I got those amp: Mono 6B4G tube amp and Preamp - Canuck Audio Mart
from someone who built those tube amp. I was so excited that I didnt really cared about a couple issue, and litteraly, the sound. I'm used to SS amp, so at first listening, I was super impressed, but now, 600$ later, and a couple of listening test, I'm a little less happy.
First of all, there's not a hum like written in the ad. However, they are super sensitive. If I walk to hard on the floor, it may have the little "shhhh" nsound. Hard to eplain but I'm sure what I mean. Sort of a electro-static sound?
Second of all, the sound. While not bad, there's something just not right. IT lacks dynamic, soundstage, presence? Hard to explain. The bass is nice. The midrange is aggressive, strong. Sound good at first sight, but tends to be irritating after a while!!! I paid 600$ for this, and damn, I dont know what to do.
Can anyone be gentle enough to take a look at the pictures, and tells me things to change in order to give this amp a second life? What can be wrong, what shouldn't be there.
ps: I wil have the schematic soon. the technician is out of town for a while...
It's in push-pull configuration...
I know that a crazy request, but I really don'T know where to start neither what to do. I can use this forced "project" to get my hand dirty for the fist time and learn some stuff about tube amp. My hope is that this amp's got potential that just need to be unleashed?.........
thanks
from someone who built those tube amp. I was so excited that I didnt really cared about a couple issue, and litteraly, the sound. I'm used to SS amp, so at first listening, I was super impressed, but now, 600$ later, and a couple of listening test, I'm a little less happy.
First of all, there's not a hum like written in the ad. However, they are super sensitive. If I walk to hard on the floor, it may have the little "shhhh" nsound. Hard to eplain but I'm sure what I mean. Sort of a electro-static sound?
Second of all, the sound. While not bad, there's something just not right. IT lacks dynamic, soundstage, presence? Hard to explain. The bass is nice. The midrange is aggressive, strong. Sound good at first sight, but tends to be irritating after a while!!! I paid 600$ for this, and damn, I dont know what to do.
Can anyone be gentle enough to take a look at the pictures, and tells me things to change in order to give this amp a second life? What can be wrong, what shouldn't be there.
ps: I wil have the schematic soon. the technician is out of town for a while...
It's in push-pull configuration...
I know that a crazy request, but I really don'T know where to start neither what to do. I can use this forced "project" to get my hand dirty for the fist time and learn some stuff about tube amp. My hope is that this amp's got potential that just need to be unleashed?.........
thanks
Damn. That's a bummer. But it may be fixable. I bet once you get a schematic drawn up, you'll get some helpful responses.
Tubes are somewhat sensitive to vibration. That may be what you hear when you stomp on the floor or tap the tubes (carefully!) with the eraser end of a pencil. That's pretty normal. Some tubes are optimized for low microphonics. I don't know if 6B4G is one of them. I'm guessing not... You could place the amp on some sort of suspension. Think the kinds of stuff people use for their turntables.
~Tom
Tubes are somewhat sensitive to vibration. That may be what you hear when you stomp on the floor or tap the tubes (carefully!) with the eraser end of a pencil. That's pretty normal. Some tubes are optimized for low microphonics. I don't know if 6B4G is one of them. I'm guessing not... You could place the amp on some sort of suspension. Think the kinds of stuff people use for their turntables.
~Tom
Tubes in an amp shouldn't be so sensitive that walking on a relatively solid floor near them causes noise. Probably one of them has developed a loose mount inside the tube and become badly microphonic. I have replaced many tubes in music amps for that problem. It can also cause distortion by the electric field inside the tube causing the loose mount to vibrate.
The wiring and construction looks a little "dodgy". Seems that it was put together in a hurry and worse, banged around a lot, especially the preamp. The transformer on the power amp also looks damaged. I think a few forumers did warn you against these points earlier regarding this amp.
Anyway, maybe you will have to go through the connections and solder points one by one and make sure there are no loose connections/dry joints ( a major cause of unidentified noise especially when it is so sensitive to vibrations ). The banging around probably contributes the most to this problem.
