Just sharing...I'm not related to the seller.
I found a seller (K4_Pacific) with NOS power & output transformers made by Basler Electric in Highland, Illinois (although the label says made in Mexico).
1500 ohm CT primary (no UL taps)
120 W 4/8/16 secondary
I can't find the listing number but description is
Basler Tube Amp Output Transformer 1500 Ohms CT - 4,8,16 Ohm 120 Watt BE32780001
Upon inquiry, only info seller had was that they were for the Kustom Double Cross, using 6 x 6L6. I got one to try with a pair of 6C33C-B's PP for likely no more than half that power.
Arrived today. I didn't weigh it, but it appears to be made with EI-137H laminations (power transformer thickness, not 29 g), 1-1/4" stack, 4-1/8" x 3-7/16. End bells & L-brackets. Decent size, 2009 date code.
Was $34.50+$6.50 USPS flat rate
I found a seller (K4_Pacific) with NOS power & output transformers made by Basler Electric in Highland, Illinois (although the label says made in Mexico).
1500 ohm CT primary (no UL taps)
120 W 4/8/16 secondary
I can't find the listing number but description is
Basler Tube Amp Output Transformer 1500 Ohms CT - 4,8,16 Ohm 120 Watt BE32780001
Upon inquiry, only info seller had was that they were for the Kustom Double Cross, using 6 x 6L6. I got one to try with a pair of 6C33C-B's PP for likely no more than half that power.
Arrived today. I didn't weigh it, but it appears to be made with EI-137H laminations (power transformer thickness, not 29 g), 1-1/4" stack, 4-1/8" x 3-7/16. End bells & L-brackets. Decent size, 2009 date code.
Was $34.50+$6.50 USPS flat rate
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OK...another pig transformer with lipstick...and I get to keep it because I shared the source :O). No IT's, spiffy or non-.
It'll do something for me...TBD what...maybe 30W...reduced drive.
I looked at that Roessler (sp?) design today (for hifi), and it looked straightforward, although I didn't look at signal levels...because there was a solution to that problem already there!
This is yet another reason why I don't finish projects. At least my house has ballast weight in it.
It'll do something for me...TBD what...maybe 30W...reduced drive.
I looked at that Roessler (sp?) design today (for hifi), and it looked straightforward, although I didn't look at signal levels...because there was a solution to that problem already there!
This is yet another reason why I don't finish projects. At least my house has ballast weight in it.
250 VDC B+ for 6C33's (220 Vss at each grid I take to be Euro notation for 220 V p-p)
400 VDC/21 mA dropped to 240 VDC for 6BL7 drivers and 330 VDC for 6SL7 first stage
330 VDC dropped to 200 for 6SL7.
I want to play the Hedge PP-self-split cascode driver stage card, but my card game is still at the luck before strategy stage. I admit to being an armchair achiever (minus the arms).
400 VDC/21 mA dropped to 240 VDC for 6BL7 drivers and 330 VDC for 6SL7 first stage
330 VDC dropped to 200 for 6SL7.
I want to play the Hedge PP-self-split cascode driver stage card, but my card game is still at the luck before strategy stage. I admit to being an armchair achiever (minus the arms).
I suggested an OT instead of the 'blow your socks off amp designer's 1000V supply for the driver to his cathode follower output stage.
First of its kind all tube amplifier. | The Gear Page
$65 shipping...I see maple leaf by your name...when I lived near Detroit it was extremely frustrating that mailing something to Windsor, ON, across the river still got international shipping rates.
The first of its kind article...I lost track of whether I completed reading the second or third of eleven pages thus far and it had already devolved into a urination competition and I lost interest...
I don’t want to build or buy anything that isn’t mostly on hand already...and I have too much on hand already.
Best of luck to Mr. Relentlessness...
Maybe I’ll read more this weekend.
Ulrich Neumann’s co-authored book on Guitar Amplifier Overdrive will be in my mailbox today or tomorrow or Saturday. That should delay any hands-on work for a while.
The first of its kind article...I lost track of whether I completed reading the second or third of eleven pages thus far and it had already devolved into a urination competition and I lost interest...
I don’t want to build or buy anything that isn’t mostly on hand already...and I have too much on hand already.
Best of luck to Mr. Relentlessness...
Maybe I’ll read more this weekend.
