I've decided to stop threadjacking the PLC thread and start my own...
I'm in the early breadboarding stage of building a stereo 300B SE amp using the following iron, already purchased:
One Electron UBT-3 output transformers (3K input impedance)
One Electron PRC-1 choke wired in parallel (5.5H, 32ohms, 230mA)
NOS UTC R-5 power transformer (385-0-385 @ 180mA, 5VCT @ 4A, 2.5 VCT @ 6A, 6.3VCT @ 5A, and finally a 5V winding @ 4A) The 2.5VCT winding won't be used, and neither will the 5V filament tap. I have two 5VCT hammond filament X-formers for the 300B's.
BTW, if anyone knows of a source for another R-5, I'd love to turn this into a monoblock project...
I'm going to be using valve rectification, type to be determined. Are there any decent ones currently being manufactured? The NOS ones are getting ridicuously spendy. I'm also curious about the possibility of using a solid state FW bridge rectifier followed by a damper diode instead of the standard FW 5U4GB, GZ37 or GZ34. Opinions? PS caps haven't been determined.
I'm planning on trying copper foil in oil coupling caps in the final build, but I'm using poly/foil orange drops for the experimenting. I haven't completely decided on resistors, but I'm thinking of tantalums for the signal path, since there won't be many and I'm curious as to what the fuss is about. I'm also considering non-inductive wirewounds.
I have bunches of used and new Sylvania 6SN7 GTA and GTB tubes and while I will try the JE labs circuit, I also want suggestions for alternates. I've seen some of the posts by KYW (really good stuff) and others, but would welcome anyone elses input.
The project I'm planning after this one is a PP2A3 amp, and really want to avoid the typical Williamson input/driver circuit. Not to slag on the Williamson (my WM-4's sound great on my Tannoy 15DMTII's), but I want to try something different. Ideas and schematics would be greatly appreciated.
The reason I'm doing this is that there isn't any way for me to hear these types of amps here in flyover land, dealers don't sell them and I'm really curious. Plus it'll keep me busy over this upcoming Minnesota winter...
Thanks in advance for any input!
I'm in the early breadboarding stage of building a stereo 300B SE amp using the following iron, already purchased:
One Electron UBT-3 output transformers (3K input impedance)
One Electron PRC-1 choke wired in parallel (5.5H, 32ohms, 230mA)
NOS UTC R-5 power transformer (385-0-385 @ 180mA, 5VCT @ 4A, 2.5 VCT @ 6A, 6.3VCT @ 5A, and finally a 5V winding @ 4A) The 2.5VCT winding won't be used, and neither will the 5V filament tap. I have two 5VCT hammond filament X-formers for the 300B's.
BTW, if anyone knows of a source for another R-5, I'd love to turn this into a monoblock project...
I'm going to be using valve rectification, type to be determined. Are there any decent ones currently being manufactured? The NOS ones are getting ridicuously spendy. I'm also curious about the possibility of using a solid state FW bridge rectifier followed by a damper diode instead of the standard FW 5U4GB, GZ37 or GZ34. Opinions? PS caps haven't been determined.
I'm planning on trying copper foil in oil coupling caps in the final build, but I'm using poly/foil orange drops for the experimenting. I haven't completely decided on resistors, but I'm thinking of tantalums for the signal path, since there won't be many and I'm curious as to what the fuss is about. I'm also considering non-inductive wirewounds.
I have bunches of used and new Sylvania 6SN7 GTA and GTB tubes and while I will try the JE labs circuit, I also want suggestions for alternates. I've seen some of the posts by KYW (really good stuff) and others, but would welcome anyone elses input.
The project I'm planning after this one is a PP2A3 amp, and really want to avoid the typical Williamson input/driver circuit. Not to slag on the Williamson (my WM-4's sound great on my Tannoy 15DMTII's), but I want to try something different. Ideas and schematics would be greatly appreciated.
The reason I'm doing this is that there isn't any way for me to hear these types of amps here in flyover land, dealers don't sell them and I'm really curious. Plus it'll keep me busy over this upcoming Minnesota winter...
Thanks in advance for any input!
Hi,
You could also consider a hybrid FWB using a pair of SS diodes and a FW tube rectifier.
Alternatively you use a FWB using damper diodes a la 6D22S.
Rectifiers currently in production_you're never really sure about this_ are the 5U4GB, 5AR4, EZ81/6CA4, 5U8 (special Russian type using a special socket), 6D22S...maybe others.
