JLTi KT88 "Unity Coupling" Tube Amplifier

[Joe Rasmussen]

Some years ago, maybe 01 or 02, you sent me some info about techniques for forcing balance in O/P stages. Is the current amp a development of that?

Both yes and no. It's a long story... so much water under the bridge since then. We are about three to four steps further down the road since then.

Some years ago, maybe 01 or 02, you sent me some info about techniques for forcing balance in O/P stages. Is the current amp a development of that?

Well, I'd sure like to come and have a listen. I gave a mate who's interested in the Elsinores, and I'm currently working at Hoxton, but even so it's not that far from home. I'll give you a call soon when I'm sure of my exact movements to arrange.

Why don't both of you call. Hoxton is minutes away from here (but give me a bit more than that advance notice). Bring some music as well.

Cheers.

Joe R.

[Antripodean]

I follow with a summary of the amp shootout. This is the tube one and the winner of this was put up against the winner of the solid state amp shootout. Please enjoy

VALVES OR SOLID STATE?

We have a decisive winner!

Source: Primare CD player (as used in the solid state amplifier shootout)

Preamp: NuForce P9 (2 box) preamplifier

Valve amplifiers: (in order of audition on the day)

1. Cymer 13E1 push-pull monoblocs (70W/ch) (Elson) ($1600)

2. Cary 2A3 push-pull stereo (7.6W/ch) (David Cooper)

3. JLTi rebuild of Chinese integrated, 2 pairs EL34 in triode mode (Joe R) ($1600)

4. VTL 45/45, 2 pairs EL34 in ultralinear mode (Stephen Chen) ($4500)

5. Copland 501 (Walter Koll)

Speakers: Orpheus Aurora 3 (kindly supplied by Kiat Low of Duntech and Orpheus)

Cables: as used in the solid state amplifier shootout, 5 identical pairs of unbalanced interconnect and flat Nordost speaker cable (bi-wire)

Aim (paraphrasing John Sawley’s introduction in the April Newsletter)

At this meeting we compared the various valve amplifiers and determined a winner.

We then compared the winner to the solid state winner, the AKSA, from the meeting two months ago. This was a lot of fun and gave members an idea of what is out there in the market place at various price points and what they sound like.

The problem with shootouts is that although they are informative and give a basic understanding of the bang you get for your buck, they do not give you an understanding of what they sound like in a fully tweaked and fine tuned system. If you are interested in listening to a more finely tuned (and synergistic) system, how about asking other members what systems they own? Then invite yourself around for a listen. I’m sure most members would be delighted to show off their systems to you and then you will be better able to judge for yourself in a friendly domestic environment,

what the various components sound like when tweaked to that member’s taste. It’s also a great time and a lot of fun.

Last Month’s Meeting

Methodology

For the first stage, 1½ minutes from the same three tracks were played on each of the 5 amplifiers in turn, which were identified by number only, and blinded to the audience.

Levels were matched with Joe Rasmussen’s SPL meter.

For the second stage, 1½ minutes were played, with the order of the amplifiers selected at random.

All members scored each track out of ten, as in the previous meeting; compiled the scores, and ranked the amplifiers. The rankings of all members were then compiled to determine the overall winner.

And the winner is>.. JLTi integrated, by a decisive margin!

The runners up were:

2. VTL

3. Copland

4. Cary

5. Cymer

Discussion

These were some of my thoughts during the process, not being able to identify which amplifier was which. I personally thought that many of the recordings were too closemiked and strident for my liking. This removed some of the discriminatory value for the process, however, having said that, a good amplifier should have the resolving power to clearly distinguish good from bad recordings and performances.

Amplifier 1, I found to be detailed but strident and lacking in bass. Amplifier 2 had a giveaway from behind the screen, saying that the gain was close to maximum. There were sonic giveaways with the frequency balance being all midrange, not much at the extremes and discontinuousness. Amplifier 3 was the frontrunner from the beginning being more continuous and seamless from lows to highs. Amplifier 4 started slowly but picked up as the survey continued. Amplifier 5, I found to be bass heavy.

Tube versus transistor

3 successive tracks were played on each of the 2 amplifiers with the audience being again blinded.

1. (great track, but sorry no one can remember its name)

2. Keb Mo’

3. Neil Young: Old Man (live version) – my musical highlight

I found the first one smoother and the second one to have a more nasal quality to the voices; more detailed but etched. I guessed right in a 2 horse race and so did the majority of the audience who preferred the sound of the tubed to the transistor amp.

So, congratulations Joe, maybe some justice has been done after the low ranking of your CD player in the shootout.

Conclusion

Being the owner of the VTL, I acknowledge that the JLTi did sound better on the day.

Possible explanations could be:

1. The inherently sound (pdp) design of the Chinese amplifier which makes it amenable to modification

2. The improved linearity due to the permeability enhancer (I will give serious consideration to having this mod done)

3. Operation in triode mode

One limitation of the study was the absence of really complex music, like orchestral and choir or pipe organ.

I know that this would not make it past my hospital’s ethics committee but writing this like a scientific paper is my idea of fun!

Stephen Chen

[awhw]

Interesting read. Thanks!

[Bronal]

This thread is looking more like an advertorial with every post.

I notice all of Joe Rasmussen's posts to date are in this thread.

[Joe Rasmussen]

This thread is looking more like an advertorial with every post.

I notice all of Joe Rasmussen's posts to date are in this thread.

I am sorry you feel this way. That certainly has not been my intention. Note that I did not initiate this thread and what others have posted they have done so unsolicited. I think the above contributors will attest to that. Please read the entire thread and you will see that I have only being responding to other posts and not conducting a drive.

If anybody wants to offer a critique of anything that I have made or have a hand in, they are quite free to do so. I expose myself to both praise and criticism.

Re the ASoN Amp Shoot-out I was asked to participate. When the ASoN Newsletter came out I posted it on my website last week. That's all. If others wish to quote my website, that is their prerogative.

Cheers.

Joe R.

[Orpheus]

I don't have any criticism of you, Joe.

However, while the "shoot-out" may have been interesting, I have agree with Stephen's implicit admission that it was not particularly rigorous or reliable when he said that it would not make it past his hospital's ethics committee.

THe particular set-up clearly played to the strengths of some rather than others.

I don't know any of the gear well, but the most glaring example of this lies with the Cary, which you say is rated at about 8 watts per channel.

Clearly it is designed to be teamed with very, very efficient speakers.

Not surprisingly, it struggled, as you observed.

I am sure that plenty of other examples of the "non-level playing field" you set up could be given by those who know more about the equipment used.

[Joe Rasmussen]

I don't have any criticism of you, Joe.

I understand.

I

However, while the "shoot-out" may have been interesting, I have agree with Stephen's implicit admission that it was not particularly rigorous or reliable when he said that it would not make it past his hospital's ethics committee.

My views on shoot-outs are well known to ASoN members.

But I get the response that they are good fun. But when you get a good result you go with the flow - at least it proves the amp is worthwhile as a consideration.

BTW, I didn't write the article, just posted it without editorial content. It was written by Stephen Chen whom I have know for near 20 years but would never presume to instruct in anything. (I will out myself, he uses an FVP-5B preamp that I have made - Stephen is really into vinyl and that it what the FVP-5B excels at.)

I don't know any of the gear well, but the most glaring example of this lies with the Cary, which you say is rated at about 8 watts per channel.

Clearly it is designed to be teamed with very, very efficient speakers.

Not surprisingly, it struggled, as you observed.

I didn't say the Cary was only 8 Watts per channel. I didn't actually realise that until you pointed it out. The speakers I happen to know are very very easy to drive (the designer Brad Serhan is a good friend of mine and dare I say he has incorporated some of our our shared developments into them - but didn't know they were going to be used beforehand) and we were able to get decent SPL out of all the amps.

All I can say is that the shoot-out was enjoyed by a bunch of audiophiles that may have a secret desire to be reviewers.

But a real review would be taking a product home and then write his thoughts without any pressure. But I think that readers can discern the difference between the two, shoot-out versus review and take that into account.

Here is a link to Stephen's article as I posted it on my website without any addtional editorial input by me. Anybody can read it as is and make up their own mind.

www.customanalogue.com/jlti_el34_shootout.htm

Oh, I just remembered something, Antripodean asked me if he could read the ASoN article and I emailed it to him in PDF format. He posted the text from that. The link I have posted now show pics and all, not just text. Read it and take whatever you need from it, if only for entertainment value.

Cheers.

Joe R.

Edited June 1, 2009 by Joe Rasmussen

[tuyen]

I've heard a modded Yaqin EL34 changed to just a power amp by Joe. Would put most 3-5x the $ power amps to shame. Although them being hooked up to Lenehan ML-1 speakers would of helped too

[kesa32]

Hi, l actually bought this amp off roger recently ..... l was in the market for an affordable tube amp, somthing decent at a reasonable price , and this came up for sale .

After getting it home l tested all the bias's after hearing a slight hum from the right speaker....it turned out one of the kt88's was faulty ( would'nt bias) ...it must'nt have liked the trip home....anyway l have since replaced all the kt88's with a new qaud of kt88-z "treasures" ( thanks Copperhead for the buying link) , these have made a marked difference, smoother, better detail/soundstage etc.....VERY happy with these tubes! , so if anyone with a vavle amp is looking at renewing/replacing vavles l highly recommend these....l've heard nothing but glowing reports by everyone who has got them...BIG thumbs up!

cheers ken

[tuyen]

I recently received my Yaqin EL34 amp from Joe after doing his modifications. Improvements were phenominal. It is now configured as just a poweramp (removed dirty volume pot and input selector), changed to triode mode and added his unity coupling board. Now I just need to change the input rca sockets and speaker posts to pure copper ones, change a few caps with jensens and I should be laughing.

Should then be ready to challenge any other EL34 amp out there

Note: Already using Phillips PCC88 NOS tubes and Svetlana Wing-C EL34 tubes.. was huge improvement over the stock china ones!

