Dennis Had Inspire Amps

[Bombadil]

Originally Posted by guitardave

I can post a pic when I receive it. I think it is shipping today. I have seen multiple pics as build progressed. It looks great!!

Do you have your new amp? First impressions?

[FloridaBoy]

Originally Posted by Bombadil

I thought the first number in your table, the max DC output current, was the primary factor in how hard the output tubes are driven. The stock 274B is 225, the 5V4GA is 175, and the 5Y3GT is 125. Then the voltage drop is the sag in those volts when the rectifier is driven hard, i.e. how much voltage can be drawn on peak demands. So if one subtracts the sag, the 274B drops 44 volts to a max of 181 on peaks, the 5V4GA is 150, and the 5Y3GT is just 65.

Now, I'm no expert on such things and I could be wrong. If the above is true, then the 274B should always be able to deliver more voltage than a 5V4GA. And the 5AR4/GZ34 is highly desired by those wanting to get max power out of the output tubes, as it can deliver up to 250V with a sag of just 10V, thus it is almost linear in its output.

The first number is DC millivolts. The plate voltage is what drives the tube. That less the drop is what the tube plate sees. Google 5 volt rectifier table and click the 'fourwater' link. It is a better table. These amps are single ended and the tubes may sound better not driven as hard as in a push pull amp.

The Russian 6P14P-EV can handle more voltage on the plate than regular EL84's but I don't know how they would sound in your amp.

[FloridaBoy]

Originally Posted by Bombadil

Do you have your new amp? First impressions?

What speakers are you driving?

[FloridaBoy]

Originally Posted by Analog Addict

Speaking of tube rolling, I had an afternoon off last week, so I went over to the shop with a bag full of vinyl and a bag full of old toobs.







Also did a little measuring on the bench, but that's a story for when I have more time.....


Also saw this lying around on the assembly bench....

That appears to be the same amp that Twanny, Musica and I have. However, they are triode strapped and have less power. The last pic looks like the innards of a LP27a. I'm curious about the measurements.

[Analog Addict]

Originally Posted by FloridaBoy

That appears to be the same amp that Twanny, Musica and I have. However, they are triode strapped and have less power. The last pic looks like the innards of a LP27a. I'm curious about the measurements.

I'm not fessing up until I get enough of the tubes that Dennis and I both liked the most.....

[Bombadil]

Originally Posted by FloridaBoy

The first number is DC millivolts. The plate voltage is what drives the tube. That less the drop is what the tube plate sees. Google 5 volt rectifier table and click the 'fourwater' link. It is a better table. These amps are single ended and the tubes may sound better not driven as hard as in a push pull amp.

The Russian 6P14P-EV can handle more voltage on the plate than regular EL84's but I don't know how they would sound in your amp.

Okay, so then most of the time if I am using a 5V4GA the plate voltage will be 400V vs when using the 274B it will be 381V. The drop should only occur on volume peaks / maximum demand. As I am filtering sub-100Hz signals from the amp, there may be few drops occurring.

I do have the 5V4GA back in right now. Running a comparison between it vs the 274B, a 5U4G, and a 5Y3GT. But using a different 5V4GA, this one is a very old RCA and the glass has a slight bronze'ish cast. Very pretty when lit up. The one I used the other day is an ancient Remington Rand. Perhaps it wasn't up to spec. This one is sounding better.

As to being driven hard, Dennis' current KT88 amp that produces 17 watts per channel, is driving that tube at its estimated max in single-ended mode.

[Analog Addict]

I don't know if it's been commented on before, but logically, Dennis is an amp designer, not a tube collector. In general, he doesn't care if that expensive set of NOS Tung Sol Black Plate 6550s only last 2000 hours instead of 5000 hours. Instead he is looking to squeeze maximum performance out of the tubes so that the amps perform to the max. One of my favorite "Dennisisms" is when a tube starts to look just a little bit orange around the plates, hardly noticeable unless you turn out the lights...."Its good for them!"

[guitardave]

Originally Posted by Bombadil

Do you have your new amp? First impressions?

Yes, I have had if for about a week or so. Very nice amp. I am still burning it in, but currently using a 5u4 with 6sn7, a pair of KT 88's, and a pair of Pope 6v6's. Very nice combination! I am driving it with an Audionotekits Mentor preamp.
The amp has a nice "live" sound. Very open, detailed, and nuanced.

[FloridaBoy]

[QUOTE=Bombadil;796799]Okay, so then most of the time if I am using a 5V4GA the plate voltage will be 400V vs when using the 274B it will be 381V. The drop should only occur on volume peaks / maximum demand. As I am filtering sub-100Hz signals from the amp, there may be few drops occurring.

I do have the 5V4GA back in right now. Running a comparison between it vs the 274B, a 5U4G, and a 5Y3GT. But using a different 5V4GA, this one is a very old RCA and the glass has a slight bronze'ish cast. Very pretty when lit up. The one I used the other day is an ancient Remington Rand. Perhaps it wasn't up to spec. This one is sounding better.

As to being driven hard, Dennis' current KT88 amp that produces 17 watts per channel, is driving that tube at its estimated max in single-ended mode.

It just may have been your 'state of mind' when you heard the edginess. Sometimes I'll think my rig sounds weird and it often occurs during the daytime. Rectifiers of the same type should not sound different but to my ears they do. It appears that you have the issue resolved and that's all that matters.

[Bombadil]

Originally Posted by FloridaBoy

It just may have been your 'state of mind' when you heard the edginess. Sometimes I'll think my rig sounds weird and it often occurs during the daytime. Rectifiers of the same type should not sound different but to my ears they do. It appears that you have the issue resolved and that's all that matters.

Rectifiers of the same type usually sound the same to me. Perhaps it was a time of day thing. But perhaps it was just a 60 to 70 year old tube not being at its best anymore.

I'm going to keep on rolling them. Having 4 different tube types and about 10 rectifier tubes in all gives me a project.

Neil Young playing now ...