Tea-Bag

I like photo 18. Very nice.

Generg, what does your BJ2 look like now?Sorry been off list for some time. Shamefully I removed R100's I had from BJ2 to try J2R1 looking thing and caught one of pair on fire.So had to get some more. It's on the short list now.I am considering throwing in a 22v tranny instread to take adjantage of cascode as AR2 did. Matters not too soon. Hot as pavement over here right now. no Listening.

Well, found two more round one's. I couldn't help myself.Any more thoughts ZM on this science project? Some SiC Fet owners are getting fussy and uncreative that they don't have anything to build with them. : to_become_senile:

It's okay I guess. Health is okay, just work and housework have been over the top lately.Alway's want to do more than I have time or energy for.

I've gotten more mileage on the F2J lately, the sound stage is much more solid now, and the setup very relaxed. I am liking it.BJ2 is sorta on the bench, trying to make revA alterations, but have been away from the bench for a bit.

No way, you cant really finish....Was J2 rev0, rev1, BJ2?My Brain is thinking about F3 likeish amp, without cascode, for R085.ZM - did you drop Susy SemiSouth idea?

I had some help! and thanks!Yes, Lowthers in Open Baffles, 200hz on up I guess, ran them without a low-pass x-over. This time I was using the DX4's (not PM5As) which are a bit more clinical, and harder to tame. No added Tweeter which I normally use.People may not like lowthers, but they are all I know since started using them in 1998. I liked the fact back then they made your ears bleed when Miles blows his horn. They are a bit tamer now. The PM5As need no notch filter. They have no hi-ferric and copper voice coils. I got them, used, and they didn't come without problems.I've done open baffle for 2-3 years. Before that BLH, but it couldn't fill room well in Living/Dining area room 35 x 20. I have no listening room. In old house I did, but in USA, everyone was buying selling houses in the last decade - making or losing lot's of money.

The BJ2 is supringly easy on the ears. I didn't suspect this Should be F2J. edited your previous post according to that ZM btw . YGM

Okay, so here are some observations. Only somewhat based in reality, as all systems are different, and my BJ2 is not built anymore to spec.Listening MaterialHerbie Hancock - Possibilities - Track with Paul SimonHerbie Hancock - Gershwins World - SummertimeHerbie Hancock - Joni Letters - The Jungle Line (sung by leonard cohen)Alison Krauss - A collection - Get me through DecemberAlison Krauss - A collection - Jakobs dream.AmpsF2J, per Nelsons recommendations, Biased at 12vBj2 - specs aboveI listened to the same tracks on both amps, trying to be objective about the whole thing. These albums seem decently recorded to my ears, and are not produced to sound too warm like some T. Bone Burnett stuff.BJ2:Pros: Wide, precise soundstage, dynamic. Really smooth upper end of female voices like Alisons. No midrange bloom, but I think this is a good thing. It does not sound like a tube amp. It sounds like R100 in other circuits in general. Clean mids and top end. (below 120hz, another amp.). This amp might be a hair mellow only if comparing to F5 amp.Cons: Soundstage depth is a bit 2D, or missing a bit of front to back location of sounds. I think the F5 did this better.F2J: Pros: excels at detail, more depth to soundstage, but 'imaging' or where stuff is, is more vague and sounds more like two speakers at times , - but this is relative to BJ2. Imaging is not bad, just not as good.You can pick up say guitar plucks and decay with a bit more precision on the F2J.Cons: Well, you got to play with the sideways notch filter. Less wide soundstage, and less dynamic punch. The ambient detail seems to be less. If you want more precise detail, this may be the amp. Things will jump out at you. Is you listen at 90db like I often do, then it loses steam and distorts. Top and Bottom are not as refined. Not as silky as the BJ2.Conclusions: well, I might change my mind later - so that's not a good way to start it.The F2J is supringly easy on the ears. I didn't suspect this. The inner detail at times is great. It's flaw is soundstage precision and range of punch over the whole spectrum isn't the same as BJ2. The BJ2's statement sound in this configuration is great vocals. Best I have heard. It has a broad paintbrush and uses it to it's advantage to give a good musical performance. The way I like the R100's to sound is clean, and not bloomy or fat. It's not these things. If you want it to sound like a old dynaco, or super-warm - this isn't the way to go. These amps are both crisp and detailed and fun to listen to.

sp300,How would you describe the sound of your setup?Do you get similiar results?

