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

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PostPosted: 31 Jul 2010, 07:19 
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Cold Macaroni wrote:
I was thinking really hard about a SE 300B design, but I don't think I'm quite ready to appreciate one of those yet.

Hi. Nice build. I have only two tube amps under my belt, a KT88 oddwatt and a 300B SE.

If you want lots of clean, undistorted power for rock music, build the oddwatt using KT120s and 50 watt OPTs. You WON'T be disappointed.

The 300B amp is only going to give you 8 watts or so of clean power per channel, the oddwatt KT120 up to 40 watts/channel. The 300B is a great amp, but unless you have very efficient speakers, OR, you offload the bass to a subwoofer to reduce the power demands on the 300B you just simply won't be able to get a lot of volume.

The nice thing about the 300B is the "graceful" distortion. It compresses before it distorts audiby, and it has a very rich, warm, full sound. What your actually hearing is a lot of 2nd order harmonic distortion, but under 8 watts or so you won't perceive it as distortion as most people think of it. If you like classical or acoustic music it's great, but for rock, go with the oddwatt.

Just my observations having listened to both now for an extened period. I wouldn't part with either. Even better idea - build both at the same time like I did. :headphones:

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PostPosted: 31 Jul 2010, 07:41 
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sampleaccurate wrote:
Cold Macaroni wrote:
I was thinking really hard about a SE 300B design, but I don't think I'm quite ready to appreciate one of those yet.

Hi. Nice build. I have only two tube amps under my belt, a KT88 oddwatt and a 300B SE.

If you want lots of clean, undistorted power for rock music, build the oddwatt using KT120s and 50 watt OPTs. You WON'T be disappointed.

The 300B amp is only going to give you 8 watts or so of clean power per channel, the oddwatt KT120 up to 40 watts/channel. The 300B is a great amp, but unless you have very efficient speakers, OR, you offload the bass to a subwoofer to reduce the power demands on the 300B you just simply won't be able to get a lot of volume.

The nice thing about the 300B is the "graceful" distortion. It compresses before it distorts audiby, and it has a very rich, warm, full sound. What your actually hearing is a lot of 2nd order harmonic distortion, but under 8 watts or so you won't perceive it as distortion as most people think of it. If you like classical or acoustic music it's great, but for rock, go with the oddwatt.

Just my observations having listened to both now for an extened period. I wouldn't part with either. Even better idea - build both at the same time like I did. :headphones:

Thanks for the perspective.

The K12g is is only rated at 8 watts itself, and I'm running it in UL mode now (I'm told this brings power down a tad, though I haven't measured before or after). The K12g amp with the speakers I have are a pretty good match for my apartment (power/volume wise), so if I can get a solid 8 watts out of a pair of SE 300Bs, I may go that route anyway.

How well do your 300Bs do with bass and heavy-handed guitars and drums under 8 watts? I have a lot of acoustic and "mellower" music I listen to, but I also have a bunch of Foo Fighters and The Who (plus the odd Metallica track, among others).

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PostPosted: 31 Jul 2010, 08:30 
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Cold Macaroni wrote:
The K12g is is only rated at 8 watts itself, and I'm running it in UL mode now (I'm told this brings power down a tad, though I haven't measured before or after). The K12g amp with the speakers I have are a pretty good match for my apartment (power/volume wise), so if I can get a solid 8 watts out of a pair of SE 300Bs, I may go that route anyway.

How well do your 300Bs do with bass and heavy-handed guitars and drums under 8 watts? I have a lot of acoustic and "mellower" music I listen to, but I also have a bunch of Foo Fighters and The Who (plus the odd Metallica track, among others).

If you keep it WELL under 8 watts the 300B will sound punchy and clean on drums and bass, but again it must be well under the maximum power before perceptible distortion occurs. It's definitely not 8 watts of punchy power. If you push it on the Foo Fighters (Everlong, Learn to Fly) the bass is a little "flabbly" and the drums will sound compressed. Your taste will dictate whether you like it. 8 watts of SE power isn't the same as 8 watts of push-pull power based on my listening experience. The PP will give better definition and uncompressed bass and drums than the same power SE amp. You may however find the compression and the "harmonic enhancement" that the 300B gives very pleasant on the mellow and acoustic stuff. I do. I like classical, and on strings such as violins I think the 300B sounds awesome. I just wish I could crank it up. I'm almost tempted to tap the output of the 300B and feed it into my oddwatt just to get the rich, slightly compressed but very pleasing sound at a higher volume level. You might be able to achieve the same effect with a triode preamp feeding an oddwatt (much cheaper!).

