Hi! I have now finnished a preamplifier using Gary Pimm Battery CCS's loaded #27'a and a 0A2WA regulated/BBMCCCS fed B+ supply.
Here are a schematic. It's quite like Garys own 26 / 85 pre.
I'm using the Mu output.
http://www.angelfire.com/ut/Likkhalt/index3.htm
I am experiencing a lot of broadband noise. I think this is coming from the VR tubes. I have poked around with a oscilloscope and everything is clean except the B+ supply. I suspect that the Mu output is pretty sensitive to noise on the B+...
How can I get rid of the noise? I have tried changing the 0,056uF cap over the VR tubes, with no luck. I have tried changing the VR tubes (and the 27's too.) I even tried with no cap, and then the VR tubes started oscillating at a very low frequency!
Something strange is going on and I'm out of ideas! I've tried grid stoppers but it didnt take the ringing away.
The freq. resp. at -3dB is 340kHz, and there is a resonance peaking at 300kHz. About 5-6dB higher than the avarage.
I also did some square wave tests, and I also have a lot of ringing on the leading edge. Check out pic's...
100Hz
1KhZ
10kHz, and so on... 🙂
So, I need some quick advice please!!! I have to get this amp fixed during this weekend!
Stigla
Here are a schematic. It's quite like Garys own 26 / 85 pre.
I'm using the Mu output.
http://www.angelfire.com/ut/Likkhalt/index3.htm
I am experiencing a lot of broadband noise. I think this is coming from the VR tubes. I have poked around with a oscilloscope and everything is clean except the B+ supply. I suspect that the Mu output is pretty sensitive to noise on the B+...
How can I get rid of the noise? I have tried changing the 0,056uF cap over the VR tubes, with no luck. I have tried changing the VR tubes (and the 27's too.) I even tried with no cap, and then the VR tubes started oscillating at a very low frequency!
Something strange is going on and I'm out of ideas! I've tried grid stoppers but it didnt take the ringing away.
The freq. resp. at -3dB is 340kHz, and there is a resonance peaking at 300kHz. About 5-6dB higher than the avarage.
I also did some square wave tests, and I also have a lot of ringing on the leading edge. Check out pic's...
100Hz
1KhZ
10kHz, and so on... 🙂
So, I need some quick advice please!!! I have to get this amp fixed during this weekend!
Stigla
Hi,
Have you checked the PSU noise in front of the CCS?
In case you notice a similar result, try swapping around the leads at the bottom of the CM chokes and see if that improves things.
Cheers,😉
Have you checked the PSU noise in front of the CCS?
In case you notice a similar result, try swapping around the leads at the bottom of the CM chokes and see if that improves things.
Cheers,😉
Trouble shooting tips.
1. Power Supply, Place a 10K resistor 20W or greater accoss the supply before the switch. Check the DC ripple is it acceptable?
2. Remove the resistor load in step1.
3. Yank out the regulator tubes and subsitute the 10K resistor, is the noise gone? If it is the regulator tubes are the culprit. If the noise is still there?
4. Try substituting a ~1250 ohm 2 W or greater resistor for the 32mA CCS. Still got noise then its not the 32 mA CCS?
5. Try substition of the 5mA CCS with a 30K 2W or greater, measure the noise on the plate of the tube. If you still have noise there then your #27 tubes are at fault.
1. Power Supply, Place a 10K resistor 20W or greater accoss the supply before the switch. Check the DC ripple is it acceptable?
2. Remove the resistor load in step1.
3. Yank out the regulator tubes and subsitute the 10K resistor, is the noise gone? If it is the regulator tubes are the culprit. If the noise is still there?
4. Try substituting a ~1250 ohm 2 W or greater resistor for the 32mA CCS. Still got noise then its not the 32 mA CCS?
5. Try substition of the 5mA CCS with a 30K 2W or greater, measure the noise on the plate of the tube. If you still have noise there then your #27 tubes are at fault.
thanks for great help!
I checked the noise in front of the CCS feeding the VR'tubes and it was clean too. But I checked the CM choke connection, and it was correct.