Why? - you thinks it's as good as it can get?A bit back, someone suggested biasing down a bit.I will give it a good listening session this wednesday.My F2J is up and running , so some comparisons will be done.

Okay, got the offset problem under control - I think. Looks like the bf245 may have been shorted with the leads touching under the pcb. I am further exploring source resistance mods. R22 .47R R29 1R .620v R36 1R 1.0v R30 1R R37 .47R .500v R31 .47R The amp now runs quite hot, with sinks at 52c. Once warmed up, the sound gets more relaxed and softer, but still has a dynamic punch to it. The soundstage now seems well focused now.

Zen Mod, Did you take a look at the measurements I sent to your geemail account?I too find the source resistor changes a thing for the better. Less aggressive sounding, a bit more relaxed.Not that some will believe it, but it sounded better after about 20 hours of listening. More champagne sound and smoothness.Not in a rush on this. But if I want to take cap off fullranger I want to get the offset lower.

ChangesR2, R21, R24 4.7kR25 500R PotR26 390R22 .47RR29 1RR36 1RR30 2RR37 .47RR31 1RThe new values are below the orange higlights if they changed. The last swap was only on R25,R26.current offset in the channel .5v runs steady at least. Other channel is .01v and is stready.Listening right now. The above channel runs at ~ .6v bias, the good offset channel .520v. The higher bias and offset channel sounding a touch warmer sonically.Let me know if you need anything else.

Zen Mod, Did you get my last set of measurements? And more importantly, did they make sense? Despite it's penchant for acting bad, it's playing music quite well.

Well, I will remeasure voltages later, but you get a tiny bit of output. The offset is a bit off with new opto. The power resistors still measure the same.I've been feeling pretty good since I went to see an acupuncturist. The nausea will occasionally take over though, and well most people know how that feels. Not being a carnivore for 6 months or so is going to be real tough. Always lessons every year on how fragile the body and mind are.

R28 is 200R,Voltage was 1.01vI swapped Optocoupler out, no it's .7v, but I put a 390R resistor back into R26.R26 is 390R in other channel.Q7 and Q8 seem to have close voltages on both channels.I noticed (even before optocoupler change), after listening session last night, while on bench, that signal went real low on output, as in could hear very little music.Also when I hooked up speaker, to this channel, the tranny started buzzing. So this channel has gotten more ill. I suppose a transistor or something here is failing or dead. I may have crossed something taking DVM measurements.

ZM,I sent the measurements to your sc)))) gmail account. No hurries. I'm gonna try to listen to it.

Zen,I will. I still might try to swap JFETs just to see if it's any better. But I think other peoples hunches are likely true, something else if off here.

I will check the resistors cold and voltages again. What's got me is why it biased okay with 'normal' source resistors.And this is the channel that didn't have the original issues with things blowing up

R23 measures .585 and confirmed 47R :blum3:The other channel measures the same.If no other concerns here, I am going to try a different pair of 100's - see what they do.

Look better, no - my amp's are all ugly. I tried to boot up laptop for some test music last night, blue screened and core'd. Several times, so I just went and played X-Box with my son.

I have not checked it since swapping Power resistors to sp300b's values.The resistor should be 47R. I will check the value later, before swapping out R100's.

So update. No listening yet. My large offset got cured by a huge resistor change from default of 390 to 2k with 500R pot.What bothered me more, was now the bias was up to 720mv. I swapped the resistors out of the other channel, and offset from +1v was easily dialed in with R12. Bias at .560mvSo I am thinking that at the bias change has somehow made the Fets less matched, as they do with different levels of current.I am going to swap out with my last matched pair on this channel, go back to basics for R26 and see how this goes.

Well, still working on getting it right, need to add a little more R to get offset lower.Then will need to work on the other channel. So I am not sure I will get a good listen for a few days now.