Get the schematic and let us have a look so that we can get some pointers as to your problems.
Anyway, maybe you will have to go through the connections and solder points one by one and make sure there are no loose connections/dry joints ( a major cause of unidentified noise especially when it is so sensitive to vibrations ). The banging around probably contributes the most to this problem.
Get the schematic and let us have a look so that we can get some pointers as to your problems.
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That sounds like not quite enough gNFB to clean up the H3 and take the edge off. Need to see a schemo, though.
Could be an unused grid pin just floating and picking up anything (which it will). The lower part of the amp chassis is wood correct ? No screening !
If I take the lower cover off my tube preamp and put the unit on top of the CD player.....it picks up the mpu clock noise.
richy
I found with my DHT amp that the sound improved surprisingly when I changed from AC heating to a Coleman type system. It appears that in DHT's the heating arrangements matter much more in say dynamics than regards to hum than you would expect.
There's solid advice by previous posters, my advice would be to try out at least CCS heaters on the DHT's.
There's solid advice by previous posters, my advice would be to try out at least CCS heaters on the DHT's.
The noise you describe sounds like microphony, which seems to be fairly common for direct heated triodes.
Even if the sound isn't quite where you want it, I think you made out pretty good on the deal. I usually end up spending $600+ in parts and shipping alone to build something comparable. It may just require a little tweaking. Even if it needs a re-design you have tubes, iron and chassis.
The other thing is that lower powered tube amps with little to no feedback are very picky in the speakers you try to pair them up with. Not nearly as flexible or forgiving as solid state amps or high feedback high powered tube amps. But when you do find the right match, it's capable of sounding very good.
Even if the sound isn't quite where you want it, I think you made out pretty good on the deal. I usually end up spending $600+ in parts and shipping alone to build something comparable. It may just require a little tweaking. Even if it needs a re-design you have tubes, iron and chassis.
The other thing is that lower powered tube amps with little to no feedback are very picky in the speakers you try to pair them up with. Not nearly as flexible or forgiving as solid state amps or high feedback high powered tube amps. But when you do find the right match, it's capable of sounding very good.
Construction quality leaves a lot to be desired, but there are a lot of good parts inside and you have the making for a good amplifier I believe.
I'm not a fan of the particular coupling caps used - I've found them to be quite colored sounding. (This of course is a subjective opinion) I'd recommend the inexpensive Russian Teflon FT-3 type as a possible replacement - it's sonically and electrically better. (No issue with leakage currents as they age either.)
Not necessarily the case that this design uses global feedback, my PP triode amps don't, but without seeing the schematic it is hard to know.
IMLE the 6B4G is quite microphonic as are many dht power tubes, the solution is to make sure they are well isolated from footfalls and other sources of vibration. They can also vibrate in tune to the music with some interesting and unwanted results - I have had actual cases of acoustic feedback with the 26 dht in low level stages - the problem with power tubes is not usually this severe.
The speakers you are using may or may not be synergistic with this amp as designed - what are they exactly?
I think you have the platform for a very good set of amplifiers.
The pre-amp is based on op-amps and could be a questionable choice IMHO for someone interested in an all tube system. If you have a CD player with variable out I would run that directly into the power amps and see what you end up with sonically just as a test. Choice of op-amps used can influence the performance in audible ways - in that vein what op-amps are used in this pre-amp?
I'm not a fan of the particular coupling caps used - I've found them to be quite colored sounding. (This of course is a subjective opinion) I'd recommend the inexpensive Russian Teflon FT-3 type as a possible replacement - it's sonically and electrically better. (No issue with leakage currents as they age either.)
Not necessarily the case that this design uses global feedback, my PP triode amps don't, but without seeing the schematic it is hard to know.
IMLE the 6B4G is quite microphonic as are many dht power tubes, the solution is to make sure they are well isolated from footfalls and other sources of vibration. They can also vibrate in tune to the music with some interesting and unwanted results - I have had actual cases of acoustic feedback with the 26 dht in low level stages - the problem with power tubes is not usually this severe.
The speakers you are using may or may not be synergistic with this amp as designed - what are they exactly?
