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Old 15th October 2010, 05:17 AM   #51
gRF is offline gRF  Singapore
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Yesterday I received Helder's buffer I ordered over eBay.
And I wasn't happy with the sound - at all. Lack of bass, and ear-piercing highs.

Just to give it another shot, I went to audio store in my neighborhood, and bought one of JJ's 12au7 (Slovakian). Boy! Everything got much sweeter, and bass improved so much!

This buffer can really do small wonders, but with the right tube, I guess.

If you are buying this buffer, do yourself a favor, and order the buffer WITHOUT a tube. If you can't find some Mullard, RCA or Sylvania in nearby shops - there's hundreds of ppl selling them on eBay.
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Old 19th October 2010, 06:46 PM   #52
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Quote:
Originally Posted by gRF View Post
Yesterday I received Helder's buffer I ordered over eBay.
And I wasn't happy with the sound - at all. Lack of bass, and ear-piercing highs.

Just to give it another shot, I went to audio store in my neighborhood, and bought one of JJ's 12au7 (Slovakian). Boy! Everything got much sweeter, and bass improved so much!

This buffer can really do small wonders, but with the right tube, I guess.

If you are buying this buffer, do yourself a favor, and order the buffer WITHOUT a tube. If you can't find some Mullard, RCA or Sylvania in nearby shops - there's hundreds of ppl selling them on eBay.
Took your advise and bought some Sylvania JAN 6189 (Military spec 12AU7) on eBay. Read that these are dead quiet from microphonics, also have an RCA black plate (top getter) and an Amperex orange label waiting for the buffers. I am assembling a Helder TA2020 MKIII and a Helder TK2050 with these buffers. Can't wait for them to arrive. Helder's Stacy said they were out of 12AU7 tube stock, so I said ship them without.
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Old 30th October 2010, 02:34 PM   #53
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I received the tubes, they were not JAN 6189 but plain Sylvania 12AU7, so they went back for the correct ones. Meanwhile I am using an Amperex NOS. Quite smooth.

Finally finished the amp, it consists of 2 Arjen TK2050 monoblocks and the tube buffer.

I made a mistake and bypassed the output capacitors (big reds) on the buffer against Arjen's advice. I should have listened. The sound was brittle, hardly any bass, there was some hiss and the volume pots were scratchy every time you touched them. I was ready to tear the tube buffer out when I decided to put some capacitors that I had from a x-over where the red ones used to be on the buffer. It was the last effort before tearing things up. All the problems above cleared up. No more scratchiness on the volume pots, no hiss, better bass, and the sound is no longer brittle. The result is a very detailed and great sounding amp. Thanks to all the relays on the 2050 monoblocks, there are no pops when on/off. I'll post some pics when I am back on my computer. The capacitors I used are Dayton Precision Audio 4.7 uF / 250 Volts.
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Old 30th October 2010, 07:24 PM   #54
julcat is offline julcat  Mexico
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Whaleman:

Does the Arjen tube buffer introduces some noise in the signal??? My TK2050 Monoblocks are almost dead quiet alone.
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Old 30th October 2010, 11:56 PM   #55
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Whaleman:

Does the Arjen tube buffer introduces some noise in the signal??? My TK2050 Monoblocks are almost dead quiet alone.
Not at all, it is dead quiet at idle. You do have more chances of introducing noise in this setup though. You must route all your signal cable away from power supplies and I would braid the signal cables provided with the buffer. Have some girl do it, they are great at it. This keeps the potential of acting like an antenna down. I also only use twisted pair or shielded cable for the signal level cabling, it helps.

Also, you left the buffer output caps in place?
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Last edited by whaleman; 31st October 2010 at 12:03 AM.
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Old 2nd November 2010, 12:29 AM   #56
Opher is offline Opher  Israel
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Quote:
Originally Posted by whaleman View Post
Not at all, it is dead quiet at idle. You do have more chances of introducing noise in this setup though. You must route all your signal cable away from power supplies and I would braid the signal cables provided with the buffer. Have some girl do it, they are great at it. This keeps the potential of acting like an antenna down. I also only use twisted pair or shielded cable for the signal level cabling, it helps.

Also, you left the buffer output caps in place?

Whaleman, What kind of case are you using to house the monoblocks, buffer and PSU? Are you powering all of them from the same PSU? Doesn't the buffer require lower voltage?
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Old 2nd November 2010, 02:22 PM   #57
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Originally Posted by Opher View Post
Whaleman, What kind of case are you using to house the monoblocks, buffer and PSU? Are you powering all of them from the same PSU? Doesn't the buffer require lower voltage?
The Case comes from eBay seller wonderco_buy in Taiwan. It is just tad tight for this setup but it works. It is a blank box, so you must drill your own holes and provide your own knobs, etc.