O.K....Here's the one we talked about before, with a paraphase input.
The basic circuit is kept simple, the PS and heater circuit is deliberately kept simple for "economical" reasons. A bit of a cost cutting exercise if you like.
Of course you're free to change that if you like.
Cheers,
You could also consider a hybrid FWB using a pair of SS diodes and a FW tube rectifier.
Alternatively you use a FWB using damper diodes a la 6D22S.
Rectifiers currently in production_you're never really sure about this_ are the 5U4GB, 5AR4, EZ81/6CA4, 5U8 (special Russian type using a special socket), 6D22S...maybe others.
O.K....Here's the one we talked about before, with a paraphase input.
The basic circuit is kept simple, the PS and heater circuit is deliberately kept simple for "economical" reasons. A bit of a cost cutting exercise if you like.
Of course you're free to change that if you like.
Cheers,
Attachments
frank, i have that amp on breadboard, but before completing it i was trying to get a DC regulated filament for my other 2A3.
isn't it that the calculation for the DC out is ACV x 1.44 - diode voltage drop?
i have a 3.3V AC that passes through a bridge configured 1N5402 and 4,700uF cap. but under load, it is only 1.6VDC for the 2A3 filament.
now, you schematic has lower ACV for the filament. care to tell me how that works?
isn't it that the calculation for the DC out is ACV x 1.44 - diode voltage drop?
i have a 3.3V AC that passes through a bridge configured 1N5402 and 4,700uF cap. but under load, it is only 1.6VDC for the 2A3 filament.
now, you schematic has lower ACV for the filament. care to tell me how that works?
Hi,
If we do the math using 1.8 VAC FWB rectified into a capacitive load we arrive at 2.592 VDC.
The bridge loses about 0.5VDC but I suspect my xformer is about 25% too high on current (not just the heater winding).
When measured I arrive at a little short of 2.3 VDC which is still fine for the 2A3s.
In fact I do have a little advantage here as my bias is more stable and the tubes will last longer this way as well.
3.3 VAC * 1.44 = 4.752 VDC - (2 * 0.6 VDC) = 3.552 VDC
Where you're losing half of the voltage I really don't know.
Did you measure the voltage without the load attached to the supply?
Cheers,
If we do the math using 1.8 VAC FWB rectified into a capacitive load we arrive at 2.592 VDC.
The bridge loses about 0.5VDC but I suspect my xformer is about 25% too high on current (not just the heater winding).
When measured I arrive at a little short of 2.3 VDC which is still fine for the 2A3s.
In fact I do have a little advantage here as my bias is more stable and the tubes will last longer this way as well.
3.3 VAC * 1.44 = 4.752 VDC - (2 * 0.6 VDC) = 3.552 VDC
Where you're losing half of the voltage I really don't know.
Did you measure the voltage without the load attached to the supply?
Cheers,
hi frank, without load it measures 3.6VDCfdegrove said:Did you measure the voltage without the load attached to the supply?
Cheers,
what bridge rectifier did you use? i'm ordering BR81 from RS Components.
will i have higher voltage drop with 4 x 1N5402 compared to 1 x BR81? sorry for the newbie questions
ps. i just saw the BR81 specs, it says 1.1VDC voltage drop per element at 4A DC. what do you think of the "per element" spec?
BHD, i made a JE Labs 300B myself, the deluxe circuit - it is here in derek walton's world 300B builders - http://indigo.ie/~walton/world300b.html see the Arnold Cruz entry.
5U4-GB are cheap in the Philippines, from the right source.
this amp will have its heaters changed to DC once i get my Altec open baffles tomorrow right now the hum level is 7mV which does not bother me on my current Infinity Kappa.
5U4-GB are cheap in the Philippines, from the right source.
this amp will have its heaters changed to DC once i get my Altec open baffles tomorrow
right now the hum level is 7mV which does not bother me on my current Infinity Kappa.
Hi,
I suspect you're measuring 1.6 VDC at either pin with respect to chassis ground...If you put the pins of your DVM across the heater pins you should measure 3.2VDC.
I used a Philips BR150 or something similar.
In theory that should mean per output. The only datasheet I found so far says "low voltage drop"...Great...
Cheers,
I suspect you're measuring 1.6 VDC at either pin with respect to chassis ground...If you put the pins of your DVM across the heater pins you should measure 3.2VDC.
I used a Philips BR150 or something similar.
In theory that should mean per output. The only datasheet I found so far says "low voltage drop"...Great...