Then, I sub'ed the BBMCCCS on the anodes with 33k, 2W resistors and the noise went away!!! (still using the VR tubes)
The ringing is also gone, and it puts out a nice square now.
I had all sorts og strange effects with the BBMCCCS in, oscillation at 300kHz when the volume-pot was at either stop end...
But I must admit, even though I use Gary Pimms own boards, I am not using the correct type of Batteries. See images. I have normal button cells cramped together with heatshrink tubing... I had a very generous supply of these lithium batteries, so I thought I could get away using them... that was obviously a mistake
(please don't tell Gary!! 
🙂
Do you think that this sollution with the batteries of mine is the culprit? I tried to bypass the Cathode resistors with 100uF caps, and then one of the channels had a 300kHz oscillation with about 8V on the output! lucky I didnt connect it to the poweramp!
I checked the noise in front of the CCS feeding the VR'tubes and it was clean too. But I checked the CM choke connection, and it was correct.
Then, I sub'ed the BBMCCCS on the anodes with 33k, 2W resistors and the noise went away!!! (still using the VR tubes)
The ringing is also gone, and it puts out a nice square now.
I had all sorts og strange effects with the BBMCCCS in, oscillation at 300kHz when the volume-pot was at either stop end...
But I must admit, even though I use Gary Pimms own boards, I am not using the correct type of Batteries. See images. I have normal button cells cramped together with heatshrink tubing... I had a very generous supply of these lithium batteries, so I thought I could get away using them... that was obviously a mistake
(please don't tell Gary!! 🙂Do you think that this sollution with the batteries of mine is the culprit? I tried to bypass the Cathode resistors with 100uF caps, and then one of the channels had a 300kHz oscillation with about 8V on the output! lucky I didnt connect it to the poweramp!
hmmm.... Just realised... I'm using International Rectifiers IRF820's, and them chips are so called HEXFET... Is this anything near mosfet's? Maybe they are making the CCS's behave the way they do?
thanks..
thanks..
CCS
I would get the batteries Gary reccomends , you can get them at Mouser. If you are not going to use a CCS in series with the reulator tube then you should lower the resistor value from 33K because you are now starving the amplifier stage for current.
I would get the batteries Gary reccomends , you can get them at Mouser. If you are not going to use a CCS in series with the reulator tube then you should lower the resistor value from 33K because you are now starving the amplifier stage for current.
Hi Stig,
The first thing I want to ask is do you have a resistor connected between the MU output and the output jack? The mosfet does not like to see capacitive loads directly on the source. I usually use a 47 ohm resistor here.
Hexfet is International Rectifiers trade name for their version of power mosfet. I have had good luck with them in the past.
Have you connected the output to the plate of the 27? This is a good step when looking for problems.
Also, what value did you use for R3? In the older versions I used 2.2K resistors and increased them to 4.7K in the newer versions. Most of the need for the higher value was because the IRF82B is a faster part. Increasing the value of R3 slows down the curcuit.
The peak at 300K is normal as is the ringing. If you zoom in on the ringing and measure the frequency it should be around 300K.
The oscillation at full volume or 0 volume kind of makes me think you might have a grounding issue. I'm just not sure how though.
Another question. What is you plate voltage and the regulated B+ voltage? Want to know how much voltage the CCS is dropping.
That's all I can think of know. I'll chekc back soon to see whats happening.
Gary
The first thing I want to ask is do you have a resistor connected between the MU output and the output jack? The mosfet does not like to see capacitive loads directly on the source. I usually use a 47 ohm resistor here.
Hexfet is International Rectifiers trade name for their version of power mosfet. I have had good luck with them in the past.
Have you connected the output to the plate of the 27? This is a good step when looking for problems.
Also, what value did you use for R3? In the older versions I used 2.2K resistors and increased them to 4.7K in the newer versions. Most of the need for the higher value was because the IRF82B is a faster part. Increasing the value of R3 slows down the curcuit.
The peak at 300K is normal as is the ringing. If you zoom in on the ringing and measure the frequency it should be around 300K.
The oscillation at full volume or 0 volume kind of makes me think you might have a grounding issue. I'm just not sure how though.
