Many
different Output Transformers transformers for sale.
Latest Update to this page :- August 2107.
This page give full information for type numbers OP1 to OP16, and
very brief information for OP17 to OP58.
Between 2008 and now, 2017, I sold most of the popular OPTs for PP
KT8 but I still have 90% of the many
different types unsold. The number of people who have ask me for a
pair of OPTs has dwindled to less than one a year.
If anyone wants an OPT, they should email me at
I may or may not have something that suits their requirements.
Many of the transformers I have may require air gap to be altered,
varnishing, holding brackets for mounting on a chassis, wire leads
and painting and labelling. I quoted prices after 2008 which
included costs of the wire, iron, packing, and labour involved to
allow a DIY hobbyist
to just bolt the transformer to the chassis after unpacking the
item.
I do not have any prices here for anything I have for sale now,
and I am not prepared to do any additional work mentioned above.
If anyone wants anything they see, they can make an offer which I
may or may not accept. This will proove to me whether someone is
keen to
make an amplifier or not, and not just abusing me by expecting me
to sell anything for less than the scrap metal value.
Freight will have to be considered.
Any DIY hobbyist must already have sufficient skills and workshop
facilities.
EXAMPLE 1 :-
Here are pictures of the last set of output transformers. OP22,
sold February 2011 with a pair of 1.9H chokes...
The picture shows the pair of OP22 on the left plus a pair of
filter chokes on the
right sold in Feb 2011 to a customer who is building a stereo amp
with 4 x EL34
in each channel.
There are multiple leads to the OPT for Secondary speaker
winding, Two Primary windings, one with 75% of turns
for anode, and other for 25% of turns for cathode for CFB.
There are 25% turns from anode winding for bootstrapping
the driver stage.
Support brackets are made using 3mm thick aluminium plates and 5mm
threaded rod bolts. The OPT have labels indicating
connections. A thick coat of black paint has been applied.
EXAMPLE 2 :-
30W OPT with C-cores, mounted inside octagonal steel steel pots
with polyester casting resin. The pot was made by
hand on bench and top fastened to sides with pop rivets. The
inside joins of metal work were sealed with silicone
before filling each metal pot with concrete using 50% slow cure
casting resin and 50% find dry sand.
The OPT was used for a pair of EL34 with 50% UL taps.
List of OP1 to OP56 for hi-fi use :-
Most of the OPT have only two ways to arrange multiple secondary
windings for RLa-a : 4r0 with all sec parallel,
or RLa-a : 16r0, with 1/2 of secs in series with other 1/2 of
secs.
For PP use, it is best to use RLa-a : 5r5 ratio, eg, 3k1 : 5r5
with all secs parallel, and all speakers above 3r0
will work OK. For SE use the secs are in series which gives 775r :
5r5. and all speakers above 3r0 work OK.
Other tubes than listed may be used but outcome is determined by
clever appraisal of data to get high amount
of class A po with low Fsat for hi-fi. Triode PP AB1 always gives
less max Po but same initial class A Po.
Use of SE triode gives lowest max Po.
OP1. Weight 7.4Kg, oa size 176mm x 132mm x 138mm.1 pair available.
PP UL or CFB or triode, 130W AB1, 4 x 6550, 3k1 : 5r5, Ea = +500V,
Iadc = 150mA, 17W class A.
SE CFB, SEUL, +air gap, 45W A1, 4 x 6550, 6 x EL34, 775r : 5r5, Ea
= +320V, Ia = 350mA.
SE Triode, +air gap, 35W, 4 x 6550, 6 x EL34, 775r : 5r5, Ea =
+365V, Ia = 310mA.
Primary = 1,496t x 0.45mm Cu dia, 11 layers 136tpl.
Secondary = 12 layers 63t of 1.0mm Cu dia, Ns = 63t or 126t. ZR =
564 : 1 or 140 : 1.
PP Interleaving = 11P x 12S, P-S insulation = 0.22 Nomex. Core =
T52, S52, L76, H28mm.
OP2. Weight 7.6 Kg, oa size195mm x 130mm x 153mm. 1 pair
available.
PP UL or CFB or triode, 60W AB1, 4 x 6550, 6k8 : 5r5, Ea = +500V,
Iadc = 150mA, 20W class A.
SE CFB, SEUL, +air gap, 47W A1, 4 x 6550, 1k25 : 5r5, Ea = +400V,
Iadc = 280mA.
