My version was built using the attached schematics. Duplicate power supplies. All built on one chassis with the preamp section physically separated. I have a large piece of copper sheet (~4X12") which is the star ground for all. I'm using Nichicon KX audio electrolytics for the 330uF caps. The .47uF in the PS I'm using a Clarity SA cap. The 1uF in the preamp is a Russian PIO cap. The 0.1uF in the preamp is two Russian teflon 0.22uF caps in series. Almost all of the resistors are Vischay-Dale military grade. I've rolled several different 6CW5's, 12AX7's, 12AU7(A)'s, and 12BH7A's. The tube rolling resulted in minor improvements here and there...but like I said the biggest tube rolling gain came from the Mullard gold plated 5651's. Lastly...I have a Goldpoint 500k attenuator using 0.1% IRC resistors. I recently purchased a bunch of 70uF, 22uF and 1uF film in oil caps...not sure if these are of use here? I tried to keep lead lengths as short and equal as possible...
Posts #324 and #327 have external and internal pics. If you have any further suggestions for improvement...I'm willing to try them!
Attachments
Hi,
You're just using the buffer + volcontrol, right?
How's the Goldpoint attenuator wired up? Ladder? PCB?
I admit to have no idea what the ruskie teflon caps sound like so we'll leave them in for the time being.
How about silver solid core wire? Any objection?
Tube sockets?
No electrolytics past the regs?
Cheers, 😉
You're just using the buffer + volcontrol, right?
How's the Goldpoint attenuator wired up? Ladder? PCB?
I admit to have no idea what the ruskie teflon caps sound like so we'll leave them in for the time being.
How about silver solid core wire? Any objection?
Tube sockets?
No electrolytics past the regs?
Cheers, 😉
Hi,
First of all, that Goldpoint attenuator sound like a ladder type of some sorts.
Personally I'm more favourable to the voltage divider type where you just have two resistors in series with the signal at any given position.
Forget about military grade, they're OK for the military but that's about it.
ISo of using silver plated stuff which often sounds shrill and anemic you might want to try solid core silver wire. 0.6mm or 0.4mm should be fine.
Insulation isn't that important, PTFE or polyamide should do.
Solid core is what's important sonically.
As for the sockets, gold plating is secundary to having a good contact.
Cheers, 😉
First of all, that Goldpoint attenuator sound like a ladder type of some sorts.
Personally I'm more favourable to the voltage divider type where you just have two resistors in series with the signal at any given position.
Forget about military grade, they're OK for the military but that's about it.
ISo of using silver plated stuff which often sounds shrill and anemic you might want to try solid core silver wire. 0.6mm or 0.4mm should be fine.
Insulation isn't that important, PTFE or polyamide should do.
Solid core is what's important sonically.
As for the sockets, gold plating is secundary to having a good contact.
Cheers, 😉
Hi,
Where, do you get the transformers for this project? Who do you recommend to do the winding?
Where, do you get the transformers for this project? Who do you recommend to do the winding?
Hi,
The powersupply xformers I used were just off the shelf stuff from RS Components in the UK.
No idea if they still carry them though.
Cheers, 😉
The powersupply xformers I used were just off the shelf stuff from RS Components in the UK.
No idea if they still carry them though.
Cheers, 😉
I would be willing to bet the sonics, if indeed improved or changed from the rolling of this tube, are due to the difference in the actual voltage referenced across the OG3 type. Probably the entire B+ has changed ever so slightly which would have significant changes on the operating points of the preamp tubes. Just my take on it. I could not otherwise see how this could possibly afffect the sound of the preamp stage. Have you checked the B+ with each of the different types of tubes placed in this position? I would be very curious to know if the B+ is slightly different with each tube type.
It is interesting b/c I actually purchased one of each Amperex and Mullard OG3 about 5 mins before reading this post. I intended to try each of them to see if this made any adjustment on the B+ final voltage, which is my point above.
If anybody else could offer another explaination on how the OG3 tube rolling could affect the sonics of this preamp I would love to hear their take on this interesting observation.
Chow!
Several other possibilities:
Differences in noise spectrum?
Effect of pulling tubes in and out on socket-to-pin contact integrity?
Effect of plating on contact integrity?
Propensity of VR tubes to have reference voltage wander?
Maybe there's no real difference?
The last will be controversial, but one must admit the possibility.
Oh, I certainly am willing to accept that there could be a sonic difference, in fact I would argue that in the case of a swap between tubes that had slightly (or even grossly) different reference voltages there would neccessarily be a sonic difference. Any significant change in the B+ would change the sonics for sure and I think a variance in reference voltages between the tubes would change the B+ some. In fact that is why I think the biggest audible difference would occur in swaping this tube when compared to others.
My arguement is that aside from a change in B+ due to the OG3 swap, I can't see how a sonic difference could be heard (not saying it can't, just that I can't figure out why)
Seems the aruguements you make are similar, for instance poor contact on the pins might alter the referencce voltage....
