There are several posts on this in Audio Asylum, maybe they've been discussed here as well. Replacing the coupling caps with Auricaps and using Svetlana tubes appear to be the most popular mods to these. I've also replaced the PSU caps with Panasonic TSHA/TSHB, added a "snubber" on the B+ supply, and rerouted the ground connection on the heater wiring. One of my Svetlana tubes (old Russian military stock bought on eBay) died while trying to clean the pins, so I'm back to the stock Ei tubes. The Svetlanas hummed much more too, I don't know why.
I think they sound pretty good, but I don't have any prior experience with tubes, so I have nothing to compare them against.
I think they sound pretty good, but I don't have any prior experience with tubes, so I have nothing to compare them against.
Hi Saurav;
>>>...The Svetlanas hummed much more too, I don't know why...<<<
Interesting. I'm getting into the 6BM8 on my latest DIY amp that's under construction, so it's of some importance over here.
Does the ASL Wave 8 use AC or DC on the heaters? If there's a difference between cathode and heater voltages, that can cause 'hum' in AC heaters. IIRC Svetlana 12AX7's are not recommended for amps with AC heating either.
If it's a real bother, you could always add a rectifier board for the heaters. It needn't be more than a bridge rectifier and a 2200uF 16V cap.
All the best,
Morse
>>>...The Svetlanas hummed much more too, I don't know why...<<<
Interesting. I'm getting into the 6BM8 on my latest DIY amp that's under construction, so it's of some importance over here.
Does the ASL Wave 8 use AC or DC on the heaters? If there's a difference between cathode and heater voltages, that can cause 'hum' in AC heaters. IIRC Svetlana 12AX7's are not recommended for amps with AC heating either.
If it's a real bother, you could always add a rectifier board for the heaters. It needn't be more than a bridge rectifier and a 2200uF 16V cap.
All the best,
Morse
I'm pretty sure it's AC.
Good point which I hadn't considered. I'll have to look at the schematic again. I know it has the R+R to ground for the noise currents, but I don't remember seeing a voltage divider to bring the heaters up close to the cathode voltage. How does that work anyway on a multiple-section tube like the 6BM8? The cathodes of the triode and pentode sections could be at pretty different voltages, so which one do you set the heater voltage for?
With the Ei tubes, I can't hear the hum from my seating position (about 8' away from 96dB speakers), so I haven't fretted over it too much. The Svetlanas hummed quite a bit more, and I think those would have been audible. However, I used old Russian stock, and I think Svetlana produced (or still produces) 6BM8s very recently, so those might behave differently.
Try this link for a schematic for the Wave 8s. For some reason, linking directly to the image doesn't work.
http://hifiaudiolabs.tripod.com/waveav8info/
Hi Saurav;
>>>...The cathodes of the triode and pentode sections could be at pretty different voltages, so which one do you set the heater voltage for?...<<<
Good question. The more vulnerable cathode is the one on the small signal triode, since the amount of induced hum in that cathode to the signal will proportionately be larger than the amount of hum induced in the output pentode's cathode with respect to the signal there. Since the small signal triode is only floated by +.6V, it could just be that the valve is particularly vulnerable to AC heater induced hum - definitely I'm going to use DC on mine after reading this (I have 4 Svetlanas and 4 Ei's on hand so I want to be able to work with either).
It's a trickier question when you have something like a SRPP. Some people will use 2 filament windings, each floated separately and split the functionality of the circuit so that all the "high" cathodes are on one dual triode and all the "low" cathodes are on the other. If I decide to use a single filament winding (being a penurious audio nut), my own rule of thumb is to split the difference between the two voltages for the heater. That's the approach I used on my 2A3 (which uses a cathode follower with one cathode set much higher than the other).
Of course this is all coming down to a "if in doubt use DC" type of thing (assuming that the valves heaters are AC/DC compatible - the 6BM8's are, according to the Svetlana tech sheet at their website). And also assuming that you're not exceeding the max cathode/heater voltage limits.
As usual, just my 2 pence worth!
By the way, what 96dB speakers are you using?