[Once was an audiophile]

I recently received my Yaqin EL34 amp from Joe after doing his modifications. Improvements were phenominal. It is now configured as just a poweramp (removed dirty volume pot and input selector), changed to triode mode and added his unity coupling board. Now I just need to change the input rca sockets and speaker posts to pure copper ones, change a few caps with jensens and I should be laughing.

Should then be ready to challenge any other EL34 amp out there

Note: Already using Phillips PCC88 NOS tubes and Svetlana Wing-C EL34 tubes.. was huge improvement over the stock china ones!

you still have caps to go tuyen,then it will boogie even more.i cant wait to mod it for you and wait for your ears to hear what caps do.

[kesa32]

tuyen , is there a reason why joe does'nt do "the lot " when he mods valve amps ? your EL34 sounds like it's making some nice music for you over there....it'll be interesting to see what your thoughts are after the next upgrade ( never ending is'nt it )

What speakers are you running with this?

ken

[tuyen]

hi Ken,

it sure is making beautiful music im not too sure why joe doesnt do 'the lot'. the point to where his mods take the amp can be compared to very high end el34 amps already. the extra mods i explained just takes it to the next level kinda thing.

i mean even some so called 'high end' amps still use cheap $2 gold plated rca sockets and speaker binding posts. dont even talk about capacitors.. just makes me laugh

[Once was an audiophile]

tuyen , is there a reason why joe does'nt do "the lot " when he mods valve amps ? your EL34 sounds like it's making some nice music for you over there....it'll be interesting to see what your thoughts are after the next upgrade ( never ending is'nt it )

What speakers are you running with this?

ken

price is a factor and looks for joe.caps that will be going in will be around $400us

also they will not fit inside the amp.they will be outside in a wooden box(or shoebox)but its worth every penny.some resisitors can be changed aswell.

[kesa32]

Ok, l did'nt realise the caps would be that big ...l'll wait and see how these go in/with tuyen's amp as l'd probably upgrade my hawthornes first before l spent anymore on the amp at this stage .... looking forward to hear how this goes

cheers ken

ps......is the "shoe box " hardwired or can it be disconnected for transportation etc?

Edited September 23, 2009 by kesa32
just an added thought

[Hugh Dean]

Joe,

My warm congratulations, excellent shootout, beautifully done by Stephen.

Don't be concerned with Bronal's negative comment. He regards all designers and sellers in this forum as Darth Vader. I say the forum needs all comers, and if the commercial guys are restrained, it richens the environment.

That was some heady company, Joe - a Copland, VTL, no less!

Hugh

[Antripodean]

Ok, l did'nt realise the caps would be that big ...l'll wait and see how these go in/with tuyen's amp as l'd probably upgrade my hawthornes first before l spent anymore on the amp at this stage .... looking forward to hear how this goes

quote]

The important point to understand is that Joe is about making great sounding gear that represents value. The most important part, before changing caps, tubes etc etc, is the circuit design. Get that right and your are 95% of the way there.

[kesa32]

Ok, l did'nt realise the caps would be that big ...l'll wait and see how these go in/with tuyen's amp as l'd probably upgrade my hawthornes first before l spent anymore on the amp at this stage .... looking forward to hear how this goes

quote]

The important point to understand is that Joe is about making great sounding gear that represents value. The most important part, before changing caps, tubes etc etc, is the circuit design. Get that right and your are 95% of the way there.

Yes l agree mate , thats why l'd upgrade my speakers next as that'd more beneficial l reckon ..... unless my financial situtation changes for the better it'll be a slow work in progress anyway

cheers ken

[Guest]

The most important part, before changing caps, tubes etc etc, is the circuit design. Get that right and your are 95% of the way there.

Regarding tube amps

Circuit then iron all other thing's will fall place .

Cheers

[tuyen]

kesa32: pure red copper speaker posts can be bought from ebay (brand CMC) for like $40. If you have a soldering iron, be silly not to do it

I will report back when 'stage 2' of the mods are done on mine

[andyr]

kesa32: pure red copper speaker posts can be bought from ebay (brand CMC) for like $40. If you have a soldering iron, be silly not to do it

Just as a matter of interest, tuyen, how do you prevent these pure copper binding posts from oxidising?

Regards,

Andy

[tuyen]

Can't say I know Andy. I just hope all the copper im using doesn't oxidize too fast as all my power cord ends, speaker cables, posts, input sockets are all copper

[andyr]

Can't say I know Andy. I just hope all the copper im using doesn't oxidize too fast as all my power cord ends, speaker cables, posts, input sockets are all copper

Well then I guess, unfortunately, you'll never know what your missing out on. I suggest your sound will just degrade minutely each week ... but a year later, can you remember what it sounded like then?

That's why man invented gold plating!

Regards,

Andy

[tuyen]

I might give gold plated copper a try but if i dont like what i hear, I think i'll stick to my oxidising pure copper connections

thanks Andy

[andyr]

I might give gold plated copper a try but if i dont like what i hear, I think i'll stick to my oxidising pure copper connections

thanks Andy

If and when you do (try it out) please don't forget to report back on the comparison.

Regards,

Andy