SE Triode, +air gap, 38W A1, 4 x 6550, 1k25 : 5r5, Ea = +436, Iadc
= 257mA.
Primary = 868t x 0.45mm Cu dia, plus 2 x 181t x 0.30mm Cu dia =
1,230t total for PP. ZR = 1,235 or 308 : 1.
For SE use, the pair of 181t are paralleled and in series with
868t for 1,049t. ZR = 900 or 225 : 1
Secondary = 8 layers x 35tpl, 1.8mm Cu dia for Ns = 35t or
70t.
PP Interleaving = 9P x 8S, P-S insulation = 0.22 Nomex. Core =
T56, S50, L76, H28mm.
OP3, SOLD. Weight 5.6Kg, o/a size 150mm x 140mm x 133mm. NOT
available.
PP, UL or CFB or triode, 88W AB1, 4 x 6550, 4k8 : 5r5, Ea = +500V,
Iadc =150mA. 14W class A.
SE, CFB, SEUL, +air gap, 45W A1, 4 x 6550, 1k2 : 5r5, Ea = +400V,
Ia = 280mAdc.
SE Triode, +air gap, 37W A1, 4 x 6550, 1k2 : 5r5, Ea 430V, Iadc =
260mA.
Primary = 2,360t of 0.60mm Cu dia, 20 layers 118t.
Secondary = 10 layers 80t of 1.0mm Cu dia, Ns = 80t or 160t. ZR =
870 : 1 or 218 : 1.
PP Interleaving = 10P x 10S, Ips = 0.22 Nomex. Core = T38,
S50, L88, H33mm.
OPT4. Weight 5.5Kg, o/a size 152mm x 105mm x 130mm. 1 pair
available.
PP, AB1, UL or CFB or triode, 72W AB1, 4 x 6550, 6 x EL34, 3k5 :
5r5, Ea = +400V, Iadc = 280mA. 34W class A.
SE Po limited by primary wire Cu dia = 0.3mm.
SE, CFB, UL, +air gap, 29W A1, 3 x 6550, 4 x EL34, 3k5 : 5r5, Ea =
+506V, Iadc = 130mA,
SE, Triode, 25W, 3 x 6550, 2k5 : 4r0 or 16r0, 4 x EL34, Ea = +500,
Ia = 125mAdc.
Primary = 1,661t of 0.30mm Cudia, 11 layers 151t.
Secondary = 10 layers 66t of 0.75mm Cu dia, Ns = 66t or 132t. ZR =
633 : 1 or 158 : 1.
PP Interleaving = 11P x 10S, Ips = 0.22 Nomex. Core = T48,
S50, L62, H25mm.
OP5. Weight 5.5Kg, oa size 152mm x 140mm x 133mm. 2 pairs
available.
PP, UL or CFB or triode, 79W AB1, 4 x 6550, 6 x EL34, 2k9 :
5r5, Ea = +400V, Iadc = 280mA. 28W class A.
SE, CFB, UL, +air gap, 29W A1, 3 x 6550, 4 x EL34, 2k9 : 5r5, Ea =
+462V, Ia = 145mAdc.
SE Triode, 22W A1, 3 x 6550, 4 x EL34, Ea = +505V, Ia = 145mAdc.
Primary = 1,520t of 0.30mm Cu dia, 10 layers 152t.
Secondary = 11 layers 66t of 0.75mm Cu dia, Ns = 66t or 132t. ZR =
530 : 1 or 133 : 1
PP Interleaving = 10P x 11S, Ips = 0.22 Nomex. Core = T48,
S50, L62, H23mm.
OP6. Weight 5.2Kg, oa size 140mm x 94mm x 118mm. 1 pair available.
PP, UL or CFB or triode, 110W AB1, 4 x 6550, 6 x EL34, 1k8 : 5r5,
Ea = +400V, Iadc = 300mA. 20W class A.
SE, CFB, UL, +air gap, 33W A1, 3 x 6550, 4 x EL34, 1k8 : 5r5, Ea =
+390V, Ia = 195mAdc.
SE Triode, 24W A1, 3 x 6550, 4 x EL34, Ea = +400V, Ia = 166mAdc.
Primary = 1,540t of 0.35mm Cu dia, 11 layers 140t.
