I tried driving something in that same 86 dB/m range before my Zu Omens arrived, and it definitely ran out of steam - particularly in the bass range. Your experience may vary - so please report back!

Inspire KT88 SE triode wired
 

New guy here. I just ordered an Inspire KT88SE triode strapped. It will have less power than the ultra linear version. Will post more after it arrives.

I have been a tube-a-holic for years and I excited about this amp. :D

Welcome FloridaBoy! Interesting variation. What does "triode strapped" mean? And how much power with which tubes? It's named after a pentode tube, so confusing. :scratch2:

My KT-150 runs at 10 - 12 watts when running KT-88's depending on rectifier.

The amp I am getting is single ended but wired in triode. It will produce less power but the sonics are, IMHO, seductive. Most of the amps Dennis has produced are single ended but are ultra linear. More power is produced with the ultra linear iteration. My speakers are 99db so I opted for triode. I have seen one Inspire that had a switch to toggle back and forth between the two.

FloridaBoy... Welcome to AA! :wave:

Still interesting! Makes me think about upgrade possibilities that might be possible for my amp. Switch between triode and UL, hmmm.

Now you've done it! :lala:

.

Should receive my IFA-1 today via FedEx.:banana:

Dennis mentioned in our correspondence that he's made some circuit upgrades on my particular amp. Not sure what they are but he was very pleased with the results.

I'll report back when I get it installed in my system.

The :music: is what matters. Low power tube amps and efficient speakers sound the best to me too.

The metal base Mullard 5AR4 is regarded as the best and they are not cheap.
However, the black base double D getter 5AR4 from the same era is a sonic twin and a lot cheaper. I have both and will post pic when I figure out how.

Okay so I received the IFA-1 today and everything arrived in fine order thanks to Dennis' great packing.

The Bryston Mini T's don't seem to be a problem for my particular IFA-1, which I believe is about 12 wpc and KT88 based. I had Dennis install a Blue Velvet Alps stereo potentiometer and I'm listening at my desired level with the knob at about 2:00.

More break-in required for sure but so far Antonio Forcione's "Tears of Joy" is sounding magnificent! Great bass (a bit looser than my Hegel 160's), full and deep, beautiful extended highs and of course, that gorgeous midrange that only tubes can do.

I do have a low oscillating hum that I can't seem to get rid of. It is not affected by the volume control, so any helpful suggestions are welcome here. I've tried both shielded and unshielded power cords on the amp, but no difference.

I am ecstatic at the performance I'm hearing right now!

Those tubes are priced on rarity. New production power tube are the equal to and often better than NOS. There are some exceptions, like Pope 6V6's.

We would not have the selection of new production tubes available today without the guitar guys. They use more tubes than us audio types.

If the impedance of the speaker is flat it should be easy to drive with a low power amp.

I've had those 70's 3 hole 6550's too. Nice tubes and Kevin Deal thinks they are the best vintage. *I* wouldn't pay the premium for the late 50's black plates.

I've not used the GL GZ34. Have you compared it to a Mullard? It's great to have some new production options.

The 45 amp is a true SET amp. I have had 300B amps and a Korneff 45. *I* preferred the 45. I was considering the Inspire 45 but did not want to get back into the $400+ a pair for tubes. He has one on the bay recently and it was $2595 with EML mesh plate 45's that cost $629 a pair. If you have speakers that can sing with 2 watts, IMHO, a well executed 45 amp is the bomb. :music:

What speakers are you driving?

I have a 6V6 Decware Mini Torii and the Pope's are excellent. The inexpensive Russian black glass 6V6's are very good too but they need a lot of hours. The Tung Sol reissue 6V6 is an excellent tube too.

How many hours did you have on the KT150's?

Is the IFA-1 an integrated?

Do you have cable coming in to your system anywhere? I had to add a noise blocker on mine, but it cured it.

My IFA-1 has an Alps Blue Velvet stereo potentiometer (volume control) built-in but it's technically not an integrated.

No cable TV connections in my 2 channel system.

Which noise blocker worked for you?

The blocker is a Jensen VRD-1FF "ISO-MAX". Specific for the 75ohm incoming cable connection. I've seen many reports that this has been 100% effective for this particular problem with cable interference.

