[Unison845]

Here is my latest built amp. Another 211 SE (20W), this time using all DHT. Input/Driver is 10Y.

[Freo-1]

Those look great!   
 
Best they sound great, too.

[Guy 13]

Hi Unison845 and all Audio Circle members.
Did you say you built those by yourself?
It is as nice looking as a unit built by a amplifier manufacturer.
A real professional look.
Why use the 211 instead of the 845?
Your name is Unison845 not Unison211.
Looking more closely at the top of the amplifier,
look as if you have used wood, not metal. Is that right?

Guy 13

[Ericus Rex]

Looking more closely at the top of the amplifier,
look as if you have used wood, not metal. Is that right?

Guy 13

Brushed anodized aluminum maybe?

[Unison845]

Yes, it is brushed Aluminum anodized like all my previous amp, wrapped with hardwood. This amp was originally intended for 845 and 211 tubes. Due to low mu of 10Ytube, it takes 2.5vrms for max power with 211, for 845 it will takes around 7vrms. This all DHT tube amp is a pain to build because it needed 3 separate heaters, and regulated for low noise, it tooked a while to finish, but is worth it. It serve as an experiment for couple more exotic amp that is in the work.

[FullRangeMan]

The 845 gain is only 6, the 211 gain is 12 and the great sound 805 tube has a gain of 50.
Indeed low gain is a prob for the builders. These amps are really beautiful.

[DaveC113]

Just saw this thread, thanks for posting your work Unison845!   

I am looking into building a higher powered SET than my EL34 SET amp, but it is not cheap... 

I built an Aikido preamp that uses 6SN7s and has a gain of 10x (20 dB), it drives EL34s without the amp needing a driver stage. This works really well but it is only a 5.5 wpc amp in triode mode. I am curious what output tube / driver combo you would recommend to get 15+ wpc rms when used with the Aikido preamp, the input sensitivity could be in the 10-15V rms range... also, the Aikido has a relatively low output impedance and uses a cathode follower output tube.

[Unison845]

Most DHT has low mu, there is a variety of tube that you can use without any problem driving them, it's just that I want to try the 10Y as input and driver, I built a preamp long time ago using the 10Y and I like it very much,

The 805 even though is a high gain tube, but the problem is you have to use in class A2 + negative feedback. I prefer the pure sound of DHT without negative feedback.

The 845 gain is only 6, the 211 gain is 12 and the great sound 805 tube has a gain of 50.
Indeed low gain is a prob for the builders. These amps are really beautiful.

[Unison845]

For a 15W, I definitely recommend the 6C33C SE, on page 4, the second amp picture from top is the 6C33C SE that I have built. This is a great sounding tube, it does not have the midrange purity of DHT 845/211/212... , but it sounded so coherent from top to bottom, very clean. For an amp to sound better than the 6C33C, you will have to spend quite a large amount of money for a good pair of output/interstage transformer, then even more for the tubes! The rugged 6C33C tubes at less than $40, is the greatest bargain of all time!

Just saw this thread, thanks for posting your work Unison845!   

I am looking into building a higher powered SET than my EL34 SET amp, but it is not cheap... 

I built an Aikido preamp that uses 6SN7s and has a gain of 10x (20 dB), it drives EL34s without the amp needing a driver stage. This works really well but it is only a 5.5 wpc amp in triode mode. I am curious what output tube / driver combo you would recommend to get 15+ wpc rms when used with the Aikido preamp, the input sensitivity could be in the 10-15V rms range... also, the Aikido has a relatively low output impedance and uses a cathode follower output tube.

[FullRangeMan]

Most DHT has low mu, there is a variety of tube that you can use without any problem driving them, it's just that I want to try the 10Y as input and driver, I built a preamp long time ago using the 10Y and I like it very much,

The 805 even though is a high gain tube, but the problem is you have to use in class A2 + negative feedback. I prefer the pure sound of DHT without negative feedback.

Unison: Congratulations for your beautiful amp, built a tube amp is not for anyone.
Iam able to do only the wood chassis and stock parts, the difficult work is assembly and testing the unit.

Of course Class A2 is not good.
I feel the 805 in Class A2 is necessary only for hi power over 30/40 output Watts.
This is correct??

[FullRangeMan]

For a 15W, I definitely recommend the 6C33C SE, on page 4, the second amp picture from top is the 6C33C SE that I have built. This is a great sounding tube, it does not have the midrange purity of DHT 845/211/212... , but it sounded so coherent from top to bottom, very clean. For an amp to sound better than the 6C33C, you will have to spend quite a large amount of money for a good pair of output/interstage transformer, then even more for the tubes! The rugged 6C33C tubes at less than $40, is the greatest bargain of all time!

Great post, I have this question in mind for years, Thanks for informing us.

Iam a fan of the 6C33, GM70 and 805. The 6C33 OPTs are not expensives, I like this tube especially for its low impedance, metal plate and ready avaliable hi quality sockets at low prices.