Another question. What is you plate voltage and the regulated B+ voltage? Want to know how much voltage the CCS is dropping.
That's all I can think of know. I'll chekc back soon to see whats happening.
Gary
Hi MIKET: yeah maybe you're right with the batteries... As of the CCS, it seems like the one feeding the VR tubes is dead quiet so it's sticking! (it was the anode CCS's I replaced with 33k R's)
Hi gary, and thanks for helping me out!
No, I hav not done this. I will try it out today for sure!
I'm not using the anode as output for the amplifier. I probed the anode under my testing though, and the noise was only slightly lower. Probing the cathode revieled a completly noise free cahtode.
I am using 4.7k. Though, I'm using 1x IRF820 and 1x IRF510 per CCS. (and not 2x IRF820 as in the recent circuit).
That is completely correct! The ringing is right there in the peaking area. So, whenever I get this noise fixed, I'll still have the ringing and the peak?
that might be... I have a partly star-grounding, using the volume pot neg. pin as star point for signals (cathode, volume and input sockets and the VR tubes's gnd as star point for Mu output and chassis and so on... (assuming that the mu outputs is drawing current directly from the VR tubes...)
Plate voltage is around 145V and around 298V for the B+, so the CCS is dropping about 153-156V at 5 mA.
What do you think of my battery solution? do you think they are making the nois? (can a bad contact on one of the batteries make nois perhaps?)
I've inkluded schematic. I must say, I am very impressed with the BYM26C's rectifiers and series resistors. I have no visible switching noise from the PSU at all... (using a 100MHz scope...)
I have used the amp for a couple of weeks now before I could get here and start fault-finding it. I am very impressed with the sound so far dispite the noise.
Thanks alot! Btw, 'grats on the new web site! Is that a EL84 PP with 6AU6 driver amp on the front pic? (like the 47PP)
Schema:
http://www.angelfire.com/ut/Likkhalt/27PreSchema.jpg
and some photos of the finished amp:
http://www.angelfire.com/ut/Likkhalt/FerdigFront.jpg
http://www.angelfire.com/ut/Likkhalt/FerdigBak.jpg
Hi gary, and thanks for helping me out!
No, I hav not done this. I will try it out today for sure!
I'm not using the anode as output for the amplifier. I probed the anode under my testing though, and the noise was only slightly lower. Probing the cathode revieled a completly noise free cahtode.
I am using 4.7k. Though, I'm using 1x IRF820 and 1x IRF510 per CCS. (and not 2x IRF820 as in the recent circuit).
That is completely correct! The ringing is right there in the peaking area. So, whenever I get this noise fixed, I'll still have the ringing and the peak?
that might be... I have a partly star-grounding, using the volume pot neg. pin as star point for signals (cathode, volume and input sockets and the VR tubes's gnd as star point for Mu output and chassis and so on... (assuming that the mu outputs is drawing current directly from the VR tubes...)
Plate voltage is around 145V and around 298V for the B+, so the CCS is dropping about 153-156V at 5 mA.
What do you think of my battery solution? do you think they are making the nois? (can a bad contact on one of the batteries make nois perhaps?)
I've inkluded schematic. I must say, I am very impressed with the BYM26C's rectifiers and series resistors. I have no visible switching noise from the PSU at all... (using a 100MHz scope...)
I have used the amp for a couple of weeks now before I could get here and start fault-finding it. I am very impressed with the sound so far dispite the noise.
Thanks alot! Btw, 'grats on the new web site! Is that a EL84 PP with 6AU6 driver amp on the front pic? (like the 47PP)
Schema:
http://www.angelfire.com/ut/Likkhalt/27PreSchema.jpg
and some photos of the finished amp:
http://www.angelfire.com/ut/Likkhalt/FerdigFront.jpg
http://www.angelfire.com/ut/Likkhalt/FerdigBak.jpg
Hi again;
I have now tried to put a 47R resistor in series with the output cap.
It didn't take the noise away... 🙁
I could see no other changes either... Hmmm... really annoying.
Just realised I could try to probe for noise somewhere directly on the CCS boards... perhaps on the gates og the MostFets?
will try it soon.
edit:
Tried to probe arond locally on the BBMCCCS and i found the highest amount of noise so far.
