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I have a few questions about the Reichert 300b Flesh and Blood. Herb suggest parallel AB resistors. I assume he is referring to 2W resistors to get the 24k and 27k values. What values parallel to these two choices?
Do you think the Lundahl transformers would be good a good substitute for the Tango 5k transformers?
Why are there no builds of this amp anywhere?
Thanks!
Mike
Follow Ups:
Like Jeff, I'm concerned at the lack of PSU decoupling between stages. I personally go even further and have separate supplies (from the same mains TX) for the two stages of a 2 stage amp; this is highly recommended! It contributes to fast clean leading edges, transients and to good sound generally. I keep making this suggestion and seem to get few takers ... your loss, IMHO! :-)
6CJ3 damper diodes work very well; I use them a lot; very low voltage drop. Highly recommended for the output stage PSU.
I have used Lundahl LL1620 and Hashimoto H20-3.5U (at 3.5K) OPTs in 300B SETs and highly recommend the Hash; I suggest you avoid the Lundahls.
ugh - I threw about five of the 6cj3's in the dumpster last night! It seems like no one likes this design. T.Loesch had a design using a more sophisticated power supply and a 417a first stage. Lots more iron. Mike
Hi !!HEY !! The use of two 27K resistors in the driver stage MAY have been intentional, and if not, it should have been.
Two Rs, when EXACTLY matched, will outperform a single R in the same location. You have two wire paths for superior transfer efficiency, two electron flow paths, and two will dynamically outperform a single 13.5K R, as long as their Ohmic values are PRECISELY the same, so that one R does not smear the other.
You can advantageously parallel (exactly-matched) Rs (and even go from one to two TCSS wires), because these so-called "passive" (they aren't, they are active!!) devices can be electrically the same, (but this is seldom the case with paralleling active tube sections.)
Just listen to closely-matched paralleled Rks, versus one Rk, and you will "get it" right away for yourself.
--------------------------------------
As I recall, there is a design flaw in the Flesh and Blood design, as the driver stage and the output stage run off the same B+ supply, and there is NO decoupling of the driver stage from the output stage.
Ripple, PSUD simulated, was about 133 mVAC, which is no problem at all for the low mu finals, but "I" believe 133 mVAC is too much ripple for the driver stage, as it amplifies this ripple as AUDIO signal, to the grid of the 300B. I'd like to see about 2 mVAC or so on the driver stage's B+, so that the ripple is a non-factor when listening.
The 3 HY choke Herbie used BTW was a ESPEY, from Fair Radio, ....3 HY at 24 Ohms DCR. I personally baptized Herbie, (and his buddy JC), into low DCR way back then, and turned Herbie on to my favorite sounding choke. I have just two of those ESPEY babies left if anyone is interested.
Also, by today's standards, the 5R4 rectifier tube choice is whimpy / high Z, but, at least, its a directly heated vacuum rectifier. I'd use a 5U4 or a 5V3 instead today.
Three stage amps to power a 300B are destined to only be "average" in performance.
They should be just two stages, and I prefer DC amps, not amps with series-cap-couples. Ugh, there are TWO 0.1 uF cap-couples in the case of the F and B, and a direct couple will "creme" that topology.
A two stage will always be more transparent sounding than a three stage amp. A two stage amp is "the best configuration" IMHO for highest possible audio performance in the SE world. The extra stage is not really needed, you "pay a price" for the added third stage complexity, anti-transparency and a cap couple or even a unnecessary transformer couple.
So, maybe that is why we don't see a lot of Flesh and Bloods these days. You asked, I answered. Just my humble opinion. Cheers.
Jeff Medwin
Edits: 03/14/12 03/14/12
If I remember correctly, Herb R said that he was trying to achieve a particular sound presentation, hence the article's title. He said that he did a lot of comparative listening to get it to the end result. He got what he was looking for by listening, much like yourself. His destination was different than yours from the start but he got where he wanted to go.
The F&B is a decent sounding amp, I built a similar one when the article came out. It's not for everyone but it's still a good amp.
For what it's worth, I prefer the JE labs take on a 3-stage 6SN7 - 300B design. And in that the first and second stages are direct coupled, getting rid of at least one cap. Over the years I've built a ton of 300B amps using everything from direct coupled 417a to 300b to a traditional WE style using a pentode front end. I personally prefer a "less is more" design. If you use the right driver (like a 417a) with a CCS one stage is all that's needed. But of course we all have different design goals, systems, etc.
It's been a long time since I've done a 3 stage SE amp but I did do a couple, years ago. I'm a 2 stage SE guy for the most part. If your preamp has the gain and can put out the voltage, you can use almost any good tube as the input on your amp. eg A 2B6 is a good driver for a 300B but needs about 17 volts on the grid and has a hard to find socket. They look sharp as well.
You need to use a great Iron ,otherwise it's just an average amp. Audio Note or Tango are only choices. It is a spectacular Iron ,hmm just expensive.
I've built it, it is a nice amp. Search the SET forum.
Mike
You asked the same question on Tubes
and I gave you the answer.
24K = 62K & 39K
27K = 62K & 47K
You want another answer,
ask another question.
DanL
to create a 13500 ohm resistor for the driver stage. (Herb actually mentions a 12k resistor) (13k5 is close enough)
To infinity and beyond!!!
Thanks DanL,
I did not see your other post - I must have forgotten to check the little box to see replies. It is so strange to me that it ten years most all of the parts chosen have become unavailable.
Does anyone have any first hand experience with how different the Amorphous core Lundahls sound? Do they meet Herbs requirement of be less than 40 degrees out of phase under 100hz?
Mike
The 2 * 27k resistors are to create a resistor with the value 13500 ohm.
The 24k is just a single 3 watt version.
The Flesh and Blood is just not in vogue at the moment. It might be just right for you...or not. You'll have to try it.
Lundahls are good transformers. But the Flesh and Blood is all about tone. So I'm not sure you'll get a Flesh and Blood.
To infinity and beyond!!!
Here is a calculator for answering your first question
"You don't need to be a Weatherman to know which way the wind blows"
Aren't you a genius? Now all I need to do is go thru 400 calculations to determine where the needle is in the haystack!
24K: 62K + 39K
27K: 62K + 47K
for example
"You don't need to be a Weatherman to know which way the wind blows"
teach a man how to fish and he throws the rod back in your face.
To infinity and beyond!!!
If you ask how to get to a destination and you are told that isn't the way, then why'd you ask.
I really don't know how many ways you can spell ungrateful.
As DanL said, he asked the question on a different Asylum Forum and Dan told him the answer, then he again asks here.
I thought the calculator was fairly idiot proof
"You don't need to be a Weatherman to know which way the wind blows"
laugh about the whole affair. But I have a suspicion that he is a grown man!
Nothing wrong with not knowing something or making a mistake. But being cynical with someone who is trying to help you is too much.
To infinity and beyond!!!
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