[aeroes]

Im about to finish my order but I have a question.

Can I use 25v for C7L/R position?

 

[drewd]

Quote:

Originally Posted by aeroes Can I use 25v for C7L/R position?

Yep!

 

[Jaypetermen]

Quote:

Originally Posted by drewd Yep!

Good news.

The http://hybrid.fluidlight.com/ web page mentions that the voltage rating for C1, C7L/R, 9L/R & C10L/R should be no less than 35V.

So a 100uf/35V electrolytic cap can be used in the C1, C7L/R, 9L/R & C10L/R positions?

The http://hybrid.fluidlight.com/ web page also mentions that the output coupling caps determine the low frequency cutoff point. For 100uF is the lowest recommended value. For headphones with impedances <150 ohms, up to 470uF is appropriate.

What value would be the best for a 300Ohm can like the HD-650. Would 100uf be a good fit for these cans?

Also, can 220uf/35V caps be used in the Millit-Hybrid’s C1, C7L/R, 9L/R & C10L/R positions?

Quote:

Originally Posted by amb ...f = 1 / (2 * pi * R * C)...

So for 300ohm 650s and a 220uf cap the -3dB point is 4.42Hz. Okay, is this a good thing?

 

[Finch&Music]

Quote:

Originally Posted by drewd Yep!

This induces some incertainty for me.

What is the lowest possible V rating for c7L/R?

When a lower voltage rating in that position is really possible than there is more flexibility to choices for electrolytic output caps. Not only pricewize.

Is there any danger when one of the tubes is going defect or disfunctioning? 35V is may be also a safety level in reference to the primarily supply voltage?

If so, than you can better use 35V in that output position!

Greetings

Pieter Vink

 

[n_maher]

Peter and others,

I'm sure Drew will chime in here with more accurate advice but I think the root of the cap voltage issue has a few layers. One, there are certain caps on the board which see the full supply voltage. So for those caps, you want to make sure that you have the correct rated caps, plus a little headroom (no pun intended). Two, while a power supply may be rated for 24V oftentimes it will fluctuate up and down. Based on my own observations this can easily be a volt or so. So if it were me, I wouldn't use 25V caps for those positions, even if techinically you could. I think that's why Drew put the 35V min in the docs.

The bummer of it is that 25V caps seem to be more easily found in the values that we're all looking for, especially when in comes to the Elna and Nichcon caps.

The caps that I recommend in the BOM will be rated for 50V DC if for no other reason than to have convenient lead spacings. I don't think that folks will run into any issues choosing higher rated caps in terms of sound quality, but I'll be trying to test this for people as well.

HTH,

Nate

 

[drewd]

When I have my electrial engineering hat on, I would say that any caps in the amplifier should have a voltage rating of at least twice the voltage that they may be subjected to. In the case of C7L/R, the maximum voltage is V+ or 24V. That assumes a couple of things:

• The power supply is delivering 24V
• The bias is set at 24V
• The amplifier is either broken or terribly misadjusted

So, as an EE, I would use a 50V cap on the output.

From a pragmatic point of view, if V+ is present on the output, you'll know that something is wrong right away. You most certainly will not be listening to anything.

A 25V cap will block the DC at V+. And it's not going to explode or anything like that - in fact, it's not going to fail even if the voltage drifts up above 25V because you're not going to be listening to anything - you'll be turning it off because it sounds terrible! So, 25V is fine.

There are a couple of reasons that I specified 50V caps when I made up the BOM on the website. Pete's original amplifier used them. The original amp that I built used them. And I was looking at the caps with an engineer's eye for design.

Since there are also 5mm pin spacings on the board, lower voltage caps can be substituted. Also, please bear in mind that 100uF is not a magic value. I get the impression that Pete must have had a bunch of them on hand, so that's what he used. There's nothing wrong with using larger caps. They're bypassed with low ESR film caps, so there is no impedance issue.

I hope that I haven't made things more confusing. The bottom line is that the power caps will see 24V all the time and the signal caps will see about half of that all the time. The specific value of the caps is not critical - well, C7L/R depends on your headphones, but, practically speaking, it's not really critical.