All the best,
Morse
>>>...The cathodes of the triode and pentode sections could be at pretty different voltages, so which one do you set the heater voltage for?...<<<
Good question. The more vulnerable cathode is the one on the small signal triode, since the amount of induced hum in that cathode to the signal will proportionately be larger than the amount of hum induced in the output pentode's cathode with respect to the signal there. Since the small signal triode is only floated by +.6V, it could just be that the valve is particularly vulnerable to AC heater induced hum - definitely I'm going to use DC on mine after reading this (I have 4 Svetlanas and 4 Ei's on hand so I want to be able to work with either).
It's a trickier question when you have something like a SRPP. Some people will use 2 filament windings, each floated separately and split the functionality of the circuit so that all the "high" cathodes are on one dual triode and all the "low" cathodes are on the other. If I decide to use a single filament winding (being a penurious audio nut), my own rule of thumb is to split the difference between the two voltages for the heater. That's the approach I used on my 2A3 (which uses a cathode follower with one cathode set much higher than the other).
Of course this is all coming down to a "if in doubt use DC" type of thing (assuming that the valves heaters are AC/DC compatible - the 6BM8's are, according to the Svetlana tech sheet at their website). And also assuming that you're not exceeding the max cathode/heater voltage limits.
As usual, just my 2 pence worth!
By the way, what 96dB speakers are you using?
All the best,
Morse
I also wondered if the Svetlanas might be more susceptible to picking up hum from the transformers... don't know if that's a possibility.
My speakers are sealed Adire HE12.1s.
My speakers are sealed Adire HE12.1s.
An externally hosted image should be here but it was not working when we last tested it.
There is a cathode-heater breakdown voltage that should not be exceeded. That probably has nothing to do with hum. However, I've also read that in voltage gain triodes, the cathode might pick up hum if the heater is negative w.r.t. the cathode, and I've seen designs which keep the heater at a slightly higher potential than the cathode, by using a voltage divider from B+ to ground. Are you saying that that's not true, and the voltage divider isn't needed?
Or maybe you were commenting on the statement about Svetlana 12AX7s. It's not too clear from your post.
Or maybe you were commenting on the statement about Svetlana 12AX7s. It's not too clear from your post.
Hi guys;
As far as the Svetlana 12AX7 is concerned, I'd swear I'd read that about it somewhere - but now I can't find it (embarrassment reigns supreme at the moment).
And, maybe I'm wrong about there being a correspondence between high heater/cathode voltages and AC hum pickup, but I've got a JAN Philips 12AX7WA that sure follows that rule. Darned if I know where I first read a claim of that correspondence, but it was a "oh that's what's causing this" kind of moment. If that's not it, I'm darned if I know.
Anyway, if it's the worst mystery I ever face or the worst mistake I ever make, I'll live with it. Sorry to hand out questionable info.
All the best,
Morse
As far as the Svetlana 12AX7 is concerned, I'd swear I'd read that about it somewhere - but now I can't find it (embarrassment reigns supreme at the moment).
And, maybe I'm wrong about there being a correspondence between high heater/cathode voltages and AC hum pickup, but I've got a JAN Philips 12AX7WA that sure follows that rule. Darned if I know where I first read a claim of that correspondence, but it was a "oh that's what's causing this" kind of moment. If that's not it, I'm darned if I know.
Anyway, if it's the worst mystery I ever face or the worst mistake I ever make, I'll live with it. Sorry to hand out questionable info.
All the best,
Morse
HUM.
Hi,
What you may have read is that the SOVTEK 12AX7LPS sports a special S "spiral wound" filament to prevent hum when AC fed on the heaters.
This is correct.
The voltage is almost always stated in the datasheets, usually in the 120 to 150 V range.
When you do exceed it you will have some HF coupling and you risk that the heater and cathode will "stick" causing a short.
No, that's not what I'm saying.
Biasing the heaters is good practice, wether the tube is AC or DC heated is not relevant though.
Hope this clarifies it a little,
Hi,
What you may have read is that the SOVTEK 12AX7LPS sports a special S "spiral wound" filament to prevent hum when AC fed on the heaters.
This is correct.
The voltage is almost always stated in the datasheets, usually in the 120 to 150 V range.
When you do exceed it you will have some HF coupling and you risk that the heater and cathode will "stick" causing a short.
No, that's not what I'm saying.
Biasing the heaters is good practice, wether the tube is AC or DC heated is not relevant though.
