Beresford Bushmaster DAC

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Originally Posted by Colin151

Part of the mystery here is that the Quad 606 has a very high input sensitivity compared to other power amps around. It's nothing whatsoever to do with power output levels. Even a 3 watt per channel 2A3 valve amp can have very high input sensitivity. The Quad 606 input sensitivity is a very high 0.5V for full output rather than the usual 1.6V or so. Its due the the current dumping circuit and its also a deliberate part of the design. Quad preamps such as the 66 or 99 etc have very little gain, because they lack gain stages that can potentially degrade the sound.

I actually sold my 606 because a mate of mine in the USA told me that configuring the output transistors for such high output puts them past their linear point and the sound suffers to some extent. After carefully comparing to some other power amps of normal input sensitivity I did indeed find this was the case with the 606 (I did find the sound was a little crude and rough in comparison). The Quad pre/power amp philosophy seems to be that the preamp is low gain but high quality in terms of SQ and the power amp is high gain but less good sound quality, - the two kind of balance each other out. I used my Quad 606 with a 99 preamp for a while and the sound was very good. I did still run out of volume level though which is why I sold both. The 99 preamp has insanely low max output levels, - you even get far less max output than the unity gain available from a passive preamp (for example)

Anyway (sorry to ramble on a diversion) the reason your Caiman volume control is not used very high up with the Quad 606 is because of its high input sensitivity. Even a passive preamp can be used with a Quad 606 (despite the low input impedance of the 606).

I use my Caiman sometimes with its variable out into my NAD and Aragon power amps and it works well. I have to put the pot level pretty high, - around 12 to 3 o clock depending on the material, but the max volume level on the pot is Quite a lot more on mine, - around 5 o' clock. Its not an issue in my opinion as I've never run out of volume.

I had a Quad 99 preamp for a while. The Caiman variable output has loads more output level than that. The 99 outputs only 0.75 mv. The Caiman does 2V.

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Thanks for answering that one, I was wondering if it was power related or something else. Bearing in mind what you have said I don't suppose you could recommend a DAC to be used as a preamp with my Quad 606? I will be seeking an upgrade this summer.

Just want to add that I use the variable output in my main setup... as seen in my signature

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Originally Posted by pumpkineater23

Thanks for answering that one, I was wondering if it was power related or something else. Bearing in mind what you have said I don't suppose you could recommend a DAC to be used as a preamp with my Quad 606? I will be seeking an upgrade this summer.

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Well, as we know, there is nothing that's very cheap on the DAC front that has a variable output,- apart from the Caiman (and the Bushmaster when the variable option on that comes out). So you could potentially sell your 7520 and get a used Caiman for example. I have not compared the two but I hear the Caiman is quite a lot better than the 7520. When I get the Bushmaster you are welcome to borrow my Caiman to hear how much difference there is.

You have other options too. The Quad 606 power amp does work quite well with a passive preamp. You would get a more transparent sound in some regards if you tried that. The dynamics with that combo would still not bad as the 606 has so much gain. The Quad 606 does have a low input impedance though so there might be some roll off in the bass and treble. A passive preamp and buffer is an even better option (you don't get the roll off), - something like a DIY Pass B1 clone buffer or the DCB1. When used with the 7520 fixed outputs either of these options (passive pre, or passive pre with buffer) will definitely give you a more transparent sound than using the 7520 variable outputs, as would using a low gain Quad active preamp. I've had both the 66 and 99 preamps before and both sound great with the 606, - particularly the 99. A Quad pre/power setup would likely again outperform the 7520 variable out but it all depends on your budget (a Quad preamp would not be too cheap, - around £250-350) and you would have to take into account the limited max volume level. What speakers do you use? Their sensitivity is v important with regards to this as the Quad preamps have so little gain. This is the reason the Quad preamps sound better than the Caiman/7520 variable output ( I compared at length when I had the 99 preamp), - it would be near to be impossible for the Caiman/7520 varable output to sound better as it has so much higher output.

For me (with the Quad pre/power combo), it was just a dealbreaker on the max vol issue when used with my insensitive speakers.

The Quad preamp option is pretty expensive though it could be worth trying is you have the funds, - you could always sell the preamp on if you did not think the change was worth the expense. For a v cheap change to try out, I would say to use the 7520 fixed output with a passive preamp into your Quad 606 and see how you like the sound. You could even build a passive pre for a tenner or so. It will certainly be more transparent that using the variable output of the 7520. The dynamics with a passive pre were the dealbreaker for me, but some people don't find it so much of a problem, and (like I say) it is likely to be less of a problem with the Quad 606. I also have a passive pre you could borrow if you are interested in trying it out.

