DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 18 Oct 2019, 00:23

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 86 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 9  Next
Author Message
PostPosted: 25 Jun 2010, 22:07 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
Just one image of the KT120s in the Be Bamp.
Attachment:
KT120ss.jpg


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
PostPosted: 27 Jun 2010, 07:35 
Offline

Joined: 26 May 2009, 18:51
Posts: 130
Location: Lilburn, Georgia USA
After aging my KT120 quartet on the shelf for almost two weeks and reading about everyone else liking them I must say I am pleasantly surprised at them. Right off the bat they came on almost balanced. Maybe 2 ma off on each pair. And oh yes, more power. I balanced them out and put in a classical CD Swan Lake Ballet by Tchaikovsky. Wow what fine tubes these are. It sounds perfect to me with only 15 minutes on them. To me I can`t tell any difference in Out put transformer impedence. Happy tunes, Robert Parzych


Top
 Profile  
 
PostPosted: 27 Jun 2010, 08:44 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
rparsh wrote:
After aging my KT120 quartet on the shelf for almost two weeks and reading about everyone else liking them I must say I am pleasantly surprised at them. Right off the bat they came on almost balanced. Maybe 2 ma off on each pair. And oh yes, more power. I balanced them out and put in a classical CD Swan Lake Ballet by Tchaikovsky. Wow what fine tubes these are. It sounds perfect to me with only 15 minutes on them. To me I can`t tell any difference in Out put transformer impedence. Happy tunes, Robert Parzych

I just had a very discerning listener here who claimed "this is the best amp you have ever built". We played a balance of classical, pop and opera and finally jazz vinyl from new LPs some from the mid 70s. The KT120s give weight with finesse and can deliver the bass big tine. I’m sold.

_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
PostPosted: 27 Jun 2010, 13:05 
Offline
User avatar

Joined: 14 Feb 2010, 13:13
Posts: 663
Location: Lisbon, Portugal
As you may already read on any of my previous posts, i´m very happy with the EL34´s soudstage (OddWatt).

Though i´m still after some more output power. I´ve been tempted to go for the KT88´s, but there´s an issue...

The tubes will run very close to each other, by 1,5 inch at the most on my chassis ( 4 tubes in line ).

According to datasheets, tube manufacturers suggest much much more space (which i´m not already having with the EL34´s).

So this has been my only concern to swap for KT88´s.

Now I see pictures with KT120 running extremely close to each other.

I don´t have any opinion regarding this issue.

I assume they run quite hot ( EL34´s do! )...

I would like to hear some of your feedbacks! ;)


Cheers,

Miguel


Top
 Profile  
 
PostPosted: 27 Jun 2010, 16:50 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
As you can see from the pictures of my Be Bamp there is a lot of open space around the KT120s. For me it is no issues. I think if tubes are in the open air they should be OK. But I have never considered tube cooling before.

_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
PostPosted: 27 Jun 2010, 16:57 
Offline

Joined: 26 May 2009, 18:51
Posts: 130
Location: Lilburn, Georgia USA
what I can`t stand is this: I ordered and received a quad of E34L JJ blue tubes. This morning I plugged in my new E34L JJ blue tubes and found they were from another planet. 8 to 10 ma out of balance and would not balance at all. What is the deal here? Are the E34L different from the EL34 tubes? I plugged in my four new KT120 tubes and they rule! stay within .2ma at all times. Deadly bass and clear mids and highs. Wow what a tube! Don`t let anyone fool you, these plug right in the place of KT88s and rock! Just try Golden Earring track 5 Are you receiving me. I love it. Robert Parzych


Top
 Profile  
 
PostPosted: 27 Jun 2010, 17:06 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
Bruce found the KT120s very stable too. Indeed some basic tests I did on my Be Bamp should same idle current in both tubes. What other brands of KT120s are out there?

_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
PostPosted: 27 Jun 2010, 17:18 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4031
Location: Arizona, USA
Hi Rparsh, PM me on the details of the JJ 34 bit. Where did they come from? Circuit voltages etc. I have a quad of them and they behave just fine. JJ Blue KT88s, JJ KT77s and JJ 6L6GCs all behave nicely in my amps as well. Most curious. If there is something that is causing them to act poorly then it should be brought to the attention of the diyers. Plus I would like to design it out or at least understand what is happening so I can warn others. The KT120s seem to be great tubes. I'm now working on a design and prototype of an "Oddwatt" that uses them to their full ability. The transformers used in the original projects can not provide the power needed (I tried - they run out of gas) and the outputs should be a higher rating and initially I determined that the impedance ought to be in the 6-6.5K region for Oddwatt use not the 8K of the other amps..

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
PostPosted: 27 Jun 2010, 18:48 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
Your 15w edcors are probably not the best suited for you idle current, they should be gapped closer to 70mA or so. You may want to double check. If you have access a beefier set of output iron, I'd expect you'd get even better sound.


mwhouston wrote:
I have run the tests on the Be Bamp with KT120s. Few supprises and confirmations:


HT+ =400V, idle current =112mA, cathode R =300, bias =34V.

All test done into 6.8ohm 5W resistor (this was a mistake-haha). The reason for 6.8ohms and not 8ohms is my speakers are 6ohms. I figured tests I did with this resistance would come closer to what I could expect to hear in listening.

Lower 3db point =26hz upper 3db point =36khz. My OPTs are Edor open 15W 5K units. Max power was with 23Vpp across the 6.8ohm R. This translates to 9.7W RMS. The reason for the "haha" above is the load R was rated 5W. I touched the resistor to see if it felt like it was disipating close to 10W and burnt my finger - haha! Yes there was definitely 9.7W there - ouch!!

One observation was the 400V HT+ did not sag at max power. It sayed dead on 400V. But my power tranni is rated 175mA on the HT. I'm now pulling excessive current. The power tranni does get very hot. I can still hold my hand on it for a short time so I think it is OK.

The suprise was 112mA idle current. I thought it had not changed from the KT88s at 93mA. But as Bruce has said the current should have been higher for me to see a few extra watts. He was right. With the KT88s I get 7.5W. Just dropping in the KT120s I'm getting a full 2W more in class A SE UL mode. For me that's a good improvement and confirmation of original rough test. I think with the extra power I'm getting better bass control. Definitely but possibly not related, is a better mid-range. With a vocal track I am playing now and have played to death in the past, vocals are much clearer and crisper, snappier!

Image to follow.


Top
 Profile  
 
PostPosted: 27 Jun 2010, 22:38 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
rock4016: Must checkout better OPTs.

_________________
Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 86 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 9  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Majestic-12 [Bot] and 16 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy