Better Head?

[Foxbat]

I recently finished yet another head preamp and it is now fully tested and calibrated. Since I have the Otari MTR-12 and Studer A80R sitting side-by-side, both with direct outputs, I added the input switch - space is becoming scarce and I wanted to use one preamp with these two machines.

Naturally a question popped up - which one would produce better sound? Both machines are in excellent condition, their heads have low to moderate wear, just a bit more on Studer, but both have perfectly shaped wear patterns.

Their heads designs are somewhat different. The Studer has butterfly heads, and Otari - what I would call the truncated butterfly, with wide guard band, but poles forming a shallow X, their points slightly trimmed.

Ideally for such comparison two identical tapes would be best... which I didn't have... but I had a superb 2xHD La Network tape and a safety copy, made on my best dubbing setup... so I decided to run it one way and then swap the tapes.

For the first run the original tape was on the Otari. It did not take long for me to realize this setup produced far better sound. But one big variable remained - could that be the copy's lower quality?

So I swapped the tapes and the result was - Otari still sounded better. At this point I realized that I forgot to check the gains - as we know, we tend to prefer the louder sounds.

I put the test tape on both machines, and bummer... Studer was louder by full 2dB. It also had just a tiny amount less noise.

Interestingly, the sound quality the Studer produced immediately reminded me of the typical Studer sound - something I never liked, but that people typically assign to their electronics contribution.

However, if this experiment has any validity, it means it is the heads, not the electronics, that dominate the Studer sonic signature.

The Studer still remains one of the most pleasant machines in use and its fast rewind pack is as perfect as I have ever seen.

Would putting the Otari heads on a Studer produce the best possibly playback system? I am afraid the answer to this question is going to remain a mystery.

But one thing is certain - with Otari's available for a small fraction of Studer cost they do make one hell of a bargain.

 

[adrianywu]

Hi Victor, which of the BAT phono stages did you modify ? Are you using the step-up transformers ? How much gain is it providing to the heads ? What is the inductance of the two heads ? If there is a significant difference in inductance, this could account for the difference in the sound. Perhaps adjusting the input resistance and capacitance loading to see if you can improve the sound from the A80R ? What are the deficiencies you have identified from the Studer ?
Most important question, any plan to offer this variant as a tape head preamp commercially ?

 

[Foxbat]

Hi Adrian! They are all based on our top of the line models, starting with VK-P10SE, then P12SE, and now the P90. I have seven of them in the system, and they are all slightly different, dependent upon their application. Most of them have two EQ options, either the 15-30ips selection (used with 30ips capable machines), or 15ips IEC-NAB. One or two are single EQ, set to IEC. Most of the time I am using their direct inputs, only in one case of a very low output head on Ampex 445 I am going through the on-board step-ups. The gain at 1kHz is usually close to 50dB, which is in the "plenty-to-too-much" range in my system - my volume control usually sits in the -20dB zone.

In this particular case the two heads had similar inductance of around 160mH. But the Studer head has much lower resistance. I am not using any input capacitance besides that of the interconnects. The Otari head is loaded just as it is normally, and the Studer started with high load of 332K, but then it was changed to its normal 47K, with no obvious effect.

The two sounds were easy to tell apart, with the Otari one being more clear and free-floating. I verified that by putting my wife in front of the system - she is not an audiophile by any stretch of the imagination, but loves music and has good ears. She immediately said the correct words, and when played randomly, correctly identified the source.

But no, no plans for making them commercially. I would estimate there are 100 to 1000 phono stage customers out there for every high end tape user. We sell good volume of the phono stages, and at this point it almost seems like there is one producer for every head preamp customer.

 

[christensenleif@msn.com]

my tape tech says a Studer head as new should be about 220mH and if it´s down at 160 or below it´s worn out and not even relappable....

 

[Foxbat]

You will hear many different opinions in that regard. The spec for new head is 200mH, and JRF puts the end of life at 60%, or 120mH, so a head with 160mH would be at about mid-life.

 

[christensenleif@msn.com]

but Studer have 2 different series of Butterfly heads for the A80 2t 1/4
one is 6K hours and slightly soft and considered to sound the best
the other series is 10K hours and harder

 

[Foxbat]

That is cool... can you tell them apart based on their resistances?

 

[christensenleif@msn.com]

The 316 heads are softer and have shorter life (6000 h) while the 317 are harder (10000h)
product no on side of heads

corrected fro 216 to 316

 

[Foxbat]

Yes, I know, but I don't think it is possible to see it. I will look again.

 

[christensenleif@msn.com]

on left side of head...maybe you need to take off headblock cover...2 countersunk hex...

 

[Foxbat]

Any idea on their resistances? The one I have is about 50 Ohms.

 

[christensenleif@msn.com]

have a list somewhere

 

[Foxbat]

I found it, but it doesn't list resistances.

Bummer... On the shield I can see the traces of the adhesive where the label once was, but no label.

Ditto for the record head.

 

[adrianywu]

Hi Adrian! They are all based on our top of the line models, starting with VK-P10SE, then P12SE, and now the P90. I have seven of them in the system, and they are all slightly different, dependent upon their application. Most of them have two EQ options, either the 15-30ips selection (used with 30ips capable machines), or 15ips IEC-NAB. One or two are single EQ, set to IEC. Most of the time I am using their direct inputs, only in one case of a very low output head on Ampex 445 I am going through the on-board step-ups. The gain at 1kHz is usually close to 50dB, which is in the "plenty-to-too-much" range in my system - my volume control usually sits in the -20dB zone.

In this particular case the two heads had similar inductance of around 160mH. But the Studer head has much lower resistance. I am not using any input capacitance besides that of the interconnects. The Otari head is loaded just as it is normally, and the Studer started with high load of 332K, but then it was changed to its normal 47K, with no obvious effect.

The two sounds were easy to tell apart, with the Otari one being more clear and free-floating. I verified that by putting my wife in front of the system - she is not an audiophile by any stretch of the imagination, but loves music and has good ears. She immediately said the correct words, and when played randomly, correctly identified the source.

But no, no plans for making them commercially. I would estimate there are 100 to 1000 phono stage customers out there for every high end tape user. We sell good volume of the phono stages, and at this point it almost seems like there is one producer for every head preamp customer.

Have you tried the Flux Magnetic heads on the Studer ? Are they a significant upgrade ?
My Nagra T has a regular head with a 2.75mm track width and a 700mH inductance, pretty high for a modern machine. It sounds great with my tube tape head pre.
Are you selling the preamps you have modified ? I know someone who might be interested.

 

[Foxbat]

Adrian - the only FM head I have is mounted on my MCI. Is it a significant upgrade from the stock head? It is a good head, for sure, but how much better than the stock one I can't honestly tell, as I have not ran a well controlled comparison.

700mH is very high, you would need very high input resistance, probably on the order of 150K to work with it, not hard to do with tube preamps. I have one head that is 600mH, but most are much lower.

Sorry, at this point I am not selling any preamps, as all but one are currently assigned.

 

[adrianywu]

Adrian - the only FM head I have is mounted on my MCI. Is it a significant upgrade from the stock head? It is a good head, for sure, but how much better than the stock one I can't honestly tell, as I have not ran a well controlled comparison.

700mH is very high, you would need very high input resistance, probably on the order of 150K to work with it, not hard to do with tube preamps. I have one head that is 600mH, but most are much lower.

Sorry, at this point I am not selling any preamps, as all but one are currently assigned.

Yes. I have 300K on each phase of the balanced input. I got the response at 20KHz to -1.5dB on CCIR.

 

[Foxbat]

I presume you are talking about 15ips, correct? Then you would typically have close to zero loss at 20KHz, so I am wondering what causes that 1.5dB drop. Two possibilities come to mind. One is the head's gap losses. The other is presence of some differential resistance not accounted for.

It would be interesting to find out. I mean - such a loss would not be detrimental to the sound, but I would be curious regarding its cause.

It could also be just the way you adjust your HF EQ. This is all about personal choices. Some people would keep it as flat as possible for as long as possible, with no raise anywhere, and the resulting top frequency drop would be more visible.

I usually allow for some small raise, basically splitting the difference. Typically I shoot for +.3 to .+.5dB at 16KHz. There is no logical explanation for that, just personal preference.

 

[christensenleif@msn.com]

I found it, but it doesn't list resistances.

Bummer... On the shield I can see the traces of the adhesive where the label once was, but no label.

Ditto for the record head.

asked someone and guess I´ll have a reply within a few hours

 

[Foxbat]

Thank you, looking forward to it!

 

[adrianywu]

I presume you are talking about 15ips, correct? Then you would typically have close to zero loss at 20KHz, so I am wondering what causes that 1.5dB drop. Two possibilities come to mind. One is the head's gap losses. The other is presence of some differential resistance not accounted for.

It would be interesting to find out. I mean - such a loss would not be detrimental to the sound, but I would be curious regarding its cause.

It could also be just the way you adjust your HF EQ. This is all about personal choices. Some people would keep it as flat as possible for as long as possible, with no raise anywhere, and the resulting top frequency drop would be more visible.

I usually allow for some small raise, basically splitting the difference. Typically I shoot for +.3 to .+.5dB at 16KHz. There is no logical explanation for that, just personal preference.

Yes, -1.5dB loss at 20kHz on 15ips. It is flat at 16kHz. Probably insignificant, and the best I could do with my preamp setup. I didn't want to increase the input resistance any further. Also hard to know whether the MRL tape I have is flat up to 20kHz.