I don't know if it is possible that a cable box on the same AC circuit could cause the hum even if not connected to the 2-channel system.

Brainstorming......... You said you tried shielded and unshielded power cords. Do you mean with and without ground or literally the shielding? Sometimes a "ground lift" can fix ground loop hums. Also by grounding components to each other directly (like the amp to your source or other combos). Both are easy to test. The first with a three to two conductor power adaptor ($2); the second with a piece of wire from one chassis to another - you can just touch without having to attach until you find the problem.

Thanks for the clarification on the attenuator. I was a bit confused! From looking at his last IFA-1 ebay sale, it seems you can run the same tubes as us SEP folks. So many possibilities that it's dangerous to the wallet when you mix in perfectionism! It also says 7+ watts with KT-88's. If triode mode reduces power, that makes sense since my SEP runs about 12 wpc with the bigger tubes.

Thanks Pete for the brainstorming. I will do some troubleshooting tonite after work.

Actually Dennis just called me on my cell to check on things and make sure I am pleased. He seems like a great guy and it has been a pleasure dealing with him.

BTW, the IFA-1 sounds incredible if I didn't mention that already. My Bryston Mini T's are presenting no problem but then I don't listen at loud levels anyway.

Beatle, would you please post a pic of your amp? Just curious.

FloridaBoy.... he did post the photos from Dennis a page or two back.

My apologies both to FloridaBoy and Beatlebum - I conflated your amps as you both started posting about them at the same time and I wasn't paying close enough attention. So a comment or two that I've made was about the "other" amp and might have been confusing.

FB - I see you've replied to a number of old posts, some quoting me. I'll take a look and reply where appropriate later today. Often, things change, particularly when it comes to favored tubes!

I'm probably putting some stuff out there that is obvious, but just in case.....

Is the hum from one speaker or both? If one, swap power tubes, reverse left & right speaker cables, etc., to see if you can narrow down what is at fault. If from both speakers, try a different rectifier and driver just to make sure one of them isn't acting up.

Finished amp
 

Dennis finished the amp and will ship it on Monday. It is single ended and triode wired. No switch to go ultra linear but that could be done. 6SN7/6SL7 driver, 5Z3 rectifier...the daddy of the 5U4G, KT88's. The 5Z3 has different pins and draws 3 amps. I have an adapter to enable the use of other rectifiers. I have a pair of KT150's on the way. In triode they are reported to have the midrange of a KT88 with the drive of a KT120. He said he will be building a few more of these soon.



[IMG]http://i58.tinypic.com/4t6cgl.jpg[/IMG]

There is a Russian 6L6 equivalent, 6p3s-e, that is inexpensive and well regarded. They are more transparent than the TS big bottle you decide to try them, get them from a seller that tests them properly. I have not heard the KT150 yet....but will soon.

The Pope 6V6's should not sound bright. What driver tube are you using?

I wanted to get enough posts to get past moderator approval. :thumbsup:

Beatlebum, is the hum you hear a low hum through your speakers when there is no input to your amp?

Yes that is the case!

I have the same with my 6L6 Fire Bottle.

I have had several tube amps in the past (807 based, KT88 based, EL34 based) and never had a problem with a loud hum in my systems so hope it's something electrical/mechanical, like a resistor, that's got a problem. The amp sounds amazing :yes: and I'm looking forward to getting it back.

Is Dennis taking care of the hum issue?

Yes! I shipped the amp back to him yesterday. He should receive it on Monday or Tuesday and he said he would promptly address the issue. Great guy!

Let me know how that works out, as I may want him to resolve the issue in mine as well. Have a great 4th

The info below came from another forum:

Dennis said the amp can also use the following tube combination:
5 watts per channel - 6V6 output tubes and 5Y3 rectifier tube
7 watts per channel - 6L6, KT66, 5881 output and 5U4 rectifier
10 watts output - KT88, EL34, 6550, KT99, and KT120 output and 5U4/274B rectifier
12 watts output - KT-88, KT-120, KT-150 and 5AR4 rectifier

Power ratings are for the Ultra linear versions.

Looks familiar! From post #3 in this thread on 11-28-2013:

What is that other forum?

It was posted on Audio Asylum.

Did you try a cheater plug? It could possibly be a ground loop.