Cheers,
Well, here's my $0.02:
In my 2A3/300B SE amp I use hybrid full-wave rectification with a pair of Hexfreds snubbed with 0.1uF MKPs in series with either a GZ37 and GZ34. (Note: I have separate HT supplies for my input/driver stage and output stage. The GZ37 is for my driver stage and the GZ34 for my output stage.) Much better bass than the tube rectifiers alone. For caps, I use oil caps and Unlytics. No electrolytics in my B+ supplies.
There are plently of cheap NOS rectifiers available. Instead of the usual suspects, try maybe some damper diodes (i.e., 6CJ3s, etc.) (people have reported great performance from these and the specs are very impressive). I plan to use damper diodes for my upcoming PP DHT project(s). One thing to note, these are half-wave rectifiers, meaning you need two to replace a single full-wave rectifier. Also, they require a special Novar socket which you might have a difficult time sourcing. Additionally, you can venture into the world of mercury vapour rectifiers. You can find some pretty cheaply too. I plan to use some in my upcoming headphone project as well.
Its a matter of colorations. Pick your poison. I use REL Exotica TFT and Jupiter Beeswax caps as coupling caps. The teflon caps are clear and detailed; while the beeswax caps have nice tone and body. The balance of both works for me. I use Roederstein metal films, Mills wirewound and Kiwame carbon film resistors. Depending on application. The metal films and Kiwame are cheap enough. For the pricey Mills you can swap the cheaper Dales.
Leave the 6SN7s for the input stages as voltage amplifiers. Try 6V6, 6L6, 6W6 (triode connected and choke-loaded) as drivers. My 6SN7-6V6-2A3/300B amp sounds sweet, robust with nice extension and way powerful.
I'm also planning a DHT PP amp. I assume your are familiar with Lynn Olson/Gary Dahl's work, and Allen Wright's work.
You can find Lynn's schematics here: http://www.nutshellhifi.com/triode1.html
Allen's work can be found here: http://www.vacuumstate.com/schematics.htm
Well, if you're ever in NYC you can stop by my studio to listen to my amp on my Cornwall IIs.
Amp chassis:
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Power supply chassis:
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Konnichiwa,
The Shuang 274B Copy, the russian 5U4 and GZ34 Clones are all not bad. But you can still get a lot of nice NOS Rectifiers, if sometimes with UX-4 basing. Just look around.
This can be done (and has been by many people), but I'd recommedn at least making the whole halve of the bridge in Valve Rectifiers (damper or others). A "beware" for modern dampers, they often have cathode cap's, that can be VERY dangerous.
There are maybe 4 - 6 basic circuits that come in many variants.
1) The Early Masters - WECO 91 with a pentode driver
2) The Triode Renaissance - 6SL7 SRPP or other SRPP Drivers, sometimes with extra preamp stage
3) The Triode Renaissance - 6SN7 Cascade (DC ala JEL or RC ala Reichert/Shindo also 5687 Cascade or 56/5687 Cascade ala Loesch/Wiesner
4) The Triode Enlightenment - High Transconductance triodes or triode wired pentodes IT, DC or LC coupled, eg. 6S45, WE 417A/437A, E180F/280F/810F et al.
5) The Romantic - Medium transconductance Pentodes reminices the 91, but with cojones, the circle closes, the serpent swallows it's own tail
There are some more, but they tend to be all pretty far out or are variations of the original Theme
Well, consider the PP Amplifier two SE Amplifiers with common cathode resistors and a balanced input. Create the balanced input from a really good line transformer. Finished.
Otherwise I find the Concertina Phasesplitter the least offensive, if you can get enough +B voltage so that splitter can swing enough voltage for 7 Class A Watts (usually needs self biased 2A3 in Class A1 @ 250V/45V Bias).
You could mostly rip off the ANJ Neiro for a 6072 SRPP that has the right "sound" and linearity, the use a 5687 - both sections parallel with 51K in the Cathode and Anode from an around +550V supply (eg solid state full wave voltage doubler from the +250V main supply) and you are off to a good start in my view....
Sayonara
BHD said:
The Shuang 274B Copy, the russian 5U4 and GZ34 Clones are all not bad. But you can still get a lot of nice NOS Rectifiers, if sometimes with UX-4 basing. Just look around.
BHD said:
This can be done (and has been by many people), but I'd recommedn at least making the whole halve of the bridge in Valve Rectifiers (damper or others). A "beware" for modern dampers, they often have cathode cap's, that can be VERY dangerous.