This plave was on the source of the IRF820 and the drain on the IRF510. Is this saying that perhaps the SEC IRF510 is the noise-generators?
I also probed the batteries, and there was only small (ish) amount of low freq. ripple (less then 0,5mV), no noise at all.
stigla
I have now tried to put a 47R resistor in series with the output cap.
It didn't take the noise away... 🙁
I could see no other changes either... Hmmm... really annoying.
Just realised I could try to probe for noise somewhere directly on the CCS boards... perhaps on the gates og the MostFets?
will try it soon.
edit:
Tried to probe arond locally on the BBMCCCS and i found the highest amount of noise so far.
This plave was on the source of the IRF820 and the drain on the IRF510. Is this saying that perhaps the SEC IRF510 is the noise-generators?
I also probed the batteries, and there was only small (ish) amount of low freq. ripple (less then 0,5mV), no noise at all.
stigla
Possible Alternate
You can also use Deplition Mode FET's, they worked for me.
Here is a link for the DM CCS.
http://home.zonnet.nl/horneman/mosfet.htm
Here is my post take a look at the latset amp schematic
http://www.diyaudio.com/forums/showthread.php?s=&threadid=27855
You can also use Deplition Mode FET's, they worked for me.
Here is a link for the DM CCS.
http://home.zonnet.nl/horneman/mosfet.htm
Here is my post take a look at the latset amp schematic
http://www.diyaudio.com/forums/showthread.php?s=&threadid=27855
Hi Stig,
Yep, the amp on my home page is the 6BQ5 version of the 47 amp. It's big but that was planned. I want to have room to experiment and do a bunch of testing to learn more about how the circuit works. Too darn hard in the 47 chassis. Way too much stuff crammed into a small space. If you look real close, you can see that the holes in the chassis for the output tubes are large enough to take the 5 pin sockets or octals. The 9 pin mini sockets are mounted on plates under the chassis. After all the testing is done this might become the final home for the 47's.
When everything is working correctly you will still have the ringing on squarewaves. Fortunatly, we don't have many input signals with 300Khz content...
Try totally disconnecting the mu output for grins. Just a shot in the dark.
There is definatly something wrong in the CCS. I just went and did some probing in the 85 line stage. There should not be any noise on the drain of Q1/source of Q2. I don't know if the battery stacks can cause a problem or not. The circuit is sensitive to parts location (learned during layout attemps) and the larger battery stacks does change the stray capacitance distrubution of the board. Also, if the circuit is not real stable, sticking a scope probe into the circuit can make it oscillate.
If you have them, try putting an IRF820 in the Q1 position. After blowing up a few 510's from clumsy probing I just started using the 820's everywhere. Found the circuit worked better that way as a plus.
Troubleshooting the CCS's in a live circuit is hard as you have
2 active circuits working against each other (triode and CCS). As a test you can replace the 27 with a 10K resistor. The "plate voltage" will drop to 50 volts and the CCS will drop more voltage but that won't hurt anything. If the noise goes away it could point to cross talk/ground loop problems.
Grounding wise, the input jacks, volume pot, cathode resistor, output jacks, and .056 cap/VR tubes should be a single point ground.
In the power supply area use a ground buss that connects to the single point ground at one end. The floating end of the buss should be connected to the negative end of the bridge rectifier. As you go down the buss towards the single point ground end you would connect the first cap, then the secon cap+bleeder resistor followed by the input end of the common mode choke. Only the output end of the common mode choke and the final 1uf cap should be connected to the single point ground. This keeps the high circulating currents in the input end of the power supply out of the signal ground.
Keep us posted on your progress.
Gary
Yep, the amp on my home page is the 6BQ5 version of the 47 amp. It's big but that was planned. I want to have room to experiment and do a bunch of testing to learn more about how the circuit works. Too darn hard in the 47 chassis. Way too much stuff crammed into a small space. If you look real close, you can see that the holes in the chassis for the output tubes are large enough to take the 5 pin sockets or octals. The 9 pin mini sockets are mounted on plates under the chassis. After all the testing is done this might become the final home for the 47's.