-Drew

 

[Finch&Music]

Quote:

Originally Posted by drewd When I have my electrial engineering hat on, I would say that any caps in the amplifier should have a voltage rating of at least twice the voltage that they may be subjected to. In the case of C7L/R, the maximum voltage is V+ or 24V. That assumes a couple of things: The power supply is delivering 24V The bias is set at 24V The amplifier is either broken or terribly misadjusted So, as an EE, I would use a 50V cap on the output. From a pragmatic point of view, if V+ is present on the output, you'll know that something is wrong right away. You most certainly will not be listening to anything. A 25V cap will block the DC at V+. And it's not going to explode or anything like that - in fact, it's not going to fail even if the voltage drifts up above 25V because you're not going to be listening to anything - you'll be turning it off because it sounds terrible! So, 25V is fine. There are a couple of reasons that I specified 50V caps when I made up the BOM on the website. Pete's original amplifier used them. The original amp that I built used them. And I was looking at the caps with an engineer's eye for design. Since there are also 5mm pin spacings on the board, lower voltage caps can be substituted. Also, please bear in mind that 100uF is not a magic value. I get the impression that Pete must have had a bunch of them on hand, so that's what he used. There's nothing wrong with using larger caps. They're bypassed with low ESR film caps, so there is no impedance issue. I hope that I haven't made things more confusing. The bottom line is that the power caps will see 24V all the time and the signal caps will see about half of that all the time. The specific value of the caps is not critical - well, C7L/R depends on your headphones, but, practically speaking, it's not really critical. -Drew

1. With the above pre-requisites of a 24 v supply and a max bias at 24 V: could there be not any problem presented to your (pricey!) headphones when elco's of 25 v are executed? (Forgive me my little electronic insights, I am only looking for some insurance against stupid implementations with risk of damaging my headphones!

2. In general your EE approach gives me more confidence feelings than looking for the lowest possible voltages or values for a little less cents.

3. By the way:what will be the maximum practical bias volt adjustment to expect with the different tube types that will be practised? Is'nt that maximum also to determine the max supply voltage and the practical voltage of the electrolytic's?

4. I am planning a supply-set at 30V (STEPS based on talema 25va/2*15v; see earlier posts). In that case I assume that after regulation at 30V a 35V range (minimum) on all caps is mandatory, even in the position of C7.

5. That strategy gives me - as far as I can imagine - the most flexibility in bias adjustment. Or is that bias-aspect fully separate of the (max) supply voltage in all other positions?

6. In regard to the question of leadspace (and the added flexibility) I want to remark that - if funds gives you the space - do not go for the lowest level possible. I think the amp will benefit from some headroom in the supply and in the (quality) capacities on board. Than I am speaking of a balance between quantity, quality and (local) price.

greetings.

Pieter Vink

 

[drewd]

Quote:

Originally Posted by Finch&Music 1. With the above pre-requisites of a 24 v supply and a max bias at 24 V: could there be not any problem presented to your (pricey!) headphones when elco's of 25 v are executed? (Forgive me my little electronic insights, I am only looking for some insurance against stupid implementations with risk of damaging my headphones!

No, the voltage rating is not a measure of how much voltage the capacitor will block, but a measure of how much voltage can be applied to the capacitor over a long period of time. When I mentioned a maximum bias of 24V, I meant that to describe a failure condition - that would indicate that the bias pot had failed and the cathode was at ground. You would quickly hear that something was wrong - but even a 25V cap will block 30V of DC, although I would recommend that you use a 50V cap in that case because it's a good design practice. Obviously you wouldn't want the cap to block 30V for any great length of time.

Quote:

2. In general your EE approach gives me more confidence feelings than looking for the lowest possible voltages or values for a little less cents.

As an off-topic aside, when I design memory modules (my day job), I have to make a pretty good case for placing bypass caps that have even a small amount of voltage margin. For about a quarter of a cent per capacitor (and around 20 capacitors) difference between the different caps, that five cents becomes a major issue for the marketing and sales department. Fortunately, in the case of building our own amps, we get to make the decision on our own!

Quote:

3. By the way:what will be the maximum practical bias volt adjustment to expect with the different tube types that will be practised? Is'nt that maximum also to determine the max supply voltage and the practical voltage of the electrolytic's?

The bias is up to your ears. As a practical upper limit, the tubes were designed for automotive use, so 14V is as high as you should go. The nominal value is, I think, 12.6V. Higher bias will give more gain at the cost of more distortion - this amplifier has no feedback, so the distortion is a little on the high side in comparison to a solid state amplifier.

The maximum supply voltage is actually a function of the heaters in this amplifier. They are nominally rated at 12V, with a maximum of 15V. Since they are wired in series, each heater drops half of the power supply voltage. Your 30V power supply is at the upper limit of the heaters' voltage. They won't last as long as they might at a lower voltage, but keep in mind that their lifetime at 12V is rated at 10,000 hours and they're pretty inexpensive.

Quote:

4. I am planning a supply-set at 30V (STEPS based on talema 25va/2*15v; see earlier posts). In that case I assume that after regulation at 30V a 35V range (minimum) on all caps is mandatory, even in the position of C7.

Yes, that is an appropriate voltage value in your case.

Quote:

5. That strategy gives me - as far as I can imagine - the most flexibility in bias adjustment. Or is that bias-aspect fully separate of the (max) supply voltage in all other positions?