BHD said:
There are maybe 4 - 6 basic circuits that come in many variants.
1) The Early Masters - WECO 91 with a pentode driver
2) The Triode Renaissance - 6SL7 SRPP or other SRPP Drivers, sometimes with extra preamp stage
3) The Triode Renaissance - 6SN7 Cascade (DC ala JEL or RC ala Reichert/Shindo also 5687 Cascade or 56/5687 Cascade ala Loesch/Wiesner
4) The Triode Enlightenment - High Transconductance triodes or triode wired pentodes IT, DC or LC coupled, eg. 6S45, WE 417A/437A, E180F/280F/810F et al.
5) The Romantic - Medium transconductance Pentodes reminices the 91, but with cojones, the circle closes, the serpent swallows it's own tail
There are some more, but they tend to be all pretty far out or are variations of the original Theme
BHD said:
Well, consider the PP Amplifier two SE Amplifiers with common cathode resistors and a balanced input. Create the balanced input from a really good line transformer. Finished.
Otherwise I find the Concertina Phasesplitter the least offensive, if you can get enough +B voltage so that splitter can swing enough voltage for 7 Class A Watts (usually needs self biased 2A3 in Class A1 @ 250V/45V Bias).
You could mostly rip off the ANJ Neiro for a 6072 SRPP that has the right "sound" and linearity, the use a 5687 - both sections parallel with 51K in the Cathode and Anode from an around +550V supply (eg solid state full wave voltage doubler from the +250V main supply) and you are off to a good start in my view....
Sayonara
Now that I have more time...
arnoldc:
I checked out your amp - very nice. That's probably how I'm going to lay out my chassis as well.
JoseR:
What an amp! Separate PS for the driver stage and output, very tricked out! Do you have completely separate transformers for them, or two separate windings? I've wondered if getting a separate winding for the driver stage would sound as good as a separate transformer. I won't find out anytime soon, as I'm trying to keep it relatively simple this time around, but there's always next time...
I'm probably going to try a FW SS bridge rectifier with a damper diode - that way I'll at least have more voltage to play with. It should keep costs down, too. It's encouraging to hear about the better bass with your setup - I really wondered what the sonic advantage would be to such an arrangement. Mercury rectifiers have that retro cool, but aren't they a too noisy for a headphone amp? Please let us know how it turns out!
I'd forgotten about the VSE 2A3 PP amp. I don't have a balanced preamp, but I'm sure it sounds great. I hadn't considered the Jupiter caps, I'll have to check into them. As far as 6L6 as a triode strapped driver, I have couple of those, so into the queue...
And thanks for the most generous offer, BTW. I'm planning on heading over to Europe next year and I just may arrange a stop over and take you up on it! If you're ever in flyover land, I'll put you up and take you to the Pavek Museum of Broadcasting. Vacuum tube heaven with some of the coolest goodies you wouldn't believe!
KYW:
Konnbanwa,
The 274B copy interested me, but it's a bit pricey for a first attempt. Perhaps in a future project. I went through the article on damper diodes in VTV and there are plenty that I can use that don't have anode caps, so it's cool.
Thanks for summing up so many driver choices. I must say that I'm leaning towards a single driver stage if I can pull it off (really interested in the 6S45), but I can try several options with just the tubes I have on hand, so we'll see what happens. Any opinions on the 12SX7GT? I got a bunch of them cheap a long while back, and they're supposed to sound pretty good (for a 12V 6SN7). Could you go into more detail about the medium transconductance pentodes? I think I remember reading a thread where you posted info on that (maybe even a link), but I've been studying Franks, SY's and your posts for MONTHS now and I can't seem to find that thread...
BTW, I want to take a moment and thank you, Frank, SY (and others), for all the time you guys spend here making this place so much cooler than A Asylum.
'nuff said.
arnoldc:
I checked out your amp - very nice. That's probably how I'm going to lay out my chassis as well.
JoseR:
What an amp! Separate PS for the driver stage and output, very tricked out! Do you have completely separate transformers for them, or two separate windings? I've wondered if getting a separate winding for the driver stage would sound as good as a separate transformer. I won't find out anytime soon, as I'm trying to keep it relatively simple this time around, but there's always next time...
I'm probably going to try a FW SS bridge rectifier with a damper diode - that way I'll at least have more voltage to play with. It should keep costs down, too. It's encouraging to hear about the better bass with your setup - I really wondered what the sonic advantage would be to such an arrangement. Mercury rectifiers have that retro cool, but aren't they a too noisy for a headphone amp? Please let us know how it turns out!