When everything is working correctly you will still have the ringing on squarewaves. Fortunatly, we don't have many input signals with 300Khz content...
Try totally disconnecting the mu output for grins. Just a shot in the dark.
There is definatly something wrong in the CCS. I just went and did some probing in the 85 line stage. There should not be any noise on the drain of Q1/source of Q2. I don't know if the battery stacks can cause a problem or not. The circuit is sensitive to parts location (learned during layout attemps) and the larger battery stacks does change the stray capacitance distrubution of the board. Also, if the circuit is not real stable, sticking a scope probe into the circuit can make it oscillate.
If you have them, try putting an IRF820 in the Q1 position. After blowing up a few 510's from clumsy probing I just started using the 820's everywhere. Found the circuit worked better that way as a plus.
Troubleshooting the CCS's in a live circuit is hard as you have
2 active circuits working against each other (triode and CCS). As a test you can replace the 27 with a 10K resistor. The "plate voltage" will drop to 50 volts and the CCS will drop more voltage but that won't hurt anything. If the noise goes away it could point to cross talk/ground loop problems.
Grounding wise, the input jacks, volume pot, cathode resistor, output jacks, and .056 cap/VR tubes should be a single point ground.
In the power supply area use a ground buss that connects to the single point ground at one end. The floating end of the buss should be connected to the negative end of the bridge rectifier. As you go down the buss towards the single point ground end you would connect the first cap, then the secon cap+bleeder resistor followed by the input end of the common mode choke. Only the output end of the common mode choke and the final 1uf cap should be connected to the single point ground. This keeps the high circulating currents in the input end of the power supply out of the signal ground.
Keep us posted on your progress.
Gary
Hi again!
this is what i've done yesterday. (from today and on I don't have any measurment tools available so now it's testing using the ears 🙂
I buildt up one of the circuit MIKET suggested (thanks!), as I had some DN2540's laying around. Only resistors and Mosfets version.
I put it in one of the channels and measured for noise, and it was still there! This is getting wierd... I still have to try to change the CCS feeding the VR tubes, will try a 2,5k resistor here sometime soon.
Think I will resort to completely starground as Gary suggest.
Oh, and by the way... Those are not CM chokes in the PSU, those are symbols for interconnections between the separate PSU and Preamp chassis. 🙂 The only CM choke is on the mains 🙂
I also tried putting a IRF820 in the IRF510 place, and still noise present... (it was an ST micro though... all I had.)
I also took one of the CCS's completely out of the amp, and hooked it on a clean 12V battery, and hooked a 1k resister in series with the - output and probed for noise. Well, I think I saw some noise, but it might be that since the resistance to gnd is 1/10th and the voltage is 1/20th, the noise should also be considerable less, yes?
Anyway, then I subbed the '510 with the '820 and I imagined I saw less noise, but putting it in the amp again I still had the very amount of noise present...
I'm starting to suspect grounding troubles more and more...
will keep you informed.
btw; I also measured Channel Separation, and I got ca. -70dB. I don't consider this particulary good... What do you have in your own amp gary? We drilled some extra holes in the chassis (thats what the small rectangular plate in the front is hiding.) so as to alow an extra set ot 0A2 tubes. I think we will do that, it will probably increase the CS... unless its the Voulme pot and input selector that's "talking" too much between channels 🙂
this is what i've done yesterday. (from today and on I don't have any measurment tools available so now it's testing using the ears 🙂
I buildt up one of the circuit MIKET suggested (thanks!), as I had some DN2540's laying around. Only resistors and Mosfets version.
I put it in one of the channels and measured for noise, and it was still there! This is getting wierd... I still have to try to change the CCS feeding the VR tubes, will try a 2,5k resistor here sometime soon.
Think I will resort to completely starground as Gary suggest.
Oh, and by the way... Those are not CM chokes in the PSU, those are symbols for interconnections between the separate PSU and Preamp chassis. 🙂 The only CM choke is on the mains 🙂
I also tried putting a IRF820 in the IRF510 place, and still noise present... (it was an ST micro though... all I had.)
I also took one of the CCS's completely out of the amp, and hooked it on a clean 12V battery, and hooked a 1k resister in series with the - output and probed for noise. Well, I think I saw some noise, but it might be that since the resistance to gnd is 1/10th and the voltage is 1/20th, the noise should also be considerable less, yes?
Anyway, then I subbed the '510 with the '820 and I imagined I saw less noise, but putting it in the amp again I still had the very amount of noise present...
I'm starting to suspect grounding troubles more and more...
will keep you informed.
btw; I also measured Channel Separation, and I got ca. -70dB. I don't consider this particulary good... What do you have in your own amp gary? We drilled some extra holes in the chassis (thats what the small rectangular plate in the front is hiding.) so as to alow an extra set ot 0A2 tubes. I think we will do that, it will probably increase the CS... unless its the Voulme pot and input selector that's "talking" too much between channels 🙂
Hi again,
In a weird way, the fact that you still have noise with the DN2540 CCS is good! It means the battery biased CCS is most likely working ok...
To test the CCS out of circuit you need more than 12 volts in your test jig. It takes 12 volts across the CCS as an absolute minimum to get it to start to work. With the 1K resistor needing to drop 5 volts you are not getting the CCS biased up properly. Got another 12 volt battery? 24 volts would be plenty, 5 volts for the resistor and 19 volts for the CCS. Another good thing about testing using batterys is you get total isolation from the outside world, no ground loops to mess up low level measurments.
I have not measured cross talk in my amps/preamps so I have no clue if what you measured is normal or not. Something else to put on the list...
Have fun!
Gary
In a weird way, the fact that you still have noise with the DN2540 CCS is good! It means the battery biased CCS is most likely working ok...
To test the CCS out of circuit you need more than 12 volts in your test jig. It takes 12 volts across the CCS as an absolute minimum to get it to start to work. With the 1K resistor needing to drop 5 volts you are not getting the CCS biased up properly. Got another 12 volt battery? 24 volts would be plenty, 5 volts for the resistor and 19 volts for the CCS. Another good thing about testing using batterys is you get total isolation from the outside world, no ground loops to mess up low level measurments.
I have not measured cross talk in my amps/preamps so I have no clue if what you measured is normal or not. Something else to put on the list...
Have fun!
Gary
Hi again!
Just wanted to say that I've found the source for the noise.
It was the Battery CCS's after all! I have now ordered some batteries of the proper type.
After a day of intensive tweaking, trying to get rid of the noise, I tried once again to replace one of the BBMCCCS's with a DN2540 cascode CCS, and behold, the noise in that channel was gone!
This has led me to belive that my alternative solution with normal coin cells (and not PCB mounted types) is the culprit, and that I never should have considered using them 🙂
So, I'm sorry if this thread have made anyone doubt the performance of the marvelous BBMCCCS, as all the problems I met was entirely my fault.
Thanks for all the help from you guys!
Stigla
Just wanted to say that I've found the source for the noise.
It was the Battery CCS's after all! I have now ordered some batteries of the proper type.
After a day of intensive tweaking, trying to get rid of the noise, I tried once again to replace one of the BBMCCCS's with a DN2540 cascode CCS, and behold, the noise in that channel was gone!
This has led me to belive that my alternative solution with normal coin cells (and not PCB mounted types) is the culprit, and that I never should have considered using them 🙂
So, I'm sorry if this thread have made anyone doubt the performance of the marvelous BBMCCCS, as all the problems I met was entirely my fault.
Thanks for all the help from you guys!
Stigla
Ok, waking up an old thread...
Some updates on the noise problem;
- Got the noise down to acceptable levels by adding a cathode bypass cap. This removed perhaps 3/4 of the noise!
- Discovered that the noise is dependable on the position of the volume pot. The most noise is generated at 0% and 100% positions(!).
- Also got some weird oscillations when volume pot is at 80-100%... (300kHz, 5-8V!)
So, this tells me that i've probably got some (more) layout problems.
I have changed all the batteries on my BBMCCCS's to the correct PCB mounted types, so I guess this rules out the current sources as noise generators.
Tried to take all current sources out and replacing them with resistors (anode loads and VR tube loads), and then all the noise was gone...
