{"id":6453,"date":"2017-06-03T13:13:51","date_gmt":"2017-06-03T12:13:51","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=6453"},"modified":"2017-07-08T07:53:33","modified_gmt":"2017-07-08T06:53:33","slug":"2k2m-dhp-test","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2017\/06\/03\/2k2m-dhp-test\/","title":{"rendered":"2K2M DHP Test"},"content":{"rendered":"

\"\"<\/a><\/p>\n

The 2K2M is an unknown directly heated pentode from Russia with has variable mu. I have several pieces of these, and was wondering how useful they could be. This is part of my on-going saga of the “Mule<\/a>“.<\/p>\n

There is not much information around this valve. Here is the data sheet<\/a> and here is in Russian:<\/p>\n

\"\"<\/a> \"\"<\/a><\/p>\n

It is also interesting to read this<\/a> “confidential” report from the CIA about this valve. <\/p>\n

The filaments have low requirements: 2V and 60mA. The maximum anode voltage is 120V and transconductance is about 1mA\/V. Anode current is about 2mA. The internal resistance in pentode mode is about 1M\u03a9 .<\/p>\n

The first test I conducted was in pentode mode, albeit being vari-mu, you should expect a high distortion, H2 in particular:<\/p>\n

\"\"<\/a><\/p>\n

 <\/p>\n

 <\/p>\n

The circuit is simple. A gyrator load with a load resistor (RA) as explained on this post<\/a>. The screen regulator is actually a gyrator PCB <\/a>modified with the addition of a current limiter transistor. The output follower is added given the high anode resistance and limited current drive capability. This was already covered in the previous post here<\/a>. <\/p>\n

So, a simple test was made with this valve in pentode:<\/p>\n

\"\"<\/a><\/p>\n

The minor dip at 1.5kHz wasn’t noticeable in other sample valves. Either way, you can see a nice 56kHz bandwidth for 32dB gain. The gain is set by RA, 68k\u03a9 in our case and the transconductance. <\/p>\n

Let’s see the distortion profile:<\/p>\n

\"\"<\/a><\/p>\n

As expected with a vari-mu valve, the H2 is high. We get 0.33% for 1V, which ramps up to 0.65% for 2Vrms. If you would like to use it as second stage in a RIAA amp, then probably it will add too much H2 distortion in my opinion. <\/p>\n

Now, for a guitar FX stage, this may be an interesting valve in pentode mode.<\/p>\n

Well, what about triode?<\/p>\n

We always need to experiment and see if we can get better performance out of them. Let’s see.<\/p>\n

Wired as triode, the gain is about 16-17. Very nice for a DHT:<\/p>\n

\"\"<\/a><\/p>\n

A lovely 180kHz bandwidth for nearly 24.5dB. Not bad at all!<\/p>\n

Well, let’s see the distortion in triode mode then:<\/p>\n

\"\"<\/a><\/p>\n

Which is very low 0.0081% for 1Vrms output, so for 10V is still below 0.05% which is outstanding:<\/p>\n

\"\"<\/a>the harmonic profile is what we want. Hey, I think we have another candidate for the Mule. I should wire it up and listen to it, hopefully soon.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

The 2K2M is an unknown directly heated pentode from Russia with has variable mu. I have several pieces of these, and was wondering how useful they could be. This is part of my on-going saga of the “Mule“.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[5],"tags":[1042,1043,1044,864,632,1045,6,1039,44,666,789],"class_list":["post-6453","post","type-post","status-publish","format-standard","hentry","category-valves","tag-2k2m","tag-2k2m-pentode","tag-2k2m-valve","tag-bartola-gyrator","tag-bartola-valves","tag-dhp","tag-dht","tag-dht-riaa","tag-gyrator","tag-gyrator-load","tag-riaa"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1G5","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6453","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/comments?post=6453"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6453\/revisions"}],"predecessor-version":[{"id":6463,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6453\/revisions\/6463"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=6453"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=6453"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=6453"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}