I am looking for two new or used high quality OPT's for push-pull
EL84's (6BQ5's) for a pair of 10 -15 watt monoblocs I am planning to
build (the "Mullard 5-10" circuit.) 8,000 ohms plate to plate, UL
type preferred (43% screen taps), but others considered.
Please email me at "analogdino 'at' rogers 'dot' com" (formatted
correctly.)
Ideally, I'd like to find these in the Greater Toronto Area (GTA),
Ontario, Canada, to avoid shipping costs, also customs costs if from
outside Canada, but this may not work out.
Thanks for all replies
Cheers,
Roger
GTA (Toronto), Canada.

Being this an EL84 project, and since You're in Canada, I'd look no further
than Hammond ( http://www.hammondmfg.com/1608.htm ). They're generally good
enough for their price. OK, there are some better ones in terms of quality,
but I know only European suppliers.
The type 1608 is the basic solution; if You want something better, the 1650E
has more "iron", therefore more power and bandwidth.

Ciao

Fabio


"Engineer" ha scritto nel messaggio
...
I am looking for two new or used high quality OPT's for push-pull EL84's
(6BQ5's) for a pair of 10 -15 watt monoblocs I am planning to build (the
"Mullard 5-10" circuit.) 8,000 ohms plate to plate, UL type preferred (43%
screen taps), but others considered.
Please email me at "analogdino 'at' rogers 'dot' com" (formatted
correctly.)
Ideally, I'd like to find these in the Greater Toronto Area (GTA),
Ontario, Canada, to avoid shipping costs, also customs costs if from
outside Canada, but this may not work out.
Thanks for all replies
Cheers,
Roger
GTA (Toronto), Canada.

Engineer wrote:

I am looking for two new or used high quality OPT's for push-pull
EL84's (6BQ5's) for a pair of 10 -15 watt monoblocs I am planning to
build (the "Mullard 5-10" circuit.) 8,000 ohms plate to plate, UL
type preferred (43% screen taps), but others considered.
Please email me at "analogdino 'at' rogers 'dot' com" (formatted
correctly.)
Ideally, I'd like to find these in the Greater Toronto Area (GTA),
Ontario, Canada, to avoid shipping costs, also customs costs if from
outside Canada, but this may not work out.
Thanks for all replies
Cheers,
Roger
GTA (Toronto), Canada.

ElectroSonic can supply any Hammond product. I'm surprised you are in
Toronto & not aware of that. Phone (416) 494-1555

See at www.e-sonic.com

Cheers, John Stewart PEng

"John Stewart" wrote in message
...
Engineer wrote:

I am looking for two new or used high quality OPT's for push-pull
EL84's (6BQ5's) for a pair of 10 -15 watt monoblocs I am planning
to
build (the "Mullard 5-10" circuit.)

(snip)

ElectroSonic can supply any Hammond product. I'm surprised you are
in
Toronto & not aware of that. Phone (416) 494-1555

See at www.e-sonic.com

Cheers, John Stewart PEng

Don't be surprised, I've already got a quote from them!
BTW, the 1650F looks the best bet.
However, I'm still looking on the used/recycled market.
Cheers,
Roger

"Fabio Berutti" wrote in message
...
Being this an EL84 project, and since You're in Canada, I'd look no
further than Hammond ( http://www.hammondmfg.com/1608.htm ). They're
generally good enough for their price. OK, there are some better
ones in terms of quality, but I know only European suppliers.
The type 1608 is the basic solution; if You want something better,
the 1650E has more "iron", therefore more power and bandwidth.

Ciao

Fabio

Thanks. And the 1650F has even more iron!
Cheers,
Roger

(snip)

On Sun, 29 May 2005 20:47:12 +0000, Engineer wrote:

"Fabio Berutti" wrote in message
...
Being this an EL84 project, and since You're in Canada, I'd look no
further than Hammond ( http://www.hammondmfg.com/1608.htm ). They're
generally good enough for their price.

The Hammond units, in terms for bang for the Canadian buck,
really aren't very good.

Got an LCR bridge? Measure the primary inductance for the
1650F vs our Z565. You probably can't, most folks can't measure
over 1,000 henries @ 60 Hz with several hundred volts on the
primary.

The 1650F, depite having more core material, has WORSE bass
response than our Z565. This a documented fact.


--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com

Ned Carlson wrote:

On Sun, 29 May 2005 20:47:12 +0000, Engineer wrote:

"Fabio Berutti" wrote in message
...
Being this an EL84 project, and since You're in Canada, I'd look no
further than Hammond ( http://www.hammondmfg.com/1608.htm ). They're
generally good enough for their price.

The Hammond units, in terms for bang for the Canadian buck,
really aren't very good.

Got an LCR bridge? Measure the primary inductance for the
1650F vs our Z565. You probably can't, most folks can't measure
over 1,000 henries @ 60 Hz with several hundred volts on the
primary.

The 1650F, depite having more core material, has WORSE bass
response than our Z565. This a documented fact.

Tell us more about the Z565.

I am sure we'd all like to know : -

The maximum iron µ of the core material.
The primary turns,
The complete size list, tongue, stack, window size, wire sizes.
All the secondary interleaving details and and insulation thicknesses,
marterials,
method of winding, layer, or random groups?

Then we could apply a few formula to check any claims made about
performance.

As for the 1650F, I have no idea if its any good or not, since I have never
used one
or stripped one down to find out how its wound.
The exact design is secret, so I guess I'll always be guessing, since
unless somebody forces me to build an amp for them with a Hammond
OPT within, I will wind my own, or buy something which i know to be
suitable,
and priced right, and that depends on the amount of guranteed to be correct

information that is available for a give product..

If you want an OPT for PP EL84, then
one must assume there will be an R load of say 10k a-a.
Since Ra-a of a pair of EL84 in pentode = 76k,
the resultant load + Ra-a source impedance will be about 8.8k.

If the primary inductance a-a is 70H, then the -3dB point in the response
due to inductive shunting will be 20 Hz.

The inductance of an OPT varies with the applied a-a voltage,
and in effect the permability, µ, rises to a maximum then falls as
saturation
begins.
Max µ is reached when B = about 0.8 tesla.

But the rise in µ for GOSS from a low value at very low Va-a is very
sudden,
and by about 50V a-a, the µ is at over 70% of the maximum attainable,
and so large signals across the load of typically 400V a-a will
have the maximum amount of inductance across the tranny,
and the phenomena of changing Lp
will result in better LF extension than at low level signals.

The original 1947 Williamson had a core with tongue = 32 mm,
stack = 44 mm, and had 4,400 turns on the primary.
Such an OPT had 100H at 5V a-a, rising to about 600H at
higher Va-a and at 50 Hz.
Fco at LF was about 3 Hz at low levels with a triode output stage.
The full details written out in a simple paragraph for all to see is in the
RDH4.
I expect all sellers of OPTs to provide the same info.
The GOSS core would have had µ max = 5,000,
but today's core material can have a µ = 17,000 for E&I,
I know, because I wind OPTs with such material made in Aust.

The LF cut off with the high µ material is exceptionally low,
even at low level when Lp is relatively low, perhaps 1/10 of the maximum
value possible.

But what determines the primary turn count is the saturation frequency
for an applied voltage equal to the mid frequency rated power level,
and 15 watts into 10k = 387vrms only.

Material with high or low µ will still all saturate at a similar F,
and this is the F where the distortion caused by the iron rises above
5% when the applied mid F full power voltage is applied.

Now I am being nit-picking and damned irritating to all when i mention such
issues and raise
so many questions, but I sure hope to irritate anyone who would make any
claim that their OPT is better than what Hammond make.

So, I see a two line claim like this one:-

"The 1650F, despite having more core material, has WORSE bass
response than our Z565. This a documented fact. "

What I don't see is any attempt at proving the claim to be true.

I'd expect at least a couple of pages of fully detailed proof,
but a simple specification paragraph about your OPTs as it is written about
the
Williamson design in RDH4 will do fine.

Patrick Turner.






--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com