Hope this clarifies it a little,
Hi Frank;
I've made many mistakes over the years (specializing in mainframe systems programming just in time to watch the invention of microcomputers trash the market for IBM BAL programmers tops the list), but mistaking Sovtek for Svetlana is NOT one of them.
I just finished a lengthy search online and here goes: there were numerous reports of AC heater hum problems with the original Svetlana 12AX7 when it came out in 2000. I made a note of this at the time because the Jolida 202 that I had then used AC heaters. Just go over to the 'other' forum and enter "Svetlana + 12AX7 + hum" into the search engine - you'll get a number of hits.
Anyway, everything changes over time and perhaps the current production has cured the problem. None of the vendors I usually shop with still posts warnings about JoLidas and Svets FWTW, and there are posts about the "new" Svetlana 12AX7 claiming that the old problems have been fixed. Personally, I wouldn't know since I stocked up on JAN Philips 12AX7WA's at the time and haven't bought a 12AX7 since.
It's definitely my mistake for commenting on a brand name without doing the research. As far as the NOS Svetlana 6BM8's are concerned, I've got examples from 1975-1980 production years. 'Til I get the wiring done on this 6BM8, I'm going to assume that they'll have problems with AC heaters as Saurav noted in his post - and I'll stick to regulated DC.
Hope this clarifies things,
Morse
I've made many mistakes over the years (specializing in mainframe systems programming just in time to watch the invention of microcomputers trash the market for IBM BAL programmers tops the list), but mistaking Sovtek for Svetlana is NOT one of them.
I just finished a lengthy search online and here goes: there were numerous reports of AC heater hum problems with the original Svetlana 12AX7 when it came out in 2000. I made a note of this at the time because the Jolida 202 that I had then used AC heaters. Just go over to the 'other' forum and enter "Svetlana + 12AX7 + hum" into the search engine - you'll get a number of hits.
Anyway, everything changes over time and perhaps the current production has cured the problem. None of the vendors I usually shop with still posts warnings about JoLidas and Svets FWTW, and there are posts about the "new" Svetlana 12AX7 claiming that the old problems have been fixed. Personally, I wouldn't know since I stocked up on JAN Philips 12AX7WA's at the time and haven't bought a 12AX7 since.
It's definitely my mistake for commenting on a brand name without doing the research. As far as the NOS Svetlana 6BM8's are concerned, I've got examples from 1975-1980 production years. 'Til I get the wiring done on this 6BM8, I'm going to assume that they'll have problems with AC heaters as Saurav noted in his post - and I'll stick to regulated DC.
Hope this clarifies things,
Morse
Just to add something I found over at Triode Electronics re: Svetlana 12AX7's (it's right under the spot to order the things, not in the description at the top of the page):
"Not for use in some amplifiers with AC filaments (Jolida, Dyna SCA35, etc), may pick up too much filament hum.In some amps OK in some postions but not others. No problem with DC filaments as in most hifi preamps."
So maybe they didn't fix it after all.
Morse
"Not for use in some amplifiers with AC filaments (Jolida, Dyna SCA35, etc), may pick up too much filament hum.In some amps OK in some postions but not others. No problem with DC filaments as in most hifi preamps."
So maybe they didn't fix it after all.
Morse
AH....
Hi,
Morse,
I did just spot that too.
The problem can be caused with badly made tubes, meaning the insulation between cathode and heater isn't respected.
In which case it would be wise not to use those at all, regardless of whether these are AC or DC heated such tubes are likely to oscillate and no amount of trickery is going to prevent it.
BTW, just for info, Sovtek is not a manufacturer but a marketing name.
They source their tubes from a number of ex-USSR factories.
I didn't mean to offend anyone by this, it's just that under normal operating conditions such AC hum to cathode coupling is almost impossible to occur IME.
Cheers,
Hi,
Morse,
I did just spot that too.
The problem can be caused with badly made tubes, meaning the insulation between cathode and heater isn't respected.
In which case it would be wise not to use those at all, regardless of whether these are AC or DC heated such tubes are likely to oscillate and no amount of trickery is going to prevent it.
BTW, just for info, Sovtek is not a manufacturer but a marketing name.
They source their tubes from a number of ex-USSR factories.