Secondary = 12 layers 86t of 0.55dia, Ns = 86t or 172t. ZR = 320 :
1 or 80 : 1.
Interleaving = 11P x 12S, Ips = 0.22 Nomex. Core = T44, S38,
L62, H22mm.
OP7. Weight 3.2Kg, oa size 100mm x 108mm x 105mm. 1 pair
available.
PP, UL or CFB or triode, 48W AB1, 2 x 6550, 2 x EL34, 4k5 : 5r5,
Ea = +400V, Iadc = 300mA. 12W class A.
SE, CFB, UL, +air gap, 25W A1, 3 x EL34, 1k1 : 5r5, Ea = +280V,
Iadc = 213mAdc.
SE Triode, 17W A1, 3 x EL34, 1k1 : 5r5, Ea = +350V, Ia = 177mAdc.
Primary = 1,694t of 0.35mm Cu dia, 14 layers 121tpl.
Secondary = 8 layers 59t of 0.85mm Cu dia, Ns = 59t or 118t.
ZR = 824 : 1 or 206 : 1.
PP Interleaving = 7P x 8S, Ips = 0.22 Nomex. Core = T25, S50, L62,
H22mm.
OP8, SOLD
Sold, no need to record data, only 1 pair was available.
OP9, Weight 2.6Kg, o/a size 102mm x 95mm x 95mm.1 pair available,
PP, UL or CFB or triode, 40W AB1, 2 x 6550, 3k5 : 5r5, Ea = +350V,
Iadc = 300mA. 11W class A.
SE, CFB, UL, +air gap, 20W A1, 2 x 6550, 3k5 : 5r5, Ea = +430V,
Iadc = 110mAdc.
SE Triode, 15W A1, 2 x 6550, 3k5 : 5r5, Ea = +470V, Ia = 110mAdc.
Primary = 2,160t, 0.35mm Cu dia, 18 layers 120tpl.
Secondary = 9 layers 86t, 0.55mm Cu dia, Ns = 86t or 172t. ZR =
631 : 1 or 158 : 1.
PP Interleaving = 10P x 9S, Ips = 0.22 Nomex. Core = T25, S38,
L62, H22mm.
OP10. Weight 2.6Kg, o/a size 102mm x 95mm x 95mm. 1 pair
available.
PP, UL, CFB or triode, 30W AB1, 2 x EL34, 11k4 : 5r5, Ea = +450V,
Iadc = 115mA, 17W class A1.
SE, CFB, SEUL, +air gap, 17W A1, 2 x EL34, 2k8 : 5r5, Ea = +350V,
Iadc = 115A.
SE Triode, +air gap, 12W A1, 2 x EL34, 2k8 : 5r5, Ea = +380V, Iadc
= 95mA.
Primary = 2,688t, 0.28mm Cu dia, 16 layers 168tpl.
Secondary = 8 layers 59t, 0.85dia, Ns = 59t or 118t. ZR = 2075 : 1
or 519 : 1.
PP Interleaving = 9P x 8S, Ips = 0.22 Nomex. Core = T25. S38, L62,
H22mm.
OP11. Weight 3.2Kg, oa size 102mm x 95mm x 95mm. 1 pair available.
PP, UL, CFB, triode, 60W AB1, 4 x EL34, 1k6 : 5r5, Ea = +300V,
Iadc = 200mA, 20W class A.
SE, CFB, SEUL, +air gap, 25W A1, 1k6 : 5r5, 3 x EL34, Ea = +335V,
Iadc = 180mA.
SE Triode, +air gap, 17W, +1k6 : 5r5 ohms, 2 x 6550, 3 x EL34, Ea
= +400, Iadc = 140mA.
Primary = 1,696t, 0.40mm Cu dia, 16 layers 106tpl.
Secondary = 9 layers 98t, 0.45mm Cu dia, Ns = 98t. ZR = 299 : 1.
PP Interleaving = 10P x 9S, Ips = 0.22 Nomex. Core = T26, S50,
L62, H22mm.
OP12. Weight 4.0Kg, oa size 115mm x 90mm x 98mm. E&I laminated
core, GOSS. 1 pair available.
PP, UL, CFB, triode, 33W AB1, 2 x EL34, 5k6 : 5r5, Ea = +350V,
Iadc = 144mA. 14W class A.
SE is not possible because E&I laminations cannot easily be
dismantled then re-assembled with air gap.
