Best moderate price interstage transformer

[mashaffer]

In the $50-$75$ price range are there any better options for interstage phase splitting transformers than hammond for US buyers. Bonus for even lower prices but that would be miraculous I think.

 

[Bigun]

I believe not but people do turn up with amazingly cheap offerings from time to time. Perhaps in large enough volume you could find something. Maybe accepting some compromises you could look at transformers designed for other applications that could be pressed into service, like power transformers.

 

[Shoog]

Of all the uses I have press-ganged power toroidals transformers into - Interstage duty was by far the least successful. Massively to high interwinding capacitance to allow decent hi-freq performance. Could possibly work if some form of powerdrive were used to drive the Toroidal.
I can guarantee that EI's will be totally unusable.

Shoog

 

[kodabmx]

I've used Hammond 124B and liked them.

A1 Parts (index) has the best prices on Hammond anything BTW. They list the 124B for $46 CAD.

 

[bigwill]

The best interstage transformer is an LTP

Edit: To add content, an LTP isn't really much more complicated than a transformer (though the simplicity may appeal), but has a bandwidth advantage (at both extremes) and distortion advantage.

To add, arguably a transformer is actually a lot more complicated than active phase splitting (if the aim is "purity"). If more people actually knew of all the sectioning and interleaving inside a decent audio bandwidth transformer as well as their ugly behaviour at the extremes, the "purist" approach may be active

 

[claudiomas]

the Hammond 124F wit 6CG7 differential stage :
input hammond 560Q 1:1 to 6CG7 +B300V 23mA RK220ohm
124F both secondary paralleled on10Kohm
=1Vinput// output //11V 0.02% thd
=1.5Vinput//17.7V 0.05%thd
2.5V input//29.5V 0.17%thd
with 6N6P you can reach 0.01%thd but lower gain 1Vin/8.7Vout
edit
i'm not sure if test was on paralleled secondary or one secondary only
but you can read:
1v/11+11V
1.5V/17.7+17.7V
2.5V in/29.5+29.5V out 0.17%

 

[directdriver]

I would use an input bridging transformer to split the phase, such as Jensen, Peerless, UTC, etc... You get balance input and not have to deal with DC on the primary, which makes it much less technically demanding to make, and you get perfect phase splitting for push-pull. And it's cheaper than an interstage transformer.

 

[claudiomas]

mashaffer ask for " interstage phase splitting transformer" not for cap coupling directdriver input bridging transformer like 560Q hammond its required for double triode to drive correctly interstage phase splitting transformer the goal its no anode resistors no coupling caps only one cathode resistor or negative bias

 

[soulmerchant]

I've heard the Hammond 124F before, and it was pretty darn good for the price.

Please note that I generally do not like Hammond iron either. But in this case I see no other realistic option. I would not feel like playing roulette with china iron for this...

 

[claudiomas]

input 560Q 10K 1:1 really good 42euro 124F 45euros its good for low power PP like 2A3, i will soon build stereo amp by thems it can also drive two 2A3 follow by bigger IT(lundhal or better sowter) for 845/GM70 etc PP i see in high fidelity commercial amp SE 6E6P-E triode mode driving 2A3PP by 124B interstage, also very good splitter even if 1:3 but no DC IT

 

[pblix]

Under their "Pro Sound" category, Edcor has a number of "audio matchers" for line level work. The specs (if true) looks promising. These are US made I believe. One example is the WSM series at 1/2W, 20-20kHz <1dBu. The best part is they're under $12 for WSM. If I were looking for an interstage transformer solution, I'd test some of these. There are other series too, such as WXM and XSM. Lots or different ratios too.

 

[claudiomas]

pblix Edcor not available in France and these are low impedance line transformers for OP and transistors for tubes need high impedance transformers and i like metal can or at list potted for input transformers for first stage double triode plate to plate you have Hammond 124F,15Khom/15Kohm 5Watt with 20mA with GE 6CG7 swing 60V 0.1 %THD very linear factory test 120V 10mA very hard to find cheaper, just i like if hammond can built 20Watt or more 1:1 15KCT IT for 2A3 plates to 845 etc grids waiting budget for Sowter 9083 9083 INTERSTAGE PUSH PULL DRIVE check pg 46 UTC 1963 catalog, LS-47 20Watts for 2A3PP plates driver and LS-48 40Watts 845PP plates to 805 grids!!!

 

[stevenrotterdam]

Would a big ferrite pot-core be useful?
I ask this because i have 8 lying around....with distance between windings capacities could be kept low. Ferrite I have is a choke for 10 amp, it should be tolerant of some dc-imbalance. After rewinding, of course.

 

[claudiomas]

NO to make interstage transformer its like high impedance output transformer
need very high skilled people!!!
normal price for 845PP IT drive its 250euros!!!
with 45 euros hammond 124F you can drive 6L6PP or 2A3PP 12watts amp

 

[pblix]

pblix Edcor not available in France <snip>

Not available in France is no limitation to the OP. Searching the net reveals others have used them with success as interstage transformers in tube circuits. You get three Edcors for the same money you get one Hammond. Just saying. But as always, YMMV.

EDCOR - WSM Series
EDCOR - XSM Series

 

[claudiomas]

there its no data on impedance, need 10-15KCT/10-15K CT!!!!! these are low +- 600ohms sound very very bad

EDIT sorry i see 10/15K ohm available so OK for input ligne to grids 0.5Watts only !!! few mA !!!! for interstage need 5watts or much more for drivers triodes plates like these Edcor also hammond make145 series 3/5mA and from 2K8 to 20K ohm cost 15 euros like edcor Transformateurs audio pour montage sur chassis (143-146 Series) - Hammond Mfg. i made 76 driving 6A6 in class B PP with IT hammond 145R i like Wurlitzer sound

 

[pblix]

You are once again imposing restrictions that the OP never mentioned. I'm glad to see you finally took a look at the spec. As I said, the Edcors are conservatively rated and would work as interstage transformers in tube circuits within their limitations. Probably equal or better than the Hammonds up to 3-4W.

 

[claudiomas]

OK i see XSM can swing 50V and 10K/10K 2.5Watts
cost 26.6euros OK but 2.5watts
Edcor XSM10K/10K, 26,66 €
and 15Kohm
Edcor XSM15K/15K transformer, 26,66 €
still i prefer 5Watts 124F
edit 26.6 euros +19% VAT

 

[jrdmedford]

The only transformer product that I know that can both phase split and act as an interstage driver, at the same time, is the Lundahl 1660 and it's kin. This is not cheap for a reason, even to meet the technical requirements of both duties it requires multiple windings, managing capacitance, and a big enough core to deal with the signal levels involved. I'd simply suck it up and save your pennies and buy this part - if you need to BOTH phase split and drive a PP stage at the same time. You will have to work withing a narrow window of driver tube parameters that can stay within the current capability of the core and the impedance of the transformer.

Other than that, there are many low cost options for an input phase splitter. The more signal level - the bigger the part - and the more you will pay. You can find alot of +20dbM input transformers for under $100. Here is a superlative value (and example!) EDCOR - XS1100

 

[claudiomas]

jrdmedford your edcor XS1100 input transformer its Low Impedance for OP
not for triode grids LL1660PP no gap PP to PP or LL1660 gapped SE to SE very good to 50mA max