I'd forgotten about the VSE 2A3 PP amp. I don't have a balanced preamp, but I'm sure it sounds great. I hadn't considered the Jupiter caps, I'll have to check into them. As far as 6L6 as a triode strapped driver, I have couple of those, so into the queue...
And thanks for the most generous offer, BTW. I'm planning on heading over to Europe next year and I just may arrange a stop over and take you up on it! If you're ever in flyover land, I'll put you up and take you to the Pavek Museum of Broadcasting. Vacuum tube heaven with some of the coolest goodies you wouldn't believe!
KYW:
Konnbanwa,
The 274B copy interested me, but it's a bit pricey for a first attempt. Perhaps in a future project. I went through the article on damper diodes in VTV and there are plenty that I can use that don't have anode caps, so it's cool.
Thanks for summing up so many driver choices. I must say that I'm leaning towards a single driver stage if I can pull it off (really interested in the 6S45), but I can try several options with just the tubes I have on hand, so we'll see what happens. Any opinions on the 12SX7GT? I got a bunch of them cheap a long while back, and they're supposed to sound pretty good (for a 12V 6SN7). Could you go into more detail about the medium transconductance pentodes? I think I remember reading a thread where you posted info on that (maybe even a link), but I've been studying Franks, SY's and your posts for MONTHS now and I can't seem to find that thread...
BTW, I want to take a moment and thank you, Frank, SY (and others), for all the time you guys spend here making this place so much cooler than A Asylum.
'nuff said.
I have two custom power transformers, each with a HT winding, a negative bias winding and filament winding for each respective rectifier. From ElectraPrint Audio.
Its more economical to use separate windings; but in my case it was necessary to keep things separate.
If I were to use two windings on the same transformer for two separate stages, I would have two completely separate secondaries with their own center taps.
They generate rf hash which may or may not be audible at the output depending on implementation. I believe its doable to keep things quiet. I view it as a challenge...its boring to always play safe
My fall back will be the damper diodes.Just give a holler if you do stop over; by next year I might have another amp done, hopefully. I'm still waiting for/collecting parts for the headphone amp and one of those gainclones. The PP amp might take longer
I have a question about transformers for the 2A3 project. I may go with Hammond output iron, would there be any sonic advantage to using the 30W rated OPT to a 15W rated one? They both have 5K primaries and the price difference isn't much.
And another question: Is there an "optimum" choke inductance value for a given amp power supply? If so, how do you calculate it?
Thanks!
And another question: Is there an "optimum" choke inductance value for a given amp power supply? If so, how do you calculate it?
Thanks!
BHD, which hammond model are you talking about? 125ESE and 1628?
i have both and used them i various circuits. when the smoke cleared i ended up with MagneQuest DS-025 (2.5K) on my 2A3, Tamura F-475 (5K) on my Gemini amp (45/2A3 primarily 45), 1628 (5K) on my 807 amp, and now the 300B is left with the 125ESE (as has been bugging me to get him a Tango U-808)
i don't have the equipment to make measurements, but i got best bass from the Tamura. but take this with a bucket of salt.
the 5K will not be optimal for the 2A3 but will give you less distortion albeit lower power. i think it is the 1627 that gives you 2.5K tap.
for chokes i have used Tamura A-395, a Hammond 193J and various custom-made chokes from a winder here who was doing transformer winding for Xerox when they are still here in the Philippines. sadly, i don't know how to compute
i'd leave that to the experts here
edit:
gee, you are making a PP 2A3 so the 5K is perfect. sorry.
i have both and used them i various circuits. when the smoke cleared i ended up with MagneQuest DS-025 (2.5K) on my 2A3, Tamura F-475 (5K) on my Gemini amp (45/2A3 primarily 45), 1628 (5K) on my 807 amp, and now the 300B is left with the 125ESE (as has been bugging me to get him a Tango U-808
)i don't have the equipment to make measurements, but i got best bass from the Tamura. but take this with a bucket of salt.
the 5K will not be optimal for the 2A3 but will give you less distortion albeit lower power. i think it is the 1627 that gives you 2.5K tap.
for chokes i have used Tamura A-395, a Hammond 193J and various custom-made chokes from a winder here who was doing transformer winding for Xerox when they are still here in the Philippines. sadly, i don't know how to compute
i'd leave that to the experts here edit:
gee, you are making a PP 2A3 so the 5K is perfect. sorry.
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