[Cloud.sessions]

I’ll add a little to this, if you look at one of my older builds you notice were now using split 120v windings going to the soft start (circled red). Tom’s soft start allows us to easily change from 120 to 240v. So going forward we’ll be able to accommodate for international customers.

[dls123]

I’ll add a little to this, if you look at one of my older builds you notice were now using split 120v windings going to the soft start (circled red). Tom’s soft start allows us to easily change from 120 to 240v. So going forward we’ll be able to accommodate for international customers.

I will add that you can see the build is neat and clean.  Signal path wire is VH audio copper and the power supply and filament wiring is mil spec teflon insulated.  The preamps should be very reliable, and there are no electrolytic caps except in the regulated filament supplies.  They are very expensive to build, and they sound that way.  Depending on the tariff situation, they may get more expensive since there are single source parts, chosen from many years of experience, that come from Canada, Belgium, and Poland.  We shall see what happens.

[Presb4]

Naked foils are a singular foil with a trace etched out in them to give them specific properties and resistance. While a film resistor is a rolled up bundle of film with a groove spiraling the film to give the desired resistance. Naked foils have incredibly low inductance while also retaining very low rise and settling times. Giving them a very transparent nature. You can read about them here https://vpgfoilresistors.com/var they have many wonderful properties that make them particularly good at being a very transparent resistor.

150v is perfect for the raven I’ve played with it a bit and at 150v the raven sounds the most organic with the best flow. Higher up (200v) it starts to sound a bit harder and less organic. Don definitely nailed it.

Thanks for the link to the Z foil data. I read through it, very informative. These new Z foil resistors sure do use some high tech manufacturing practices. I love to geek out on this kind of stuff.

[Jarbs]

Can the Raven safely run CV-181 tubes, such as the original Mullard ECC32’s?

[dls123]

Can the Raven safely run CV-181 tubes, such as the original Mullard ECC32’s?

Hi... the original ECC32 has a heater current draw of .95A vs .6 A for the 6SN7.  It should not be a problem as the the pair would still be under 2A and the supply should easily run 2.5 A all day long.  That said, the gain is 32 vs 20 for a 6SN7, and most important, the Rp (plate resistance) is about 14 K ohms, vs about 7.8K ohms of the 6SN7.  The output transformer was custom made to handle the high Rp of the 6SN7.  Asking it to handle twice that value is a lot.  You won't see smoke or anything like that, but your frequency response will be off.  I would expect the bass the have a problem as you may run out of inductance in the transformer.   Or it may work fine.  My advice would be to pop a pair in and see what it sounds like if you happen to own a pair.   They need to have reasonably matched sections within each tube or bass response will suffer.   I would not however, spend hundreds of dollars chasing old stock ECC32 tubes with iffy specs, only to find out that you don't like the sound in a circuit that was optimized for the 6SN7.  It could be very expensive to get a pair of those tubes in good shape if you don't already own them.  In my opinion, the money would be far better spent on a pair of the Ray Reserve 6SN7.   Expensive, but known to be superb and the best we have heard to date in that preamp. 

I have a number of the old ECC32 in my stash and honestly, I stopped using them years ago because the flaghsip shuguang and linlai tubes sounded better to me and I could buy all I wanted.  The Ray Reservere tube is quite a step up from those..... My 2 cents...take it or leave it!

[Jarbs]

Thank you. Sounds like it’s best to keep them in their boxes. What’s another 50 years for a tube. But the higher gain might be reason enough to go with the lower gain 6sn7. Which leads to my next question.

With a 2V source, will the Raven/Blackbird set have workable gain with 99db @ 8 ohm speakers? My usual issue is not having enough attenuation on the VC/ too much gain.

[dls123]

Thank you. Sounds like it’s best to keep them in their boxes. What’s another 50 years for a tube. But the higher gain might be reason enough to go with the lower gain 6sn7. Which leads to my next question.

With a 2V source, will the Raven/Blackbird set have workable gain with 99db @ 8 ohm speakers? My usual issue is not having enough attenuation on the VC/ too much gain.