Ulrich Neumann’s co-authored book on Guitar Amplifier Overdrive will be in my mailbox today or tomorrow or Saturday. That should delay any hands-on work for a while.
I bought one of the "40 Watt" 4.5K primary ones. They are very small for 40 watts but they may do 20 watts at guitar amp frequencies. They are about the same size as a Fender Deluxe or Princeton output transformer. They are definitely NOT worth what the seller is selling them for. The seller either has no idea what he's selling or he writes a lot of BS in the description in the auctions... Buyer beware.
I felt no discomfort with the seller's self-description, the product description, the manufacturer's specs, and the seller answered my question with a disclaimer that he only knew what model guitar amp it came from.
Mine weighs 5#-9 oz. Does seem skimpy for a '120 W output transformer', but it IS for a guitar amp, and that's what I was looking for, not high fidelity. A 1.25" stack of EI-137 in mine, to me suggests a small stack of a largish lamination...
I took a look at Mojotone, who I read somewhere has their transformers made by Heyboer...let's say at least some are USA-made, and current stock, not surplus, for price comparison.
A 50W Mojotone OPT replacement for a Marshall amp weighs 4.81# and is $70. A 100W one is 7.88# AND $90.
I don't even blame Basler, the mfr., for the seemingly optimistic ratings...they were built to the requirements of, in my '120 W' example, Kustom. Kustom's product line is nowadays smaller tube amps and what look like solid state or hybrid amps. I don't know anything about them, but it seems the Kustom Double Cross was not a successful design, or a long-lived one. I assume Kustom wanted the sound of an under-rated transformer for this 'high gain' amplifier.
For my project, $41 shipped was reasonable...not dirt cheap, but comparable to used vintage 'pulls' with no specs on eBay. I only expect to get 30-50 W (on paper, but never in the house) re-purposing my selection in a completely unrelated amp circuit. I don't think I have many choices for this price that are compatible with the tubes I'm working with. I think mine was well worth what I paid. I don't care about NOS vs. current stock...$41 is $41 and my needs were met.
Seller doesn't claim to be an expert and is a surplus dealer. This is my first dealing with him and I looked up the amp it was used in to answer the questions he couldn't address. The only thing I found peculiar in the listing for the item I bought was the 'translation' of 120 W to 120 VA. I get where that logic came from, but it's so out of context I don't think it could be misleading or misinterpreted. Nobody measures power factor speaker impedances, do they?
So I agree with the buyer beware part, but not the value part. I assume yours was priced similarly.
There is another eBay seller I think tends to exaggerate the suitability of what he sells, but it comes down to expectations. I'm amazed at the satisfaction level people get from 70V line transformers that only have enough inductance for 100-200 Hz (-3 dB), and using them for SE applications drops my jaw a bit.
So, my purpose for sharing the listing is for guitar amp builders. If they are all for the same genre of Kustom amplifier hell-bent on saturation and distortion, that's the caveat, folks. I just double-checked I posted this under instruments and amps :O)
Mine weighs 5#-9 oz. Does seem skimpy for a '120 W output transformer', but it IS for a guitar amp, and that's what I was looking for, not high fidelity. A 1.25" stack of EI-137 in mine, to me suggests a small stack of a largish lamination...
I took a look at Mojotone, who I read somewhere has their transformers made by Heyboer...let's say at least some are USA-made, and current stock, not surplus, for price comparison.
A 50W Mojotone OPT replacement for a Marshall amp weighs 4.81# and is $70. A 100W one is 7.88# AND $90.
I don't even blame Basler, the mfr., for the seemingly optimistic ratings...they were built to the requirements of, in my '120 W' example, Kustom. Kustom's product line is nowadays smaller tube amps and what look like solid state or hybrid amps. I don't know anything about them, but it seems the Kustom Double Cross was not a successful design, or a long-lived one. I assume Kustom wanted the sound of an under-rated transformer for this 'high gain' amplifier.
For my project, $41 shipped was reasonable...not dirt cheap, but comparable to used vintage 'pulls' with no specs on eBay. I only expect to get 30-50 W (on paper, but never in the house) re-purposing my selection in a completely unrelated amp circuit. I don't think I have many choices for this price that are compatible with the tubes I'm working with. I think mine was well worth what I paid. I don't care about NOS vs. current stock...$41 is $41 and my needs were met.
Seller doesn't claim to be an expert and is a surplus dealer. This is my first dealing with him and I looked up the amp it was used in to answer the questions he couldn't address. The only thing I found peculiar in the listing for the item I bought was the 'translation' of 120 W to 120 VA. I get where that logic came from, but it's so out of context I don't think it could be misleading or misinterpreted. Nobody measures power factor speaker impedances, do they?
So I agree with the buyer beware part, but not the value part. I assume yours was priced similarly.
There is another eBay seller I think tends to exaggerate the suitability of what he sells, but it comes down to expectations. I'm amazed at the satisfaction level people get from 70V line transformers that only have enough inductance for 100-200 Hz (-3 dB), and using them for SE applications drops my jaw a bit.
So, my purpose for sharing the listing is for guitar amp builders. If they are all for the same genre of Kustom amplifier hell-bent on saturation and distortion, that's the caveat, folks. I just double-checked I posted this under instruments and amps :O)
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The 1,500r is an excellent fit to the 6C33 push-pull (two bottles). About 80 Watts out. Damping Factor about 4. Potentially a fine hi-fi amp. (So we may get thrown out of this section.)
For "normal audio" tubes, a first-crack at bias and drive is K*Vp/Mu. K may be 0.6 for class A and 0.8+ for class B.
(Why? Vg=0V is normally the max current we can use. To get all the power we paid for, we want to run from there to cut-off. Cut-off grid voltage is nominally Vp/Mu. In A we bias "halfway"; which with Child's Law tends to be 0.6 of the way on the grid. Pure B would be cutoff at idle. We don't go that far.)
300V on plate and Mu of 2.7 is 111V on G1!
And 6C33 is not "normal audio", it is a Pass Tube aimed at low drop in operation. The ratings get funky over 250V. For better design, go to the curves.
http://www.jogis-roehrenbude.de/Russian/6C33C/6C33C-B-6S33S-VExtendedDatasheetMB.pdf
Rated Pdiss at 300V is 30W and to hit 100mA at 300V you need to put G1 between the 110V and 120V lines. In push-pull the lines will curve from this point to the active load-line. Which indeed skims the 60W Pdiss allowed at lower swing voltage and is safe.
On another thread with a guy with 350V supply I penciled drivers to make 60V-70V peak. (His original plan barely did 32V.) A 115V peak from 300V supply is possible with high-V transistors in push-pull; with resistor loading you can only get there with huge driver current, drain loads nearing 10K (to drive the 6C33's rated 200K grid leak). Like 9 Watts heat in a push-pull driver.
I would not be picking your driver tubes before you fully outline what they have to do to justify stoking coal into those 6C33 bottles.
> PP-self-split cascode driver stage card
DOUBLE the drive voltage (at least!).
> reduced drive.
If 115V makes 80 Watts, and you can reasonably make 57V drive, now it is a 20W amp. There are easier ways to get there. (FWIW, six 6L6 (a 666 amp?) is still an option even at 300V-400V. 6V6 Mu(g2) is 10, so only 30V-45V drive is needed to slam over 80W.)
For "normal audio" tubes, a first-crack at bias and drive is K*Vp/Mu. K may be 0.6 for class A and 0.8+ for class B.
(Why? Vg=0V is normally the max current we can use. To get all the power we paid for, we want to run from there to cut-off. Cut-off grid voltage is nominally Vp/Mu. In A we bias "halfway"; which with Child's Law tends to be 0.6 of the way on the grid. Pure B would be cutoff at idle. We don't go that far.)
300V on plate and Mu of 2.7 is 111V on G1!
And 6C33 is not "normal audio", it is a Pass Tube aimed at low drop in operation. The ratings get funky over 250V. For better design, go to the curves.
http://www.jogis-roehrenbude.de/Russian/6C33C/6C33C-B-6S33S-VExtendedDatasheetMB.pdf
Rated Pdiss at 300V is 30W and to hit 100mA at 300V you need to put G1 between the 110V and 120V lines. In push-pull the lines will curve from this point to the active load-line. Which indeed skims the 60W Pdiss allowed at lower swing voltage and is safe.