Another option could be to get a cheap valve preamp (and again use the 7520 fixed output), though that's more likely to be a sideways step (in general) compared to the variable output and a subjective one, - some people like what valves add to the sound. If you wanted to try that I would suggest getting a valve preamp with an cathode follower, - such as a Yaqin MS12B (this is the one I use, - it's pretty cheap at around £200.) The Cathode follower is really needed with solid state amps such as the Quad 606 (due to their low input impedance.)

If you want a more certain improvement to some areas of the sound (such as pureness and transparency) I would look at a passive preamp, or Quad preamp. With the passive pre dynamics and roll off at the frequency extremes could be an issue. Those are not issues with a Quad preamp, - the problem with the latter is really just the cost of the preamp. Or (like I mentioned at the start), upgrading from the 7520 to the Caiman (and also using its variable outs) is a likely good option and not too pricey at all once you've resold the 7520.

So three immediate options I can see for you. Waiting for the Bushmaster variable out option is another of course.... I am betting that will sound even much better than the Caiman variable out.

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Originally Posted by slate

Just want to add that I use the variable output in my main setup... as seen in my signature

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hmmm.......:scratch:

So it seems some people do rely on the variable output. I guess it's more likely people that use the variable out on this forum than in general though. I am guessing the the majority of people buy Stan's DACs for the good quality headphone amp built in and cheap all in one solution for headphones. The headphone ability was the main reason I bought my Caiman in the first place (to mainly use it with a PC), - then I tried the Caiman on my Cd player/Hifi with speakers.... and didn't look back. So it doubles up for me, it's such a flexible little device.

It is a bit of a shame the Bushmaster does not have variable output right off the bat but I know Stan wanted to price the Bushmaster lower than the Caiman, and something had to give to achieve this. I am glad he choose the variable out rather than the headphone amp ability (for example), and at least there is going to be the add on variable output to come in the future.

Those who rely on the variable output might be a bit stuck on the upgrade path for a while until the add on comes out. I would have suggested a passive preamp or simple attenuator in between DAC and power amp as a potential way around this, but Stan said yesterday that's a no no due to the Bushmasters DC output, - apparently a scratchy sound will result. I am intrigued with his mention of using caps though to sort this out. Where would you put the caps Stan? In between Bushmaster and attenuator?, or in between attenuator and power amp?:scratch: (I am not that technical!)

Quite a few folks here on AoS do that Colin - it was quite a revelation to some.

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Originally Posted by The Grand Wazoo

Quite a few folks here on AoS do that Colin - it was quite a revelation to some.

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You mean using the fixed output of the DAC and a passive preamp?

I really like the transparency of that option. I have one of those LDR passive preamps and its really transparent (far more so even than a passive pre with a normal contact pot).
With a passive preamp the lack of dynamics just bothered me after a while. It's much less of an issue with some material than others of course, and a somewhat subjective thing. I know many people swear by passive preamps. A passive pre and a buffer is a pretty good compromise IMO (I have a clone Pass B1 I use sometime with my LDR preamp). That's like a half way house (half way between a totally passive preamp and an active preamp), - you get some dynamics back and you get greater extension at frequency extremes (especially when running into a solid state power amp) whilst still getting the passive type transparency.

No, I was affirming what you had surmised when you said this:

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hmmm.......

So it seems some people do rely on the variable output. I guess it's more likely people that use the variable out on this forum than in general though.

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Originally Posted by The Grand Wazoo

No, I was affirming what you had surmised when you said this:

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Ahh I see. Yeah, The variable output is a v useful option for some people (with the Caiman etc) and it does sound very good. The other preamps I use are not better sounding, just different. Variable output is a money saver for sure.

I suppose something had to give for Stan to price the Bushmaster so competitive. Like I just mentioned, I am guessing the headphone amp section of this DAC is what more people use in general and would consider to be more important than variable out.

Perhaps the attenuator/cap option when using the fixed output could be a way around this for some potential Bushmaster buyers, until the variable output option comes out....

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Originally Posted by jandl100

Hmm ... sounds like Our Stan has done it again!

Put me down for one as well, please, Stan. :)

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Originally Posted by StanleyB

I have already put you at the top of the list ;).

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Hey, Stan. You're the Man! :cool:

I fondly recall - many years ago! - when I did an ebay impulse buy on the old mk2 Beresford 7510 DAC. Intended as a bit of a laugh to use with my minidisc player (tbh, at it's £100 price point I was expecting it to sound shite and return it for a refund!) I tried it on my main rig ... and the dang thing blew me away. :doh:

I think that the Beresford DAC was the very first of my now infamous "Jerry Hype Forum Fad" threads to appear on the Wigwam. Boy, did that cause a stir! :lol:

... I've also just invested in the Tracy (no 'e') Chapman CD that folks have been on about - £1.69 delivered from good ol' Amazon Market Place. :)