The output transformer is a 4:1 step down, so going from mu of 20 for the 6SN7 to 32 for the CV181 is not as huge as you think.  It is mainly the Rp that worries me.  Again, you will not harm the transformers at all by using that tube.  You may or may not like the sound, but no harm in trying.  The gain totally depends on the sensitivity of your amps as well.  The Raven has between about 4.5 X gain.  With 99 dB speakers and any reasonable amp I cannot imagine that being a problem.  In my system, with 95 dB speakers and the Blackbird amps, which are about 1.5V to clip and a balanced Lampi DAC I am at 30-40 on the 64 step Khozmo.  The Khozmo is set up to be log taper, so it gets loud quite slowly.  I would expect you to have moderate volume in the 20-30 range unless your amps are either really sensitive or insensitive.  Really, I would expect that you will be just fine with plenty of adjustability.  It is fine to listen at 15 or 50.  It is just an attenuation ahead of the preamp circuit and the Khozmo only has a single naked foil resistor in the signal path for each channel at any volume setting.  So there is no sonic penalty to be at any setting.  They all sound the same.

[Jprod]

Speaking of the khozmo, is it normal to hear a subtle click through the speakers as you adjust volume ?

[dls123]

A really slight click on the Khozmo is no problem..... pretty normal.

[kenk]

A quick question, with many newer dacs that can outupt like 6V or more, is the a maximum voltage on input?  Thansk.

[dls123]

A quick question, with many newer dacs that can outupt like 6V or more, is the a maximum voltage on input?  Thansk.

XLR inputs go straight in and do not pass through the input transformer.  So there is no limit at all for XLR.  RCA inputs pass through a studio grade custom input transformer to convert them to balanced.  That transformer can easily handle 3V.   Should not be a problem as the RCA output on most things is 2V max.

[hxt2403399]

Hello Don,

I already have a passive pre (phasemation CM2200) and very satisfied with it.
I would like to use raven preamplifier as a unity gain stage between my dac and my CM2200 to add some tube characteristic but still use the CM2200 to attenuate the output signal.

My system is fully balanced, DAC output 4V rms for XLR with 200 Ohm output impedance, per my understanding, when using XLR, the raven balanced tube circuit (I guess it's common) has gain of 4.5 with volume control positioned at farest right. With raven's 4:1 output transformer (per my understanding it replaced the output capacitor and blocked the common mode high voltage), I got 72V on the vaccum tube and 18V rms on the output, correct?
Is putting the VC knob on the farest position(no input attenuation at all will cause clipping in the circuit)?
Do you know which volume number can make the gain to be 0dB, which need 1/4.5 attenuation on the input I guess.

Plus, I tried to order a raven through spatial audio but haven't got a reply from them.

[dls123]

Hello Don,

I already have a passive pre (phasemation CM2200) and very satisfied with it.
I would like to use raven preamplifier as a unity gain stage between my dac and my CM2200 to add some tube characteristic but still use the CM2200 to attenuate the output signal.

My system is fully balanced, DAC output 4V rms for XLR with 200 Ohm output impedance, per my understanding, when using XLR, the raven balanced tube circuit (I guess it's common) has gain of 4.5 with volume control positioned at farest right. With raven's 4:1 output transformer (per my understanding it replaced the output capacitor and blocked the common mode high voltage), I got 72V on the vaccum tube and 18V rms on the output, correct?
Is putting the VC knob on the farest position(no input attenuation at all will cause clipping in the circuit)?
Do you know which volume number can make the gain to be 0dB, which need 1/4.5 attenuation on the input I guess.

Plus, I tried to order a raven through spatial audio but haven't got a reply from them.

HI
First, I am sure if you call David he will get back to you fairly fast regarding an order.   That said, you would be crippling the Raven by using a passive pre behind it.  That unit you have is a transformer volume control.  Nothing inherently wrong with that, but you would have a transformer (Raven output) driving a transformer, which is adjustable.  Unpredictable results.  I would bet  you that the Raven driving your amps (especially if XLR inputs on the amps) will sound better than the passive, and better than the Raven plus the passive behind it.  If you want to try a Raven I believe they have a 30 day money back (less shipping) policy.  So your experiment would cost you shipping and tying up your funds for a bit.  My bet is on the Raven alone being the best.

The unity gain on a Raven depends on how it is set up.  It is generally around 40 - 50 on the Khozmo display.  The Raven sounds the same at any setting other than the attenuation, so you would experiment.  I would have to have a production one on the bench to tell you what unity gain is.  Again, I would highly advise you to run the Raven with nothing but a power amp behind it.