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 15 Jun 2019, 18:36

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 247 posts ]  Go to page Previous  1 ... 17, 18, 19, 20, 21, 22, 23 ... 25  Next
Author Message
 Post subject: Re: 6EM7 power amp
PostPosted: 04 Nov 2013, 04:37 
Offline

Joined: 24 Feb 2009, 03:24
Posts: 562
Location: USA
...."Ceramic resistors can include the metal-oxide types, which are excellent sounding..... like the Yageo SQP or NSP types :D".....But this res. is that You don't like, Geek....Cheap From ChinaTown.... :)

_________________
Hi End is back proportional to the number of composite parts!
Projects: OTL 6AS7 Gen, Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, PP 6005 Gen. Ellectric , headphone ampl. OTL Loftin White 6AS7 RCA....SE E84L& E80CC Siemens&Tel-n.
http://azazello-sound.blogspot.com/


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 04 Nov 2013, 06:05 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
I judge by my ears, not "country of origin" ;)

I actually had a client come back asking me to pull the Dale power resistors for Yageo's.... he never asked me to pull the Yageo.

To each their own :up:

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 04 Nov 2013, 20:15 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5104
Location: Australia
http://retro-thermionic.blogspot.com.au/2013/11/abstinence-6em7-power-amplifier.html There are a few words here about the new amp.

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


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 05 Nov 2013, 17:34 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5104
Location: Australia
I received a lot of comments on other forums about the fact I used a motor start as first cap in the PS. One member claims he has had them explode after 150 hours and strongly suggested I remove the cap. Since I cannot use the Sophia Electrics rec tube I wanted I have replaced the troublesome cap with two 47uf\450V electros in series for better than 20uf. I have snubbed this cap also.

This amp was dead quiet before. As I stated on another forum pressing my ear into either driver of my moderately efficient two ways there is a BIG FAT NOTHING. I thought The Silver Dragon quiet with it all polypropylene filter caps but this amp takes the cake. Am yet to try it on HPs.

I tried an old Australian made 5U4GB as the rec tube. Firstly it produce the HT is seconds and secondly the HT rose slightly. The 5Y3 I am using takes about 5 seconds or more to slowly bring up the HT. This gives the 6EM7 a few seconds to start to warm before being hit with near 280V. Yes the HT is up a bit but I think it is OK. Any comment? Bias on the power triode is 32V. Each power triode is carrying 42mA. Total current draw for the amp is 98mA.

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


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 08 Nov 2013, 18:30 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5104
Location: Australia
I put Abstinence under CRO:

Frequency response:10hz < -3db > 22Khz (this is a little low. Most of my builds do better than 30kz with some power amps hitting over 50kHz)
Power (max): 1.6W RMS (@1khz into 8.2ohms resistive load) I would have thought more as this amp sounds loud. Louder than Arabella. @10khz 2.28W RMS showing the limit of the cheap OPTs
Power into 4.7ohms: 1.2W
Power into 15ohms: 2.28W again showing up the OPT.
The upper frequency limit remained constant at low power or higher power outputs
Slight imbalance in the channels R:10.5V L:9.69Vpp a 7% difference. Not sure I would hear this difference. I would have liked them closer. In the past I have swapping the tubes with each other which can provide a better balance. I'll try it.
Noise (inputs shorted): R 1.2mVRMS, L 0.6mVRMS. You can hear absolutely nothing at the speakers. Easy to see why.
The 100hz and 10khz SQR wave responses are poor and the 1Khz response has a slight slope down. Other 6EM7 amps have tested better. Once more the cheap OPTs and letting down test measurements. There is no ringing though.

I spent 6 hours straight listening to Abstinence last night and it sounds so much better than it tests. Sibilance is well controlled but not perfectly controlled as with earlier builds. More "SSS" then "SSH" but once more the limits of the OPTs are apparent. Amp plays my small 2-ways to their lower limit. With a test CD good volume at 40hz and you can just hear it starting to roll off at 50hz. My stereo sub-woofers pickup the bottom end and extend it down to 31hz so I'm not fussed. But by themselves the amp drives well down to 50hz. Easy amp to listen to and I enjoyed every second of my 6 hours of listening last night. The amp and music got me emotional on three separate occasions. Can't be too bad then.

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


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 08 Nov 2013, 19:05 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5104
Location: Australia
Swapping the tubes and testing at the Xover (external) to the speakers firstly I read 2V (analogue meter) at the right speaker and 1.9V at the left @1Khz from test CD. This agrees with test bench measurements into 8.2ohms. Swapping the tubes and bring the right up to 2V I then read 2.2V of the left. Easy to see one tube (originally right tube) has more gain than the left tube. Also swapping the tubes has made the problem worse. Time to swap them back and get some more Sylvania 6EM7s.

A difference of 0.1V in 2V is 5%. I know my ear would never pick that up. So maybe I'm not to worried.

On a retest the difference was probably closer to 0.2V in 2V. About 10%. Should I chase it or leave it?

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


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 08 Nov 2013, 21:57 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1583
Location: US Pacific Northwest
mwhouston wrote:
On a retest the difference was probably closer to 0.2V in 2V. About 10%. Should I chase it or leave it?
Excessive analytical tinkering can kill the emotion in an amp. IMHO. I'd leave well enough alone. But that's just me.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 09 Nov 2013, 01:50 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
Suncalc wrote:
mwhouston wrote:
On a retest the difference was probably closer to 0.2V in 2V. About 10%. Should I chase it or leave it?
Excessive analytical tinkering can kill the emotion in an amp. IMHO. I'd leave well enough alone. But that's just me.


x2 this sentiment.

10% is quite fine :D

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 09 Nov 2013, 19:19 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5104
Location: Australia
Geek wrote:
Suncalc wrote:
mwhouston wrote:
On a retest the difference was probably closer to 0.2V in 2V. About 10%. Should I chase it or leave it?
Excessive analytical tinkering can kill the emotion in an amp. IMHO. I'd leave well enough alone. But that's just me.


x2 this sentiment.

10% is quite fine :D

This is fine by me and I feel better that others are not fussed also. I really don't want to purchase more tubes as part of the reason to build this amp was to use the last pair I have. I had two pair but the guy who purchased Paris wanted a spare pair and I think this is wise, it is now his main amp.

Thanks for the input.

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


Top
 Profile  
 
 Post subject: Re: 6EM7 power amp
PostPosted: 13 Nov 2013, 03:34 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5104
Location: Australia
Just a look underneath. Three gold solid brass cones. The bottom plate is recessed so just the last half of the cones are visible giving the impression the amp is floating. And yes I spray my bottom plates.
Attachment:
Bottom.jpg
Attachment:
AbstinenceIV.jpg


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


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


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 247 posts ]  Go to page Previous  1 ... 17, 18, 19, 20, 21, 22, 23 ... 25  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users 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