Primary = 2,592t, 0.28mm Cu dia, 16 layers 162tpl.
Secondary = 8 layers 81t, 0.5dia, Ns = 81t or 162t. ZR = 1,024 :1
or 256 : 1.
PP Interleaving = 9P x 8S, Ips = 0.22 Nomex. Core = T38,
S40, L57, H19mm.
OP13. Weight 2.6Kg, o/a size 100mm x 75mm x 82mm. E&I
laminated GOSS core. 1 pair available.
PP, UL, CFB, triode, 25W AB1, 2 x EL34, 5k5 : 5r5, Ea = +320V,
Iadc = 150mA. 15W class A.
SE is not possible because E&I laminations cannot easily be
dismantled then re-assembled with air gap.
Primary = 2,000t, 0.28dia, 16 layers 125tpl.
Secondary = 4 layers 63t, 0.60mm Cu dia, Ns = 63t or 126t. ZR =
1,008 : 1 or 252 : 1.
PP Interleaving = 5P x 4S, Ips = 0.22 Nomex. Core = T32, S40, L48,
H12mm.
OP14. Weight 3.2Kg, oa size 102mm x 95mm x 95mm. 1 pair available.
PP, UL, CFB, triode, 60W AB1, 4 x EL34, 1k6 : 5r5, Ea = +300V,
Iadc = 200mA, 20W class A.
SE, CFB, SEUL, +air gap, 25W A1, 1k6 : 5r5, 3 x EL34, Ea = +335V,
Iadc = 180mA.
SE Triode, +air gap, 17W, +1k6 : 5r5 ohms, 2 x 6550, 3 x EL34, Ea
= +400, Iadc = 140mA.
Primary = 1,696t, 0.40mm Cu dia, 16 layers 106tpl.
Secondary = 9 layers 98t, 0.45mm Cu dia, Ns = 98t. ZR = 299 : 1.
PP Interleaving = 10P x 9S, Ips = 0.22 Nomex. Core = T26, S50,
L62, H22mm.
OP15. Weight 3.2Kg, oa size 102mm x 95mm x 95mm. 1 pair available.
Only SE possible.
SEUL, SECFB, +air gap, 20W A1, 2 x 6550, 3 x EL34, 3k5 : 5r5, Ea =
+435V, Iadc = 115mA.
SE Triode, +air gap, 16W A1, 2 x EL34, 3k5 : 5r5, Ea = +390V, Iadc
= 105mA.
Primary = 2,440t, 0.35mm Cu dia, 20 layers 122tpl.
Secondary = 10 layers 96t, 0.5mm Cu dia, Ns = 96 or 192. ZR = 646
: 1 or 162 : 1.
PP Interleaving = 11P x 10S, Ips = 0.22 Nomex. Core = T26, S50,
L62, H22mm.
OP16. Weight 3.8Kg, oa size 115mm x 105mm x 102mm. 1 pair
available.
Only SE possible.
SEUL, CFB, +air gap, 18W A1, 2 x 6550, 2 x EL34,4k2 : 5r5, Ea =
+445V, Iadc = 100mA.
SE Triode, + air gap, 15W A1, 4k2 : 5r5, 2 x 6550, 2 x EL34, 4k2 :
5r5, Ea = +450V, Ia = 10mAdc.
Primary = 1,830t, 0.35mm Cu dia, 15 layers 122tpl.
Secondary = 8 layers 66t, 0.75dia, Ns = 66 or 132. ZR = 769 : 1 or
192 : 1.
PP Interleaving = 9P x 8S, Ips = 0.22 Nomex. Core = T32, S50, L62
H22mm.
---------------------------------------------------------------------------------------------------------
OP17 to OP56. Brief details only :-
FOR SINGLE ENDED AMPLIFIERS :-
OP17 SE, 3k0 : 4r0, 20W, 1.8Kg, C-cores, 2pcs.
OP18 SE, 408r : 6r0, 30W+ +, 6Kg, C-cores, potted, 2pcs.
OP24 SE, 1k2 : 1r0 or 4r0, 30W, 4Kg, C-cores, 2pcs.
OP25 SE, 2k9 : 4r0 or 16r0, 30W, 4Kg, C-cores, 2pcs.
OP25A SE, 800r : 8r0, 25W, 4Kg, C-cores, 1pc.