I didn't mean to offend anyone by this, it's just that under normal operating conditions such AC hum to cathode coupling is almost impossible to occur IME.
Cheers,
Hi guys;
Yep, it's confusing to track "who made what" these days (particularly when it came out of Russia!). Here's a site that can help: http://www.ominous-valve.com/russtube.html Adding to the confusion, the last 6BM8's I bought in Sovtek boxes have plate structures and original markings that are appropriate for the "Svetlana" factory - and now I'm hearing that the latest Svetlana EL34's look an awful lot like EH products (yikes - this is getting REALLY confusing!). I wouldn't know on the EL34's since I stocked up on EH's a few years back and haven't bought one since.
Anyway, whether it's the Reflektor works (most Sovtek) or whatever, anybody can make the occasional dud - including posts. If I've offended anyone with the tone in my posts on this thread I'd like to apologise and stay on good terms.
Peace to all,
Morse
Yep, it's confusing to track "who made what" these days (particularly when it came out of Russia!). Here's a site that can help: http://www.ominous-valve.com/russtube.html Adding to the confusion, the last 6BM8's I bought in Sovtek boxes have plate structures and original markings that are appropriate for the "Svetlana" factory - and now I'm hearing that the latest Svetlana EL34's look an awful lot like EH products (yikes - this is getting REALLY confusing!). I wouldn't know on the EL34's since I stocked up on EH's a few years back and haven't bought one since.
Anyway, whether it's the Reflektor works (most Sovtek) or whatever, anybody can make the occasional dud - including posts. If I've offended anyone with the tone in my posts on this thread I'd like to apologise and stay on good terms.
Peace to all,
Morse
Relax Guys...
Hi,
Don't worry...
The reason I took a firm stand here is that I didn't want people to get the impression that AC hum can be solved by just replacing the tube as a general rule.
There are of course some badly made tubes out there and as far as I'm concerned they go "back to sender" linea recta.
Anyone in the business knows, or should know, what they're selling and if they don't cover their behind than that's their problem not the customers'.
Anyways, just to clarify some misconceptions:
Well, EH doesn't manufacture tubes either...however they could have enough clout (read $) to have some run of the mill tubes re-socketed for them.
So, don't be surprised to see so called 7027s, 7591s and other rare animals with the exact same internals as a bog standard 6L6 or whatever.
Remember the KT90? Just an EL509 on an octal socket really...
You'll be paying mucho money for these, but don't say I didn't warn you...
There's little point in me unravelling the innersecrets of the tube industry in public but I welcome any private e-mail from members when in doubt.
Cheers and you're all perfect gemtlemen BTW,
Hi,
Don't worry...
The reason I took a firm stand here is that I didn't want people to get the impression that AC hum can be solved by just replacing the tube as a general rule.
There are of course some badly made tubes out there and as far as I'm concerned they go "back to sender" linea recta.
Anyone in the business knows, or should know, what they're selling and if they don't cover their behind than that's their problem not the customers'.
Anyways, just to clarify some misconceptions:
Well, EH doesn't manufacture tubes either...however they could have enough clout (read $) to have some run of the mill tubes re-socketed for them.
So, don't be surprised to see so called 7027s, 7591s and other rare animals with the exact same internals as a bog standard 6L6 or whatever.
Remember the KT90? Just an EL509 on an octal socket really...
You'll be paying mucho money for these, but don't say I didn't warn you...
There's little point in me unravelling the innersecrets of the tube industry in public but I welcome any private e-mail from members when in doubt.
Cheers and you're all perfect gemtlemen BTW,
Build level on these is somewhat limited as one would expect at the price (ie the local dealer has had some of the input sockets pull apart when used with high quality -- read tight -- interconnects)
An aquaintance of mine has 4 of these and here is a post he made on them:
I spent the few extra dollars it will cost ant buy the fancy version with the cage and the IEC detachable power cord. Don't use the cage as it makes things sound worse however the IEC allows you to use a quality after market power core and that is well worth the few extra dollars.