I also read good talk about the 6C33 treble and the bass is notoriously powerful.
The 6C33 & GM70 are cheap tubes, the 805 are rare and expensive.
So the way to go for a powerfull SET is only 6C33 or GM70, IMO.

[Unison845]

The 6C33C is a very low Rp tube so the output transformer design can have very wide bandwidth, the plate is graphite by the way. The GM70 is also a great sounding tube that can compete head to head with the 845, but for a fraction of the price at less than $50 a piece, the GM70 amp is harder to build since the required voltage is about 5 times the 6C33C.
So save your money on these Russian tube and spend as much as you can for the power/interstage transformer, you will end up with a nice sounding amp.

By the way, I like the 6C33C tube so much that I built a tri-amp system, with 6 dedicated 6C33C amp with built active xover, the system sounded spectacular.

Great post, I have this question in mind for years, Thanks for informing us.

Iam a fan of the 6C33, GM70 and 805. The 6C33 OPTs are not expensives, I like this tube especially for its low impedance, metal plate and ready avaliable hi quality sockets at low prices.

I also read good talk about the 6C33 treble and the bass is notoriously powerful.
The 6C33 & GM70 are cheap tubes, the 805 are rare and expensive.
So the way to go for a powerfull SET is only 6C33 or GM70, IMO.

[FullRangeMan]

Why do you like so much interstage transformers in your amps??
Any sound quality relation??

[DaveC113]

Thanks for the rec, I was thinking GM70 but will certainly check out the 6C33C, I had not considered that tube before.

In your 6C33C amp, what are you using for a driver tube and what did the input sensitivity turn out to be? Can I ask how much you spent on your 6C33C and GM70 amps? My projects are modest in comparison, but I still spent A LOT of cash on parts, nearly $1k each for the Aikido and EL34 SET.

[FullRangeMan]

Thanks for the rec, I was thinking GM70 but will certainly check out the 6C33C, I had not considered that tube before.

In your 6C33C amp, what are you using for a driver tube and what did the input sensitivity turn out to be? Can I ask how much you spent on your 6C33C and GM70 amps? My projects are modest in comparison, but I still spent A LOT of cash on parts, nearly $1k each for the Aikido and EL34 SET.

GM70 OPT are expensive, same for a good socket(Yamamoto or Kara Chaffe):
http://www.tubewizard.com/tube_sockets.htm
Stay away from this crap socket:

[Unison845]

There are many advantage with intertstage transformer.
- Capacitor coupled measured better but interstage sounded so much better, the most obvious is from the bass to the midrange. I have not tried the expensive capacitor in the market (the silver and other outragously priced cap).
- With capacitor coupled the driver stage need almost twice the voltage to get the same output swing.

The ony thing is you want to get the interstage that has better bandwith than your output transformer, if not it will be the limiting factor to your amp sound.

quote author=FULLRANGEMAN link=topic=68194.msg1231491#msg1231491 date=1370560790]
Why do you like so much interstage transformers in your amps??
Any sound quality relation??
[/quote]

[Unison845]

I used the C3G tube, in both triode and pentode mode, the sensivity is about 1.5Vrms, in pentode mode the input need ony about 0.5Vrms if I remember corectly.

The GM70 is much more expensive to build, and it depends on the transformer, you can spend as much as three thousands for just a good set of interstage/output transformer. The 6C33C you can get pretty good sound without interstage, so it will cost much lower, also lower voltage parts are much cheaper.

Thanks for the rec, I was thinking GM70 but will certainly check out the 6C33C, I had not considered that tube before.

In your 6C33C amp, what are you using for a driver tube and what did the input sensitivity turn out to be? Can I ask how much you spent on your 6C33C and GM70 amps? My projects are modest in comparison, but I still spent A LOT of cash on parts, nearly $1k each for the Aikido and EL34 SET.

[FullRangeMan]

There are many advantage with intertstage transformer.
- Capacitor coupled measured better but interstage sounded so much better, the most obvious is from the bass to the midrange. I have not tried the expensive capacitor in the market (the silver and other outragously priced cap).
- With capacitor coupled the driver stage need almost twice the voltage to get the same output swing.

The ony thing is you want to get the interstage that has better bandwith than your output transformer, if not it will be the limiting factor to your amp sound.

quote author=FULLRANGEMAN link=topic=68194.msg1231491#msg1231491 date=1370560790]
Why do you like so much interstage transformers in your amps??
Any sound quality relation??

Thanks Unison for your expert advise. Much more clear now.

[J-Pak]

What interstage/OPT are you using in the 10y/10y/211 amp?

I am thinking about a 801A/211 amp (with input transformer) and was considering Tribute iron.

[Unison845]

I used Tango NC15 (the white one on the right) , mounted underneath the chassis.

I dont want to use input transformer because you will need a preamp with 600 ohms output. Also good quality input transformer is expensive.

What interstage/OPT are you using in the 10y/10y/211 amp?

I am thinking about a 801A/211 amp (with input transformer) and was considering Tribute iron.