Carnhill 9600R:600R output transformer..... what uses ?

Just want to add that UTC A24 which reaches ~300US$ (but can be bought for far less money) price tag on ebay, under the same conditions as above, measures closer to gapped than to ungapped Carnhill (20k-20kHz).

[quote author=[silent:arts]
I will keep my mouth shut until Im finished[/quote]

;D  of course. 
thanks for running these prototypes through their paces volker and syn!
kind regards,
grant

tried the ungapped version in DAOC output - just listened for now - i'd say the lower mid seems tighter/punchier than edcor 10k/600 xsm. i got a 10k/10k from Colin to try on input - i had trouble with numerous input trannies with top end roll off - but i think this is probably wiring issue - currently running direct in unbalanced - will try and sort this over next couple of days.
Also got a gapped version to try for output.
I'll let my colleague (PoBAudio - who has got ears that work!) have a play and maybe do some "mix-offs" of the different combinations - i'll ask him to post some clips if possible.

mikeyB  use individual (shielded) wires for the input and output pots. tie the shields together on one end only and attach them to the case. you should have no roll off then, with any decent input transformer.

Thanks Colin for getting these transformers.

I haven't found a source for Edcors in the UK so I'm very happy you stock these. I was thinking of using them instead of Edcors in Rotheu's "Another PoorMan 660".

J

I'll be using these for "Another PoorMan 660" as well.

Hi Syn

Nice to know you will be building one of those compressors as well. Have you started?

I was just wondering which Transformer will be better, gapped or un-gapped?

I'm not to sure what the difference is, but my instinct says gapped cause of the DC feeding the plates of the valves.

Am I correct?

J

Hi,
I'm interested too in this transformer as an interstage for this kind of comp !

Matthew :

push-pull transformers are not gapped in general : while one size "pulls" current, the other "pushes" it...

syn said:

mikeyB  use individual (shielded) wires for the input and output pots. tie the shields together on one end only and attach them to the case. you should have no roll off then, with any decent input transformer.

Click to expand...

Thanks Syn - yeah, I gone through the DAOC build thread - there's definitely something bad with the screened cable used for the pots. I had rolloff in channel 2 of -4dB at 20kHz!Changed cable to out pot - Screen cable length of about 12"/30cm. Replaced with a piece of 3 way ribbon - twisted it to see if made any difference - no. Wow! - channel has flat response - only 0.25dB down at 20kHz and 1dB down at 30kHz! Problem now is that hum induced in the cable. Need to move mains cable away from front panel and the pots.

Tried the gapped transformer  - same as the ungapped - but maybe a bit lighter on the bass - think i'll be getting the ungapped version for the second channel!

Nice one Colin  ;D

pyjaman said:

push-pull transformers are not gapped in general : while one size "pulls" current, the other "pushes" it...

Click to expand...

Isn't the gap between primary and secondary?

Actually I have no idea why the gap is there...

J

The gap is in the "magnetic circuit".

The magnetic core are made from a stck of thin laminates.... half of which are "E" shaped and half of which are "I" shaped..... the bobbin of wire is fitted on the centre "arm" of the "E" laminates.

The laminates are all stacked in a pile and you have 2 ways of doing it....

.....you can put all the "E's" directly on top of each other and all the "I's" directly on top of each other..... you then have a stack of "E's" and a seperate stack of "I's".... which you can butt together..... but there will be a minute gap between them (the size of the gap is actually controlled by the addition of a thin membrane).... you then clamp them all together with the external clamp and cover it with varnish to stop it falling apart.

.... alternately, you can vary the direction in which you stack the laminates so that they overlap..... an "E" on the left and an "I" on the right.... then the next layer will be an "I" on the left and an "E" on the right..... then the next layer will be an "E" on the left and an "I" on the right.... and so on..... there will be no gap between the laminates as they overlap.

[I forgot to say that both of these types are stock items now... VTB2290 and VTB2291].


Colin
www.audiomaintenance.com

Thanks Colin for explaining this.

Makes a lot of sense.

So if I understand correctly the difference in mechanical, based on construction technique.

Gapped and un-gapped transformers should be identical electronically (as in how they work in a circuit)  apart from a slight different frequency response.

Thanks for making these available.

Cheers

J

The gap cause the inductance to drop massively.... maybe to one quarter of the inductance without the gap.... so more current must be provided to the primary.... current requirement increases with lowering frequency.... so there is a tenadancy for them to roll-off earlier as the drive circuit cannot cope.

The benefit of the gap however is that they can be used with circuits which have a DC current flowing in the primary (like Class A amplifiers).

[I am not a transformer designer, so I will not be offended at all it someone cares to correct me.... I could be talking twoddle... often I am...].

Colin
www.audiomaintenance.com

you said it all guys.
for the DAOC you don't need gapped output transformer, OT is installed after 10uF cap so DC is already blocked there.

for the APM660 I'll go with gapped transformers for the SC, but I'm not claiming it is a must. However some of the
vari-mu compressors use gapped iron for the SC, I think 175, I'm not sure about fairchild. many fairchild users
do mention HF roll off which might be due to the use of gapped iron, just guessing.

PP in ideal world would be happy with ungapped core, but gapped core might allow for some unbalance and mismatching, i guess.

and once more, big thanks to Colin and AML, definitely the best service and  products there are.

Hello! Is this output transformer ok to use with the Sowter input transformer stated on the DLA2A BOM ? I'm building a DLA2A and the Sotwer OT is pretty pricey to get here in the US.