I am looking forward to completing my #27 tube preamp which will use this regulator....I will certainly report If I hear any differences.
Thanks for the comments!
Jeff
Well, there are two very nonideal properties of reference tubes that vary from tube to tube. First, they're noisy. The amount and nature of that noise could certainly cause variations in the noise on the power supply rail. The power supply rejection of that circuit is OK, but not outstanding... The second property is wander. If you monitor the voltage across a VR tube, it will make sudden jumps of a few volts in an erratic manner. Again, that varies from tube to tube in amount, severity, and frequency. VR tubes are pretty, but they are not very good references.
Change in operating conditions CAN be audible, but it's a pretty big leap to say that it's certainly audible. That's why it's important to qualify these analyses with the possibility that it's not a change in the sound, it's a change in the listener.
Change in operating conditions CAN be audible, but it's a pretty big leap to say that it's certainly audible. That's why it's important to qualify these analyses with the possibility that it's not a change in the sound, it's a change in the listener.
Hi,
It would be interesting if you could confirm audible differences among the various brands of OG3s.
IME they all vary a little in that there's a difference in noise and reference voltage.
I did find sonic differences but only from OG3s that were suspect to begin with...
You should however be able to detect an audible difference between an OG3 and a 5651. They're not quite one and the same tube.
The exact voltage of the B+ for the line stage is very stable, changing various OG3s could make for a change of roughly 5VDC.
I doubt you'd hear it other than perhaps a slight imbalance between channels.
You could handpick OG3s for voltage stability although I can't say I've ever witnessed any sudden voltage jumps from the lot I had.
Either way, with that much capacitance sitting behind them, most voltage variations within the PS should remain invisible to the output stage.
Again, if you notice it happening, check the VR tubes as I do not consider this normal behaviour.
Cheers, 😉
BTW the PSRR of the WCF circuit is about as good as they come, I don't see any way to improve upon it.
It would be interesting if you could confirm audible differences among the various brands of OG3s.
IME they all vary a little in that there's a difference in noise and reference voltage.
I did find sonic differences but only from OG3s that were suspect to begin with...
You should however be able to detect an audible difference between an OG3 and a 5651. They're not quite one and the same tube.
The exact voltage of the B+ for the line stage is very stable, changing various OG3s could make for a change of roughly 5VDC.
I doubt you'd hear it other than perhaps a slight imbalance between channels.
You could handpick OG3s for voltage stability although I can't say I've ever witnessed any sudden voltage jumps from the lot I had.
Either way, with that much capacitance sitting behind them, most voltage variations within the PS should remain invisible to the output stage.
Again, if you notice it happening, check the VR tubes as I do not consider this normal behaviour.
Cheers, 😉
BTW the PSRR of the WCF circuit is about as good as they come, I don't see any way to improve upon it.
I am still learning a lot about tubes each day and here's what I'm wondering. I was told by couple of experienced amp designers that the biggest audible difference can be had by the quality of output transformer. After that, the rest of the parts upgrade of tube amp is trivial in comparison. In this situation, all those tube reviews I've seen that praising tubes X, Y, Z sounding "smoother in mids", "more resolved highs"... all those fancy terminologies and etc, are these claimed changes achievable just by adjusting bias here and some voltages there? If so, that would be a good news for me especially I've spent the most on my pair of OPTs.
Don't dispair, IMO you can't go wrong using quality Iron.
There are plenty of Subjectivist vs Objectivist arguments on the forum (quite lively debates too), you should read some of them sometime.
In this particular case I am not dealing with any output transformers, just a fairly simple tube circuit.
I have a considerable amount of hearing damage from not taking care of my ears while growing up (guns, heavy farm equipment, chainsaws, shop tools) so when I get together with friends for A/B listening tests I can't generally hear what they hear at times. Often I am suspect of the validity of these claims but I have to consider my ears aren't as good as theirs. It makes sense to me that certain things could change sonics and often these are verifiable with a scope, etc.
Bias points, voltages, etc can and do change the operating points on a tube curve and these should be audible depending on the degree of change.
I still think good OPT's are a good investment and I can say I have heard the difference here. But remember: GIGO (garbage in, garbage out), if you have a great pair of output transformers and put trash into them.....you get the point.
Getting back to the VR tubes, I have never used them until now. This will be my first regulated supply too. I look forward to hearing it when I get done but the truth is (for me), I am building a regulated supply more for my addiction to building stuff than for sonic's sake. I just like doing new things and this is new to me!
