SET amp owners thread

[Blue58]

What's the feeling regarding SET designs implemented with only a single output tube, compared to so many SETs using multiple output tubes in parallel to provide more power? Seems intuitive that running multiple tubes in parallel eliminates some of the simplicity and purity that a single tube output would offer, but I'd be interested in hearing other opinions in this regard. TIA and happy new year to all!

Single tube SETs can be designed for that sole tube with all its parameters taken into account. No two tubes are alike so you can bet that in a push pull amp one tube is reacting differently to the other. Similarly parallel single ended. If you want purity then one output tube is the way to go.
However, we still have the problem where the left channel doesn’t exactly mirror the right channel. We can get close but it’s impossible IMHO.

 

[Tango]

Christoph also had some angle
View attachment 47014

Nah nah. Christoph has the wisest comment but still not the angle.

Kindest regards,
Tang

 

[christoph]

Nah nah. Christoph has the wisest comment but still not the angle.

Kindest regards,
Tang

I cautiously said "some" angle.
I wouldn't dare to say I have "the" angle (at least not with that snapshot)

 

[bonzo75]

Single tube SETs can be designed for that sole tube with all its parameters taken into account. No two tubes are alike so you can bet that in a push pull amp one tube is reacting differently to the other. Similarly parallel single ended. If you want purity then one output tube is the way to go.
However, we still have the problem where the left channel doesn’t exactly mirror the right channel. We can get close but it’s impossible IMHO.

He is asking about high powered amps. There is only one single tube amp not too well known on this forum that does that. So other single tube purity comments are too general where there are one or two such examples

 

[Blue58]

Here’s one of my little babies. Direct coupled ie. no cap, no choke and no Interstage, just three inches of Ag/Au wire between driver and output tube (EML 45 V4 Globe) with Electraprint partial silver output transformers.

 

[Steve Williams]

Single tube SETs can be designed for that sole tube with all its parameters taken into account. No two tubes are alike so you can bet that in a push pull amp one tube is reacting differently to the other. Similarly parallel single ended. If you want purity then one output tube is the way to go.
However, we still have the problem where the left channel doesn’t exactly mirror the right channel. We can get close but it’s impossible IMHO.

So my question to everyone is that if a tube goes in one channel do you replace just it or do you replace the same tube in the other channel as well or do you rely on buying from someone who will provide a perfectly matched tube to the other channel

 

[CGabriel]

Hi Caelin, as an aside, I am really looking forward to your views on the Quintet vis a vis the DeVore and the Volti.

Cheers

Both the Devore, Vittora and the Harbeth for that matter, are very well worked out products that have been optimized by their respective designers. So they are in a different class than a kit speaker with many moving parts and options. So, the PAP needs to be tweaked out with work on the crossover, wiring, baffle materials and footers. That is a lot of time and energy to invest but the good news is that the HORN1 mid/tweet is obviously exceptional. The key will be to get the bass section to integrate seamlessly with the horn. In its current state the bass section is a step behind and a bit wooly to fully match the horn. Nothing major and not unlike many speakers that mate a dynamic driver to a horn. So, we are designing a different baffle and support frame to stiffen it up. And we may make the baffle a bit wider to reduce front to back cancellation. We have already improved the crossover by using point to point wiring, bypassing the supplied PCB. This made a very substantial difference.

 

[bonzo75]

What do you think is the minimum power requirement for vittora? Also, roughly a 7m x 5m room can work or is bigger required

 

[audio.bill]

He is asking about high powered amps. There is only one single tube amp not too well known on this forum that does that. So other single tube purity comments are too general where there are one or two such examples

I wasn't asking about high powered amps, but was just curious to learn what others here think regarding a single output tube SET vs. parallel designs. Obviously multiple output tubes in parallel provide more current and power, but wondered about the trade offs such implementations incur. Thanks for your feedback so far!

 

[Steve Williams]

I wasn't asking about high powered amps, but was just curious to learn what others here think regarding a single output tube SET vs. parallel designs. Obviously multiple output tubes in parallel provide more current and power, but wondered about the trade offs such implementations incur. Thanks for your feedback so far!

One output tube does it for me in my system

 

[Believe High Fidelity]

I wasn't asking about high powered amps, but was just curious to learn what others here think regarding a single output tube SET vs. parallel designs. Obviously multiple output tubes in parallel provide more current and power, but wondered about the trade offs such implementations incur. Thanks for your feedback so far!

