My SE84CSP pre has only been in service for a month, or so, but there are these four amperex bb 6dj8's that have been burning a hole in my pocket.

This is the *redesigned* newer version CSP pre, which came with sovtek 6922's, as opposed to 6n1p's. Supposedly the newly made 6n1p's are more prone to failure which is why the 6922's are used (ElectroHarmonix might have something to do with this), which is a shame as I like them.

Well, the bb 6dj8's RULE in the CSP!! Mountains better with cd's, but vinyl also. To my ear, the more incisive effect of the sovtek 6922's is a little less sympathetic with a little less mid range body by comparison.  

I also tried an old rca 5u4g in place of the supplied sovtek 5y3. It was a over the top sounding, annoying, so I immediately went back to the 5y3. I'll try it again, as maybe it is because I'm listening to Mahler and Ravel at the moment.

Then, the next thing was to try an old rca 6dj8 in place of the 6n1p driver in the select with the CSP. The old rca 6dj8 sounds very similair to the amperex's, with only slight upper mid range differences.

I've tried 6922 and 6dj8 drivers in the select without the CSP in the chain, and have greatly preferred the 6n1p. Now, the select sounds absolutely GREAT with a 6dj8 for the driver, which was grabby and annoying sounding before. The mids and upper mids sound fuller and sing better; not over-fat, but just a lot more satisfying weight. I swapped a few times just to see if my general mood was causing a flippant observation as I'm partial to the sound of the 6n1p, but no...


FWIW,

Karl

Karl I don't have a CSP but I'll second Piglet and say try a JAN Cetron 5R4WGB. I use it in my "C" and it is my favorite rectifier in that circuit also with the 5Y3 as the design standard. It is only 15 volts more than a 5Y3 whereas a 5U4 is 30 volts more than the 5Y3 and that would explain the "in your face" signature.

Piggy,
What rectifier are you using in your "C"?

My current favorite in the select is a mullard gz32, which bested an rca 5v4 that was in itself very nice. I DO think the bass was a little more controlled and punchier with the rca 5u4 (the rca is my fav of this type, also), but the overall of the Mullard wins for my listening habits.

I didn't previously care for 6dj8's (even a nice rca branded mullard) or 6922's in the select, before having the CSP. Now, the 6dj8 is a favorite in the select, with the CSP in the front.

Thanks for the 5r4 suggestion for the CSP. Haven't tried one of those, yet.  

Karl

I agree with Karl, 6DJ8's are indeed nice in the CSP!  ;D

For the past few months, I have been using a Tung-Sol 5U4GB & RCA 6DJ8's (for L/R) and have really been really enjoying this combination.

In the Select, I am using a Mullard 5V4/GZ32 and Mullard 6DJ8 Driver tube.

I noticed I have an RCA 5R4 and am going to swap out the Tung-Sol and give this one a whirl this morning.

Thanks for the suggestion.

- Ray

[quote author=JDW  link=1102301096/0#7 date=1112027242]Ray,

Do let us know how you liked the 5R4 in your CSP. Thanks [/quote]

Listened to an RCA 5R4 in the CSP for about 3 hours on Easter and I think I like it better than the 5U4GB I had in there (a Tung-Sol). I think volatage-wise 5R4's are less aggressive? than 5U4's but it seemed to exhibit a bit more warmth in the bass and openness in the high-end than the 5U4. So far in order of preference, I like:

1. 5R4GYB
2. 5U4GB
3. 5Y3

I'd like to try something a little more aggressive (like a 5V4GA) I happen to have one of those (also an RCA) and see what happens.  ???

Speaking of that, what is the range of rectifiers we can use in thie CSP? For example, can we go with a GZ34/5AR4?

- Ray

A 5AR4 by another name..........would still be a GZ34. 5AR4 is the American Standardized nomenclature for the type, whereas GZ34 is the European Philips company coding. They are in all respects identical.

A comment here:

Different rectifiers sound different due to different plate resistances, internal capacitances, different space-charge effects (an electron repelling action between plate and cathode), and different saturation currents (the effect increasing plate voltage has on increasing the plate current).

No rectifier is perfect, and each type is a tradeoff.

Eddie

Hi Karl,

The way a particular rectifier will sound in a given circuit is 100% dependent on the power supply circuit and amplifier circuit as well. There are generalizations, but they are only that, generalizations.

For example, a power supply designed to deliver a certain target DC voltage to the amplifier using a 5AR4 will *typically* sound more relaxed and less dynamic with a 5V4 or 5U4, due to low voltage.

OTOH, a power supply designed to yield that same voltage with a 5U4 will obviously sound different with a 5AR4. Whether it sounds more aggressive due to increased voltage or not will depend on the power supply topology, amplifier circuit, tubes used, and the output stage's operating class.

Directly heated rectifiers like 5U4s perform very differently at lower AC input voltages than at very high ones. Because the electron path is quite long in a DH rectifier, the electron emission cloud is slow to be attracted to the plates, unless the plate voltage is quite high (thereby increasing the electrostatic attraction). These lethargic electrons congest the area between the cathode and plate with a negatively charged field, and since electrons all have a like negative charge, they repel each other and disrupt the electron flow further. This is called the space-charge effect.