Jeff
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Hello
very nice preamp...planing to build one :d
i`ve just received my 6h8c russian tubes a rectifier tube and 2xoa2 and and toroidal transformer(which i preordered here i`m my country and has to come these days(2x300v 100ma , 5v 4a , 6.3vx2 2.5a ))
i`m a little bit confused in deciding of what caps to use (0.033uf and 5uf)
first one is excluded because i want to use a r2r volume shunt controler
i want good caps and that`s why i`m so indecided
i see both are unpolarized but it didn`t says if they are aluminium electrolytic or film(polypropylene) or other type of audiograde caps like pio(paper in oil)
i want to ask you (specially Frank) what kind of cap should i use to get the best sound
a link where to buy in europe(i`m from romania and i need a country who ships here😀) would be great
another big question if you don`t mind is how do you recomend to use the filament of the 6h8c in cc or ca?(for the lowest hum and ground noise possible)
hope to see this project finished very soon(maximum one month😀)
thank you for the moment
very nice preamp...planing to build one :d
i`ve just received my 6h8c russian tubes a rectifier tube and 2xoa2 and and toroidal transformer(which i preordered here i`m my country and has to come these days(2x300v 100ma , 5v 4a , 6.3vx2 2.5a ))
i`m a little bit confused in deciding of what caps to use (0.033uf and 5uf)
first one is excluded because i want to use a r2r volume shunt controler
i want good caps and that`s why i`m so indecided
i see both are unpolarized but it didn`t says if they are aluminium electrolytic or film(polypropylene) or other type of audiograde caps like pio(paper in oil)
i want to ask you (specially Frank) what kind of cap should i use to get the best sound
a link where to buy in europe(i`m from romania and i need a country who ships here😀) would be great
another big question if you don`t mind is how do you recomend to use the filament of the 6h8c in cc or ca?(for the lowest hum and ground noise possible)
hope to see this project finished very soon(maximum one month😀)
thank you for the moment
Both of those heater supplies are overstressing the transformers because you are rectifying the AC and then trying to pull the rated current. The rated current is at rated voltage. Once you recitfy the voltage, you must derate current by a factor of 1/1.414 to remain within the manufacturer's power specifications.
In the case of the 12.6 1A transformer driving two 0.4A heaters you only have 1A/1.414 = 0.707 A available for driving 0.8A load.
In the case of the 14V 0.5A transformer driving one 0.4A heater you only have 0.5A/1.414 = 0.3535A driving a 0.4A load.
I would recommend upgrading your transformers.
if i correctlly understood you the problem is this way:
i can connect in series those 6.3v 2.5a each ang get 12.6v and 2.5a
the producer says the current drawn by each 6h8c is 600ma (1.2a for 2 of them) and there still remains 1.3amps(this is if u use regulated ps for filament and cc)
if i`ll use ac i`ll connect each 6h8c to each of 6.3v 2.5a rail
you didn`t said how u use yours on cc or ca?
i can connect in series those 6.3v 2.5a each ang get 12.6v and 2.5a
the producer says the current drawn by each 6h8c is 600ma (1.2a for 2 of them) and there still remains 1.3amps(this is if u use regulated ps for filament and cc)
if i`ll use ac i`ll connect each 6h8c to each of 6.3v 2.5a rail
you didn`t said how u use yours on cc or ca?
can i use 5(1uf) of this in paralel for each channel in the project ?
MPBX2 1uF/275V1 RM22.5 Condensator polipropilena - ADELAIDA - Componente electronice
MPB-1uF/400V Condensator polipropilena - ADELAIDA - Componente electronice
i see they are 275(400) Vac can i use them instead 250vdc?
sorry for the first post was logged in on the site :-"
ty:d
MPBX2 1uF/275V1 RM22.5 Condensator polipropilena - ADELAIDA - Componente electronice
MPB-1uF/400V Condensator polipropilena - ADELAIDA - Componente electronice
i see they are 275(400) Vac can i use them instead 250vdc?
sorry for the first post was logged in on the site :-"
ty:d
finished my project
but there`s a little problem with the hum :-s
for filament i used 7v ac->4 x Schottky 60V 3A (rectifier) ->10000uf->7806->10000uf and on the pins of 6h8c i`ve put 1uf 60V wima nonpolarized cap
for the anode tension i`ve used 5u3c rectifier->50uf->series resistor->50uf->sr->50uf->sr-> 2x oa2(coected in series for 300v stabilization)->sr->50uf->1n4006->b+ left channel
->1n4006->b+ right channel
1n4006 are used for channel separation or something like this so the channels won`t go in crosstalk
i think the problem with the hum is because i didn`t use choke`s
i want to order two of them one at 15(20)h 100ma and 15(10)h 100ma
THANKS FOR YOUR HELP
but there`s a little problem with the hum :-s
for filament i used 7v ac->4 x Schottky 60V 3A (rectifier) ->10000uf->7806->10000uf and on the pins of 6h8c i`ve put 1uf 60V wima nonpolarized cap
for the anode tension i`ve used 5u3c rectifier->50uf->series resistor->50uf->sr->50uf->sr-> 2x oa2(coected in series for 300v stabilization)->sr->50uf->1n4006->b+ left channel
->1n4006->b+ right channel
1n4006 are used for channel separation or something like this so the channels won`t go in crosstalk
i think the problem with the hum is because i didn`t use choke`s
i want to order two of them one at 15(20)h 100ma and 15(10)h 100ma
THANKS FOR YOUR HELP
just finished my line stage🙄
thx for the help 😎
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thx for the help 😎
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