Suggestions for preamp upgrade

[Primalsea]

The Quad 606 has an input impedance of around 22k making it not so good a candidate for a passive volume control, on paper anyway, IMO, but its not the full story, so shouldn’t be discounted as an option. However, it seems to work well by many accounts and a passive volume control with selectable inputs and a separate buffer could give you plenty of flexibility and potentially cost less. I find that these days preamps tend to have too much gain unless you have an insensitive power amp or a vintage source with a low output.

[Light Dependant Resistor]

The Quad 606 has an input impedance of around 22k making it not so good a candidate for a passive volume control, on paper anyway, IMO, but its not the full story, so shouldn’t be discounted as an option. However, it seems to work well by many accounts and a passive volume control with selectable inputs and a separate buffer could give you plenty of flexibility and potentially cost less. I find that these days preamps tend to have too much gain unless you have an insensitive power amp or a vintage source with a low output.

I use Quad 306's one channel of each amp for each channel, and their input resistance at 20k is perfect, with my LDR passive, which has a lot to do with the 306's
outstanding sensitivity of 375mv for full output. Quad 606's are similar. Sensitivity can be adjusted via R13 for 306 or R11 for 606 - which for the 306 is a 9R1 resistor
and for 606 a 7R5 ie changing R11 to 9R1 would increase its sensitivity.

[tatami]

I'm impressed by the level of knowledge here! And a bit out of my depth.

It sounds like the Schiit Saga will work with my Quad 606, and if passive mode is unsatisfactory then active would be a fallback. With regard to the input, my DAC has a variable output that can be set at 1V, 2V or 3V. Which of those would you recommend?

I'd really like to have a remote control so for me a simple pot is probably off the menu.

It's going to be about two weeks until the test unit arrives from Schiit. When it does, I'll be sure to report back.

Thanks again for all the amazing advice and encouragement and keep it coming!!!

Philip

[tatami]

Bonky mentioned that he'd been using a Dada-modified Quad 306 with his Schiit Saga. I'm conscious that my Quad 606 (Mk 1) must be over 30 years old now and would benefit from a service – something my local dealer mentioned to me. So, I've identified five options:

1. Do nothing. Wait until the 606 actually breaks down.

2. Send it to Quad for a service now.

3. Order the kit from dada and find a local technician to install it for me – http://www.dadaelectronics.eu/shop/q...d-revision-kit.

4. Send the unit to Russ Andrews for an upgrade – http://www.russandrews.com/quad-606-upgrade/.

5. Send it to Red Hill Audio for one of the two upgrade options they offer – http://redhillaudio.co.uk/hifi-upgra...stage-1?page=3 or http://redhillaudio.co.uk/hifi-upgra...stage-2?page=4.

Each of the upgrade options is different from the others and the prices vary quite a lot. As a music lover rather than a technician, I have no idea how to choose between them. If you were in my position, which would you go for and why?

Thanks in advance for your insights.

Philip

[walpurgis]

Sending away for upgrade work will probably cost a couple of hundred quid. Instead, you could sell the 606 for a decent price, add the money that would have gone on upgrades and buy a 909 or Elite power amp and still have a bit of change left over. Just a thought.

[Andy831]

A Quad service will actually check all the components which are known to degrade or drift. The good thing about Quad is they do not change stuff for the sake of changing it, if its still within spec it stays untouched. It will also still sound like a 606 when its been done too which I think is a bonus as I like the sound the 606 makes.

[Macca]

. With regard to the input, my DAC has a variable output that can be set at 1V, 2V or 3V. Which of those would you recommend?

2V is the standard so I'd start with that. If it's too loud before you've hardly moved the volume control, drop it down to 1V. If you've got to crank the volume all the way to the end before it's loud enough, step it up to 3V.

I can't envisage a situation where you'd need 3V unless using a passive pre-amp into a very insensitive power amp.

Bear in mind that recordings are all made to play back at different levels too. Rock and pop recordings tend to be more dynamically compressed than jazz and classical so you won't need as much volume to play them loud. So test with a range of recordings before deciding on a voltage output setting for the DAC.

[walpurgis]

What about a variable gain pre-amp from China. It's a Pass derived design with three gain options. I quite like the look of this and was toying with the idea of getting one myself, for use with my Quad 306.

https://www.ebay.co.uk/itm/Finished-...cAAOSw5VtZzc2k

[tatami]

Sending away for upgrade work will probably cost a couple of hundred quid. Instead, you could sell the 606 for a decent price, add the money that would have gone on upgrades and buy a 909 or Elite power amp and still have a bit of change left over. Just a thought.

That's a cool idea. I'll put it into the mix. If I go with the Schiit Saga or another similarly priced option rather than an Icon or PrimaLuna preamp, I should be able to afford to upgrade/replace the 606.

[tatami]

2V is the standard so I'd start with that. If it's too loud before you've hardly moved the volume control, drop it down to 1V. If you've got to crank the volume all the way to the end before it's loud enough, step it up to 3V.

I can't envisage a situation where you'd need 3V unless using a passive pre-amp into a very insensitive power amp.

Bear in mind that recordings are all made to play back at different levels too. Rock and pop recordings tend to be more dynamically compressed than jazz and classical so you won't need as much volume to play them loud. So test with a range of recordings before deciding on a voltage output setting for the DAC.

Really helpful, thank you, Martin