EQP1A with cascode amp circuit

[Deepdark]

allright. I know David from cinemag suggest me the CMLI-4x150D for the input, for the output I'll check out the CMOB-2. I was looking at the Hammond transformer, too. The 140QEX. It looks fine on data sheets. Generaly, I tend to work with transformers made in USA or Canada. Not because I don't trust other brands but because the CAD versus euro or GBP is not that great, the shipping is expensive and I need to pay some taxes and other duties when crossing the canadian line. So at the end, they cost a lot more.

 

[ruffrecords]

Yes I noticed you are in Quebec which is why I tried to suggest Cinemag or Jensen types. Just could not seem to find a suitable 600:600 type on their web sites.

I think there is a thread on here somewhere about transformer alternatives for the Pultec EQ.

Cheers

Ian

 

[Deepdark]

thanks. I know the CMLI-4x150D works fine, I installed it in 2 pultec clone. For the output, the CMOB-2 looks fine. Just don't know if it will be optimal for the mu-follower design

 

[ruffrecords]

thanks. I know the CMLI-4x150D works fine, I installed it in 2 pultec clone. For the output, the CMOB-2 looks fine. Just don't know if it will be optimal for the mu-follower design

You could ask them for the value of the primary inductance. If it is 12 Henries of more it should be fine.

Cheers

Ian

 

[Deepdark]

Here is the answer of cinemag about the CMOQ-2, concerning the inductance:

"Each of the four windings looks like ~800mH with steel laminations."

 

[ruffrecords]

Here is the answer of cinemag about the CMOQ-2, concerning the inductance:

"Each of the four windings looks like ~800mH with steel laminations."

OK, for 600 ohm operation you wire them in series so the inductance becomes 3.2 Henries, not much better than the much cheaper Edcor. Did they say what frequency they made the measurement?

Cheers

Ian

 

[Deepdark]

No he didn't said anything about the frequency. I could ask, thought. I'm looking with Jensen, too. I simply asked them for a line out 600:600, to be driven at 10k load and with a primary inductance of at least 12H.

 

[Deepdark]

I continued my research and found some possible alternative transformers. Carnhill has the VTB-2408M which is shielded. I think it should work has input transformer, along with the VTB-2281 you suggest me.  I would like to know if carnhill has good reputation, and are good quality audio transformers?

Sowter is too much expensive. Lundahl have some great transformers but it's a little hard to find the good one, since their spec sheet looks to not give a lot of informations.

The Hammond 140QEX looks nice on paper. Inductance of around 10H. Maybe it should work has input and output?

 

[Deepdark]

Wrong thread?

 

[ruffrecords]

Wrong thread?

Yup, moved and deleted. Sorry.

Cheers

IAn

 

[ruffrecords]

I would like to know if carnhill has good reputation, and are good quality audio transformers?

They have a first class reputation and make top quality transformers. They make transformers for Neve.

Cheers

Ian

 

[Deepdark]

allright. looks like a premium choice then. And not that expensive, too. I consult their pdf but it seems to not have all their models and not a lot of information, too. The inductance of the VTB2281 has been measured by someone in the forum? also, is teh shielded VTB-2408M a good candidate for input?

Also, looking at the filter section: If for exemple I call all my capacitors from just radio, all orange dips/JFX caps, does it Worth it or I just get all Panasonic/vishay/cornell caps from supplier such as mouser or digikey and be happy with them? I already built 2 units with Panasonic/cornell caps and it sounded really nice (all polyester film caps), but I was asking myself if taking more "audiophile focused" caps would changed anything in term of performance/sound, etc.

 

[ruffrecords]

allright. looks like a premium choice then. And not that expensive, too. I consult their pdf but it seems to not have all their models and not a lot of information, too. The inductance of the VTB2281 has been measured by someone in the forum? also, is teh shielded VTB-2408M a good candidate for input?

The VTB2281 has been measured by me. I wrote a document about transformer inductance to which several forum members contributed.:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/Iron/TransformerInductance.pdf

I have not tested the VTB-2408M but if their other 600:600 transformers are anything to go by it should be OK.

Also, looking at the filter section: If for example I call all my capacitors from just radio, all orange dips/JFX caps, does it Worth it or I just get all Panasonic/vishay/cornell caps from supplier such as mouser or digikey and be happy with them? I already built 2 units with Panasonic/cornell caps and it sounded really nice (all polyester film caps), but I was asking myself if taking more "audiophile focused" caps would changed anything in term of performance/sound, etc.

EQ circuits are one of the few places where the type of capacitor does make a difference to the sound. You should definitely be using film caps of some kind. I am not convinced there is a huge amount to choose between them. Just make sure they are rated at 50V or more. The most non-linear parts of a passive EQ are the inductors and these are probably what contributes most to the sound of the EQ.

Cheers

Ian

 

[Deepdark]

allright thank you. I go with Panasonic ECW (Polypro) caps. Inexpensive and largely available over mouser and I heard good comments about them. Di you check the VTB-2408M, by the way? Apart from being shielded, is there anything I should look at for the input transformer?

 

[ruffrecords]

allright thank you. I go with Panasonic ECW (Polypro) caps. Inexpensive and largely available over mouser and I heard good comments about them. Di you check the VTB-2408M, by the way? Apart from being shielded, is there anything I should look at for the input transformer?

Not checked the 2408 personally but as long as it is screened it should be OK for the input.

Cheers

Ian

 

[Deepdark]

ok. no need for a 600ohm t-pad I guess? And should I get the same inductance values for the input transformer of it doesn't matter in this case?

Looking at the 47uf cap before the output transformer. Can we put a film capacitor or it's better to use a electrolytic?

The 100nf grid bypass cap: Ceramic is ok? or there is better alternative?

 

[ruffrecords]

ok. no need for a 600ohm t-pad I guess? And should I get the same inductance values for the input transformer of it doesn't matter in this case?

The EQ should be unity gain overall so I see no need for a T-pad. Inductance doesn't matter so much  in this case. Screening is the priority.

Looking at the 47uf cap before the output transformer. Can we put a film capacitor or it's better to use a electrolytic?

Electrolytic will be fine.  A correct value coupling cap will have a very small voltage across it and therefore produce very little distortion.

The 100nf grid bypass cap: Ceramic is ok? or there is better alternative?

Should be film. I usually use an orange drop.

Cheers

Ian

 

[Deepdark]

Awesome thank you. I spoke to cinemag and they do not have Any transformer with such inductance so, carnhill is the way to go in my case

 

[Deepdark]

quick one. i want to replave the 7 position highs with a 6 positions. with a inductor of 269/169/69/22, and a 2k2(2k5??) high Q pot, is there something else i should change,or the filter section remain the same?

looking at individuals inductors, mouser stock a lot of them. is there some manufacturer they are Worth looking for? API Delevan, Hammond, Fastron, Murata, etc. I looked at Cinemag and Carnhill to know if they have/could make them. I know Sowter stock them, by the way.

 

[ruffrecords]

quick one. i want to replace the 7 position highs with a 6 positions. with a inductor of 269/169/69/22, and a 2k2(2k5??) high Q pot, is there something else i should change,or the filter section remain the same?

The inductor has a wider range than the original so you will need to alter the frequencies if you want the same Q curves as the original but otherwise there are no changes to make.

looking at individuals inductors, mouser stock a lot of them. is there some manufacturer they are Worth looking for? API Delevan, Hammond, Fastron, Murata, etc. I looked at Cinemag and Carnhill to know if they have/could make them. I know Sowter stock them, by the way.

Sorry, no experience of inductors for original design.

Cheers

Ian