I have had another look at my work and found that one of the secondary supplies wasn't connecting to the input of the power supply - fixing this has improved things somewhat. I'm not sure this should have worked, but it was.
I had checked output voltages etc. on the power supply and they didn't change (+24.2v and -24.6v ) from fixing up the connection to the secondaries - in this power supply they are connected with the supply having a center tap, so previously I was only getting half power (running of one secondary only?) but enough to run the amp. There is still some noise but not as noticeable as previously.
Russellc you said your amp was quiet - was this absolutely dead quiet, or just some faint noise up close. If I have mucked another joint somewhere on the power supply or have an out of spec LM for example is it possible that I can have something which is operational and sounds good, but ends up being ever so slightly noisy. Obviously I am a little new to this and while I am getting better with the theory I am not exactly sure what I should see during a build, for example is it ok to see some ac on the regulated output which is supposed to be dc. I am not sure if this is an artefact of my multimeters and only shown with the test leads oriented one way so I am not sure if this is spurious or very low level noise etc. or an indication of a problem somewhere else in the power supply.
thanks for the input so far,
Nigel.
I had checked output voltages etc. on the power supply and they didn't change (+24.2v and -24.6v ) from fixing up the connection to the secondaries - in this power supply they are connected with the supply having a center tap, so previously I was only getting half power (running of one secondary only?) but enough to run the amp. There is still some noise but not as noticeable as previously.
Russellc you said your amp was quiet - was this absolutely dead quiet, or just some faint noise up close. If I have mucked another joint somewhere on the power supply or have an out of spec LM for example is it possible that I can have something which is operational and sounds good, but ends up being ever so slightly noisy. Obviously I am a little new to this and while I am getting better with the theory I am not exactly sure what I should see during a build, for example is it ok to see some ac on the regulated output which is supposed to be dc. I am not sure if this is an artefact of my multimeters and only shown with the test leads oriented one way so I am not sure if this is spurious or very low level noise etc. or an indication of a problem somewhere else in the power supply.
thanks for the input so far,
Nigel.
You are adding 20db so of gain where you had none before (I am assuming you just had a volume pot on the gain clone). I think a little more noise is normal. Plus, you have A LOT of gain in that system (20db-ish in the BA-3, 20db in the gainclone).
I use a BA-3 with a Jung Super reg and an F5. No noise. I had it set up with a LM317/337 reg too. No noise.
Some pics might help.
I use a BA-3 with a Jung Super reg and an F5. No noise. I had it set up with a LM317/337 reg too. No noise.
Some pics might help.
I am assuming it is quiet...I haven't measured the outs on the pre, but it makes no difference when hooked up to a power amp, or no pre and amp inputs shorted. I hadn't noticed noise of any sort with F-5, BA3 power amp, F6and with most speakers, the M2. I say most, it was quiet with 85 dB mini monitors with 7" mid Bass, 93 dB Econowave (15" JBL 2235H) and 100+ db Altec A7. However, I did notice that with M2 hooked up to a newly acquired set of 98 dB Tekton Enzo speakers, with my ear inside the cone, there is a very slight electronic noise, not a hiss, Not really perceived as a hum either. Just a noise that amp is on....I guess it is a just perceivable hum? You really have to stick your ear in the cone to hear it. I just noticed it with a 91 db set of speakers with a Diappolito arrangement using 5 1/2 inch Kevlar mid woofs. Just perceivable, again with ear stuck right up into cone. Odd the 15" drivers don't exhibit this. I must restate how quiet it really is.
How are you measuring noise off the pre? Or do you mean off the power amp with speakers attached?
Russellc
Last edited:
The noise is heard through the speakers and is present regardless of volume setting.
I have attached a picture below.
Hopefully this all looks pretty straightforward. Just out of image is the volume control which is an alps blue 50k pot. I tried to route everything neatly and twisted all signal and power(ac and dc) where I could. There is a single earh point between the transformer and ps (see bolt). The standoffs are fairly low I might see if I can lift these up a bit to see if I am picking up any noise from the dc supply which run under the amp board.
http://corigin.dastatic.com/forums/images/attach/jpg.gif
I have attached a picture below.
Hopefully this all looks pretty straightforward. Just out of image is the volume control which is an alps blue 50k pot. I tried to route everything neatly and twisted all signal and power(ac and dc) where I could. There is a single earh point between the transformer and ps (see bolt). The standoffs are fairly low I might see if I can lift these up a bit to see if I am picking up any noise from the dc supply which run under the amp board.
http://corigin.dastatic.com/forums/images/attach/jpg.gif
Attachments
Hi Zen Mod,
pot is 50k - does a higher or lower value have any effect?
I am using the spec attached to the info paper, which I assume is the one used in 6l6s build guide. Not sure what gain is but I am only using 1/8th to 1/4 of volume at normal to loudish settings.
I don't have another power amp to test on - am thinking of f4 or f6 or even amp camp amps, any suggestions (looking to go to econowave or similar in future).
pot is 50k - does a higher or lower value have any effect?
I am using the spec attached to the info paper, which I assume is the one used in 6l6s build guide. Not sure what gain is but I am only using 1/8th to 1/4 of volume at normal to loudish settings.
I don't have another power amp to test on - am thinking of f4 or f6 or even amp camp amps, any suggestions (looking to go to econowave or similar in future).
Ba3 gain is 20db ish, gainclone is 30db ish. A lot of gain. Probably don't need a preamp. Noise will definitely be more evident with the ba3 than without it due to massive system gain.
I don't see a ground breaker between the chassis and psu ground, Also, I see mains wire to the transformer missing. Should be totally silent then...since it won't be working. But Iam guessing that pic was just during the troubleshooting phase.
I would add a cl60 or resistor between psu ground and chassis. Lots of ways to do this. You could have a bad ground loop between the gainclone and ba3 via house wiring because they are not isolated.
Could be a bad part/soldering error but if it's both channels and not effected by volume control I doubt it. If it's a problem of just too much gain it would be effected by the volume control. I think it might be the gainclone. Perhaps it just wasn't noticed before and now magnified by the increased gain?
I don't see a ground breaker between the chassis and psu ground, Also, I see mains wire to the transformer missing. Should be totally silent then...since it won't be working. But Iam guessing that pic was just during the troubleshooting phase.
I would add a cl60 or resistor between psu ground and chassis. Lots of ways to do this. You could have a bad ground loop between the gainclone and ba3 via house wiring because they are not isolated.
Could be a bad part/soldering error but if it's both channels and not effected by volume control I doubt it. If it's a problem of just too much gain it would be effected by the volume control. I think it might be the gainclone. Perhaps it just wasn't noticed before and now magnified by the increased gain?
Thanks zenmod the problem definitely seems to be too much gain. I put an attenuator between the BA3 pre and my gainclone and a cut of 6 to 10db (and more) removed all noise (I have attached link to schematic used). I also used another amp and the noise was there too, albeit at a little lower level, but still present.
With some attenuation, music now disappears into a very black background and exhibits the wonderful musicality seen from day one. The question therefore is how much gain should I take out and how, I don't want to have to keep an extra level of attenuation in the system. I am sure Nelson has noted this somewhere, I'll search the threads to find it but if anyone has a link I'd be grateful for it.
The other question is how much gain is enough i.e. what gain should be I be using for something like a gainclone (which I plan to use for the next 6 months or so) and what new resistor values this requires. Also what levels would be required for an F6 or amp camps versus an F4 - which is what I want to go to after the gainclone.
Hikari, I tried the cl60 as a ground breaker but this didn't reduce the noise, it seems that the existing gain structure is bringing up the noise floor to an audible level and that this will go away with a cut to overall gain i.e. pre plus power amps.
regards,
Nigel.
With some attenuation, music now disappears into a very black background and exhibits the wonderful musicality seen from day one. The question therefore is how much gain should I take out and how, I don't want to have to keep an extra level of attenuation in the system. I am sure Nelson has noted this somewhere, I'll search the threads to find it but if anyone has a link I'd be grateful for it.
The other question is how much gain is enough i.e. what gain should be I be using for something like a gainclone (which I plan to use for the next 6 months or so) and what new resistor values this requires. Also what levels would be required for an F6 or amp camps versus an F4 - which is what I want to go to after the gainclone.
Hikari, I tried the cl60 as a ground breaker but this didn't reduce the noise, it seems that the existing gain structure is bringing up the noise floor to an audible level and that this will go away with a cut to overall gain i.e. pre plus power amps.
regards,
Nigel.
Attachments
What is Gain Structure? - diyAudio
should give you a lot of clues in where and how to avoid excessive gain
should give you a lot of clues in where and how to avoid excessive gain
For what it's worth, right now in living room system, I have 98 dB Tekton Enzo towers driven by BA3 front end preamp which then drives a complete BA3 power amp. Both units are built exactly as 6l6's build threads with standard gain
There is obviously lots of gain, but this combo is silent, even with ear stuck in bass driver cones.