The bias is independent of the power supply. The heaters (and the buffers) are directly affected by the power supply voltage. I would not exceed 30V. I will say that I've been running my amplifier with a 30V Radio Shack power supply (that has absolutely terrible ripple specs), a 30V STEPS and a 30V TREAD clone and everything works quite nicely.

Quote:

6. In regard to the question of leadspace (and the added flexibility) I want to remark that - if funds gives you the space - do not go for the lowest level possible. I think the amp will benefit from some headroom in the supply and in the (quality) capacities on board. Than I am speaking of a balance between quantity, quality and (local) price.

Yes, I would say (and there has been plenty of discussion on Head-Fi to support this) that given the choice between capacitance and quality, one would do well to go for quality. A fast, low ESR cap of 100uF would be a better choice than a cheap 470uF cap. And if anybody is unsure about where to put their money on caps, the output caps are the most critical of all of the caps.

I've built five or six of these amps by now and after some pretty careful listening with a variety of headphones and sources, I think that the parts list on the web site represents the best bang for the buck. You can go down the "Mouser" column and end up with a really sweet sounding amplifier without breaking the bank.

Nate's Excel spreadsheet (which I'll be uploading this evening) is a slightly less expensive version that should deliver 95% of the sound.

But don't agonize over the choice of caps. Panasonic FC's or FM's are excellent performing caps and the Wima film caps from Mouser are pretty darned cheap - and those are the critical parts, in my opinion.

-Drew

 

[Finch&Music]

Thanks for your very explicite answers! As always it gives insight and help in choosing components and making dicisions on configurations.

On the topic of different tubes :

I have seen that a 12AE6A has another (= greater) amplificationfactor than f.e. a 12FK6. Is that factor of any significance in the sonical results?

Some other specs are also a little different. Are they of any importance? Or are that kind of different tube specs rulled out by the biassettings and/or volumesettings?


I want to add another topic to all the members of this thread:

I am in the process to choose between tube-brands. I have already chosen for a pair of each tubetype mentioned on the thread or componentlist. So I have already one pair of 12AE6E, 12FK6 and 12FM6 (all Sylvania) on my orderlist.

Because I want to do some tuberolling in the future I want to choose between some brands. I have seen on the internet some possibilities. Is there anyone under the threadmembers that can already give me some advise on brands to choose. For example on the basis of expirience with tuberolling on the original Millet amp or maybe some members has already expierience with the prototypes of the revised board.

I ask this on this moment because I have to order the possible different brands for additional tubes preferably in one order, because of all the added expenses of shipping etc to Europe.

Greetings,

Pieter Vink

 

[sbelyo]

Quote:

Originally Posted by Finch&Music I have seen that a 12AE6A has another (= greater) amplificationfactor than f.e. a 12FK6. Is that factor of any significance in the sonical results?

The 12AE6A to me didn't sound as detailed for vocals as the 12FK6, and the 12FM6 was in between. The bass wasn't as crisp either. However when running the Bias at 18 Vdc it was much better but lacked just a little compared to the FK
Quote:

Originally Posted by Finch&Music I am in the process to choose between tube-brands. I have already chosen for a pair of each tubetype mentioned on the thread or componentlist. So I have already one pair of 12AE6E, 12FK6 and 12FM6 (all Sylvania) on my orderlist.

I like the RCA 12FK6 the best with Sylvania a close second. My least favorite to listen to is Westinghouse. I have also tried Tung-Sol 12FK6's I would rank those third.

But those are just preliminary as I haven't really played too much with bias settings or chosen one recording and pair of headphones to compare the brands with.

Hope that helps.

 

[n_maher]

Another update - after Drew's comments regarding the spreadsheet, namely that the Mouser parts might in fact be considered preferred over Digikey, I went back and added a second page to the spreadsheet with all Mouser part numbers (save for the pot, no choice there). Turns out that the Mouser version is actually cheaper by my count, even including the $5 hit you'll take unless you can come up with $25 worth of parts needed from Digikey. Hopefully my email will get to Drew before he bothers to upload the previous version of the spreadsheet as it also had the wrong value for R6, D'OH!

And for those who might have missed it in the Group Buy thread the boards shipped today

.

Nate

 

[kilkil]

Thanks for all the work.

It looks like C9 and C10 should be electrolytic caps on the excel BOM

 

[drewd]

Quote:

Originally Posted by kilkil It looks like C9 and C10 should be electrolytic caps on the excel BOM

Two sets of eyes and you'd think that we'd catch that - I guess that three's the charm! It's fixed.

-Drew

 

[kilkil]

I didn't intend to validate the excel file, but one of my job at work is to make sure quality data goes out so I started validating the file without even thinking about it.

 

[n_maher]

Your validation is appreciated!