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Old 13th November 2012, 07:41 PM   #11
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I see death of Zen is a 10W class A amp. Fine if you mainly listen to strumma strumma singer songwriters on acoustic guitar with a fairly efficient speaker. Myself, I would only use that for a headphone amp. With 101 db@1W speakers, I listen at an average level of 1.5 v pp. Doubling voltage for each 10 db of dynamic range (LP's have 55 db of dynamic range) gets 32Vavg. So my dynakit ST70 tube amp at 17.5 V into 8 ohms is not quite enough, which is about what it sounds like on full orchestral music. I updated the ST70 last year with new e-caps, new output tubes, and checked the rectifier tube for not much sag at full power (17.5v @8 ohm), so it is up to original as far as I can tell. With the 7199 driver boards updated with new coupler caps, metal film >100k resistors etc, the 1% harmonic distortion is audible on piano. Much better sounding are my BJT amps, the ST120 updated with the djoffe bias circuit, and the CS800s Peavey amp.
I haven't run into any FET amps, other than nasty car amps driving by. Having blown a few irreplaceable tweeters over the years with the allegedly totally tame ST70, I'm sensitive to the tendency of symmetric direct coupled transistor amps to blow up speakers if the outputs get shorted. The ST120 has speaker coupler caps, the CS800s has speaker monitor transformers and a microprocessor to pull the speaker relays. The one FET amp that has intrigued me is the MJR-7 which has a failure resistant capacitor in the speaker path. MJR-7 Mosfet Power Amplifier. If I was to come up with some FET's at less than $8 a piece, I'd try that one. The FETs he specifies are $10 each in the US, and that is a TO3 part with the same number and a different manufacturer as the TO247 parts he is buying in Europe.
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Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300
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Old 13th November 2012, 07:54 PM   #12
Haze13 is offline Haze13  Israel
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I think those type of an amps will lead to nothing, just spending money on some projects. I know how to solder, and after Guitar tube amp, I think that I could do a Hi-fi stereo amp too... Now I am doing my "home work" - reading, learning and asking.
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Old 13th November 2012, 08:41 PM   #13
Haze13 is offline Haze13  Israel
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Friend of mine that lives in canada has same st70 amp, but his is completely stock, ecxept for the tubes of course. He uses some quality DAC than peamp that is a jadis jp200 copy and st70, and he says that this is amp can't be beaten by SS amp. In my opinion that the only thing that I can be sure of is that his amp is working, but how good this amp works If you got nothing compare to? Right?

I am not speaking about valve amps with tamura transformers, some NOS tubes, and super expencive silver paper and oil caps with silver wires just in case if Vampires or werewolves will try to attak your amp... These are legends and just have to sound good!
Same class amps with same price tag. What is better?
From the replies I see, Solid State are on the wining side, and they cost less...
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Old 13th November 2012, 10:12 PM   #14
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This is a link to the John Linsley Hood amp I mentioned earlier
A Paul Kemble web page - JLH mosfet amplifiers.
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Old 13th November 2012, 10:15 PM   #15
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Is this the ST70? DYNACO ST 70 tube amplifier - YouTube
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Old 13th November 2012, 11:36 PM   #16
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I can't do U-tube videos, this computer isn't fast enough.
My dynakit ST70 is a 1961 build that I bought used in 1970 from the minister builder who was going to Africa to become a missionary. It has the original 7199 driver board, with some plastic film caps. I have a PAS2 tube preamp he built which I had to put some plastic film caps in 2 years ago due to his burning of the wax case on one cap and his turning it so the burned part was down- thus it was the 11th cap I replaced. The plastic film caps make the PAS2 a little bright, requiring turning down the tone controls a little.
I view music reproduction is trying to reproduce the music you can hear in the concert hall. A particular warmth on voice or whatever is not what I am looking for. Some distortions are sweet, but they are distortions, IMHO. In my case, in my 60th year I found a Steinway console piano. Thus I can do listening tests of the real Steinway, versus the ones on recordings. The pianos on recordings have better bass, but the treble is pure Steinway. Coloration by the tubes is not my goal. Sounding like a real piano is my goal. The PAS2+ST70 was great over the years, until tubes became a Soviet only sourced product, but now you can buy tubes again from Slovakia! So the ST70 is back to pretty original. It is good-- but not great. My test records include Beethoven Appasionatta Sonata for the lows, and an RCA dynagroove LP Peter Nero, Young and Warm and Wonderful. On the top octave of RCA's Steinway, you can hear some IM distortion with nearly everything, especially the ST70- but not with the ST120 (djoffe bias modified) amp and not with the CS800s amp (when it is not blowing the breaker because the PS caps are too old). I also try bass drum hits from ZZ Top Afterburner which will sound like boog if time alignment of the speaker is wrong.
These Peavey SP2-XP speakers are the best I've ever owned, and come with a factory frequency response chart +- 3db, and the later SP2-2004 versions come with a harmonic distortion chart plotted 50 hz-14khz. Tell me how golden standard these speakers are that you are listening to all the imperfections of amplifiers with?
As far as amps with DC speaker protection being useless, frankly you can get a great "sound of silence" from a speaker with a blown driver. One where the vendor is bankrupt, and no exact replacement driver is available. As is nearly every speaker manufacturer except Peavey.
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Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 13th November 2012 at 11:41 PM.
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Old 14th November 2012, 02:01 AM   #17
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Quote:
Originally Posted by Haze13 View Post
Can some one say where is the line between valve and solid state designs?
There isn't one, really, but biasing FETs to match tube curves is quite a bit cheaper than using tubes proper. I'd suggest reading up on tube emulation circuits and thinking about which characteristics you want to pull across into a hi-fi amp.
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Old 14th November 2012, 08:49 AM   #18
Haze13 is offline Haze13  Israel
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JLH amp is always gets mentioned when you looking for some info about Le monstre by Hiraga, and vice versa. It's a good amp from what I read, and there is a lot of info about building one. I'll take it as an option.
St70:
Yes, that's the amp from your link in youtube. Many pople say that stock output transformers are better then the new ones from ebay let's say. But if they from Tango, Tamura, Hashimoto that's some thing different.

