[Hirsch]

Quote:

Originally posted by Rob N Hirsch,I was thinking of trying a Ken Rad as input + Hytrons as output.

IMO definitely worth a try. The key tube seems to be the gain tube (on the right). I've had some very good results using a single tube there and Sylvanias as output. I can't remember using Hytrons as output tubes only, just as trios, but there's no reason it wouldn't work.

 

[chris719]

How does the bass on the Ken-Rad's compare to the stock EH?

 

[tom hankins]

I've been using one KenRad in the right tube spot and two sylvania Vt-231's in the center and left and the combo sound's very good. I think it adds a little more bass without taking away to much of the 3 sylvania sound. I like this combo with the HP-2's the best.

 

[immtbiker]

I recently switched over from the Tara Labs RSC Axioms which were very broken in, to the Cardas Neutral Reference IC's (brand new, without burn-in) using the EH 6SN7's that came with the Supra amp, and the difference was startling. I am awaiting a trio of slightly used 1940's Sylvania VT-231's, and will experiment with the different positions of the different tubes. I imagine with the NOS tubes and the Cardas IC's burned in, I will have a whole new toy to play with. Interconnects do make a difference.

 

[Hirsch]

Quote:

Originally posted by Rob N Hirsch,I was thinking of trying a Ken Rad as input + Hytrons as output.

I've just been trying a Ken-Rad as input and a pair of Sylvanias as output (depending on year, the Hytrons are likely to be very similar to Sylvanias). This is the combination Tom Hankins described, and IMO it works very well indeed. It doesn't give up the midrange magic that the Sylvania's have, and adds the bass impact of the Ken-Rad. The converse, using Ken-Rads as output with Sylvania an input does not sound as good to me.

 

[Hirsch]

Quote:

Originally posted by chris719 How does the bass on the Ken-Rad's compare to the stock EH?

Just saw this. I haven't done a direct comparison, however, the Ken Rad VT-231 is often referred to as the very best 6SN7 for low end, and I've heard nothing to contradict that.

 

[Rob N]

I've tried a Ken-Rad VT231 smoked glass version as input with Hytrons as output and the bass in truely enormous and it seems to have a bigger soundstage,although it doesn't quite have the smoothness of Hytrons in all three positions.

How about an RCA VT231 gray glass in the input position with Hytrons or Sylvanias as output?

 

[Rob N]

Almost forgot both the Ken-Rads I've got appear to be used (but test good) and both are a little microphonic,is this normal for these tubes?

The Hytrons I got from Mikhail appear to be unused aand have no microphonics.

 

[Rob N]

Can you use an ECC32/33 in place of 6SN7 in the MPX3?

I've seen some good write ups on the Mullard ECC32/CV181 in both the 'normal' 6SN7 bottle shape or the larger ST shape.

 

[Hirsch]

I would say that at least 60% of the 6SN7's I've seen exhibit some sort of microphonics. I was talking about this to Kevin Deal at Upscale Audio at one point, and he placed the figure closer to 90%. Non-microphonic 6SN7's are pretty rare, actually. So, I'd say microphonics (at least up to a point) are normal for the tube. IME microphonics are unimportant in the output tubes. It's relatively easy to detect a microphonic tube in the gain stage (right tube). Simply tap on the chassis of the amp (not the tube) and you'll hear it. However, those same tubes in the output stage may not produce any audible response to the tap at all. I've used tubes with microphonic tendencies in the gain stage, and in most cases (but not all) cannot tell a difference between a non-microphonic tube of the same type. However, if there's an option, I'd try and keep a known microphonic tube as an output.

I'm not familiar with the ECC32/33, and would recommend asking Mikhail if the tube is interchangeable. I know that the 5692, often used as a 6SN7 substitute, won't work in my Supra (although it might work in the MPX-3 with its higher plate voltage).

 

[Rob N]

I actually discovered one of my Ken-Rads was slightly microphonic when I turned the volume down to zero and the volume hit the 'end stop',you could hear this is one of the channels.Tapping the chassis made no sound.

I think the only difference between an ECC33 and 6SN7 is the gain?

 

[bobjew]

Received a set of the Sylvania VT-231's last week and have been burning them in. I had been using two CBS Hytrons as outputs and one EH as the gain tube. I think the Sylvanias are almost NOS as they seem to need burn in but burned into the system in only about 5 days. There was an overall improvement in everything with the three VT-231's, but not huge. I had a feeling that rolling was going to be in my immediate future again, but wanted to get a good idea of what the baseline all VT-231 "sound" was like. My first roll was to use two Hytrons as outputs and a VT-231 as the gain. Put'em in and the first thing I noticed was broken in tubes stay broken in; they don't lose it like solid state when power is absent. Cool! They just pick up where they left off. I let everything play and gel for about 4 hours out of superstition, anyway. Despite being in the output position the Hytrons had the most influence in this case. The overall sound went warmer and rounder, the soundstage became less layered, more recessed and less dynamic. The "Wall of Sound" quality of the amp (MPX3) is still there but in a different way. If you just tuned in you would think this is bad stuff, but it's not at all bad. What you get is the most amazing open midrange and highend. Super transparent and with big air and yes, you do still have Bass. The sound is light, ethereal, romantic and beautiful.
The other combination I've enjoyed since last night was to have the two outputs be the Sylvanias and a Hytron as the gain. This combination yielded the best synergy. The sound is equal to more than either tube. This is what I'm keeping in the MPX3 until I get ready to roll in a Ken Rad coming next week. This combo is the very best I've tried so far. Big soundstage, excellent "Wall of Sound", (I need to get some Phil Spector) layers and layers of imaging; very 3D images. Sound can be fast or slow, very good bass, mids, excellent highend detail and dynamics- better than using the VT's and Hytrons by themselves.

I was lucky to have Synergy with me this week.

 

[Hirsch]

Quote:

Originally posted by Rob N I think the only difference between an ECC33 and 6SN7 is the gain?

The u of the ECC33 is 35, while the u of the 6SN7 is 20, indicating higher gain for the ECC33. Most of the other parameters are similar, although it would take a tube expert to decipher them (I don't know enough to make sense, at least not yet).

 

[Hirsch]

Quote:

Originally posted by bobjew I was lucky to have Synergy with me this week.

Yes, it helps. I'm becoming convinced that the final tube combination that will end my tube rolling on this amp may be two different tubes as gain and output. My favorite output tube so far is still the Sylvania VT-231. It reflects the sound of the gain tube, but seems to do so while imposing very little of itself on the sound. While the Ken-Rads are great as a gain tube, and great with each other, you can hear their influence if you try and use them as an output tube with any other brand. Right now, I'm breaking in what could be the best so far:

Tung Sol round plate 6SN7GT: what can I say? This tube in front of a pair of Sylvania's seems to do it all. Exquisite detail, strong bass, glorious midrange and extended highs. The strong points of every other tube I've heard so far, and if there's a weakness I don't know it yet. I've just gotten another pair, and am warming them up as output tubes as I type, so more info will appear once the new ones are broken in. Caution: These tubes cost $$, unless you get very lucky indeed.

 

[Carlos3]

On the subject of mixing 6SN7s, here's an interesting little quote I've taken from a tube dealers' (?) webpage:

Quote:

One thing became clear based on customer feedback, combining 6SN7 types seems to work better than using all 6SN7s of the same type. With so many preamps and amps using this tube, you can end up with Six 6SN7s per channel. It appears combining tubes like the VT-231s as voltage amplifiers and 6SN7Ws or 6SNGTA/GTBs as driver tubes you gain the strengths of all. Using one type seems to accentuate the tube's weaknesses.