Probably a NO-NO ... Submissive + Quad 303 solid state?

altec604e · 7468

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Offline altec604e

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Hi,

Bringing in transistor based amplifers on the forum is probably a NO-NO, but I need some help here.

I have a pair of Quad 303`s that runs as separate monoblocks.
I also have a Submissive pre.

I just found this site :
http://www.briarsfield-hifi.co.uk/quad_303_overview.htm

I want to try out my Submissive as a passive pre for my Quad 303`s.

This guy says that a pair of Quad 303`s = 25k Ohm load.

I do not understand this term, but maybe someone out there could tell me if the submissive is a good match or not.


All help will be appreciated.

Signal Source : Thorens TD 124 MkI / SME 3012 / Denon DL103

Setup : Quad 44 / Bottlehead Stereomour / Altec 604E in DIY 612C cabs


Offline Paul Birkeland

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Reply #1 on: January 24, 2014, 05:42:13 AM
It's kind of funny, as the guy on that page uses a 100K passive preamp to drive his 303's, which is not such a stellar idea.

The Submissive will work with your 303's, but a preamp with lower output impedance would be helpful in the long run.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline altec604e

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Reply #2 on: January 24, 2014, 07:07:23 AM
Hmm..

What output specs do the Submissive pre have ?

I know there are three settings I can switch between on my Quad 303`s  ( they`ve been modified with new boards )


The input sensitivity can be set to 0.5mV , 1.5mV and 5mV.
Has these settings something to do with Gain ?

To be honest I do not know where the 25K ohm load comes into the picture.
This is why I`m posting....





Signal Source : Thorens TD 124 MkI / SME 3012 / Denon DL103

Setup : Quad 44 / Bottlehead Stereomour / Altec 604E in DIY 612C cabs


Offline Paul Joppa

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Reply #3 on: January 24, 2014, 07:36:55 AM
The circuit of the 303 is online, and shows an opamp with 22K to the virtual ground , so 25K sounds reasonable.

What I found on the web says it's normally 0.5 volt, not 0.5 millivolt. The simplest and hence most likely modification would be a series resistor, raising it to 75K and 125K for the 1.5v and 2.5v respectively.  You'd need a circuit of the modification to be sure, though.

A classic from the early days, before PNP power transistors were available to make complementary symmetry circuits. There's another cult classic amp with that type of circuit; I forget the brand.

Paul Joppa


Offline altec604e

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Reply #4 on: January 24, 2014, 08:12:27 AM

You are correct:
The specs are not in milivolt , but volt.

So there are one jumper in each 303 to switch between 0.5 Volt and 1.5 Volt and 5 Volt input sensitivity. 
Thank you so much for checking this out...

but cant say I`m following you...
 
Do you mean changing the circuit of the submissive or my quad 303`s ?

I`m hoping you`re meaning the submissive....



 






 




Signal Source : Thorens TD 124 MkI / SME 3012 / Denon DL103

Setup : Quad 44 / Bottlehead Stereomour / Altec 604E in DIY 612C cabs


Offline altec604e

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Reply #5 on: January 24, 2014, 08:59:45 AM
I`ll leave it be.

Thanks for the input !



Signal Source : Thorens TD 124 MkI / SME 3012 / Denon DL103

Setup : Quad 44 / Bottlehead Stereomour / Altec 604E in DIY 612C cabs


Offline Paul Joppa

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Reply #6 on: January 24, 2014, 02:05:29 PM
Oh - sorry I was not clear. I mean that whatever modification was done to the Quad 303 would more likely than not increase its input impedance (making it more suitable for the Submissive) when set for a higher input voltage.

I would not hesitate to use the submissive - the recommendation is for a 30K minimum but it's been used successfully with 25K.

Paul Joppa


Offline altec604e

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Reply #7 on: January 24, 2014, 09:53:07 PM
Understand .

I`ll try the submissive with my Quad 303`s.

If this works well I will build a second passive pre for my Quad equipment.


Thanks !

Signal Source : Thorens TD 124 MkI / SME 3012 / Denon DL103

Setup : Quad 44 / Bottlehead Stereomour / Altec 604E in DIY 612C cabs