I used store BA3 boards for both pre and power amp, standard bom. Wiring for both is exactly like 6l6 did in his build guides. Both units use all Toshiba jfets as well as MOSFETs on the boards. Don't think that makes a difference, just saying what I used.
Russellc
There is obviously lots of gain, but this combo is silent, even with ear stuck in bass driver cones.
I used store BA3 boards for both pre and power amp, standard bom. Wiring for both is exactly like 6l6 did in his build guides. Both units use all Toshiba jfets as well as MOSFETs on the boards. Don't think that makes a difference, just saying what I used.
Russellc
Thanks Russellc, do you know what the gain of the ba3 power amp is? I tried to follow the build guide very closely, and think I did, apart from using fairchild mosfets (and 1k pots as suggested). I wonder if the toshiba devices are quieter? Also what is the gain of the power amp versus the gainclone? In my system (using 85db spendors) I need very little volume control to get loud. My interpretation of the gain structure article is that whatever low level noise is coming out of the devices in the amp is getting amplified by the overall gain of my system (which is high), along with the music signal which we want amplified. As I have seen, attenuating the signal into the power amp completely covers the background sound/hash, giving a dead silent background, leaving the music to dominate - plus I still have lots of gain in reserve. I'd like to think that cutting the gain will leave the very obvious musicality intact while pushing the noise floor right down. As noted previously I was looking to go to an F6 but if I had any doubts about loss of performance with cutting gain I guess I would consider an F4 (with its 0 gain) which would require the fuller voltage swing of the BA3. Regards Nigel.
Last edited:
Mine is standard bom and schematic from 6l6 article, some say 30 dB, some say no way Me, I have no idea. Volume pot is 25k ladder Chinese deal from eBay. I showed it on 6l6 BA3 FE as pre build thread. Sounds like you have fixed the problem, I would just enjoy!
As an aside, these Tekton Enzo speakers are the bomb. I just bought them and had them delivered, really figured I would send back...
Uh. No way!
As an aside, these Tekton Enzo speakers are the bomb. I just bought them and had them delivered, really figured I would send back...
Uh. No way!
Last edited:
Gainclone is 30db gain. F6 is 15db. F4 is 0. Ba3 front end has 20ish db of gain.
For a gainclone I would just use a buffer. For an f6 or f4 I would stick with the stock gain values in the ba3 front end. Also, the pots after the ba3 you are using are pretty much the same thing as having a volume control on the gainclone and just turning it down. It's raising the impedence of the incoming signal which you don't want.
Curious... You said the noise did not raise in level with the volume control. Which indicates something other than too much gain. If it was noise amplified by too much gain it would go up as the raise the volume.
With my Lm3886 DIY Amps ( not Chi Fi ones either) all 3 had inherent noises of varying annoyance.
No dead silence.. by any imaginative stretch.
Could consider building an amp worthy of the 3?
My F6 is ..dead.. silent and with simple stoopid cheap pots as 'pre', it goes to 'fear for my drivers ' loudness... 95 db gizmos though.
No dead silence.. by any imaginative stretch.
Could consider building an amp worthy of the 3?
My F6 is ..dead.. silent and with simple stoopid cheap pots as 'pre', it goes to 'fear for my drivers ' loudness... 95 db gizmos though.
Yes Hikari, the noise is independent of the volume settings so does this suggest to you that the gainclone (an audiosector deluxe version, built to the recommended plan) is the more likely issue or how it is working with the ba3 pre. I am wondering now about the earthing. In testing the connection between ba3 and gainclone the hiss starts as soon as the earth connects on the interconnects i.e. before the hot or signal connect is made. I see that hiss from gainclones is not uncommon and various solutions are mentioned including reducing gain and paying extra attention to the earth layout. I have only ever used the gainclone with passive pres, for several years now, and it has always been dead quiet (which is why I had initially wondered about the ba3, as it was the ne link in the chain). I tried your suggestion regarding a ground breaker (CL60) on the ba3 and it made no difference at all to the hiss. I wonder if I should look at a ground breaker on the gainclone or revisit my grounding on the ba3. I am going to start on my f6 amp soon but would like to at least be able to use the gainclone in the meantime. Using the attenuator before the gainclone does help with the, admittedly low level, noise but does take something away from the sound quality, although it is still a long way ahead of just having the attenuator. Regards Nigel.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.