To indianajo:
Actualy there is no golden standart speakers that I listening to, but I have 8 ohm, Sanyo 3 way speakers with westra drivers (from germay) with passive crossover, that I got with Marantz 2225 reciver form 1974 made in japan.
It had some noise problem on the right channel I wanted to repair and to modefy this reciver but at the time I didn't heave enough brains to know were to start and it was just standing in the corner of the room. Then my wife sad to me that if I want to do some thing with, I better to get started, if not - just throw it away. I think you know what happened next and thats the reason why I am here. PC cheap stereo is no good for me now

My expiriense with tubes and Transistors: As I sad before I play guitar, and I had two transistor amps, one tube amp from Carvin, and now I have Marshall clone that I made from the parsts that I ordered.
Carvin had a lot of switching fets in signal chain, active 5 band tone controles (with 4558 IC's) and Active graphic EQ (with same 4558).
This one was modefied by me: changed quality of the caps, different gain stages, Post PI master volume... It was a combo with Carvin USA made 12' speaker. Sound become mutch better to me and other who had listened to it. In that moment I realised that I have to build an Amp.
Marshall have only tubes in it and I like it the most. The circuit is so mutch simplier then carvin.
In the same time I was working on chorus effect that works the best with a clean channel, so basicly it's an analog modulation effect. Builded two of those. One is standard version: 1% metal film resitors, Poly caps and ceramic caps for small values, 5088 - 3904 transistors, 4558 op-amp in signal chain, and the other is with the chainges like: jfet 2sk170GR as a Buffer instead of BJT, Wima FKP2 (Polypropelyne Film and Foil) in signal chain, LM4562 instead of 4558, bc549 transistors in other places. I was working step by step and always compearing them. Caps at the first, then op-amp (used OPA2604, but lm4562 is better to my ears) etc...
In the end these almost identical schemes sounds different. The moded version is so transperent and Musical then other. The original circuit is from early 80's. Amp that I used was marshall clone on clean channel.
If it works here, is there a reason why it won't work in HI-fi audio?
30 or 40 years ago people were using what they could get at that time, and they were happy with the results. Now we have and opportunity to use same shemes, but with new standarts. The technology moves on...
Why not use this? That's what I trying to do...
By the way aren't SED power tubes not good enough? Alot people loves them and they made in Saint Petersburg, Russia!
Some times I proud to be a Russian
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Old 14th November 2012, 09:19 AM   #19
Haze13 is offline Haze13  Israel
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To twest820:
Erno Borbely in JFETS: The New Frontier, Part 1 says the JFETS behaves like pentode vacuum tube and, the most important part, they can sound iven better then tubes... Just need to know how to do it
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Old 14th November 2012, 10:44 AM   #20
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If you are looking for a home for your JFETs, John Curl's JC2 preamp design line amps are good if you care to research them. There is an Ebay kit to get ideas from but a good layout and overall design is necessary to get the best from the parts.
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