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:

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

Cheers

Ian

 

[Brouilly]

Very cool

 

[Brouilly]

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]

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

 

[Brouilly]

Ah OK, thanks

 

[mashaffer]

Impressive build!

 

[bichela]

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:

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

Cheers

Ian

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

 

[HollowState]

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]

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.

An externally hosted image should be here but it was not working when we last tested it.

Cheers

Ian

 

[fotios]

That is what exactly i was searching to include in the tube preamplifier which i will build as a companion of the SET monoblock power amplifiers.
Excellent work Ian! That is exactly what i like, a well documented and focused design. Very nice built! I will be in contact with you - if you allow me - for any technical advice in the near future.
Thank you in advance.

Fotis

 

[ruffrecords]

That is what exactly i was searching to include in the tube preamplifier which i will build as a companion of the SET monoblock power amplifiers.
Excellent work Ian! That is exactly what i like, a well documented and focused design. Very nice built! I will be in contact with you - if you allow me - for any technical advice in the near future.
Thank you in advance.

Fotis

Thanks for the kind words. It is always nice to know tyour efforts are appreciated. The design has pregressed quite a lot from this early prototype.I now have PCBs for the Pultec and Helios EQs available if you are interested. You can find further details here:

Index of /EzTubeMixer/docs/EzTubeMixer/Helios69EQ

and here:

Index of /EzTubeMixer/docs/EzTubeMixer/3BandPultec

PCB prices and on overview of the projects is here:

http://www.ianbell.ukfsn.org/EzTubeMixer/

Cheers

Ian

 

[speakerfritz]

nice...I have this on my list to do as well