Just my 2 cents.

Here are my "babies" side by side:
(sorry about the mess)

Image

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PostPosted: 31 Jul 2010, 09:26 
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I was thinking about one of the dual triodes for the preamp section (6sn7 or 6sl7), is that what you're talking about? Or are there any recommended single triode preamp tubes?

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PostPosted: 31 Jul 2010, 10:57 
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sampleaccurate wrote:
I just wish I could crank it up. I'm almost tempted to tap the output of the 300B and feed it into my oddwatt just to get the rich, slightly compressed but very pleasing sound at a higher volume level. You might be able to achieve the same effect with a triode preamp feeding an oddwatt (much cheaper!).

DO IT!!!!! Let us know how it turns out :)

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PostPosted: 31 Jul 2010, 11:58 
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Cold Macaroni wrote:
sampleaccurate wrote:
I just wish I could crank it up. I'm almost tempted to tap the output of the 300B and feed it into my oddwatt just to get the rich, slightly compressed but very pleasing sound at a higher volume level. You might be able to achieve the same effect with a triode preamp feeding an oddwatt (much cheaper!).

DO IT!!!!! Let us know how it turns out :)

I just might. With a dummy load and a resistive divider or a matching transformer It would be easy to do. It would be one heck of an inefficient preamp, but I'll bet it would sound good. I could drive the 300B as easy (for clean punchy sound) or hard (for compression and harmonics) as I wanted to then feed the oddwatt to amplify it to thunderous volume levels. I live in a house that's surrounded by brick walls so I can crank it up as loud as I want to.

I use a 6SN7 to drive the 300Bs. Don't know if a 6SL7 would do the job, but the 6SN7 or even a Russian 6H8C equivalent works great. Actually the 300B was easier to build than the oddwatt. Simpler circuit. I used the same one that's posted on this website.

Another alternative (this is what I do) is to use the 300B only for midrange and treble and use a powerful SS subwoofer. Purists would shun this approach, but IMHO it sounds fantastic.

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PostPosted: 01 Aug 2010, 03:35 
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You have me keen to do a 300B. After the delightful results of my 6AS7 (6080) SET tube amp I am extremely keen to investigate other SET. All that is mystic about SET is true - or so I have found.

I am planning a ATS-25 (807) / 6SN7 SET (designed by Suncalc) which hopefully will give me a different sound to the 6AS7 (6080). A 300B version should give me another variation on the theme.

Also the two images of amps are very nice. Good build. Nice to see craftsmanship rather than some tubes plonked on a metal chassis.

sampleaccurate: I love the 6SN7 as a driver tube. I think this is very under-rated and cheap tube for preamps and driver stages. I have only used the 6SN7 as a driver but may use the same cct. as a preamp (can't see why not). Will post any results.

Also I would never bi-amp with different amps but see no issue with a powered sub.

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PostPosted: 19 Aug 2010, 12:38 
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Hi, Sorry, I've been a bit tardy with looking at the forum this month. In answer to an earlier question -Sierra Vista, Bisbee is just over the hill. PM me if you want to chat about old or future times.

I always like to give credit when due, and the S-5 Electronics K-12 tube amp kit is a great starter project and fun to tinker with. It has always been short in the bass area, but rather nice in the mids and top range. As a basic kit the price is right. Again welcome to diy audio.

Good listening
Bruce

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PostPosted: 19 Aug 2010, 14:50 
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Cold Macaroni wrote:
I ordered a copy of SE amp CAD. I thought I'd play with it a little before I started building.[/url]

I just browsed your post. Funny thing...this morning I started a thread about some board design software. I never tried SE amp CAD, but did try some others. They hurt my brain.

Please let us know how the CAD program works.

And thanks for trying out the Edcors. You saved me some $$$! I'll also go with the three 300uF caps instead of the 220/100/22uF that the schematic shows.


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PostPosted: 19 Aug 2010, 17:04 
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Gio: If you use the OPTs with the K-12 kit you would probably suffer bass constipation. As you know on one of my three K-12 tube amp kit builds I used Big Hammond OPTs (still have this one amp-other two sold years ago). A lot better with the bigger and better OPTS. A pair of Edcors would work just as well. Its an easy upgrade even for the beginner. When I bought the last few of my K-12s from S5 I ordered without OPTs. They did back then provide parts of the kit. Not sure they still do it.

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