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sharing eBay find: OPT from Kustom Double Cross
sharing eBay find: OPT from Kustom Double Cross
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Old 28th March 2018, 11:42 PM   #1
multi-volti is offline multi-volti  United States
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Default sharing eBay find: OPT from Kustom Double Cross

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
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Last edited by multi-volti; 28th March 2018 at 11:45 PM.
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Old 28th March 2018, 11:57 PM   #2
PRR is offline PRR  United States
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Yes, around 60W with a team of 6C33; but you need 110V peak drive per grid! That suggests 500+V to the driver, while the power jugs want 250V-300V. Awkward design unless you have a spiffy interstage transformer.
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Old 29th March 2018, 12:10 AM   #3
multi-volti is offline multi-volti  United States
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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.
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Old 29th March 2018, 12:42 AM   #4
multi-volti is offline multi-volti  United States
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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).
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Old 29th March 2018, 12:45 AM   #5
multi-volti is offline multi-volti  United States
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...and part-time optimist...my glass is always full when I look (even if it's full of air).
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Old 29th March 2018, 05:34 PM   #6
Printer2 is offline Printer2  Canada
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Quote:
Originally Posted by PRR View Post
Yes, around 60W with a team of 6C33; but you need 110V peak drive per grid! That suggests 500+V to the driver, while the power jugs want 250V-300V. Awkward design unless you have a spiffy interstage transformer.
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
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Old 29th March 2018, 05:41 PM   #7
Printer2 is offline Printer2  Canada
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There is a 40W one for $35 with a 4.5k primary. Might be easier to play with. The $65 shipping kills it for me.
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Old 29th March 2018, 07:24 PM   #8
multi-volti is offline multi-volti  United States
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$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.
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Old 30th March 2018, 01:36 AM   #9
danFrank is offline danFrank  United States
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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.
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Old 30th March 2018, 05:37 AM   #10
multi-volti is offline multi-volti  United States
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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)
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Last edited by multi-volti; 30th March 2018 at 05:44 AM.
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