On another thread with a guy with 350V supply I penciled drivers to make 60V-70V peak. (His original plan barely did 32V.) A 115V peak from 300V supply is possible with high-V transistors in push-pull; with resistor loading you can only get there with huge driver current, drain loads nearing 10K (to drive the 6C33's rated 200K grid leak). Like 9 Watts heat in a push-pull driver.
I would not be picking your driver tubes before you fully outline what they have to do to justify stoking coal into those 6C33 bottles.
> PP-self-split cascode driver stage card
DOUBLE the drive voltage (at least!).
> reduced drive.
If 115V makes 80 Watts, and you can reasonably make 57V drive, now it is a 20W amp. There are easier ways to get there. (FWIW, six 6L6 (a 666 amp?) is still an option even at 300V-400V. 6V6 Mu(g2) is 10, so only 30V-45V drive is needed to slam over 80W.)
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I bought a batch of OPT's from an Ebay seller nearly 20 years ago. They were custom made by Schumacher for ADA. They look and are packaged just like these, except mine are 6600 ohms to 0-4-8-16. They also look like the transformer in my 80's vintage Schumacher automotive battery charger, which is 6 or 12 Volts, 6 Amp.
NOS Woodward Schumacher Output Transformer 4, 8, 16 Ohm Taps Bassman Super 2 6L6 | eBay
The transformers you linked were made by Bassler electric. Both of these companies primarily make power transformers, but will do custom work. I had the Schumacher spec sheet for my transformers but it has been lost over 20 years and two moves. It was a single page with mostly mechanical specs, dimensions, weight, wire color....The only electrical specs were 6600 ohms to 0-4-8-16, 80VA, 80Hz to 5KHz. These are the type of specs you would provide to a company who makes power transformers.
I took one of these transformers apart to see how it is made. One entire half - primary is wound on the paper bobbin, followed by the entire tapped secondary with the entire remaining half - primary, wound over it with slightly thicker wire due to the extra winding length. Laminations are thick, as you would expect in a power transformer. There is zero interleaving.
How do they work? The 80Hz to 5KHz spec would tend to rule these out for HiFi work, yet I had a pair in my 300B P-P amp. Measured frequency response was 30 Hz to 20 KHz at 25 watts. Feed the same OPT's with EL84's and you will get more like 40 Hz to 12 KHz. The low primary inductance, and high capacitance mean that these OPT's work best when driven by a low impedance source. Mine also perform better when used as a 3300 ohm to 0-2-4-8 OPT. In this configuration I can drive them to 60 watts from 30 Hz to 18 KHz with a pair of big TV sweep tubes using local feedback around the output stage to lower the tube's output impedance. I have also been to 175 watts at 1KHz without issue. I do not use any GNFB around these transformers due to phase shift in the audio range. They sound good playing music, or as a rock group's PA just touching clipping in a 125 WPC amp. Just don't let the bass player run through the PA......He had an SVT anyway.
You may find the same tricks apply to the Basslers. My experience's with 6C33's weren't so great, so my preference would go to TV sweep tubes for an under 100 watt amp into a 1500 ohm load. You could drive them with a 12AX7!
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You can "easily" make >115V peak drive if you go 700V on the driver. This could be as "simple" as using a 550V CT transformer to make 350V each side of CT, grounding the - end to make +350V and +700V. The 350 to the big jugs and the 700 to the driver.
Or one big PT for the big jugs and another 350V supply stacked on top.
Given ample supply voltage, the driver can reduce to a half-12AX7 and a modest MOSFET cathodyne. I've modeled this but with a way too big old MOSFET and it was fading at 1KHz. When I tried to hack a smaller newer MOSFET my SPICE blew-up.
The same could be done with a 3W triode but it needs a floating heater supply or a very high heater-cathode rating.
An alternative is a stretch 5F6a longtail, but lunch is ready.
And there is the Bereskin 3,000-Watt driver.
Or one big PT for the big jugs and another 350V supply stacked on top.
Given ample supply voltage, the driver can reduce to a half-12AX7 and a modest MOSFET cathodyne. I've modeled this but with a way too big old MOSFET and it was fading at 1KHz. When I tried to hack a smaller newer MOSFET my SPICE blew-up.
The same could be done with a 3W triode but it needs a floating heater supply or a very high heater-cathode rating.
An alternative is a stretch 5F6a longtail, but lunch is ready.