I think you have the platform for a very good set of amplifiers.
The pre-amp is based on op-amps and could be a questionable choice IMHO for someone interested in an all tube system. If you have a CD player with variable out I would run that directly into the power amps and see what you end up with sonically just as a test. Choice of op-amps used can influence the performance in audible ways - in that vein what op-amps are used in this pre-amp?
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okay, well THATS encouraging!!!!!! I didnt get the pre-amp, only the tube amp.
The sensitivity is for both mono blocks. If I touch either one, the "problem" is there.
I dont have a schematic, now, so for now, I'll put this at hold.
I really hope I can get one, but bit scared that I wont, if I cant have a schematic, is it dramatic.
The thing is, the technician had a inondation (flood?) so for the moment, is really unavailable...
Thanks guys, this gives me hope! Really
BTW, I use some good old dynaco A-25's
The sensitivity is for both mono blocks. If I touch either one, the "problem" is there.
I dont have a schematic, now, so for now, I'll put this at hold.
I really hope I can get one, but bit scared that I wont, if I cant have a schematic, is it dramatic.
The thing is, the technician had a inondation (flood?) so for the moment, is really unavailable...
Thanks guys, this gives me hope! Really
BTW, I use some good old dynaco A-25's
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Just an idea,
Get a large piece of paper,
Put circles on it with tube numbers in them, plus all components (screwed to the chassis) on the paper in the same place as on the amp draw the circuit as a wiring diagram then transfer it to a schematic. There are only a few components from the look of it you only need to draw the one if they are mono block! Post your schematic if its wrong some one will say!
You can look up the tube connections.
Take care of stored charge in capacitors! Test before you touch.
Regards
M. Gregg
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hi everyone, I still dont have a schematic, however I talk to one user, and I decided to swap my jenson caps for russian ft-3.
Now, there's something weird, one channel seems to slightly sound louder then the other. I dont even know if I'm imaginating stuff, but I dont think anymore. Just a slightly more clear from the left channel. This surprise me, I would have thought that if I had a problem from one channel, well it would be clearly audible, but the problem is just mild. What can cause this? I swapped all the tubes from one side to the other side block, and the problem is still there. Bear in mind that the problem is subtle, not huge... the problem also comes from the monoblock which the buzzing sound. I'm not even sure theirs a problem, anyway thought I pitch this in.
Also, now that I swap the caps for russian in the audio signal, what else obvious thing I should upgrade?
thanks a lot folks for your help, I dont know what I could do without you, and this really pushes me to dimyself something. I'll probably make a phono stage as a beginner project.
thanks...
Now, there's something weird, one channel seems to slightly sound louder then the other. I dont even know if I'm imaginating stuff, but I dont think anymore. Just a slightly more clear from the left channel. This surprise me, I would have thought that if I had a problem from one channel, well it would be clearly audible, but the problem is just mild. What can cause this? I swapped all the tubes from one side to the other side block, and the problem is still there. Bear in mind that the problem is subtle, not huge... the problem also comes from the monoblock which the buzzing sound. I'm not even sure theirs a problem, anyway thought I pitch this in.
Also, now that I swap the caps for russian in the audio signal, what else obvious thing I should upgrade?
thanks a lot folks for your help, I dont know what I could do without you, and this really pushes me to dimyself something. I'll probably make a phono stage as a beginner project.
thanks...
hi everyone, I still dont have a schematic, however I talk to one user, and I decided to swap my jenson caps for russian ft-3.
Now, there's something weird, one channel seems to slightly sound louder then the other. I dont even know if I'm imaginating stuff, but I dont think anymore. Just a slightly more clear from the left channel. This surprise me, I would have thought that if I had a problem from one channel, well it would be clearly audible, but the problem is just mild. What can cause this? I swapped all the tubes from one side to the other side block, and the problem is still there. Bear in mind that the problem is subtle, not huge... the problem also comes from the monoblock which the buzzing sound. I'm not even sure theirs a problem, anyway thought I pitch this in.