Tried many other things, like grid stoppers, grid caps to ground in the pF range, shielding output caps, resistors in series with outputcaps, different tubes, no VR tubes etc, but nothing have worked. The noise is at acceptable levels now, but I want to get rid of it all right at the source and not just swamping the effects...
Need help! Still! 🙂
Some updates on the noise problem;
- Got the noise down to acceptable levels by adding a cathode bypass cap. This removed perhaps 3/4 of the noise!
- Discovered that the noise is dependable on the position of the volume pot. The most noise is generated at 0% and 100% positions(!).
- Also got some weird oscillations when volume pot is at 80-100%... (300kHz, 5-8V!)
So, this tells me that i've probably got some (more) layout problems.
I have changed all the batteries on my BBMCCCS's to the correct PCB mounted types, so I guess this rules out the current sources as noise generators.
Tried to take all current sources out and replacing them with resistors (anode loads and VR tube loads), and then all the noise was gone...
Tried many other things, like grid stoppers, grid caps to ground in the pF range, shielding output caps, resistors in series with outputcaps, different tubes, no VR tubes etc, but nothing have worked. The noise is at acceptable levels now, but I want to get rid of it all right at the source and not just swamping the effects...
Need help! Still! 🙂
Gary's BBMCCCS
Just a question from the sideline, as I'm fiddeling with these circuits myself (Gary's BBMCCCS):
How important are capacitor grade in the BBMCCCS? I see Gary has put a 10nF teflon in some of his, I can't see what 0.1uF caps he is using... is metalized polyprop fine or should I aim for audiograde stuff?
Just a question from the sideline, as I'm fiddeling with these circuits myself (Gary's BBMCCCS):
How important are capacitor grade in the BBMCCCS? I see Gary has put a 10nF teflon in some of his, I can't see what 0.1uF caps he is using... is metalized polyprop fine or should I aim for audiograde stuff?
Old thread coming up! 🙂
I have not done any direct experiments myself, but as you surely know Gary himself claim that this is an important component and I belive him. 🙂
Myself I use Film&Foil Polyprops, small blue ones... The amplifier really sounds great!
I have recently just tried out the new self biased CCS types, using them to feed the VR-tubes. They are really great! real slow turn-on. They are a bit demanding on the voltage drop though, but this poses no real problem.
Since I am already posting an answer on this thread I want to say a bit about the recent development of my amplifier.
The noise is still present, though very acceptable. We have been listening to it for over a year and it has worked flawlessly. Since last we have cashed out for premium components, Hovland outputcaps(3uF), Kiwame and Holco resistors, BlackBeauty pot, ASC 20uF B+ cap, cardas silverwire, MultiCap RTX VR-bypasscap, BG cathode bypass.
This really elevated the soundquality to unexpected levels!
But the fact that the noise still is there is really anoying (for an engineer)!!!
The problem we have now is finding good pairs of #27's. Many NOS tubes are very humming. I got an excelent pair of silvertone's but they hum like an old dishwasher!
Stigla
I have not done any direct experiments myself, but as you surely know Gary himself claim that this is an important component and I belive him. 🙂
Myself I use Film&Foil Polyprops, small blue ones... The amplifier really sounds great!
I have recently just tried out the new self biased CCS types, using them to feed the VR-tubes. They are really great! real slow turn-on. They are a bit demanding on the voltage drop though, but this poses no real problem.
Since I am already posting an answer on this thread I want to say a bit about the recent development of my amplifier.
The noise is still present, though very acceptable. We have been listening to it for over a year and it has worked flawlessly. Since last we have cashed out for premium components, Hovland outputcaps(3uF), Kiwame and Holco resistors, BlackBeauty pot, ASC 20uF B+ cap, cardas silverwire, MultiCap RTX VR-bypasscap, BG cathode bypass.
This really elevated the soundquality to unexpected levels!
But the fact that the noise still is there is really anoying (for an engineer)!!!
The problem we have now is finding good pairs of #27's. Many NOS tubes are very humming. I got an excelent pair of silvertone's but they hum like an old dishwasher!
Stigla
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