And there is the Bereskin 3,000-Watt driver.
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Thanks George & PRR.
G: The xfmr construction is both disappointing and inspiring...(-): looks like a power transformer tweaked to pass low bar (transformer equation & a little more) for audio performance perhaps with desired shortcomings. (+): reality check: If one winding over the other with no interleaving ‘functions’, then double-digit # of interleaves, pie-wound, etc. I don’t need. Somewhere in between is a step up.
PRR: Your Pspice must have been the low-voltage edition��.
Multiple supplies & elevated filament supply are OK...I’m obsessed with cascodes anyway so I anticipate the need.
I tend to get parts first so when I have time I can get moving, but it does result in some cart-before-horse planning...who needs the horse, anyway?
G: The xfmr construction is both disappointing and inspiring...(-): looks like a power transformer tweaked to pass low bar (transformer equation & a little more) for audio performance perhaps with desired shortcomings. (+): reality check: If one winding over the other with no interleaving ‘functions’, then double-digit # of interleaves, pie-wound, etc. I don’t need. Somewhere in between is a step up.
PRR: Your Pspice must have been the low-voltage edition��.
Multiple supplies & elevated filament supply are OK...I’m obsessed with cascodes anyway so I anticipate the need.
I tend to get parts first so when I have time I can get moving, but it does result in some cart-before-horse planning...who needs the horse, anyway?
I was thinking maybe the 1500 ohm for KMG's Fet amp design. A little high though.
Fet power amplifier with transformer output
Fet power amplifier with transformer output
> a half-12AX7 and a modest MOSFET cathodyne
This works but wants 750V supply, and bias-trim on the triode because at best it just-misses bottoming or topping-out.
That IRF part is WAY too fat; I had to scale down to 100Hz to avoid top-loss. Much more suitable parts are available, and the caps do not need to be so big.
The MOSFET needs the usual ~~1K gate stopper and (if not internal) a 15V Zener. This also limits the 12AX7's cold-voltage to 370V which means it is within all ratings.
This works but wants 750V supply, and bias-trim on the triode because at best it just-misses bottoming or topping-out.
That IRF part is WAY too fat; I had to scale down to 100Hz to avoid top-loss. Much more suitable parts are available, and the caps do not need to be so big.
The MOSFET needs the usual ~~1K gate stopper and (if not internal) a 15V Zener. This also limits the 12AX7's cold-voltage to 370V which means it is within all ratings.
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Yeah, he was selling the "40 watter" for the same price as the "120 watter". The 120 watter seems like a good deal, not so with the "40 watter".
It has taken me several years of collecting, but I have all the big stuff needed for "the last amp ever," or "the big one," or whatever I call it on any given day. The big one would be a stereo HiFi amp in the 1 KW range. It must also be capable of eating my guitar playing and be suitable for outdoor PA use at full crank for hours, even though it may never see such use.
Obviously the OPT's would be the big ticket item, and one pair were the first parts I collected. These were found in post # 6 here, almost 11 years ago:
Eight 807's in Push Pull?
I got a second larger set of these OPT's from another forum member a couple of years ago. They have the same guts potted into a shiny metal can.....much heavier though.
I have acquired 3 X 600 VA isolation transformers with a pair of 120 volt windings on each side. The primaries can be fed with 120 or 240 volts. Each 120 volt secondary will have a bridge rectifier and a cap for 6 X 160 volt supplies which can be series connected Tektronix style for any B+ voltahe needed at big power levels. There is a 200 amp breaker panel 10 feet from my bench with ample 120 or 240 volts available.
I now have driver boards capable of driving nearly any tube well beyond their limits, and a few boxes full of big TV sweep tubes......so the cart is nearly full.
The "horse" is the knowledge, skill, patience, and workspace necessary to pull this off. We have seen a few BIG amp builds attempted on these forums, but very few successes. I believe that I would have made something that might have worked, and might have lasted for a year or two, or might have just blown up on the initial power up, if I had jumped into it 10 years ago. I believe that I can pull it off today, but I still have two untested technologies that I will work with at a lower power level with budget friendly parts first.
One is a new concept for an output stage that I have been tinkering with for several years, and the other is an efficiency improvement scheme that I developed at Motorola for use in RF power amps. Both have technological hurdles that must be overcome.
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