The buffer and TK2050s run at differing voltages, so I use a dual section Toroidal for the monoblocks and a separate power transformer from Hammond on the tube buffer. These are linear supplies that I built using individual brigde rectifiers and filtering caps. I am not a fan of SMPS just yet. Believe it or not, all fits in the case but there is no room to spare. To me it sounds outstanding.
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Old 6th November 2010, 08:48 AM   #58
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Quote:
Originally Posted by gRF View Post
Yesterday I received Helder's buffer I ordered over eBay.
And I wasn't happy with the sound - at all. Lack of bass, and ear-piercing highs.

Just to give it another shot, I went to audio store in my neighborhood, and bought one of JJ's 12au7 (Slovakian). Boy! Everything got much sweeter, and bass improved so much!

This buffer can really do small wonders, but with the right tube, I guess.

If you are buying this buffer, do yourself a favor, and order the buffer WITHOUT a tube. If you can't find some Mullard, RCA or Sylvania in nearby shops - there's hundreds of ppl selling them on eBay.
I'm using some Hammond silkscreened 12AU7's I bought for about $10 each. They were new old stock, unused (NOS). You can still buy these tubes for not much money here and there ... hopefully that won't change TOO much after this post.

These were either made by Raytheon (up to about 1961) or RCA (afterwards). Mine are dated June 1960, Raytheons from appearance and from the usually reliable sources with regard to whom Hammond bought their tubes from.

The Hammonds are marked with an EIA code of 260, which is incorrect for Raytheon (280). However, at the time, EIA codes were sometimes just lifted and used for OEM-branded output. There is no assigned 260 code for tubes (the EIA codes are component-specific; ie transformers, tubes, etc may have different codes assigned to a manufacturer).

The 260 code points to Philco, but Philco never had a tube fab, the Philco EIA code only applies to Radio and TV sets, and Philco sold it's radios without tubes supplied (much, much later, in the 70's, they used Philco-branded Sylvanias, and are marked with Sylvania's EIA 312, but that was after a corporate merger). The EIA 260 is unassigned for tubes.

Since every other aspect of the tube is consistent with Raytheon, right down to the welds, I'm pretty sure that's what they are. It's not hard to study the construction of a tube by a given manufacturer and identify tubes that way, although subtle differences do matter.

Baldwin screened 12AU7's are the same thing, basically. The organ manufacturers had a tight spec contract with the tube factories (meant paying a premium on the contract), and required that they were individually tested and selected for low noise before they could be branded. All tube factories ground up any tubes that did not meet the standard spec, so there's no chance that there are labeled "seconds" out there.

Broadly speaking these are the better units from production that were selected at the factory before going to silkscreen. Because of the contract, the organ companies could return any units that didn't meet the tighter spec, so care was taken by Raytheon/RCA to avoid having tubes rejected.

I would expect that any organ-branded tubes would be tighter than ordinary production, although that doesn't mean ordinary production wouldn't meet that spec either, it's just that only some of them would. Might be worth remembering if you need other tube types.

Sounds very good in the buffer. I bought one and a spare, and considering the tube life of this type can go beyond 10,000 hours, I would suggest to anyone to just get a decent tube (or a pair) and run with it.

I ran the board in with the Hammonds before any mods, and it sounded good as is. I've since replaced the 0.47uf caps with WIMA MKP10 160/100V and the 2.2uf's with the basic Mundorf M-caps @ 250V, and gone to a SMD-constructed 31-pos resistive attenuator. The caps don't fit easily in the space on the board, just so everyone knows. I'm done with the mods, though ... works wonders driving a T-amp board, no question.

Last edited by Johnny2Bad; 6th November 2010 at 09:17 AM.
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Old 8th November 2010, 10:43 PM   #59
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Finally got the Sylvania JAN 6189 military spec 12AU7, it is great! Here is a shot a few minutes ago. This is a great setup with the TK2050. This is a good tube.
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Old 30th November 2010, 12:50 AM   #60
Homl is offline Homl  Canada
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Default Awsome with the Electo-Harmonix & his TK2050s

Bought a set of Helder's TK2050 and the tube buffer. I replaced the stock tube with a regular Electro-Harmonix version.
The TK2050s by themselves sound just like a typical T-amps. However, couple them with his buffer and the Electro-Harmonix tube, they sound amazing. Much more pleasant, and the strange thing is that the imaging becomes razor sharp.

To get rid of the buffer pop, add more filter caps to the buffer supply, so the TK2050 relays cut off the speakers before the buffer supply runs out of juice.
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