The parts count inside is very good and I did not feel that replacing caps and resistors would yield a big enough difference to justified the expense. The amp can and does respond to bypass caps and these are most cost effective and easy to install. Bypass the power supply caps with 1000 Volt ceramic disk caps. I replaced C8 with a 100 micro farad 350 volt cap don't go any higher in value as you will then be likely to have problems. This new cap gives extra smoothing to the ripple coming out of the supply. All large value caps were bypassed with 0.1 uf plastic caps (despite what people say Mylar sound fantastic) All the small value caps were bypassed with 0.01 uf plastic caps.
I removed the "bell" or "end" caps from the output and power transformers. I then installed an electrostatic copper wrap shield around both of the transformers and in my case turned the output transformer 90 degrees to the power transformer and re mounted both transformers on rubber grommets to reduce vibration to the chassis. Removal of the "Bell" caps really opened up the sound and gave a sense of life and new dynamics. I have found this to be true on other amplifiers also. I did not do a direct before and after comparison with the physical orientation of the two transformers however with two chokes you want them aligned this way to place one in the exact electrical/magnetic "null" of the other an so minimize coupling between the two. This makes sense so I decided to do it with the two transformers even though it did involved making some of the lead wires longer.
The second last change that I made was to replace the input interconnect and to shield the power on/off wires which run to and from the front of the chassis to the back to the chassis. This one is up to you to do as you see fit.
Last but by no means least I froze the tubes down to liquid nitrogen temperature. If you haven't tried this do so as it is a great upgrade all on it's own. Sound is smoother and there is more detail with greater resolution and an apparent increase in dynamics. I can assure you that once bit (frozen) you will never go back to non frozen tubes or other parts for that matter.
Next go to Elliott Sound Products and read his article on a passive volume control "project 01" build one to use with your "Wave" amplifiers and then you will enjoy a level of performance you probably have never dreamed you even reach. The price of entry is a laugh. You will now be able to make your "Audiophile" friends so sick with what they own and with what they paid for it that they will in the words of J C Morrison "want to go and find a high place from which to throw off their gear".
dave
An aquaintance of mine has 4 of these and here is a post he made on them:
I spent the few extra dollars it will cost ant buy the fancy version with the cage and the IEC detachable power cord. Don't use the cage as it makes things sound worse however the IEC allows you to use a quality after market power core and that is well worth the few extra dollars.
The parts count inside is very good and I did not feel that replacing caps and resistors would yield a big enough difference to justified the expense. The amp can and does respond to bypass caps and these are most cost effective and easy to install. Bypass the power supply caps with 1000 Volt ceramic disk caps. I replaced C8 with a 100 micro farad 350 volt cap don't go any higher in value as you will then be likely to have problems. This new cap gives extra smoothing to the ripple coming out of the supply. All large value caps were bypassed with 0.1 uf plastic caps (despite what people say Mylar sound fantastic) All the small value caps were bypassed with 0.01 uf plastic caps.
I removed the "bell" or "end" caps from the output and power transformers. I then installed an electrostatic copper wrap shield around both of the transformers and in my case turned the output transformer 90 degrees to the power transformer and re mounted both transformers on rubber grommets to reduce vibration to the chassis. Removal of the "Bell" caps really opened up the sound and gave a sense of life and new dynamics. I have found this to be true on other amplifiers also. I did not do a direct before and after comparison with the physical orientation of the two transformers however with two chokes you want them aligned this way to place one in the exact electrical/magnetic "null" of the other an so minimize coupling between the two. This makes sense so I decided to do it with the two transformers even though it did involved making some of the lead wires longer.
The second last change that I made was to replace the input interconnect and to shield the power on/off wires which run to and from the front of the chassis to the back to the chassis. This one is up to you to do as you see fit.
Last but by no means least I froze the tubes down to liquid nitrogen temperature. If you haven't tried this do so as it is a great upgrade all on it's own. Sound is smoother and there is more detail with greater resolution and an apparent increase in dynamics. I can assure you that once bit (frozen) you will never go back to non frozen tubes or other parts for that matter.
Next go to Elliott Sound Products and read his article on a passive volume control "project 01" build one to use with your "Wave" amplifiers and then you will enjoy a level of performance you probably have never dreamed you even reach. The price of entry is a laugh. You will now be able to make your "Audiophile" friends so sick with what they own and with what they paid for it that they will in the words of J C Morrison "want to go and find a high place from which to throw off their gear".
dave
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