see if it is coupling.
Pete
You may need to ground the volume control bushing. If it is installed in a grounded metal chassis, that will do it.
It looks like you have the ground loop breaker D1 installed, and no jumper on JP1. You can try shorting JP1 to connect AC ground to audio ground. That removes some noise for most people.
For the low level hum, try moving the transformers even farther apart, to see if it is coupling.
Pete
Hi,
My amp was completed 3 years ago and I have always had this hum problem.
The power transformer is separate of the main box by a distance of 1 meter, connected by a shielded power cable and coated by mumetal. Even if the hum is reduced, I can still ear it in my sennheiser HD650.
Yesterday, I did "the mod" with 220ohms resistors and removed R20, R21, R22, R23. this changed nothing for the hum but I lost power and I have to turn up the volume untill halfway to have a decent level of music.
The strangest thing is that today, I removed the 220ohms resistors and I have no more hum... And also no more gain in volume... Normaly, without resistors I should have more gain?
I am lost in this story...
is that someone could help me understand?
Thank you,
Alex
My amp was completed 3 years ago and I have always had this hum problem.
The power transformer is separate of the main box by a distance of 1 meter, connected by a shielded power cable and coated by mumetal. Even if the hum is reduced, I can still ear it in my sennheiser HD650.
Yesterday, I did "the mod" with 220ohms resistors and removed R20, R21, R22, R23. this changed nothing for the hum but I lost power and I have to turn up the volume untill halfway to have a decent level of music.
The strangest thing is that today, I removed the 220ohms resistors and I have no more hum... And also no more gain in volume... Normaly, without resistors I should have more gain?
I am lost in this story...
is that someone could help me understand?
Thank you,
Alex
Yeah, something there does not make sense. You are saying that you removed the 220 ohm "hum mod" resistors (and replaced them with wire, I assume), and the gain did not return to its original state?
Removing R20 and R21 will not make much of a gain difference in any case.
In the original circuit, removing R22 and R23 does not make a big gain difference either. However, if you insert the 220 ohm resistors as in the hum mod, then you would have very low gain unless you remove R22 and R23.
220 ohms is too high for many low-Z headphones, but should be fine for higher-Z headphones like an HD650. It will lower the gain some, by around 6dB, from what it was with no resistor. As far as I can tell, the only way that this helps hum is to attenuate the output a bit, so the hum drops along with the signal...
Anyway... if your power transformer is that far away there certainly is no magnetic coupling.
Thank you Pete for your answer.
I do not understand also. This is a photo of my amp after the mod:
R20 has been removed after the photo.
Yes I did this.
I do not understand also. This is a photo of my amp after the mod:
An externally hosted image should be here but it was not working when we last tested it.
R20 has been removed after the photo.
Yes I did this.
thanks Pete
i will check the grounding tonight for the buzzing. it also occurred to me that the input jacks are not currently grounded to the chassis either and i will try grounding that as well.
i will spread the transformers even further to eliminate the hum, but i am puzzled as to why it is only noticeable on the 60r headphones
i will check the grounding tonight for the buzzing. it also occurred to me that the input jacks are not currently grounded to the chassis either and i will try grounding that as well.
i will spread the transformers even further to eliminate the hum, but i am puzzled as to why it is only noticeable on the 60r headphones
no luck. i shorted jp1 and mounted the input jacks on the chassis and the buzz is still there, but only until i connect to the source and then it immediately and completely goes away. it is quiet with the volume low and increases as the volume pot increases
the hum is also still there for the 60r phones. i moved the transformers around up to 12" away from each other (the length of the wire harness) and it has no effect at all.
the hum is also still there for the 60r phones. i moved the transformers around up to 12" away from each other (the length of the wire harness) and it has no effect at all.
That pretty much says that the buzz is a ground loop / ground noise problem, I think. Quite often EMI filters on equipment plugged in to the same circuit (computers are particularly bad) inject noise back onto the safety ground.
Not sure what you can try. Changing grounding, moving equipment, changing interconnect cables - all can make a difference. But sometimes it's always there, though usually at a low enough level to not be a bother.
As for the hum that is there at all times - you can try bigger filter caps. Some of this may be just power supply ripple getting through the output stage.
Pete
the buzz is fixed. i put 220r resistors across the L/R inputs to ground and the buzz went away. it does not appear to have affected the output levels.
i will try changing the filter caps to larger. these are C9 & C10? any suggestions as to values?
would changing the values of R4 & R3 have any effect?
i will try changing the filter caps to larger. these are C9 & C10? any suggestions as to values?
would changing the values of R4 & R3 have any effect?
Finished my Amp
Well, I finally finished my Jonokuchi. This will be a Christmas present for my daughter Blake. She loves old music and records.
So I only ran in to a few minor issues. First, if you use the Front Panel Express chassis you need to use different sockets than specified in the BOM. The ceramic sockets are too large for hole and the board will not mount correctly. Also, the sockets go on the opposite side of board from components.
I am using Sennheiser 600's and 90DB efficiency Blumenstein speakers. I had a very bad buzz that varied with the volume on the first start up. I went back and grounded the input jacks straight to the AC ground on the power module. No more buzz. ZERO.
I have a very very very faint hum. It can only be heard with no music and does not vary with volume. You need to almost strain to hear it. Not an issue in the slightest and with the Sennhieser you most people that I let listen can't hear it. It is a very low rumble.
This was the easiest build that I have had. With the board, all the files, and the chassis instructions you can not go wrong. I find there to be plenty of power. With the headphones I don't go past 1/2 and mostly stay around 1/4. When connected to speakers I still have not maxed the volume but it is in a small room and the sub is powered by its own amp.
Well, I finally finished my Jonokuchi. This will be a Christmas present for my daughter Blake. She loves old music and records.
So I only ran in to a few minor issues. First, if you use the Front Panel Express chassis you need to use different sockets than specified in the BOM. The ceramic sockets are too large for hole and the board will not mount correctly. Also, the sockets go on the opposite side of board from components.
I am using Sennheiser 600's and 90DB efficiency Blumenstein speakers. I had a very bad buzz that varied with the volume on the first start up. I went back and grounded the input jacks straight to the AC ground on the power module. No more buzz. ZERO.
I have a very very very faint hum. It can only be heard with no music and does not vary with volume. You need to almost strain to hear it. Not an issue in the slightest and with the Sennhieser you most people that I let listen can't hear it. It is a very low rumble.
This was the easiest build that I have had. With the board, all the files, and the chassis instructions you can not go wrong. I find there to be plenty of power. With the headphones I don't go past 1/2 and mostly stay around 1/4. When connected to speakers I still have not maxed the volume but it is in a small room and the sub is powered by its own amp.
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.
An externally hosted image should be here but it was not working when we last tested it.
I've scrapped the idea of designing and building my first amp. I have instead decided to build this one P2P. The only mod I want to make is the OPT. I would like to use torroidal OPT. I plan to use this amp mostly with desktop speakers so a lower impedance transformer may be in order. Any suggestions?
I do believe that SY uses torroidal pp transformers on some builds but a single ended torroidal is very difficult to one. No gap. You will find few posts on this subject in the forum.
Piltron out of Canada makes some. I think a member Yves (?) manufactures transformers over in Europe. Some of the more experienced members here could tell you more.
Piltron out of Canada makes some. I think a member Yves (?) manufactures transformers over in Europe. Some of the more experienced members here could tell you more.
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