Because of the space-charge effect, a given rectifier may perform very differently in a lower voltage/lower current application than in a higher current/higher voltage application. An example would be a simple preamp using say, an EF86 front end with a 6DJ8 cathode follower, or a low voltage spud amp, powered by a choke-filtered, capacitor input power supply. Here, the total current draw may be very small, and each leg of the power transformer secondary may only be around 180 volts. The voltage drop across a directly heated rectifier at low plate voltages increases sharply at low plate voltages with only a very small increase in current demand, due to the space-charge effect. This renders the 5U4 unstable at low plate voltages.

An indirectly heated cathode-sleeve rectifier with a very short electron path, like a 6X4 or EZ81, may sound very different (and likely much better) here than a 5U4, even though the output voltage yielded is almost identical. They suffer much less from the space-charge effect due to their very short electron path, but cannot produce a great deal of current the way the 5U4 can.

OTOH, in a scenario where you have a high powered PP amp that requires lots of current at some pretty robust voltages, a 5U4 may be a great choice. At higher applied AC plate voltages, rectifiers like the 5R4 and 5U4 that suffer very little from the space-charge induced instability and reduced conduction that plagues them at low plate voltages.

Mercury vapor rectifiers were developed to eliminate the space-charge effect altogether. The ionized mercury vapor has a positive charge equal to the negative space-charge, thereby counteracting it and providing an electrically neutral path for the electron emission. Mercury vapor rectifiers exhibit a certain fixed voltage drop that remains constant regardless of plate voltage, which gives them a very stable output voltage.  

The power tubes make a difference. Power triodes and beam power tetrodes/power pentodes operated as strapped triodes act differently from normally operated beam power tetrodes and power pentodes when the plate voltage is raised or lowered independent of everything else. So, a given rectifier will change the sound more or change it less depending on these things, as well as differently.

Also, with certain beam power tetrodes and power pentodes operating in Class AB, changing to a lower voltage rectifier will lower the screen grid voltage enough to substantially reduce the transconductance of the tube. This reduces the gain and increases distortion.

The power supply topology used, whether capacitor or choke input, will have a great deal on how the rectifier type affects the sound, and how much as well. Whether a cap input supply is inductively or resistively filtered will as well.

These are a few of the very basic basics. There are so many things that determine how a given rectifier will sound in a given circuit that an entire chapter of a book could be written on just it alone.

Eddie  

I bought a military 61np(from DrN) just for my CSP on order.  It does not seem that it is a favorite amongst the CSP crowd.  BB 6dj8 appear to be the favorite for the input.  I use one those for the input on my CS and I like it very much.  Does anyone remember why they switched to the BBs instead of 6n1p and 6922s?  I have read that having the same input tube in the pre/zbox and amp is not the best combination.  Any comments?

[quote author=rmt  link=1102301096/0#14 date=1138496474] I bought a military 6n1p (from DrN) just for my CSP on order.  It does not seem that it is a favorite amongst the CSP crowd.  BB 6dj8 appear to be the favorite for the input.  I use one those for the input on my CS and I like it very much.  Does anyone remember why they switched to the BBs instead of 6n1p and 6922s? [/quote]

I've tried the Holland made orange globe Amperex 6dj8, and while it's a very sweet tube it isn't my favorite. I've also tried the Mullard 6dj8, but I like it even less. I know I'm going against the crowd here, and at first I was enamored with them. But after a while the novelty wore off. I place both of those tubes in the same category: warm with lots of (artificial) bloom at the expense of spaciousness and holographic imaging. Compared to the Amperex the Mullard is even darker and more congested in the sound stage. Mullards have a flavor I described as Caramel. The amperex is less heavy, yet still relatively unfocused.

For those who wear contacts or glasses, I can relate that switching to a good 6N1P from Mullard or Amperex is like getting a new prescription. Suddenly everything opens up and the color is just right. Not overly saturated. Words are more intelligible. I consider it a very neutral transparent tube, with a little sweetness and a slight roll off of the highs. Compared to a strictly neutral tube like a Siemens, the 6n1p is less forward and IMO still lacking slightly in the holography department.

If you dig the 6n1p I must recommend the Brimar CV5358, especially cryod. OMG, this thing is a holographic nightmare and blisteringly honest. I love it.

Sometimes beer goggles are a good thing (lackluster source, etc), and I would consider Mullard the ultimate beer goggle. Amperex a good buzz. Sober, I'll take a 6n1p or Brimar CV5358 any day.

As always YMMV,

-Brett

Me too! (cryo'd)

I have 4 Brimar CV5358 (not Cryoed) on E Bay right now. These were $30 each! Auction up today.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5858053491


These are saucer getter, marked foreign.


D

BTW, these are the CV5358 with saucer getter, NOT the CV5358 with halo getter.



http://www.tubecollector.org/cv5358.htm

Thats the exact tube I'm using.  I have some brimar marked cv5358 that say 'foreign' on them that are nowhere near as good.  These do not say brimar on them anywhere.

John C.

Those are the ones  I have. Saucer getter marked foreign.

Den

Anyone modded their CSP? if so what's the value of the green tracon caps? I was thinking of replacing the .47u Daytons and the green tracons. Thanks

Do you have a more updated review of your mod?