OP26 SE, 900r : 7r5 or 18r0, 4Kg, C-cores, 2pcs.
OP27 SE, 1k2 : 8r0, 25W, 4Kg, Ccores, 2pcs.
OP28 SE, 5k0 : 4r0, 25W, 4Kg, C-cores, 2pcs.
OP29 SE, 5k0 : 8r0, 25W, 4kg, C-cores, 2pcs.
OP30 SE, 4k7 : 5r0, 25W, 4kg, C-cores, 2pcs.
OP31 SE, 700r : 8r0, 25W, 4Kg, C-cores, 2pcs.
OP42 SE, 4k5 : 8r0, 20W, 3.5Kg, C-cores, 2pcs.
OP38 SE, 2k2: 0r8 or 2r9 or 6r5, 28W, 5.5Kg, C-cores, 2pcs.
OP49 SE, 1k7 : 8r0, 18W, 1.7Kg, C-cores, 2pcs.
OP51 SE, 1k6 : 4r0, 25W, 4Kg, 1pc.
OP54 SE, 4k7 : 4r0 or 8r0 or 16r0, 30W, 5kG, Chinese made, E&I
lams, NO air gap, for parafeed, 4 pcs.
OP57 SE, 2k6 : 2r0 or 9r0 or 16r0, 25W, 4Kg, Chinese made, E&I
laminations, 1pc.
OP58 SE, 8k1 : 4r0 or 8r0 or 16r0, 25W, 5Kg, Chinese made, E&I
laminations, 2pcs.
FOR PUSH PULL AMPLIFIERS :-
OP19 PP, 6k7 : 4r0 or 16r0, 100W, 6Kg, E&I laminations, 2pcs.
OP20 PP, 6k7 : 4r0 or 16r0, 50W, 5Kg, E&I laminations, 2pcs.
OP21 PP, 5k0 : 2, 4, 8 ohms, 20W, 1.5Kg, E&I laminations,
2pcs.
OP22 PP, SOLD, See pictures above.
OP23 PP, 8k7 : 5r0, 50W, 4Kg, C-cores, 2pcs.
OP32 PP, 1k8 : 8r0, 20W, 3Kg, E&I laminations, 2pcs.
OP33 PP, 6k7 : 4r0 or 16r0, 100W, 7Kg, E&I laminations, 2pcs.
OP34 PP, 4k0 : 4r0 or 16r0, 50W, 4Kg, C-cores, 2 pcs.
OP35 PP, 5k0 : 8r0, 20W, 2Kg, C-cores, 2pcs.
OP37 PP, 3k5 : 8r0 or 32r0, 100W, 5Kg, C-cores, 2pcs.
OP39 PP, 1k9 : 8r0, 20W, 2.5kg, C-cores, 2pcs.
OP40 PP, 10k : 8r0, 20W, 2.5Kg, C-cores, 2pcs.
OP41 PP, 2k0 : 8r0 or 32r0, 50W, 5Kg, C-cores, 2pcs.
OP43 PP, 5k5 : 8r0, 30W, 2.5Kg, C-cores, 2 pcs.
OP44 PP, 3k0 : 8r0, 30W, 1.5Kg, C-cores, 2pcs.
OP45 PP, INTERSTAGE TRANSFORMER, 10k0 : 50k0, 0.5Kg, 2pcs.
OP46 PP, 3k0 : 8r0, 20W, 1.5Kg, C-cores, 2pcs.
OP47 PP, 2k4 : 8r0, 25W, UL taps, 1.5Kg, TOROIDAL; could be power
trans for 240V : 13.8V, 2pcs.
OP48 PP, 2k8 : 2r0 or 4r0 or 18r0, 30W, 3Kg, C-cores, 1pc.
OP50 PP,1k6 : 4r0 or 16r0, 50W, 4Kg, C-cores, 1pc.
OP52 PP, EXPERIMENTAL opt, unknown Z ratio, 2Kg, C-cores, 1pc.
OP53 PP, 212r : 8r0, 25W, 4kg, C-cores, 1pc.
OP55 PP, 2k4 : 4r0 or 8r0 or 16r0, 44% UL, 50W, 5Kg, Chinese made,
E&I laminations, 3pcs.
OP56 PP, 5k0 : 4r0 or 8r0 or 16r0, 44% UL, 50W, 4Kg, Chinese made,
E&I laminations, 2pcs.
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