Helios + Pultec tube EQ rack prototype.

[ruffrecords]

I have just finished building a rack mounted all tube EQ prototype. One channel is a Pultec like passive EQ but with an added mid cut section. The other channel is a tube version of the classic Helios Type 69 passive EQ. here are a few pics:










Cheers

Ian

[CSlee]

Very cool

[CSlee]

Ian, what's the reason for the bigger input transformer? Looks like a 1:10. If it isn't a preamp as well, won't it be fed from a line level signal? Or does it benefit in other ways?

Charlie

[ruffrecords]

Originally Posted by CSlee

Ian, what's the reason for the bigger input transformer? Looks like a 1:10. If it isn't a preamp as well, won't it be fed from a line level signal? Or does it benefit in other ways?

Charlie

The bigger transformer is the output transformer - it is a 1:1 (600:600) type. The smaller transformer is the input transformer - it is a 1:1 (10K:10K) bridging type.

Cheers

Ian

[CSlee]

Ah OK, thanks

[mashaffer]

Impressive build!

[bichela]

Originally Posted by ruffrecords

I have just finished building a rack mounted all tube EQ prototype. One channel is a Pultec like passive EQ but with an added mid cut section. The other channel is a tube version of the classic Helios Type 69 passive EQ. here are a few pics:










Cheers

Ian

Do you have a schematic? I would be interested in looking at the design.

[HollowState]

Originally Posted by bichela

Do you have a schematic? I would be interested in looking at the design.

Pultec EQP1A Equalizer - Pro Audio Equipment DIY - DIY Vintage Pultec (Pulse Technologies) EQP1A Program Equalizer

[ruffrecords]

Originally Posted by bichela

Do you have a schematic? I would be interested in looking at the design.

Here is the schematic of the Pultec part. It is somewhat modified from the original to allow the use of a 10K:10K bridging input transformer rather than the original 600:600 type plus mods to accommodate the additional mid cut.




Cheers

Ian