Trade off is more on the heat dept than anything. I have used a number of the Aries Cerat SET amplifiers and the Diana Forte parallel SET runs exceptionally hot. Sound quality is amazing though. You would be hard pressed to tell the difference from single tube SET amps

 

[Believe High Fidelity]

So my question to everyone is that if a tube goes in one channel do you replace just it or do you replace the same tube in the other channel as well or do you rely on buying from someone who will provide a perfectly matched tube to the other channel

Just replace them rather than trying to find one to match the existing one.

 

[Steve Williams]

Just replace them rather than trying to find one to match the existing one.

Seems logical but not everyone does this

 

[microstrip]

Single tube SETs can be designed for that sole tube with all its parameters taken into account. No two tubes are alike so you can bet that in a push pull amp one tube is reacting differently to the other. Similarly parallel single ended. If you want purity then one output tube is the way to go.
However, we still have the problem where the left channel doesn’t exactly mirror the right channel. We can get close but it’s impossible IMHO.

I was not addressing push- pull amplifiers , but tubes in parallel - this is a SET thread!

When you replace the tube the other tube, even of the same brand , the tube is not exactly the same but still sounds the same. Saying "similarly" is this case is like explaining that an helicopter can fly comparing it with a fixed wing aircraft.

 

[microstrip]

So my question to everyone is that if a tube goes in one channel do you replace just it or do you replace the same tube in the other channel as well or do you rely on buying from someone who will provide a perfectly matched tube to the other channel

You should use well matched tubes in both channels, particularly in SETs that are commonly feedback free. Otherwise you will probably have gain imbalance.

Most of the time when people swap tubes gain changes - unless we electrically calibrate the system the preliminary impressions are just caused by the difference in output level.

 

[microstrip]

So my question to everyone is that if a tube goes in one channel do you replace just it or do you replace the same tube in the other channel as well or do you rely on buying from someone who will provide a perfectly matched tube to the other channel

Being away from tube sources I usually ask manufacturers to supply me three (or five ) matched tubes ...

 

[DaveC]

I finally got around to cleaning my system's electrical contacts, so I took some pics!

First pic is my preamp, LDR w/ Aikido buffer. Next one will use silver Slagleformers and DHT tubes with same circuit. The Aikido circuit uses a triode as a plate load for the amplifying triode, which acts as an error correction circuit as distortions and the tube's "character" are reduced as the plate load is opposite vs the amplifying triode. This depends on the triodes being matched so a pre using 4 DHTs would need all 4 matched. This isn't unique as White follower and others are similar, the Aikido also nulls PS noise at the follower output.

2nd pic is my voltage gain stage using 6SL7 and 6SN7 USSR military tubes. It was an Aikido preamp but it's been changed to a driver for the amplifier. I've experimented a lot with driver circuits and think they are key and often the weak point of a tube amp and the cause of a lot of the slow, syrupy sound some associate with tube amps. This driver is seriously amazing! None of the knobs do anything anymore.

Last pic is my amp running Sophia EL34 tubes and a Japanese 5AR4 rectifier. It has negative voltage gain on it's own, so it must be used with the driver component. It started life many years ago using a PCB w/ CCS loaded driver, hence the empty hole... I never got it to my standards with the included driver circuit, CCS loaded or not. Now it's PtP wired with a CLC PS using a custom Electrprint choke, and all Clarity TC series film power supply caps, no electroytics at all. James OPTs.

 

[Kcin]

So my question to everyone is that if a tube goes in one channel do you replace just it or do you replace the same tube in the other channel as well or do you rely on buying from someone who will provide a perfectly matched tube to the other channel

Depends on the tube and I'm talking power tubes here. If you have a stash of easily attainable tubes that can effectively be matched for grid voltage and cathode current with the equal transconductance ...then yes one tube can be changed. This is most plausible for new production tubes because you have a population to choose from.

With NOS tubes it becomes more difficult as you don't necessarily have a population to choose from .. you have scarce stock if you will and just pulling one off of ebay isn't going to work. So then you go to your stock of matched pairs you previously bought from your dealer and replace the pair and you end up with an orphan.

Either way, you have a dealer that has matched the stock for you or you have the equipment to do it yourself.
For small signal tubes its is not as critical and the only real parameter that matters is noise and that takes patience and some sort of circuit to listen to the tube. Matched sections here are usually obsessed over unnecessarily. I'll take a mismatched section tube any day that is quiet over a matched section tube that is noisy. YMMV and all that. The VTV analyzer does a good job on section matching and noise analysis

 

[audioquattr]

Wow, nice job Dave!
What feets are you using, also a tweaked part?

 

[morricab]

Chris - forgot to mention. There is likely a lot of potential in your Air Scouts imho. So it would be worth doing a “project”

I told him the same thing back when he bought them