Also, now that I swap the caps for russian in the audio signal, what else obvious thing I should upgrade?
thanks a lot folks for your help, I dont know what I could do without you, and this really pushes me to dimyself something. I'll probably make a phono stage as a beginner project.
thanks...
Now, there's something weird, one channel seems to slightly sound louder then the other. I dont even know if I'm imaginating stuff, but I dont think anymore. Just a slightly more clear from the left channel. This surprise me, I would have thought that if I had a problem from one channel, well it would be clearly audible, but the problem is just mild. What can cause this? I swapped all the tubes from one side to the other side block, and the problem is still there. Bear in mind that the problem is subtle, not huge... the problem also comes from the monoblock which the buzzing sound. I'm not even sure theirs a problem, anyway thought I pitch this in.
Also, now that I swap the caps for russian in the audio signal, what else obvious thing I should upgrade?
thanks a lot folks for your help, I dont know what I could do without you, and this really pushes me to dimyself something. I'll probably make a phono stage as a beginner project.
thanks...
hi everyone, I still dont have a schematics, will come eventually.
however, I have bought the russion teflon fl-3 caps to change my jensen caps.
Now that this is done, what other thing I should swap?
ps: the little buzzing sounds are gone, I placed my amps differently (appart), and since then, the microphonic sound is gone.
however, I have bought the russion teflon fl-3 caps to change my jensen caps.
Now that this is done, what other thing I should swap?
ps: the little buzzing sounds are gone, I placed my amps differently (appart), and since then, the microphonic sound is gone.
Jason - If you're not happy with the sound, I seriously doubt you'll be happier by performing random component swaps. It would be far more likely that you can obtain happiness by changing the amplifier architecture (i.e. rebuilding it) or at the very least change the bias point. However, to advise you on this, a schematic is really needed.
hi tom, no I'm happy with the sound, just not completely in love, not freaking out, but it stils kicks any SS amp I've tried, and I tried a lot. There's a lot of things I like actually. It wasn't even clear for me at first, but I'm starting to really like the sound of it. Sorry if I didnt edit my opinion on the amp. When I tried the amp, my system wasnt like it is now, but with my system right now, I like the sound of the amp, now I just want to make it even better. should I start a new thread?
Swapping the jensen signal cap is not a "random" swap right, its suppose to change a bit my sound isn't it?
All I want to do is swap the critical components (not all of them, but like caps) and go from there...?
Swapping the jensen signal cap is not a "random" swap right, its suppose to change a bit my sound isn't it?
All I want to do is swap the critical components (not all of them, but like caps) and go from there...?
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In general, your amp looks like something my dad (retired TV repairman) would put together, with any parts he had on hand.
Anyway, many knowledgeable people have stated that carbon comp resistors (the brown ones with the stripes) have no place in a hifi amp (except as grid stoppers maybe). They tend to "go high" in value over the years and also are noisy. Now, lots of people here would advise you to go for costly exotic resistors, but i daresay that replacing them with normal carbon films will go a long way. Just swap them with equal wattage ones, in one channel only, and verify for yourself. Then, you can decide on the other channel.
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First things first.
You've described what could be basic issues (buzzing and other noises). So, get a schematic (Or draw one up yourself. It will be good experience and it is DIY). Then measure all the voltages and calculate current across all components.
Next, track down any issues of hum or noise, until you have determined that it falls within expectations for the design.
Then, and only then, consider circuit or part changes. Otherwise it is random.
Sheldon
Sorry. I must have missed something. I thought there was a serious issue with the amp that you were trying to fix. Now I understand that you like the amp but wouldn't mind if a few improvements could be made to the sound quality.
I wouldn't know one boutique capacitor brand from another. I tend to select capacitors based on which dielectric material is used, its parasitic components (like ESL, ESR), etc. I've had good results with polypropylene caps even when used in the direct signal path. Polypro caps that can handle the voltage may be a bit hard to find at regular electronic component distis, but places like Antique Electronic Supply has a nice selection of polypro caps. I like the Solen caps. They're well spec'ed (and I've confirmed some of their specs) and relatively inexpensive.
~Tom
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